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Heavy metals removal and hydraulic performance in zero-valent iron\\/pumice permeable reactive barriers
Microsoft Academic Search
Long-term behaviour is a major issue related to the use of zero-valent iron (ZVI) in permeable reactive barriers for groundwater remediation; in fact, in several published cases the hydraulic conductivity and removal efficiency were progressively reduced during operation, potentially compromising the functionality of the barrier. To solve this problem, the use of granular mixtures of ZVI and natural pumice has
Nicola Moraci; Paolo S. Calabrò
Review of Zero Valent Iron and Apatite as reactive materials for Permeable Reactive Barrier
Permeable reactive barrier (PRB) is a technology developed recently in the last years. It has obtained promising results in the removal of several contaminants present in the groundwater. This Term paper focuses the attention on two reactive materials, Zero valent iron and Apatite, employed in the PRB system, giving an overview of the reactions and types of pollutants treated to
Luca Geranio; Evert Elzinga
Modelling the remediation of contaminated groundwater using zero-valent iron barrier
This paper presents results of modelling studies on remediation of groundwater contaminated with uranium using a zero-valent iron permeable reactive barrier (ZVI PRB) at the U.S. Oak Ridge Y-12 site that are used to establish modelling techniques that are of value to other sites such as in the UK. A systematic modelling methodology has been developed to study the problem
S. Kwong; J. Small; B. Tahar
Biogeochemical dynamics in zero-valent iron columns: Implications for permeable reactive barriers
The impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe°). To evaluate potential biogeochemical impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate and sulfate
B. Gu; T. J. Phelps; L. Liang; A. V. Palumbo; G. K. Jacobs; M. J. Dickey; Y. Roh; B. L. Kinsall
EPA Science Inventory
Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, NC and the Denver Federal Center, CO sites. These ground water treatment systems use zero-valent iron filings (Peerless Meta...
SciTech Connect
The impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe{sup 0}). To evaluate potential biogeochemical impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate and sulfate containing groundwater regimes. Groundwater chemistry was found to significantly affect corrosion rates of Fe{sup 0} filings and resulted in the formation of a suite of mineral precipitates. HCO{sub 3}{sup {minus}} ions in SO{sub 4}{sup 2{minus}}-containing water were particularly corrosive to Fe{sup 0}, resulting in the formation of ferrous carbonate and enhanced H{sub 2} gas generation that stimulated the growth of microbial populations and increased SO{sub 4}{sup 2{minus}} reduction. Major mineral precipitates identified included lepidocrocite, akaganeite, mackinawite, magnetite/maghemite, goethite, siderite, and amorphous ferrous sulfide. Sulfide was formed as a result of microbial reduction of SO{sub 4}{sup 2{minus}} that became significant after about 2 months of column operations. This study demonstrates that biogeochemical influences on the performance and reaction of Fe{sup 0} may be minimal in the short term, necessitating longer-term operations to observe the effects of biogeochemical reactions on the performance of Fe{sup 0} barriers. Although major failures of in-ground treatment barriers have not been problematic to date, the accumulation of iron oxyhydroxides, carbonates, and sulfides from biogeochemical processes could reduce the reactivity and permeability of Fe{sup 0} beds, thereby decreasing treatment efficiency.
Gu, B.; Phelps, T.J.; Liang, L.; Palumbo, A.V.; Jacobs, G.K. [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.] [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.; Dickey, M.J.; Roh, Y.; Kinsall, B.L. [Oak Ridge Inst. for Science and Education, TN (United States)] [Oak Ridge Inst. for Science and Education, TN (United States)
Dechlorination of pentachlorophenol by zero valent iron and modified zero valent irons
The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in
Young-Hun Kim; Elizabeth R. Carraway
Hydraulic and geochemical performance of a permeable reactive barrier containing zero-valent iron, Denver Federal Center
USGS Publications Warehouse
The hydraulic and geochemical performance of a 366 m long permeable reactive barrier (PRB) at the Denver Federal Center; Denver, Colorado, was evaluated. The funnel and gate system, which was installed in 1996 to intercept and remediate ground water contaminated with chlorinated aliphatic hydrocarbons (CAHs), contained four 12.2 m wide gates filled with zero-valent iron. Ground water mounding on the upgradient side of the PRB resulted in a tenfold increase in the hydraulic gradient and ground water velocity through the gates compared to areas of the aquifer unaffected by the PRB. Water balance calculations for April 1997 indicate that about 75% of the ground water moving toward the PRB from upgradient areas moved through the gates. The rest of the water either accumulated on the upgradient side of the PRB or bypassed the PRB. Chemical data from monitoring wells screened down-gradient, beneath, and at the ends of the PRB indicate that contaminants had not bypassed the PRB, except in a few isolated areas. Greater than 99% of the CAH mass entering the gates was retained by the iron. Fifty-one percent of the CAH carbon entering one gate was accounted for in dissolved C1 and C2 hydrocarbons, primarily ethane and ethene, which indicates that CAHs may adsorb to the iron prior to being dehalogenated. Treated water exiting the gates displaced contaminated ground water at a distance of at least 3 m downgradient from the PRB by the end of 1997. Measurements of dissolved inorganic ions in one gate indicate that calcite and siderite precipitation in the gate could reduce gate porosity by about 0.35% per year. Results from this study indicate that funnel and gate systems containing zero-valent iron can effectively treat ground water contaminated with CAHs. However, the hydrologic impacts of the PRB on the flow system need to be fully understood to prevent contaminants from bypassing the PRB.
McMahon, P. B.; Dennehy, K. F.; Sandstrom, M. W.
Zero-valent iron nanoparticles preparation
Graphical abstract: Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}] at room temperature and a pressure of 3 atm. The synthesized nanoparticles were spherical and had diameters less than 5 nm. Highlights: ? Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}]. ? The conditions of reaction were at room temperature and a pressure of 3 atm. ? The synthesized nanoparticles were spherical and had diameters less than 5 nm. -- Abstract: Zero-valent iron nanoparticles were synthesized by hydrogenating [Fe[N(Si(CH{sub 3}){sub 3}){sub 2}]{sub 2}] at room temperature and a pressure of 3 atm. To monitor the reaction, a stainless steel pressure reactor lined with PTFE and mechanically stirred was designed. This design allowed the extraction of samples at different times, minimizing the perturbation in the system. In this way, the shape and the diameter of the nanoparticles produced during the reaction were also monitored. The results showed the production of zero-valent iron nanoparticles that were approximately 5 nm in diameter arranged in agglomerates. The agglomerates grew to 900 nm when the reaction time increased up to 12 h; however, the diameter of the individual nanoparticles remained almost the same. During the reaction, some byproducts constituted by amino species acted as surfactants; therefore, no other surfactants were necessary.
Oropeza, S. [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico)] [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico); Corea, M., E-mail: firstname.lastname@example.com [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico); Gómez-Yáñez, C. [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico)] [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico); Cruz-Rivera, J.J. [Universidad Autónoma de San Luis Potosí, Instituto de Metalurgia, Sierra Leona 550, San Luis Potosí, C.P. 78210 (Mexico)] [Universidad Autónoma de San Luis Potosí, Instituto de Metalurgia, Sierra Leona 550, San Luis Potosí, C.P. 78210 (Mexico); Navarro-Clemente, M.E., E-mail: firstname.lastname@example.com [Instituto Politécnico Nacional, ESIQIE, UPALM, Edificio Z-6, Primer Piso, C.P. 07738, Col. San Pedro Zacatenco, México D.F. (Mexico)
Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, NC and the Denver Federal Center, CO sites. These groundwater treatment systems use zero-valent iron filings to intercept an...
Estimate of the optimum weight ratio in Zero-Valent Iron\\/Pumice granular mixtures used in permeable reactive barriers for the remediation of nickel contaminated groundwater
This paper presents the results of laboratory column tests aimed at defining the optimum weight ratio of Zero-Valent Iron (ZVI)\\/Pumice granular mixtures to be used in Permeable Reactive Barriers (PRBs) for the removal of nickel from contaminated groundwater. The tests were carried out feeding the columns with aqueous solutions of nickel nitrate at concentrations of 5 and 50mg\\/l using three
P. S. Calabrò; N. Moraci; P. Suraci
Performance evaluation of a zero-valent iron reactive barrier: mineralogical characteristics
There is a limited amount of information about the effects of mineral precipitates and corrosion on the lifespan and long-term performance of in situ Fe° reactive barriers. The objectives of this paper are (1) to investigate mineral precipitates through an in situ permeable Fe° reactive barrier and (2) to examine the cementation and corrosion of Fe° filings in order to
Debra Helen Phillips; Baohua Gu; David B Watson; Yul Roh; Liyuan Liang; S. Y. Lee
Long-Term Performance of Zero-Valent Iron Permeable Reactive Barriers: A Critical Review
Permeable reactive barriers (PRBs) have shown great promise as an alternative to pump and treat for the remediation of groundwater containing a wide array of contaminants including organics, metals, and ra- dionuclides. Analyses to date have focused on individual case studies, rather than considering broad per- formance issues. In response to this need, this study analyzed data from field installations
Andrew D. Henderson; Avery H. Demond
The disappearance of pentachlorophenol (PCP) from aqueous solutions in contact with zero valent metals (ZVMs) may be due to dechlorination reactions or sorption to ZVM-related surfaces. Previously reported results on PCP and zero valent iron measured only PCP loss from aqueous solutions and attributed this loss to reaction. In this study, the total amount of unreacted PCP, both that in aqueous solution and that sorbed to ZVM-related surfaces, was measured using a modified extraction method. PCP dechlorination was confirmed by following the appearance of tetrachlorophenol isomers. The results indicate that the rate of dechlorination is much slower than previously reported. In their experiments, electrolytic zero valent iron with a surface area of 0.12 m{sup 2}/g resulted in an observed first-order rate constant of 3.9 x 10{sup {minus}3} h{sup {minus}1} or a half-life of approximately 7.4 days. Normalized to surface area, the rate constant (k{sub SA}) is 3.2 x 10{sup {minus}4} L m{sup {minus}2} h{sup {minus}1}. Four amended irons prepared by coating iron with palladium (Pd/Fe), platinum (Pt/Fe), nickel (Ni/Fe), and copper (Cu/Fe) were also used and showed slower removal rates as compared to unamended iron. Slower reaction rates obtained with amended irons as compared to iron have not been previously reported. Overall, this study conclusively demonstrates PCP dechlorination by iron and several bimetallic ZVMs and indicates that it is essential to separate reaction and sorption processes.
Kim, Y.H.; Carraway, E.R.
In situ removal of arsenic from groundwater by using permeable reactive barriers of organic matter\\/limestone\\/zero-valent iron mixtures
In this study, two mixtures of municipal compost, limestone and, optionally, zero-valent iron were assessed in two column\\u000a experiments on acid mine treatment. The effluent solution was systematically analysed throughout the experiment and precipitates\\u000a from both columns were withdrawn for scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry\\u000a analysis and, from the column containing zero-valent iron, solid digestion and sequential
O. Gibert; J. de Pablo; J.-L. Cortina; C. Ayora
Enhanced reduction of nitrate by zero-valent iron at elevated temperatures
Kinetics of nitrate reduction by zero-valent iron at elevated temperatures was studied through batch and column experiments. It was hypothesized that under increased solution temperatures, the zero-valent iron may accelerate the reduction of nitrate by overcoming the activation energy barrier to nitrate reduction. The results of the batch experiment showed the synergistic effects of elevated temperature (75°C) and a buffered
Se Chang Ahn; Seok-Young Oh; Daniel K. Cha
Degradation of chlorinated phenols by nanoscale zero-valent iron
Chlorophenols (CPs), as important contaminants in groundwater, are toxic and difficult to biodegrade. Recently nanoscale zero-valent\\u000a iron received a great deal of attention because of its excellent performance in treating recalcitrant compounds. In this study,\\u000a nanoscale zero-valent iron particles were prepared using chemical reduction, and the reductive transformations of three kinds\\u000a of chlorinated phenols (2-CP, 3-CP, and 4-CP) by nanoscale
Rong Cheng; Jianlong Wang; Weixian Zhang
Low frequency electrical properties of zero valent iron: Implications for performance monitoring of permeable reactive barriers (PRBs)
The permeable reactive barrier is an in-situ remediation technology for groundwater contaminants. Long term performance monitoring of PRB is critical to the estimation of barrier efficiency. Iron corrosion and mineral precipitation are recognized as the primary causes of barrier performance reduction and can serve as a proper indicator of barrier efficiency. Electrical signature is sensitive to iron corrosion processes. This
Yuxin Wu
Estimate of the optimum weight ratio in zero-valent iron/pumice granular mixtures used in permeable reactive barriers for the remediation of nickel contaminated groundwater.
This paper presents the results of laboratory column tests aimed at defining the optimum weight ratio of zero-valent iron (ZVI)/pumice granular mixtures to be used in permeable reactive barriers (PRBs) for the removal of nickel from contaminated groundwater. The tests were carried out feeding the columns with aqueous solutions of nickel nitrate at concentrations of 5 and 50 mg/l using three ZVI/pumice granular mixtures at various weight ratios (10/90, 30/70 and 50/50), for a total of six column tests; two additional tests were carried out using ZVI alone. The most successful compromise between reactivity (higher ZVI content) and long-term hydraulic performance (higher Pumice content) seems to be given by the ZVI/pumice granular mixture with a 30/70 weight ratio. PMID:21885195
Calabrò, P S; Moraci, N; Suraci, P
Assessment of zero?valent iron as a permeable reactive barrier for long?term removal of arsenic compounds from synthetic water
Zero?valent iron (ZVI) has great potential to be used as a remediation material for the removal of a wide range of pollutants from groundwater. The present study assessed the potential of ZVI for arsenic remediation by investigating (i) the removal kinetics of arsenic by ZVI in a batch reactor and (ii) the longevity of ZVI to remove arsenic in a
Yunho Lee; Jeyong Yoon
A small-scale field test was initiated in September 1994 to evaluate the in situ remediation of groundwater contaminated with chromate using a permeable reactive barrier composed of a mixture of zero-valent Fe, sand and aquifer sediment. The site used was an old chrome-plating f...
The use of zero valent iron, permeable reactive barriers (PRBs) for groundwater remediation continues to increase. An exciting variation of this technology involves introducing anaerobic bacteria into these barriers so that both biological and abiotic pollutant removal processes ...
Dechlorination of ?-hexachlorocyclohexane by zero-valent metallic iron
This study investigated the rates and pathways of ?-hexachlorocyclohexane (?-HCH) dechlorination by granular zero-valent iron under different pH, iron dosage and temperature conditions. It was found that ?-HCH was rapidly reduced to benzene and chlorobenzene (CB) with benzene as the major product and that the dechlorination likely follows three steps of dichloroelimination to benzene, or two steps of dichloroeliminations and
Zhiyuan Wang; Ping'an Peng; Weilin Huang
A presentation on the use of zero valent iron (ZVI) for groundwater remediation at the Memphis Defense Depot Site in Memphis, TN, will be given at a public meeting in Memphis on February 24. The presentation is being given in response to a request by a citizen's group associated...
Modeling of arsenic immobilization by zero valent iron
Ground waters in geothermal regions contain arsenic concentrations that exceed the recommended drinking water standards. In addition, when these regions have agricultural activities, the waters also contain high levels of nitrates and phosphates. These contaminants can be removed from the water with the use of filters containing zero valent iron (ZVI). The objective of this study was to model the
Konstantina Tyrovola; Elpida Peroulaki; Nikolaos P. Nikolaidis
NASA Astrophysics Data System (ADS)
The permeable reactive barrier is an in-situ remediation technology for groundwater contaminants. Long term performance monitoring of PRB is critical to the estimation of barrier efficiency. Iron corrosion and mineral precipitation are recognized as the primary causes of barrier performance reduction and can serve as a proper indicator of barrier efficiency. Electrical signature is sensitive to iron corrosion processes. This thesis investigated the usage of geoelectrical methods to detect and/or monitor iron corrosion and mineral precipitation processes in barriers. This research revealed clear correlation between geoelectrical signatures and iron corrosion processes, and suggested the feasibility of using geoelectrical methods as a viable means for barrier performance monitoring. In the first part of the research, electrical response of sand/iron mixtures under variable Fe0 concentrations and electrolyte chemistry was investigated. A linear relation between polarization and the surface area of Fe0 was revealed. This part also revealed the correlation between polarization, relaxation time and electrolyte activity, pH and valence. The second part examined sensitivity of electrical signatures to iron corrosion and mineral precipitation induced with simple electrolytes. This research revealed an increase of complex conductivity in response to iron corrosion and mineral precipitation. This was attributed to the increase of complex interfacial conductivity and electronic conduction. In the third part, I conducted electrical measurements on field cores. This investigation showed a significant increase in complex conductivity in reacted zones relative to non/minimally reacted zones within the cores. This experiment verified the sensitivity of electrical method to iron corrosion and mineral precipitation processes. The last part of the research examines the control of precipitate mineralogy on electrical properties of laboratory columns. This experiment revealed contrasting electrical behaviors associated with iron oxides relative to carbonate precipitate, which was attributed to differences in mineral electrical properties. This result suggests that precipitate mineralogy is an important factor influencing electrical properties of corroded iron cores and must be considered when electrical methods are applied to monitor PRB barrier corrosion processes.
Wu, Yuxin
Conceptual analysis of zero-valent iron fracture reactive barriers for remediating a trichloroethylene plume in a chalk aquifer
A novel concept, the Fe0 fracture reactive barrier (Fe0 FRB), is proposed to clean up chlorinated solvent pollution of groundwater in a chalk aquifer. Iron particles, suspended in a viscous biodegradable gel, can be injected into selected fractures to create an extended reactive zone of partly iron-filled fractures. To evaluate the feasibility of Fe0 FRB as a remediation strategy, we
Zuansi Cai; David N. Lerner; Robert G. McLaren; Ryan D. Wilson
Renewable hydrogen generation by bimetallic zero valent iron nanoparticles
Nanoscale zero valent iron (nZVI), a nanomaterial widely used in environmental remediation and toxic waste treatment, is investigated for its potential for hydrogen generation. Laboratory experiments show that the iron-normalized hydrogen production rates vary from 15.2 to 58.3mgH2kg?1Feh?1 for nZVI, which are approximately two orders of magnitude higher than those of micro-sized iron particles. By doping 1% (w\\/w) noble metal
Ku-Fan Chen; Shaolin Li; Wei-xian Zhang
The application of in situ permeable reactive (zero-valent iron) barrier technology for the remediation of chromate-contaminated groundwater: a field test
A small-scale field test was initiated in September 1994 to evaluate the in situ remediation of groundwater contaminated with chromate using a permeable reactive barrier composed of a mixture of zero-valent Fe, sand and aquifer sediment. The site used was an old chrome-plating facility located on a U.S. Coast Guard air base near Elizabeth City, North Carolina. Dissolved chromate concentrations
Robert W Puls; Cynthia J Paul; Robert M Powell
Formation of ferrihydrite and associated iron corrosion products in permeable reactive barriers of zero-valent iron
NASA Technical Reports Server (NTRS)
Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation.
Furukawa, Yoko; Kim, Jin-Wook; Watkins, Janet; Wilkin, Richard T.
Design of Zero-Valent Iron Fracture Reactive Barriers for Remediating a TCE Plume in a Chalk Aquifer
A novel concept, the Fe0 fracture reactive barrier (Fe0 FRB), is proposed to clean up chlorinated solvent pollution of groundwater in a chalk aquifer. A Fe0 FRB is an extended reactive zone where the fractures are partly filled with iron. It can be created by injecting a viscous, biodegradable gel suspended with iron particles into selected fractures via boreholes. To evaluate the feasibility of Fe0 FRB as a remediation strategy, we conducted numerical modelling simulations to assess the treatment performance of a Fe0 FRB in a hypothetical chalk aquifer. The assessment was carried out using a numerical model for flow and solute transport in a discretely-fractured porous medium coupled with an analytical expression representing degradation by iron. The hypothetical chalk aquifer was represented by a 3-D discrete fracture network model which was developed using data from a number of chalk sites. TCE reactive transport in the Fe0 FRB and mass exchange of solute between fractures and the porous matrix were fully accounted for in the model. The model revealed that the success of the remediation technology lies in how to create a highly reactive Fe0 FRB without plugging fractures and reducing flow through it. A parametric study of various design parameters for the Fe0 FRB suggested that a high treatment efficiency was likely to be achieved, by employing highly reactive nanoscale iron or by using a high proportion of microscale iron fill and fracture enlargement. The model study also provided some preliminary conclusions on the optimal design of a Fe0 FRB. A preliminary analysis of the longevity of a Fe0 FRB, which contains a small amount of highly reactive nanoscale iron, showed that its lifetime is between 5 and 50 years dependant on the TCE mass flux through the barrier.
Cai, Z.; Lerner, D. N.; McLaren, R. G.; Wilson, R. D.
A Comparison Between Field Applications of Nano, Micro, and Millimetric Zero-Valent Iron for the Remediation of Contaminated Aquifers
In the last 10 years, the number of field applications of zero-valent iron differing from permeable reactive barrier has grown\\u000a rapidly and at present are 112. This study analyzes and compares such field applications. By using statistical analysis, especially\\u000a ANOVA and principal component analysis, this study shows that chlorinated solvent contamination can be treated efficiently\\u000a by using zero-valent iron material singly
Silvia Comba; Antonio Di Molfetta; Rajandrea Sethi
Application of Emulsified Zero-Valent Iron to Marine Environments
Contamination of marine waters and sediments with heavy metals and dense non-aqueous phase liquids (DNAPLs) including chlorinated solvents, pesticides and PCBs pose ecological and human health risks through the contaminant's potential bioaccumulation in fish, shellfish and avian populations. The contaminants enter marine environments through improper disposal techniques and storm water run-off. Current remediation technologies for application to marine environments include costly dredging and off-site treatment of the contaminated media. Emulsified zero-valent iron (EZVI) has been proven to effectively degrade dissolved-phase and DNAPL-phase contaminants in freshwater environments on both the laboratory and field-scale level. However, the application to marine environments is only just being explored. This paper discusses the potential use of EZVI in brackish and saltwater environments, with supporting laboratory data detailed. Laboratory studies were performed in 2005 to establish the effectiveness of EZVI to degrade trichloroethylene (TCE) in saltwater. Headspace vials were setup to determine the kinetic rate of TCE degradation using EZVI in seawater. The reaction vials were analyzed by Gas Chromatographic/Flame Ionization Detection (GC/FID) for ethene production after a 48 day period using a GC/FID Purge and Trap system. Analytical results showed that EZVI was very effective at degrading TCE. The reaction by-products (ethene, acetylene and ethane) were produced at 71% of the rate in seawater as in the fresh water controls. Additionally, iron within the EZVI particles was protected from oxidation of the corrosive seawater, allowing EZVI to perform in an environment where zero-valent iron alone could not compete. Laboratory studies were also performed to establish the effectiveness of emulsified zero-valent metal (EZVM) to remove dissolved-phase cadmium and lead found in seawater. EZVM is comprised of a combination of magnesium and iron metal surrounded by the same oil/surfactant membrane used in EZVI. The removal of cadmium and lead from a seawater matrix is a unique challenge. It requires a system that is resistant to the corrosive nature of seawater while removing specific ions that are in a relatively low concentration compared to naturally occurring seawater salts. Laboratory studies conducted show greater than 99% removal of lead and 96% removal of cadmium from a seawater solution spiked at 5 mg/L that was treated with an Emulsified Zero-Valent Metal (EZVM). The cadmium and lead are removed from the solution as they transport across the emulsion membrane and plate out onto the zero-valent metal surface.
Brooks, Kathleen B.; Quinn, Jacqueline W.; Clausen, Christian A.; Geiger, Cherie L.
Applicability of Zero-Valent Iron With Lignite Additives as Geochemical In Situ Barrier for Acid Mine Water
Acid mine waters can contain high concentrations of metals like iron, aluminum, zinc, uranium and heavy metals. Research has been conducted for several years to establish the extent to which under the conditions of the former uranium mine of Königstein (Saxony, Germany) reduction of pollutant concentrations can be positively influenced and accelerated by storage of reactive materials in open mine
Christoph Klinger; Ulf Jenk; Jochen Schreyer
Zero valent iron remediation of a mixed brominated ethene contaminated groundwater
The suitability of a granulated zero valent iron (ZVI) permeable reactive barrier (PRB) remediation strategy was investigated for tribromoethene (TriBE), cis-1,2-dibromoethene (c-DBE), trans-1,2-dibromoethene (t-DBE) and vinyl bromide (VB), via batch and large-scale column experiments that were subsequently analysed by reactive transport modelling.The brominated ethenes in both batch and large-scale column experiments showed rapid (compared to controls and natural attenuation) degradation
Elizabeth L. Cohen; Bradley M. Patterson; Allan J. McKinley; Henning Prommer
Kinetics of zero valent iron nanoparticle oxidation in oxygenated water.
Zero valent iron (ZVI) nanoparticles are versatile in their ability to remove a wide variety of water contaminants, and ZVI-based bimetallic nanoparticles show increased reactivity above that of ZVI alone. ZVI nanoparticles degrade contaminants through the reactive species (e.g., OH*, H(2(g)), H(2)O(2)) that are produced during iron oxidation. Measurement and modeling of aqueous ZVI nanoparticle oxidation kinetics are therefore necessary to optimize nanoparticle design. Stabilized ZVI and iron-nickel nanoparticles of approximately 150 nm in diameter were synthesized through solution chemistry, and nanoparticle oxidation kinetics were determined via measured mass change using a quartz crystal microbalance (QCM). Under flowing aerated water, ZVI nanoparticles had an initial exponential growth behavior indicating surface-dominated oxidation controlled by migration of species (H(2)O and O(2)) to the surface. A region of logarithmic growth followed the exponential growth which, based on the Mott-Cabrera model of thin oxide film growth, suggests a reaction dominated by movement of species (e.g., iron cations and oxygen anions) through the oxide layer. The presence of ethanol or a nickel shell on the ZVI nanoparticles delayed the onset of iron oxidation and reduced the extent of oxidation. In oxygenated water, ZVI nanoparticles oxidized primarily to the iron oxide-hydroxide lepidocrocite. PMID:23130994
Greenlee, Lauren F; Torrey, Jessica D; Amaro, Robert L; Shaw, Justin M
[Removal of Hg in wastewater by zero-valent iron].
Kinetic characteristics of mercury ion (Hg2+) removal in wastewater by zero-valent iron (ZVI) and the influence factors were studied, and the reaction mechanism of ZVI and Hg2+ was preliminarily discussed. The removal rate of Hg2+ in wastewater reached 94.5% under the optimal removal conditions, i. e. the initial concentration of Hg2+ was 0.10 mg x L(-1), the initial pH was 5, the ZVI dosage was 0.050 g, and the temperature was 25 degrees C. There was a rapid removal process for Hg2+ in wastewater by ZVI, which could be described by the pseudo first-order reaction kinetic equation, and the rate constant was 0.010 min(-1). The removal mechanism of Hg2+ may mainly be attributed to the oxidation-reduction of ZVI, and the adsorption and flocculation precipitation of iron oxides and hydroxides. However, the passivation of FeOOH and Fe2O3-Fe3O4 on ZVI surface may be the main reason for the decrease in the removal rate of Hg2+. Humic acid (HA) in wastewater could not only form Fe-HA complex with the Fe2+ and Fe3+ produced by ZVI reduction, which increased the ratio of soluble iron and relieved ZVI passivation, but also stabilize fine iron oxide and iron hydroxide colloid, and thus enhance the adsorption of Hg2+ in wastewater. PMID:24455938
Zhou, Xin; Zhang, Jin-Zhong; Qiu, Xin-Kai; Wang, Ding-Yong
Zero Valent Iron: Impact of Anions Present during Synthesis on Subsequent Nanoparticle Reactivity
Zero-valent iron particles are an effective remediation technology for groundwater contaminated with halogenated organic compounds. In particular, nano-scale zero-valent iron is a promising material for remediation due to its high specific surface area, which results in faster rate constants and more effective use of the iron. An aspect of iron nanoparticle reactivity that has not been explored is the impact
Kirsten Moore; Brady Forsberg; Donald R. Baer; William A. Arnold; R. Lee Penn
Electrokinetics Enhanced Delivery of Nano-scale Zero Valent Iron
Nano-scale zero valent iron (NZVI) has shown promising results for remediation of a wide range of chlorinated hydrocarbons in the subsurface. Although rapid aggregation and subsequent sedimentation limit bare NZVI migration in subsurface systems, surface modifications have improved the colloidal stability of NZVI, enhancing NZVI migration through porous media in lab-scale experiments. However, delivery of NZVI through low permeability soil is still an unresolved challenge. Electrokinetics (EK) has been used extensively in low permeability porous media for the remediation of a variety of hazardous wastes and in particular heavy metals. Since NZVI has a net negative surface charge electrokinetics has been proposed to enhance NZVI transport in the subsurface. However, increased dissolved oxygen and lower pH, due to electrolysis of water at the anode, oxidizes Fe0 particles to Fe2+/Fe3+ and thus affects the remediation potential. This study focuses on minimization of NZVI oxidation and quantification of NZVI migration enhancement due to the EK application. Application of 50 and 100 mA currents delivered 6.0 and 4.8 times more NZVI through coarse sand, respectively, when compared to no EK application. This ratio increased to 21 and 31 at 50 and 100 mA currents when finer sand was used. In addition, a numerical model based on traditional colloidal filtration theory (CFT) fit the experimental results well.
Chowdhury, A. I.; O'Carroll, D. M.; Xu, Y.; Sleep, B. E.
Electrophoresis enhanced transport of nano-scale zero valent iron
Electrokinetics (EK) has been used extensively to remove heavy metals from low permeability porous media. Electrokinetics (EK) or more specifically electrophoresis (EP) has also been proposed to enhance transport of nanoscale zero valent iron (NZVI) in fine grained porous media in the subsurface. However, increased dissolved oxygen and lower pH, due to electrolysis of water at the anode oxidizes NZVI particles and thus affects the remediation potential of EP with NZVI. This study focuses on minimization of NZVI oxidation and quantification of NZVI migration enhancement through the application of EP. Application of 50 and 100 mA currents under constant current conditions with an oxygen scavenger enhanced NZVI transport from the cathode to the anode. The enhancement in transport compared to diffusion was proportional to the applied current. Predictions of a numerical model, based on traditional colloidal filtration theory (CFT), were consistent with experimental results. In developing the model, the traditional CFT based mass balance equation was modified for the case of no advection. This study suggests that EP has the potential to deliver NZVI in low permeability porous media and that the numerical simulator can be used to predict NZVI mobility with EP.
Chowdhury, Ahmed I. A.; O'Carroll, Denis M.; Xu, Yanqing; Sleep, Brent E.
Abiotic Remediation of Nitro-Aromatic Groundwater Contaminants by Zero- Valent Iron.
National Technical Information Service (NTIS)
Recent laboratory and field experiments have shown that some halogenated hydrocarbons undergo rapid reductive dehalogenation with zero-valent iron and the application of this process is being developed for in-situ remediation of contaminated groundwater. ...
A. Agrawal P. G. Tratnyek
Removal of arsenic from water by supported nano zero-valent iron on activated carbon
Nano-sized zero-valent iron is an effective adsorbent for arsenic removal from drinking water. However, its application may be limited in public water system and small scale water treatment system due to its tiny particle size. In the present work, nanoscale zero-valent iron was supported onto activated carbon (NZVI\\/AC) by impregnating carbon with ferrous sulfate followed by chemical reduction with NaBH4.
Huijie Zhu; Yongfeng Jia; Xing Wu; He Wang
Removal of methyl orange from aqueous solution using bentonite-supported nanoscale zero-valent iron
Zero-valent iron (ZVI) nanoparticles tend to agglomerate, resulting in a significant loss in reactivity. To address this issue, synthesized bentonite-supported nanoscale zero-valent iron (B-nZVI) was used to remove azo dye methyl orange (MO) in aqueous solution. Batch experiments show that various parameters, such as pH, initial concentration of MO, dosage, and temperature, were affected by the removal of MO. Scanning
Zheng-xian Chen; Xiao-ying Jin; Zuliang Chen; Mallavarapu Megharaj; Ravendra Naidu
Remediation of TCE-contaminated groundwater using zero valent iron and direct current: experimental results and electron competition model
The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation\\u000a of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the\\u000a mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted\\u000a to evaluate the effect of different arrangements of
Ji-Won Moon; Hi-Soo Moon; Heonki Kim; Yul Roh
Reduced aggregation and sedimentation of zero-valent iron nanoparticles in the presence of guar gum
Injection of nanoscale zero-valent iron (NZVI) is potentially a promising technology for remediation of contaminated groundwaters. However, the efficiency of this process is significantly hindered by the rapid aggregation of the iron nanoparticles. The aim of this study was to enhance the colloidal stability of the nanoparticles through the addition of the "green" polymer guar gum. We evaluated the properties
Alberto Tiraferri; Kai Loon Chen; Rajandrea Sethi; Menachem Elimelech
Partial oxidation (?aging?) and surface modification decrease the toxicity of nano-sized zero valent iron
Zero-valent iron (nZVI) is a redox-active nanomaterial used for in situ remediation of contaminated groundwater. To assess the effect of ?aging? and surface modification on its potential neurotoxicity, cultured rodent microglia and neurons were exposed to fresh nZVI, ?aged? (>11...
The reduction of azo dyes by zero-valent iron metal (Fe0) at pH 7.0 in 10 mM HEPES buffer was studied in aqueous, anaerobic batch systems. Orange II was reduced by cleavage of the azo linkage, as evidenced by the production of sulfanilic acid (a substituted ani...
The objectives of this study were to conduct batch and column studies to (i) assess the effectiveness of zero-valent iron for arsenic remediation in groundwater, (ii) determine removal mechanisms of arsenic, and (iii) evaluate implications of these processes with regard to the st...
The project consisted of a preliminary laboratory study; an outdoor bench scale study and an in situ field Pilot Study to which the zero valent iron and pyrite system (ZVI system) was applied. Several beakers were filled with contaminated soil, the ZVI system and a solvent then...
Entrapment of nanoscale zero-valent iron in chitosan beads for hexavalent chromium removal from wastewater
Nanoscale zero-valent iron (NZVI) was successfully entrapped in chitosan (CS) beads for reduction of Cr (VI) from wastewater. The removal mechanism may include both physical adsorption of Cr (VI) on the surface or inside of CS-NZVI beads and subsequent reduction of Cr (VI) to Cr (III). The free amino groups and hydroxyl groups on CS may contribute little to hinder
Tingyi Liu; Lin Zhao; Desheng Sun; Xin Tan
Zero-valent iron on Mars: An alternative energy source for methanogens
Zero-valent iron, montmorillonite-like smectites, and CO 2 gas are known to exist on Mars, and work was performed to investigate the ability of methanogens to subsist on these materials. After 71 days of incubation at 55 °C, mean methane concentration as percent of headspace volume was 19.80 ± 1.76% (mean ± SE) for replicates containing elemental iron and 0.50 ± 0.15% for those lacking elemental iron.
Chastain, Brendon K.; Kral, Timothy A.
Ligand-Enhanced Reactive Oxidant Generation by Nanoparticulate Zero-Valent Iron and Oxygen
PubMed Central
The reaction of zero-valent iron or ferrous iron with oxygen produces reactive oxidants capable of oxidizing organic compounds. However, the oxidant yield in the absence of ligands is too low for practical applications. The addition of oxalate, nitrilotriacetic acid (NTA), or ethylenediaminetetraacetic acid (EDTA) to oxygen-containing solutions of nanoparticulate zero-valent iron (nZVI) significantly increases oxidant yield, with yields approaching their theoretical maxima near neutral pH. These ligands improve oxidant production by limiting iron precipitation and by accelerating the rates of key reactions, including ferrous iron oxidation by oxygen and hydrogen peroxide. Product yields indicate that the oxic nZVI system produces hydroxyl radical (OH·) over the entire pH range in the presence of oxalate and NTA. In the presence of EDTA, probe compound oxidation is attributed to OH· under acidic conditions and a mixture of OH· and ferryl ion (Fe[IV]) at circumneutral pH.
Keenan, Christina R.; Sedlak, David L.
Enhanced dechlorination of chlorobenzene by microwave-induced zero-valent iron: particle effects and activation energy
Organic compounds such as chlorobenzene cannot be effectively decomposed with currently available biological and chemical\\u000a treatment methods. Preliminary studies show that nano-scale zero-valent iron particles irradiated by microwave is effective\\u000a in decomposing chemically refractive organic compounds such as chlorobenzene. In this study, microwave is applied to enhance\\u000a chlorobenzene removal using micron-scale iron particles and nano-scale zero-valent iron particles suspended in
Chien-Li Lee; Hsien-Yi Lee; Kuo-Hung Tseng; P. K. Andy Hong; Chih-Ju G. Jou
Reactive barriers that couple subsurface fluid flow with a passive chemical treatment zone are emerging, cost effective approaches for in-situ remediation of contaminated groundwater. Factors such as the build-up of surface precipitates, bio-fouling, and changes in subsurface tr...
Electrochemically fabricated zero-valent iron, iron-nickel, and iron-palladium nanowires for environmental remediation applications
Monodisperse crystalline zero-valent iron, iron-nickel, iron-palladium nanowires were synthesised using template-directed electrodeposition methods. Prior to nanowire fabrication, alumina nanotemplates with controlled pore structure (e.g. pore diameter and porosity) were fabricated by anodising high purity aluminium foil in sulphuric acid. After fabrication of alumina nanotemplates, iron, iron-nickel and iron- palladium nanowires were electrodeposited within the pore structure. The dimensions of nanowires
B.-Y. Yoo; S. C. Hernandez; B. Koo; Y. Rheem; N. V. Myung
Degradation of decabromodiphenyl ether by nano zero-valent iron immobilized in mesoporous silica microspheres
The agglomeration of nanoparticles reduces the surface area and reactivity of nano zero-valent iron (NZVI). In this paper, highly dispersive and reactive NZVI immobilized in mesoporous silica microspheres covered with FeOOH was synthesized to form reactive mesoporous silica microspheres (SiO2@FeOOH@Fe). The characteristics of SiO2@FeOOH@Fe were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy simultaneous thermal analysis, X-ray photoelectron spectroscopy,
Xinhong Qiu; Zhanqiang Fang; Bin Liang; Fenglong Gu; Zhencheng Xu
Laboratory evaluation of zero-valent iron to treat water impacted by acid mine drainage
This study examines the applicability and limitations of granular zero-valent iron for the treatment of water impacted by mine wastes. Rates of acid-neutralization and of metal (Cu, Cd, Ni, Zn, Hg, Al, and Mn) and metalloid (As) uptake were determined in batch systems using simulated mine drainage (initial pH 2.3–4.5; total dissolved solids 14000–16000 mgl?1). Metal removal from solution and
Richard T. Wilkin; Mary S. McNeil
Enhanced degradation of carbon tetrachloride by surfactant-modified zero-valent iron
Sorption of carbon tetrachloride (CT) by zero-valent iron (ZVI) is the rate-limiting step in the degradation of CT, so the\\u000a sorption capacity of ZVI is of great importance. This experiment was aimed at enhancing the sorption of CT by ZVI and the\\u000a degradation rate of CT by modification of surfactants. This study showed that ZVI modified by cationic surfactants has
Ya-feng Meng; Bao-hong Guan; Zhong-biao Wu; Da-hui Wang
Effective removal of antibiotic metronidazole from water by nanoscale zero-valent iron particles
The removal of antibiotic metronidazole (MNZ) in aqueous solution by nanoscale zero-valent iron (NZVI) particles was investigated. The experimental results showed that MNZ was completely removed by NZVI, MNZ solution at 80mg L?1 was rapidly removed by NZVI within 5min, at initial solution pH 5.60, NZVI dose of 0.1g L?1. Influencing factors such as NZVI dosage, initial MNZ concentration and
Zhanqiang Fang; Jinhong Chen; Xinhong Qiu; Xiuqi Qiu; Wen Cheng; Licai Zhu
Arsenate removal from water by zero-valent iron\\/activated carbon galvanic couples
Galvanic couples composed of zero-valent iron and activated carbon (Fe0\\/AC) were investigated for As(V) removal from water. The effects of Fe0 to AC mass ratio (FCR), solution pH, ionic strength and co-existing anions (phosphate, carbonate, silicate, nitrate, chloride and sulfate) and humic acid (HA) on As(V) removal were evaluated. The results showed that the optimum mass ratio was 1:1, and
Xiaomin Dou; Rui Li; Bei Zhao; Wenyan Liang
Chromate transport through columns packed with surfactant-modified zeolite\\/zero valent iron pellets
Chromate transport through columns packed with zeolite\\/zero valent iron (Z\\/ZVI) pellets, either untreated or treated with the cationic surfactant hexadecyltrimethylammonium (HDTMA), was studied at different flow rates. In the presence of sorbed HDTMA, the chromate retardation factor increased by a factor of five and the pseudo first-order rate constant for chromate reduction increased by 1.5–5 times. The increase in rate
Zhaohui Li; H. Kirk Jones; Pengfei Zhang; Robert S. Bowman
Removal of Chromium (VI) from wastewater using bentonite-supported nanoscale zero-valent iron
Bentonite-supported nanoscale zero-valent iron (B-nZVI) was synthesized using liquid-phase reduction. The orthogonal method was used to evaluate the factors impacting Cr(VI) removal and this showed that the initial concentration of Cr(VI), pH, temperature, and B-nZVI loading were all importance factors. Characterization with scanning electron microscopy (SEM) validated the hypothesis that the presence of bentonite led to a decrease in aggregation
Li-na Shi; Xin Zhang; Zu-liang Chen
Reduction of hexavalent chromium by carboxymethyl cellulose-stabilized zero-valent iron nanoparticles
The reduction of hexavalent chromium or Cr(VI) by zero-valent iron (Fe0) nanoparticles has received increasing attention in recent years. However, Fe0 nanoparticles prepared using conventional methods suffered several drawbacks due to their high reactivity towards surrounding media, which led to the formation of much larger flocs and significant loss in reactivity. To overcome these problems, we synthesized Fe0 nanoparticles by
Qian Wang; Huijing Qian; Yueping Yang; Zhen Zhang; Cissoko Naman; Xinhua Xu
Microbial reduction of nitrate in the presence of nanoscale zero-valent iron
Microbial reduction of nitrate in the presence of nanoscale zero-valent iron (NZVI) was evaluated to assess the feasibility of employing NZVI in the biological nitrate treatment. Nitrate was completely reduced within 3d in a nanoscale Fe(0)-cell reactor, while only 50% of the nitrate was abiotically reduced over 7d at 25°C. The removal rate of nitrate in the integrated NZVI-cell system
Kyung-Hee Shin; Daniel K. Cha
Mechanisms of NOx Removal from Flue Gas by Zero Valent Iron
Chemical reaction between nitric oxide (NO) and zero valent iron (ZVI) was studied in a packed-bed column process with high temperatures based on ZVI strong reducing abilities. For six controlled temperatures of 523–773 K and 400 ppm of NO (typical flue gas temperature and concentration), under short empty bed contact time ([EBCT] 0.0226–0.0679 sec), NO was completely removed for temperature
Shiao-Shing Chen; Chih-Yu Cheng; Jung-Chun Chang; Chih-Hui Tang
Oxidation of polyvinyl alcohol by persulfate activated with heat, Fe 2+, and zero-valent iron
The oxidation of polyvinyl alcohol (PVA) by persulfate (S2O82?) activated with heat, Fe2+, and zero-valent iron (Fe(0)) was investigated via batch experiments. It was hypothesized that elevated temperature and the addition of Fe2+ or Fe(0) into a persulfate-water system could enhance the oxidation of PVA by activated persulfate. Increasing the temperature from 20 to 60°C or 80°C accelerated the oxidation
Seok-Young Oh; Hyeong-Woo Kim; Jun-Mo Park; Hung-Suck Park; Chohee Yoon
Reductive degradation of carbaryl in water by Zero-valent iron
Reduction of carbaryl solution by zero-valent iron powder (ZVIP) was studied in a rotator batch system (70 rpm) in order to evaluate the utility of this reaction in remediation of carbamate contaminated water. Degradation with different amount of ZVIP: 0.01, 0.02, 0.03, 0.04 g\\/ml at pH 6.6 and at ambient temperature was investigated. The results show that the process exhibits
A Ghauch; C Gallet; A Charef; J Rima; M Martin-Bouyer
Effect of reduction temperature on the preparation of zero-valent iron aerogels for trichloroethylene dechlorination
Zero-valent iron (ZVI) aerogels have been synthesized by sol-gel method and supercritical CO2 drying, followed by H2 reduction in the temperature range of 350–500 °C. When applied to trichloroethylene (TCE) dechlorination, the ZVI aerogel\\u000a reduced at 370 °C showed the highest performance in the conditions employed in this study. Thus, the effect of reduction temperature\\u000a in preparing ZVI aerogels has
Jihye Ryu; Dong Jin Suh; Young-Kwon Park; Young-Woong Suh
Effective removal of AB24 dye by nano\\/micro-size zero-valent iron
The removal of AB24 dye in aqueous solution by nano\\/micro-size zero-valent iron (ZVI) was investigated. Results indicate that the degradation efficiency increases with increasing ZVI concentration and temperature but decreases with particle size of ZVI. Analysis of the results indicates that the reaction follows pseudo-first order kinetics. The rate constant increases linearly with ZVI concentration and decreases with particle size.
Yao-Tung Lin; Chih-Huang Weng; Fang-Ying Chen
Large groundwater plumes contaminated with toxic metal ions, including radionuclides, exist at several DOE facilities. Previous research indicated that both zero valent iron and sulfate reducing bacteria can yield significant decreases in concentrations of redox sensitive metals ...
Humic acid and metal ions accelerating the dechlorination of 4-chlorobiphenyl by nanoscale zero-valent iron
Transformation of poly chlorinated biphenyls (PCBs) by zero-valent iron represents one of the latest innovative technologies for environmental remediation. The dechlorination of 4-chlorobiphenyl (4-C1BP) by nanoscale zero-valent iron (NZVI) in the presence of humic acid or metal ions was investigated. The results showed that the dechlorination of 4-C1BP by NZVI increased with decreased solution pH. When the initial pH value
Yu Wang; Dongmei Zhou; Yujun Wang; Xiangdong Zhu; Shengyang Jin
Zero valent iron as an electron-donor for methanogenesis and sulfate reduction in anaerobic sludge.
Zero valent iron (ZVI) is a reactive media commonly utilized in permeable reactive barriers (PRBs). Sulfate reducing bacteria are being considered for the immobilization of heavy metals in PRBs. The purpose of this study was to evaluate the potential of ZVI as an electron donor for sulfate reduction in natural mixed anaerobic cultures. The ability of methanogens to utilize ZVI as an electron-donor was also explored since these microorganisms often compete with sulfate reducers for common substrates. Four grades of ZVI of different particle sizes (1.120, 0.149, 0.044, and 0.010 mm diameter) were compared as electron donor in batch bioassays inoculated with anaerobic bioreactor sludge. Methanogenesis was evaluated in mineral media lacking sulfate. Sulfate reduction was evaluated in mineral media containing sulfate and the specific methanogenic inhibitor, 2-bromoethane sulfonate. ZVI contributed to significant increases in methane production and sulfate reduction-compared to endogenous substrate controls. The rates of methane formation or sulfate reduction were positively correlated with the surface area of ZVI. The highest rates of 0.310 mmol CH4 formed/mol Fe0.day and 0.804 mmol SO4(2-) reduced/mol Fe0.day were obtained with the finest grade of ZVI (0.01 mm). The results demonstrate that ZVI is readily utilized as a slow-release electron donor for methanogenesis and sulfate reduction in anaerobic sludge; and therefore, has a promising potential in bioremediation applications. PMID:16136594
Karri, Srilakshmi; Sierra-Alvarez, Reyes; Field, Jim A
Zero valent iron remediation of a mixed brominated ethene contaminated groundwater.
The suitability of a granulated zero valent iron (ZVI) permeable reactive barrier (PRB) remediation strategy was investigated for tribromoethene (TriBE), cis-1,2-dibromoethene (c-DBE), trans-1,2-dibromoethene (t-DBE) and vinyl bromide (VB), via batch and large-scale column experiments that were subsequently analysed by reactive transport modelling. The brominated ethenes in both batch and large-scale column experiments showed rapid (compared to controls and natural attenuation) degradation in the presence of ZVI. In the large-scale column experiment, degradation half-lives were 0.35 days for TriBE, 0.50 days for c-DBE, 0.31 days for t-DBE and 0.40 days for VB, under site groundwater flow conditions, resulting in removal of brominated ethenes within the first 0.2 m of a 1.0 m thick ZVI layer, indicating that a PRB groundwater remediation strategy using ZVI could be used successfully. In the model simulations of the ZVI induced brominated ethene degradation, assuming a dominant reductive beta-elimination pathway via bromoacetylene and acetylene production, simulated organic compound concentrations corresponded well with both batch and large-scale column experimental data. Changes of inorganic reactants were also well captured by the simulations. The similar ZVI induced degradation pathway of TriBE and TCE suggests that outcomes from research on ZVI induced TCE remediation could also be applied to TriBE remediation. PMID:18990465
Cohen, Elizabeth L; Patterson, Bradley M; McKinley, Allan J; Prommer, Henning
Reduction of nitrate to ammonia by zero-valent iron
The reduction of nitrate to ammonia occurs with nearly complete conversion at room temperature and pressure under aerobic conditions in the presence of iron and either HCl or a pH buffer. A 50.0 mL solution of 12.5 millimolar nitrate is rapidly reduced to ammonia when exposed to 4.00 g of 325 mesh iron at pH 5.0, 0.05 M sodium acetate\\/acetic
I. Francis Cheng; Rosy Muftikian; Quintus Fernando; Nic Korte
The U.S. EPA Office of Research and Development?s National Risk Management Research Laboratory (NRMRL) and Region 8 have begun evaluating performance of a pilot-scale permeable reactive barrier (PRB) to treat arsenic-contaminated ground water at the ASARCO Superfund near Helena, ...
2,4,6Trinitrotoluene reduction kinetics in aqueous solution using nanoscale zero-valent iron
The reduction of 2,4,6-trinitrotoluene (TNT) in aqueous solution using nanoscale zero-valent iron (nZVI) was investigated. The results showed that the pseudo-first order reaction law fit the reduction of TNT. The measured apparent rate constant (Kobs) of TNT on nZVI (0.761h?1) was 7.8-fold than on conventional iron powders (0.0979h?1) at 303K. The apparent activation energy (Ea) of nZVI reducing TNT was
Xin Zhang; Yu-man Lin; Zu-liang Chen
Rapid removal of flutriafol in water by zero-valent iron powder
A study of the effect of zero-valent iron (ZVI) powder is carried out for the first time on the degradation of flutriafol ((RS)-2,4?-difluoro-?-(1H-1,2,4-triazol-1-ylmethyl)-benzhydryl alcohol, C16H13F2N3O), a bifluorinated soil and water persistent triazole pesticide using a laboratory scale device consisting of a 20ml pyrex serum vials fixed to a Vortex agitator. Different amounts of ZVI powder (10–50gl?1) at pH 6.6 and
Antoine Ghauch
Kinetics of zero-valent iron reductive transformation of the anthraquinone dye Reactive Blue 4
The effect of operational conditions and initial dye concentration on the reductive transformation (decolorization) of the textile dye Reactive Blue 4 (RB4) using zero-valent iron (ZVI) filings was evaluated in batch assays. The decolorization rate increased with decreasing pH and increasing temperature, mixing intensity, and addition of salt (100gL?1 NaCl) and base (3gL?1 Na2CO3 and 1gL?1 NaOH), conditions typical of
William J. Epolito; Hanbae Yang; Lawrence A. Bottomley; Spyros G. Pavlostathis
Methods of preparation and modification of advanced zero-valent iron nanoparticles, their properties and application in water treatment technologies
Zero-valent iron nanoparticles are commonly used in modern water treatment technologies. Compared to conventionally-used macroscopic iron or iron microparticles, the using of nanoparticles has the advantages given mainly by their generally large specific surface area (it drives their high reactivity and/or sorption capacity), small dimensions (it allows their migration e.g. in ground water), and particular physical and chemical properties. Following the applications of zero-valent iron particles in various pilot tests, there arose several critical suggestions for improvements of used nanomaterials and for development of new generation of reactive nanomaterials. In the presentation, the methods of zero-valent iron nanoparticles synthesis will be summarized with a special attention paid to the thermally-induced solid-state reaction allowing preparation of zero-valent iron nanoparticles in an industrial scale. Moreover, the method of thermal reduction of iron-oxide precursors enables to finely tune the critical parameters (mainly particle size and morphology, specific surface area, surface chemistry of nanoparticles etc.) of resulting zero-valet iron nanoparticles. The most important trends of advanced nanoparticles development will be discussed: (i) surface modification of nanomaterilas, (ii) development of nanocomposites and (iii) development of materials for combined reductive-sorption technologies. Laboratory testing of zero-valent iron nanoparticles reactivity and migration will be presented and compared with the field observations: the advanced zero-valent iron nanoparticles were used for groundwater treatment at the locality contaminated by chlorinated hydrocarbons (VC, DCE, TCE and PCE) and reacted nanoparticles were extracted from the sediments for their fate assessment. The authors gratefully acknowledge the support by the Technology Agency of the Czech Republic "Competence Centres" (project No. TE01020218) and the EU FP7 (project NANOREM).
Filip, Jan; Kašlík, Josef; Med?ík, Ivo; Petala, Eleni; Zbo?il, Radek; Slunský, Jan; ?erník, Miroslav; Stav?lová, Monika
Remediation of chromate-contaminated groundwater using zero-valent iron: Field test at USCG Support Center, Elizabeth City, North Carolina
A field test was conducted near an old hard-chrome plating facility on the USCG Support Center near Elizabeth City, North Carolina to evaluate the in situ remediation of ground water contaminated by hexavalent chromium using a passive permeable reactive barrier composed of a zero-valent iron-sand-aquifer material mixture. The remedial effectiveness of this innovative in situ technology was in situ technology
R. W. Puls; C. J. Paul; R. M. Powell
Reduced aggregation and sedimentation of zero-valent iron nanoparticles in the presence of guar gum.
Injection of nanoscale zero-valent iron (NZVI) is potentially a promising technology for remediation of contaminated groundwaters. However, the efficiency of this process is significantly hindered by the rapid aggregation of the iron nanoparticles. The aim of this study was to enhance the colloidal stability of the nanoparticles through the addition of the "green" polymer guar gum. We evaluated the properties of guar gum and its influence on the surface properties, particle size, aggregation, and sedimentation of iron nanoparticles. Commercial iron nanoparticles were dispersed in guar gum solutions, and their aggregation and sedimentation behaviors were compared to those of bare iron nanoparticles and commercial nanoparticles modified with a biodegradable polymer (polyaspartate). High performance size exclusion chromatography, charge titration, and viscosity assessment showed that guar gum is a high molecular weight polymer which is nearly neutrally charged, rendering it suitable for steric stabilization of the iron nanoparticles. Electrophoretic mobility measurements demonstrated the ability of guar gum to adsorb on the nanoparticles, forming a slightly negatively charged layer. Dynamic light scattering experiments were conducted to estimate the particle size of the different nanoparticle suspensions and to determine the aggregation behavior at different ionic strengths. Guar gum effectively reduced the hydrodynamic radius of the bare nanoparticles from 500 nm to less than 200 nm and prevented aggregation of the nanoparticles even at very high salt concentrations (0.5 M NaCl and 3 mM CaCl(2)). Sedimentation profiles of the different nanoparticle suspensions confirmed the improved stability of the iron nanoparticles in the presence of guar gum. The results strongly suggest that guar gum can be used to effectively deliver stabilized zero-valent iron nanoparticles for remediation of contaminated groundwater aquifers. PMID:18508073
Tiraferri, Alberto; Chen, Kai Loon; Sethi, Rajandrea; Elimelech, Menachem
Applicability of nano zero valent iron (nZVI) in sono – Fenton process
Fenton process is one of the advanced oxidation processes (AOPs) used to remove complex organic pollutants in wastewater. In this study, instead of iron sulfate (FeSO4), nano zero valent iron (nZVI) was used as a major source of ferrous iron (Fe2+). In order to enhance the process, ultrasound was utilized in this study. Results show that, with the aid of ultrasound, nZVI produced more Fe2+ compared to FeSO4 at pH 2. Furthermore, combination of higher intensity and longer sonication time in Fenton process acceleratde the chemical oxygen demand (COD) removal from palm oil mill effluent (POME). Through the process, 80% of COD content was removed within 2 hours instead of 24 hours of silent degradation.
Taha, M. R.; Ibrahim, A. H.; Amat, R. C.; Azhari, A. W.
Arsenic removal from geothermal waters with zero-valent iron—Effect of temperature, phosphate and nitrate
Field column studies and laboratory batch experiments were conducted in order to assess the performance of zero-valent iron in removing arsenic from geothermal waters in agricultural regions where phosphates and nitrates were present. A field pilot study demonstrated that iron filings could remove arsenic, phosphate and nitrate from water. In addition, batch studies were performed to evaluate the effect of
Konstantina Tyrovola; Nikolaos P. Nikolaidis; Nikolaos Veranis; Nikolaos Kallithrakas-Kontos; Pavlos E. Koulouridakis
Rapid and complete destruction of perchlorate in water and ion-exchange brine using stabilized zero-valent iron nanoparticles
Perchlorate has emerged as a widespread contaminant in groundwater and surface water. Because of the unique chemistry of perchlorate, it has been challenging to destroy perchlorate. This study tested the feasibility of using a new class of stabilized zero-valent iron (ZVI) nanoparticles for complete transformation of perchlorate in water or ion-exchange brine. Batch kinetic tests showed that at an iron
Zhong Xiong; Dongye Zhao; Gang Pan
Sulfur-Modified Zero-Valent Iron for Remediation Applications at DOE Sites - 13600
Many DOE remediation sites have chemicals of concern that are compounds in higher oxidation states, which make them both more mobile and more toxic. The chemical reduction of these compounds both prevents the migration of these chemicals and in some cases reduces the toxicity. It has also been shown that zero-valent iron is a very effective substance to use in reducing oxygenated compounds in various treatment processes. These have included the treatment of halogenated hydrocarbons in the form volatile organic compounds used as solvents and pesticides. Zero-valent iron has also been used to reduce various oxidized metals such as chromium, arsenic, and mercury in order to immobilize them, decrease their toxicity, and prevent further transport. In addition, it has been used to immobilize or break down other non-metallic species such as selenium compounds and nitrates. Of particular interest at several DOE remediation sites is the fact that zero-valent iron is very effective in immobilizing several radioactive metals which are mobile in their oxidized states. These include both technetium and uranium. The main difficulty in using zero-valent iron has been its tendency to become inactive after relatively short periods of time. While it is advantageous to have the zero-valent iron particles as porous as possible in order to provide maximum surface area for reactions to take place, these pores can become clogged when the iron is oxidized. This is due to the fact that ferric oxide has a greater volume for a given mass than metallic iron. When the surfaces of the iron particles oxidize to ferric oxide, the pores become narrower and will eventually shut. In order to minimize the degradation of the chemical activity of the iron due to this process, a modification of zero-valent iron has been developed which prevents or slows this process, which decreases its effectiveness. It is called sulfur-modified iron, and it has been produced in high purity for applications in municipal water treatment applications. Sulfur-modified iron has been found to not only be an extremely economical treatment technology for municipal water supplies, where very large quantities of water must be treated economically, but it has also been demonstrated to immobilize technetium. It has the added benefit of eliminating several other harmful chemicals in water supplies. These include arsenic and selenium. In one large-scale evaluation study an integrated system implemented chemical reduction of nitrate with sulfur-modified iron followed by filtration for arsenic removal. The sulfur-modified iron that was used was an iron-based granular medium that has been commercially developed for the removal of nitrate, co-contaminants including uranium, vanadium and chromium, and other compounds from water. The independent study concluded that 'It is foreseen that the greatest benefit of this technology (sulfur-modified iron) is that it does not produce a costly brine stream as do the currently accepted nitrate removal technologies of ion exchange and reverse osmosis. This investigation confirmed that nitrate reduction via sulfur-modified iron is independent of the hydraulic loading rate. Future sulfur-modified iron treatment systems can be designed without restriction of the reactor vessel dimensions. Future vessels can be adapted to existing site constraints without being limited to height-to-width ratios that would exist if nitrate reduction were to depend on hydraulic loading rate'. Sulfur-modified iron was studied by the Pacific Northwest National Laboratory (PNNL) for its effectiveness in the reduction and permanent sequestration of technetium. The testing was done using Hanford Site groundwater together with sediment. The report stated, 'Under reducing conditions, TcO{sub 4} is readily reduced to TcIV, which forms highly insoluble oxides such at TcO{sub 2}.nH{sub 2}O. However, (re)oxidation of TcIV oxides can lead to remobilization. Under sulfidogenic conditions, most TcIV will be reduced and immobilized as Tc{sub 2}S{sub 7}, which is less readily re-mobilized, ev
Fogwell, Thomas W. [Fogwell Consulting, P.O. Box 20221, Piedmont, CA 94620 (United States)] [Fogwell Consulting, P.O. Box 20221, Piedmont, CA 94620 (United States); Santina, Pete [SMI-PS, Inc., 2073 Prado Vista, Lincoln, CA 95648 (United States)] [SMI-PS, Inc., 2073 Prado Vista, Lincoln, CA 95648 (United States)
Contaminated wetlands soils from the Burnt Fly Bog Superfund site will be treated with a newly developed variety of zero-valent iron. Although zero-valent iron has been shown effective for treating chlorinated solvents, its ability to effectively treat PCBs is unproven. The tre...
Haloacetic acid removal by sequential zero-valent iron reduction and biologically active carbon degradation.
An innovative haloacetic acid (HAA) removal process was developed. The process consisted of a zero-valent iron (Fe(0)) column followed by a biologically active carbon (BAC) column that were efficient in degrading tri- and di-HAAs, and mono- and di-HAAs, respectively. The merit of the process was demonstrated by its performance in removing trichloroacetic acid (TCAA). An empty bed contact time of 10 min achieved nearly complete removal of 1.2 ?M TCAA and its subsequent products, dichloroacetic acid (DCAA) and monochloroacetic acid (MCAA). HAA removal was a result of chemical dehalogenation and biodegradation rather than physical adsorption. Preliminary kinetic analyses were conducted and the pseudo-first-order rate constants were estimated at ambient conditions for Fe(0) reduction of TCAA and biodegradation of DCAA and MCAA by BAC. This innovative process is highly promising in removing HAAs from drinking water, swimming pool water, and domestic or industrial wastewater. PMID:23079162
Tang, Shun; Wang, Xiao-mao; Yang, Hong-wei; Xie, Yuefeng F
Gas-bubbled nano zero-valent iron process for high concentration arsenate removal.
In this study, batch experiments were performed to investigate a novel process for high concentration arsenate removal in the presence of air and/or CO(2) bubbling. The pretreatment step, CO(2) bubbling at 300 mL/min for 5 min, was taken to adjust the solution pH to an acidic environment, followed by air bubbling at 300 mL/min for 10 min to increase dissolved oxygen in the solution. In the treatment period, the nano-scale zero-valent iron was applied to remove aqueous arsenate of 3000 ?g/L, while the treatment system was continuously bubbled by 300 mL/min of air. Such a process resulted in outstanding performance in arsenate removal. Furthermore, in the field groundwater application, the arsenate removal rate for the proposed process was 5 times faster than the rate measured when the system was pretreated by acidic chemical species only. PMID:21256674
Tanboonchuy, Visanu; Hsu, Jia-Chin; Grisdanurak, Nurak; Liao, Chih-Hsiang
Degradation of lindane contaminated soil using zero-valent iron nanoparticles.
Lindane, has been classified by the United States Environment Protection Agency as a potent carcinogen and teratogen. Zero-valent iron nanoparticles (nZVI) have been shown to effectively transform chlorinated hydrocarbons, organochlorine pesticides. An attempt has been made to explore the potential of nZVI for the remediation of Lindane contaminated soil. nZVI was synthesized by reducing FeCl3 with NaBH4. Lindane (10 microg/g) completely disappeared from spiked soil within 24 hours at nZVI concentration of 1.6 g/L, indicating its possible use in environmental cleanup. Reductive dehalogenation is the predominant mechanism for the removal of Lindane from spiked soil by nZVI. Dechlorination was further confirmed by the chloride ion release. PMID:21485858
Singh, Ritu; Singh, Anju; Misra, Virendra; Singh, Rana P
Field demonstration of DNAPL dehalogenation using emulsified zero-valent iron
This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nanoscale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, nonaqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (VOCs) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion.
Quinn, Jacqueline; Geiger, Cherie; Clausen, Chris; Brooks, Kathleen; Coon, Christina; O'Hara, Suzanne; Krug, Thomas; Major, David; Yoon, Woong-Sang; Gavaskar, Arun; Holdsworth, Thomas
Transport of carbon colloid supported nanoscale zero-valent iron in saturated porous media
Injection of nanoscale zero-valent iron (nZVI) has recently gained great interest as emerging technology for in-situ remediation of chlorinated organic compounds from groundwater systems. Zero-valent iron (ZVI) is able to reduce organic compounds and to render it to less harmful substances. The use of nanoscale particles instead of granular or microscale particles can increase dechlorination rates by orders of magnitude due to its high surface area. However, classical nZVI appears to be hampered in its environmental application by its limited mobility. One approach is colloid supported transport of nZVI, where the nZVI gets transported by a mobile colloid. In this study transport properties of activated carbon colloid supported nZVI (c-nZVI; d50 = 2.4 ?m) are investigated in column tests using columns of 40 cm length, which were filled with porous media. A suspension was pumped through the column under different physicochemical conditions (addition of a polyanionic stabilizer and changes in pH and ionic strength). Highest observed breakthrough was 62% of the injected concentration in glass beads with addition of stabilizer. Addition of mono- and bivalent salt, e.g. more than 0.5 mM/L CaCl2, can decrease mobility and changes in pH to values below six can inhibit mobility at all. Measurements of colloid sizes and zeta potentials show changes in the mean particle size by a factor of ten and an increase of zeta potential from - 62 mV to - 80 mV during the transport experiment. However, results suggest potential applicability of c-nZVI under field conditions.
Busch, Jan; Meißner, Tobias; Potthoff, Annegret; Oswald, Sascha E.
Nitrate Removal by Acid-Washed Sulfur Modified Iron (SMI) and Zero Valent Iron (ZVI)
Sulfur Modified Iron (SMI) and Zero Valent Iron (ZVI) have been extensively studied for its ability to reduce different contaminants, including nitrate in groundwater. Although nitrate reduction with ZVI was reported as early as 1964, research projects using the materials as an alternative for nitrate removal have emerged only recently. Therefore, further investigations are still need to maximize the efficiency of nitrate removal using SMI and ZVI. In current work, we determined the mixing ratio, effects of acidification of SMI and ZVI, and need of pH controlling to obtain the highest nitrate removal rate, increasing amount of less expensive compound, ZVI, than SMI. In the results, nitrate removal by only ZVI or SMI was 32.53% and 0.69%, respectively. Although SMI:ZVI(1:4; g/g) was the best mixing ratio for the highest nitrate removal rate, it did not improve the removal rate compared to it when we used only ZVI or SMI. However, the acidified SMI and ZVI (1:4; g/g) with 0.5 N-HCl for 8 hr increased nitrate removal from 32% to 87%. Through the test, we found that using SMI and ZVI (1:4; g/g) acidified is an appropriate method to remediate nitrate-contaminated groundwater with the highest efficiency, increasing ratio of cheaper compound ZVI. Although SMI and ZVI showed the higher nitrate removal rate in low pH in other works, in case of using acidified SMI and ZVI, pH controlling did not affect the nitrate removal rate.
Han, K.; Ko, J.; Hong, U.; Lim, J.; Park, S.; Kwon, S.; Kim, Y.
A sequential zero valent iron and aerobic biodegradation treatment system for nitrobenzene.
The remediation of nitroaromatic contaminated groundwater is sometimes difficult because nitroaromatic compounds are resistant to biodegradation and, when they do transform, the degradation of the products may also be incomplete. A simple nitroaromatic compound, nitrobenzene, was chosen to assess the feasibility of an in situ multi-zone treatment system at the laboratory scale. The proposed treatment system consists of a zero valent granular iron zone to reduce nitrobenzene to aniline, followed by a passive oxygen release zone for the aerobic biodegradation of the aniline daughter product using pristine aquifer material from Canadian Forces Base (CFB) Borden, Ontario, as an initial microbial source. In laboratory batch experiments, nitrobenzene was found to reduce quickly in the presence of granular iron forming aniline, which was not further degraded but remained partially sorbed onto the granular iron surface. Aniline was found to be readily biodegraded with little metabolic lag under aerobic conditions using the pristine aquifer material. A sequential column experiment, containing a granular iron reducing zone and an aerobic biodegradation zone, successively degraded nitrobenzene and then aniline to below detection limits (0.5 microM) without any noticeable reduction in hydraulic conductivity from biofouling, or through the formation of precipitates. PMID:14568399
Bell, L S; Devlin, J F; Gillham, R W; Binning, P J
A sequential zero valent iron and aerobic biodegradation treatment system for nitrobenzene
The remediation of nitroaromatic contaminated groundwater is sometimes difficult because nitroaromatic compounds are resistant to biodegradation and, when they do transform, the degradation of the products may also be incomplete. A simple nitroaromatic compound, nitrobenzene, was chosen to assess the feasibility of an in situ multi-zone treatment system at the laboratory scale. The proposed treatment system consists of a zero valent granular iron zone to reduce nitrobenzene to aniline, followed by a passive oxygen release zone for the aerobic biodegradation of the aniline daughter product using pristine aquifer material from Canadian Forces Base (CFB) Borden, Ontario, as an initial microbial source. In laboratory batch experiments, nitrobenzene was found to reduce quickly in the presence of granular iron forming aniline, which was not further degraded but remained partially sorbed onto the granular iron surface. Aniline was found to be readily biodegraded with little metabolic lag under aerobic conditions using the pristine aquifer material. A sequential column experiment, containing a granular iron reducing zone and an aerobic biodegradation zone, successively degraded nitrobenzene and then aniline to below detection limits (0.5 ?M) without any noticeable reduction in hydraulic conductivity from biofouling, or through the formation of precipitates.
Bell, L. S.; Devlin, J. F.; Gillham, R. W.; Binning, P. J.
Arsenic chemistry with sulfide, pyrite, zero-valent iron, and magnetite
The aim of this thesis is to study the immobilization reactions of arsenic in water. Since compounds containing iron or sulfide are common in most natural and engineered systems, the research focused on the redox reactions and adsorption of arsenic with sulfide, pyrite, zero-valent iron (ZVI), and magnetite which were studied through wet chemistry methods and spectroscopic techniques. The kinetic and thermodynamic information of the reactions of As(V) with S(-II), As(V)/As(III) with pyrite and surface-oxidized pyrite, As(V) with ZVI and acid-treated ZVI, As(III) with magnetite was used to identify mechanisms. The necessity to maintain strictly anoxic conditions was emphasized for the study of arsenic redox chemistry with sulfides and ZVI. The major findings of this research can be stated as follows. First, dissolved sulfide reduced As(V) to lower valences to form a yellow precipitate at acidic pH. The reaction involved the formation of thioarsenic intermediate species. Dissolved O2, granular activated carbon (GAC) and dissolved Fe(II) inhibited the removal of As(V) by sulfide. Elemental sulfur catalyzed the reduction of As(V) by sulfide, which implied the possible benefit of using sulfur-loaded GAC for arsenic removal. Possible reaction mechanisms were discussed. Second, As(III) adsorbed on pristine pyrite over a broader pH range than on surface-oxidized pyrite, while As(V) adsorbed over a narrower pH range with pristine pyrite. As(V) was completely reduced to As(III) on pristine pyrite at acidic pH but not at higher pH. The reduction was first-order with respect to As(V). As(V) was not reduced on surface-oxidized pyrite at pH = 4--11. The different behaviors of As(V) and As(III) on pristine and surface oxidized pyrite determines the toxicity and mobility of arsenic under oxic/anoxic environments. Third, commercial ZVI reduced As(V) to As(III) at low pH (<9) but not at higher pH. Acid-treated ZVI reduced As(V) to As(0), indicated by wet chemical analyses and by XANES/EXAFS, which could result in reduced mobility and toxicity of arsenic. Fourth, magnetite is a good adsorbent for both As(V) and As(III). As(V) was not reduced by stoichiometric magnetite even under a strictly anoxic condition. Addition of dissolved Fe(II) to magnetite did not reduce As(V) either. Under oxic conditions, the homogeneous oxidation of As(III) by dissolved oxygen was negligible. As(III) was rapidly oxidized in the presence of magnetite. The extent of the oxidation was promoted with addition of As(V). The effect is more significant at low As(III) concentrations. The effect could be important at field sites where total arsenic concentrations are low. This research is contributes to the understanding of the behavior of arsenic in sulfidic natural systems and in sites treated with GAC, ZVI-based permeable reactive barriers or injected with nano-ZVI particles. The optimum conditions and kinetic data for arsenic removal are applicable in field situations and engineered systems.
Sun, Fenglong
Generation of Oxidants From the Reaction of Nanoparticulate Zero-Valent Iron and Oxygen for the use in Contaminant Remediation
The reaction of zero-valent iron (ZVI) with oxygen can lead to the formation of oxidants, which may be used to transform recalcitrant contaminants including non-polar organics and certain metals. Nanoparticulate iron might provide a practical mechanism of remediating oxygen-containing groundwater and contaminated soil. To gain insight into the reaction mechanism and to quantify the yield of oxidants, experiments were performed
C. R. Keenan; C. Lee; D. L. Sedlak
A radiotracer study of the adsorption behavior of aqueous Ba 2+ ions on nanoparticles of zero-valent iron
Recently, iron nanoparticles are increasingly being tested as adsorbents for various types of organic and inorganic pollutants. In this study, nanoparticles of zero-valent iron (NZVI) synthesized under atmospheric conditions were employed for the removal of Ba2+ ions in a concentration range 10?3 to 10?6M. Throughout the study, 133Ba was used as a tracer to study the effects of time, concentration,
O. Çelebi; Ç. Üzüm; T. Shahwan; H. N. Erten
Characterization of zero valent iron prepared from by-product of pickling line and its decomposition reaction activity
Zero valent iron (ZVI) was produced by using wasted acid and iron oxide that are by-products of a pickling line at a steel\\u000a work. The reaction activity of the produced ZVI was evaluated through decomposition experiments of Orange II aqueous solution.\\u000a The ZVI particles produced directly from wasted acid (A-ZVI) were not easy to handle because they were very small
Byung Hoon Kim; Chol Park; Yu-Bong Kim; Dong-Suk Jung; Hyoung-Chan Cho; Sung Hoon Park; Deog-Gwan Ra; Do-Jin Lee; Sang-Chul Jung
Perchlorate reduction by autotrophic bacteria in the presence of zero-valent iron.
A series of batch experiments were performed to study the combination of zero-valent iron (ZVI) with perchlorate-reducing microorganisms (PRMs) to remove perchlorate from groundwater. In this method, H2 produced during the process of iron corrosion by water is used by PRMs as an electron donor to reduce perchlorate to chloride. Perchlorate degradation rates followed Monod kinetics, with a normalized maximum utilization rate (rmax) of 9200 microg g(-1) (dry wt) h(-1) and a half-velocity constant (Ks) of 8900 microg L(-1). The overall rate of perchlorate reduction was affected by the biomass density within the system. An increase in the OD600 from 0.025 to 0.08 led to a corresponding 4-fold increase of perchlorate reduction rate. PRM adaptation to the local environment and initiation of perchlorate reduction was rapid under neutral pH conditions. At the initial OD600 of 0.015, perchlorate reduction followed pseudo-first-order reaction rates with constants of 0.059 and 0.033 h(-1) at initial pH 7 and 8, respectively. Once perchlorate reduction was established, the bioreductive process was insensitive to the increases of pH from near neutral to 9.0. In the presence of nitrate, perchlorate reduction rate was reduced, but not inhibited completely. PMID:16572793
Yu, Xueyuan; Amrhein, Christopher; Deshusses, Marc A; Matsumoto, Mark R
Degradation of chloropicrin in the presence of zero-valent iron.
Halonitromethanes (HNMs) are a class of halogenated disinfection byproducts formed upon the addition of chlorine to water containing organic matter. Batch experiments were performed to investigate the reaction pathways and kinetics of three HNMs (chloropicrin or trichloronitromethane [TCNM], dichloronitromethane [DCNM], and chloronitromethane [CNM]) with zero-valent iron (Fe0). All three compounds reacted rapidly in the presence of Fe0 (1.8-4.4 g/L) with methylamine (MA) as the final product. The geometric surface area-normalized rate constants decreased with decreasing halogenation: TCNM (301 L/[h-m2]) > DCNM (153 L/(h-m2)) > CNM (45.9 L/[h-m2]). Nitromethane, an intermediate species, rapidly reacted to form MA (302 L/[h-m2]). These reactions all experienced some degree of mass transfer limitation (9-73%). The average carbon and chlorine mass balances for TCNM were >85%, indicating that the major reaction products were recovered. The degradation of TCNM and DCNM proceeded via the parallel reaction pathways of hydrogenolysis and alpha-elimination. For TCNM, 60.7 +/- 8.7% of reaction proceeded via hydrogenolysis and 39.3 +/- 6.4% via alpha-elimination. Knowledge of HNM reaction pathways and kinetics in the presence of Fe0 may be useful for predicting the fate of these compounds in drinking water distribution systems containing cast or ductile iron pipe and for developing treatment systems for HNM removal from water. PMID:16445082
Pearson, Carrie R; Hozalski, Raymond M; Arnold, William A
Zero-valent iron nanoparticles in treatment of acid mine water from in situ uranium leaching.
Acid mine water from in situ chemical leaching of uranium (Straz pod Ralskem, Czech Republic) was treated in laboratory scale experiments by zero-valent iron nanoparticles (nZVI). For the first time, nZVI were applied for the treatment of the real acid water system containing the miscellaneous mixture of pollutants, where the various removal mechanisms occur simultaneously. Toxicity of the treated saline acid water is caused by major contaminants represented by aluminum and sulphates in a high concentration, as well as by microcontaminants like As, Be, Cd, Cr, Cu, Ni, U, V, and Zn. Laboratory batch experiments proved a significant decrease in concentrations of all the monitored pollutants due to an increase in pH and a decrease in oxidation-reduction potential related to an application of nZVI. The assumed mechanisms of contaminants removal include precipitation of cations in a lower oxidation state, precipitation caused by a simple pH increase and co-precipitation with the formed iron oxyhydroxides. The possibility to control the reaction kinetics through the nature of the surface stabilizing shell (polymer vs. FeO nanolayer) is discussed as an important practical aspect. PMID:21193219
Klimkova, Stepanka; Cernik, Miroslav; Lacinova, Lenka; Filip, Jan; Jancik, Dalibor; Zboril, Radek
Application of green zero-valent iron nanoparticles to the remediation of soils contaminated with ibuprofen.
Zero-valent iron nanoparticles (nZVIs) are often used in environmental remediation. Their high surface area that is associated with their high reactivity makes them an excellent agent capable of transforming/degrading contaminants in soils and waters. Due to the recent development of green methods for the production of nZVIs, the use of this material became even more attractive. However, the knowledge of its capacity to degrade distinct types of contaminants is still scarce. The present work describes the study of the application of green nZVIs to the remediation of soils contaminated with a common anti-inflammatory drug, ibuprofen. The main objectives of this work were to produce nZVIs using extracts of grape marc, black tea and vine leaves, to verify the degradation of ibuprofen in aqueous solutions by the nZVIs, to study the remediation process of a sandy soil contaminated with ibuprofen using the nZVIs, and to compare the experiments with other common chemical oxidants. The produced nZVIs had nanometric sizes and were able to degrade ibuprofen (54 to 66% of the initial amount) in aqueous solutions. Similar remediation efficiencies were obtained in sandy soils. In this case the remediation could be enhanced (achieving degradation efficiencies above 95%) through the complementation of the process with a catalyzed nZVI Fenton-like reaction. These results indicate that this remediation technology represents a good alternative to traditional and more aggressive technologies. PMID:23738986
Machado, S; Stawi?ski, W; Slonina, P; Pinto, A R; Grosso, J P; Nouws, H P A; Albergaria, J T; Delerue-Matos, C
[Zero-valent iron-enhanced azoreduction by the Shewanella decolorationis S12].
Characteristics and optimal reaction conditions of anaerobic azoreduction by the Shewanella decolorationis S12 in the presence of zero-valent iron (ZVI) were evaluated in this study. The results showed that the presence of ZVI significantly enhanced the decolorization rate of azo dye. In the presence of 20 mmol x L(-1) ZVI, the decolorization rate of 1 mmol x L(-1) amaranth reached up to 100% by the Shewanella decolorationis S12 after 30 h incubation, which was significantly higher than 23.16% and 94.66% in the pure strain S12 and pure ZVI treatment systems, respectively. When 20 mmol x L(-1) of sodium formate was added in the medium, ZVI still improved the decolorization rate of amaranth by 20.54%. In addition, the presence of ZVI significantly increased the azo dye treatment amount in the ZVI plus S12 system. In the system with ZVI, 1 mmol x L(-1) amaranth was completely reduced 11 times in fed-batch process within 276 h, while the dye could only be completely reduced 3 times in the system without ZVI. The optimal pH and the Fe(0) dose for the ZVI plus S12 system was 9.0 and 60 mmol c L(-1), respectively. The microscale ZVI was more suitable for the decolorization than those with larger size and the nanoscale ZVI. This study may provide some useful information for improving the biodegradation of azo dye in the treatment system with ZVI. PMID:24028023
Zhou, Qing; Chen, Xing-Juan; Guo, Jun; Sun, Guo-Ping; Xu, Mei-Ying
Effects of nano zero-valent iron on Klebsiella oxytoca and stress response.
Nano zero-valent iron (NZVI) is a new option for contaminated soil and groundwater treatment, despite little is known on their impact on environmental microorganisms. Klebsiella oxytoca K5 strain, isolated from the NZVI-treated soil, was used to investigate the bacterial, phenotypical and molecular response to commercial NZVI exposure. Cytotoxicity assays at three NZVI concentrations (1, 5 and 10 mg mL(-1)) suggested a negligible bacteriostatic effect and the lack of bactericidal effect. Structural changes were analysed by electronic microscopy. Scanning electron microscopy revealed the presence of NZVI around some bacterial cells, but no apparent morphological changes were seen. NZVI attachment to the cell surface was confirmed by transmission electron microscopy, although most of them were not affected. A proteomic approach (two-dimensional electrophoresis, matrix-assisted laser desorption ionization time-of-flight mass spectrometry) was used to investigate NZVI impact. For the first time to our knowledge, results revealed that exposure of a soil bacterium to NZVI resulted in the overproduction of tryptophanase, associated with oxidative stress response. K5 may set up an adaptative stress response involving indole as a signal molecule to inform the bacterial population about environmental changes. These findings would improve knowledge on the molecular mechanisms underlying bacterial response to NZVI exposure. PMID:23893265
Saccà, Maria Ludovica; Fajardo, Carmen; Nande, Mar; Martín, Margarita
Two dimensional transport characteristics of surface stabilized zero-valent iron nanoparticles in porous media.
Zero-valent iron nanoparticles (INP) were synthesized and stabilized using poly acrylic acid (PAA) to yield stabilized INP (S-INP). A two-dimensional physical model was used to study the fate and transport of the INP and S-INP in porous media under saturated, steady-state flow conditions. Transport data for a nonreactive tracer, INP, and S-INP were collected under similar flow conditions. The results show that unstabilized INP cannot be transported into groundwater systems. On the other hand, the S-INP can be transported like a tracer without significant retardation. However, the S-INP plume migrated downward as it moved horizontally in the physical model, indicating that small density gradients have significant influence on two-dimensional transport. The variable-density groundwater flow model SEAWAT was used to model the observed density-driven transport patterns. This is the first time a two-dimensional transport data set is reported for demonstrating the multidimensional transport characteristics of nanoparticles. The data shows the importance of density effects, which cannot be fully discerned using one-dimensional, column experiments. Finally, we also demonstrate that the numerical model SEAWAT can be used to predict the density-driven transport characteristics of S-INP in groundwater aquifers. PMID:18323119
Kanel, S R; Goswami, R R; Clement, T P; Barnett, M O; Zhao, D
Degradation of bromamine acid by nanoscale zero-valent iron (nZVI) supported on sepiolite.
Sepiolite, a natural nano-material, was chosen as a carrier to prepare supported nanoscale zero-valent iron (nZVI). The effects of preparation conditions, including mass ratio of nZVI and activated sepiolite and preparation pH value, on properties of the supported nZVI were investigated. The results showed that the optimal mass ratio of nZVI and sepiolite was 1.12:1 and the optimal pH value was 7. The supported nZVI was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive spectrometer (EDS), and furthermore an analogy model of the supported nZVI was set up. Compared with the nZVI itself, the supported nZVI was more stable in air and possessed better water dispersibility, which were beneficial for the degradation of bromamine acid aqueous solution. The degradation characteristics, such as effects of supported nZVI dosage, initial concentration and initial pH value of the solution on the decolorization efficiency were also investigated. The results showed that in an acidic environment the supported nZVI with a dosage of 2 g/L showed high activity in the degradation of bromamine acid with an initial concentration of 1,000 mg/L, and the degree of decolorization could reach up to 98%. PMID:23109568
Fei, Xuening; Cao, Lingyun; Zhou, Lifeng; Gu, Yingchun; Wang, Xiaoyang
Zero-valent iron pretreatment for detoxifying iodine in liquid crystal display (LCD) manufacturing wastewater.
This study investigated reductive transformation of iodine by zero-valent iron (ZVI), and the subsequent detoxification of iodine-laden wastewater. ZVI completely reduced aqueous iodine to non-toxic iodide. Respirometric bioassay illustrated that the presence of iodine increase the lag phase before the onset of oxygen consumption. The length of lag phase was proportional to increasing iodine dosage. The reduction products of iodine by ZVI did not exhibit any inhibitory effect on the biodegradation. The cumulative biological oxidation associated with iodine toxicity was closely fitted to Gompertz model. When iodine-laden wastewater was continuously fed to a bench-scale activated sludge unit, chemical oxygen demand (COD) removal efficiencies decreased from above 90% to below 80% along with a marked decrease in biomass concentration. On the other hand, the COD removal efficiency and biomass concentration remained constant in the integrated ZVI-activated sludge system. Respirometric bioassay with real iodine-laden LCD manufacturing wastewater demonstrated that ZVI was effective for detoxifying iodine and consequently enhancing biodegradability of wastewater. This result suggested that ZVI pretreatment may be a feasible option for the removal of iodine in LCD processing wastewater, instead of more costly processes such as adsorption and chemical oxidation, which are commonly in the iodine-laden LCD wastewater treatment facility. PMID:18799266
Lee, J W; Cha, D K; Oh, Y K; Ko, K B; Song, J S
Synergetic decolorization of reactive blue 13 by zero-valent iron and anaerobic sludge.
Efficient decolorization of reactive blue 13 was achieved by a combined use of anaerobic sludge and zero-valent iron (ZVI), and the underlying mechanism of this process was elucidated, Addition of 1.0 g/L ZVI into sludge accelerated the decolorization, with the decoloration ratio after 1-h treatment increased by 29.4% compared with the sum of the individual systems, indicating a synergy between the sludge and ZVI. Meanwhile, substantial changes in sludge morphology and microbial community were observed. The increased dye removal by ZVI was mainly attributed to: (1) a directly chemical reduction and aggregation; and (2) creation of a more favorable pH and anaerobic environment for microorganisms. The acid production by acidogens also partially offset the pH rise in ZVI corrosion and would alleviate ZVI deactivation. This work might offer valuable implications for the optimization and practical application of ZVI-anaerobic sludge processes for treatment of azo dyes or other recalcitrant pollutants. PMID:24084202
Li, Wen-Wei; Zhang, Yang; Zhao, Jin-Bao; Yang, Ya-Li; Zeng, Raymond J; Liu, Hou-Qi; Feng, Yu-Jie
Influences of humic acid, bicarbonate and calcium on Cr(VI) reductive removal by zero-valent iron
The influences of various geochemical constituents, such as humic acid, HCO3?, and Ca2+, on Cr(VI) removal by zero-valent iron (Fe0) were investigated in a batch setting. The collective impacts of humic acid, HCO3?, and Ca2+ on the Cr(VI) reduction process by Fe0 appeared to significantly differ from their individual impacts. Humic acid introduced a marginal influence on Fe0 reactivity toward
Tongzhou Liu; Pinhua Rao; Irene M. C. Lo
Simultaneous Removal of NO and SO2 by High-Temperature Fluidized Zero-Valent Iron Processes
A new approach to simultaneously remove nitrogen mon-oxide (NO) and sulfur dioxide (SO2) by zero valent iron (ZVI) was investigated. Three different parameters, temperature, flux, and ZVI dosage, were tested in fluidized ZVI column studies containing 500 ppmv of NO and SO2, respectively. Under the ZVI dosage of 0.5 g at flux of 0.6 L\\/cm·min for temperature 573 K, there
Shiao-Shing Chen; Chih-Yu Cheng; Chung-Cheng Wei; Chao-Heng Tseng
Kaolinite-supported nanoscale zero-valent iron for removal of Pb 2+ from aqueous solution: Reactivity, characterization and mechanism
The use of nanoscale zero-valent iron (nZVI) to remediate contaminated groundwater is limited due to its lack of durability and mechanical strength. To address this issue, 20% (w\\/w) nZVI was loaded onto kaolinite as a support material (K-nZVI). More than 96% of Pb2+ was removed from aqueous solution using K-nZVI at an initial condition of 500 mg\\/L Pb2+ within 30 min under
Xin Zhang; Shen Lin; Zuliang Chen; Mallavarapu Megharaj; Ravendra Naidu
Reduction of hexachlorobenzene by nanoscale zero-valent iron: Kinetics, pH effect, and degradation mechanism
Nanoscale zero-valent iron (NZVI) particles were synthesized in the laboratory and used to investigate the reduction kinetics and degradation mechanisms of hexachlorobenzene (HCB) and the environmental effects. The rapid degradation of HCB by NZVI follows pseudo-first-order kinetics. Increasing the dose of NZVI particles enhanced the dechlorination rates of HCB. With an increase in temperature, the degradation rate increases. The activation
Yang-hsin Shih; Chung-yu Hsu; Yuh-fan Su
Degradation of model olive mill contaminants of OMW catalysed by zero-valent iron enhanced with a chelant
The aim of this study was to investigate the effect of a chelated zero valent iron as catalyst on the oxidation of six organic acids that are generally found in olive mill wastewater. The reaction was carried out in a stirred tank reactor under extremely mild conditions, a temperature of 30°C and atmospheric pressure.Solutions of 350mg\\/L of the six organic
Irama Sanchez; Frank Stüber; Azael Fabregat; Agustí Fortuny; Christophe Bengoa
The role and fate of EDTA in ultrasound-enhanced zero-valent iron\\/air system
In this study, factors such as ZVI loading, ultrasound (US) input power, reaction temperature and solution pH that could affect the EDTA degradation in the US-enhanced zero-valent iron\\/air (US\\/ZVI\\/air) system were investigated. In the system, EDTA also served as an agent for complexation with the dissolved Fe2+ and producing H2O2 that would trigger Fenton-like reaction and degrade the EDTA itself.
Tao Zhou; Teik-Thye Lim; Yaozhong Li; Xiaohua Lu; Fook-Sin Wong
Fine structure characterization of zero-valent iron nanoparticles for decontamination of nitrites and nitrates in wastewater and groundwater
The main objectives of the present study were to investigate the chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization. This work also exemplifies the utilization of field emission-scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD) to reveal the speciation
Kuen-Song Lin; Ni-Bin Chang; Tien-Deng Chuang
Enhanced oxidation of 4-chlorophenol using sulfate radicals generated from zero-valent iron and peroxydisulfate at ambient temperature
An efficient advanced oxidation process, which is based on the zero-valent iron (ZVI)-mediated decomposition of peroxydisulfate (PDS) that results in the generation of very strong oxidizing species (sulfate radicals) in aqueous solution, is reported. Experiments were conducted in the dark using ZVI loading ranging from 0.05 to 0.40gL?1 in the presence of PDS. The results showed that ZVI significantly improved
Jinying Zhao; Yaobin Zhang; Xie Quan; Shuo Chen
Remediation of s-triazines contaminated water in a laboratory scale apparatus using zero-valent iron powder
Atrazine, propazine and simazine were tested separately and in mixture by batch procedure in a laboratory-constructed apparatus. 3.75 l of a buffered s-triazines pesticide solution was treated at room temperature by 325-mesh zero-valent iron powder (ZVIP) (20 g\\/l). High performance liquid chromatography was used to separate by-products and study the decline in the pesticide's concentrations. Results obtained show that the
Antoine Ghauch; Joel Suptil
Conceptual comparison of pink water treatment technologies: granular activated carbon, anaerobic fluidized bed, and zero-valent iron-Fenton process
Pink water, explosive-laden wastewater produced in army ammunition plants is often treated using expensive and non-destructive granular activated carbon (GAC) adsorption. This paper compares GAC adsorption and two alternative treatment technologies, anaerobic GAC fluidized bed reactor and zero- valent iron-Fenton process. The bench-scale demonstration of the zero-valent iron-Fenton process with real pink water is reported. The features of three technologies
S.-Y. Oh; D. K. Cha; P. C. Chiu; B. J. Kim
Synthesis of Highly Reactive Subnano-sized Zero-valent Iron using Smectite Clay Templates
A novel method was developed for synthesizing subnano-sized zero-valent iron (ZVI) using smectite clay layers as templates. Exchangeable Fe(III) cations compensating the structural negative charges of smectites were reduced with NaBH4, resulting in the formation of ZVI. The unique structure of smectite clay, in which isolated exchangeable Fe(III) cations reside near the sites of structural negative charges, inhibited the agglomeration of ZVI resulting in the formation of discrete regions of subnanoscale ZVI particles in the smectite interlayer regions. X-ray diffraction revealed an interlayer spacing of ~ 5 Å. The non-structural iron content of this clay yields a calculated ratio of two atoms of ZVI per three cation exchange sites, in full agreement with the XRD results since the diameter of elemental Fe is 2.5 Å. The clay-templated ZVI showed superior reactivity and efficiency compared to other previously reported forms of ZVI as indicated by the reduction of nitrobenzene; structural Fe within the aluminosilicate layers was nonreactive. At a 1:3 molar ratio of nitrobenzene:non-structural Fe, a reaction efficiency of 83% was achieved, and over 80% of the nitrobenzene was reduced within one minute. These results confirm that non-structural Fe from Fe(III)-smectite was reduced predominantly to ZVI which was responsible for the reduction of nitrobenzene to aniline. This new form of subnano-scale ZVI may find utility in the development of remediation technologies for persistent environmental contaminants, e.g. as components of constructed reactive domains such as reactive caps for contaminated sediments.
Gu, Cheng; Jia, Hanzhang; Li, Hui; Teppen, Brian J.; Boyd, Stephen A.
Influence of zero-valent iron nanoparticles on nitrate removal by Paracoccus sp.
Nitrate contamination in drinking water is a major threat to public health. This study investigated the efficiency of denitrification of aqueous solutions in the co-presence of synthesized nanoscale zero-valent iron (nZVI; diameter: 20-80 nm) and a previously isolated Paracoccus sp. strain YF1. Various influencing factors were studied, such as oxygen, pH, temperature, and anaerobic corrosion products (Fe(2+), Fe(3+) and Fe3O4). With slight toxicity to the strain, nZVI promoted denitrification efficiency by providing additional electron sources under aerobic conditions. For example, 50 mg L(-1) nZVI increased the nitrate removal efficiency from 66.9% to 85.2%. However, a high concentration of nZVI could lead to increased production of Fe(2+), a toxic ion which could compromise the removal efficiency. Kinetic studies suggest that denitrification by both free cells, and nZVI-amended cells fitted well to the zero-order model. Temperature and pH are the major factors affecting nitrate removal and cell growth, with or without the presence of nZVI. In this study, nitrate removal and cell growth increased in the pH range of 6.5-8.0, and temperature range of 25-35 °C. These conditions favor the growth of the strain, which dominated denitrification in all scenarios involved. As for anaerobic corrosion products, compared with Fe(2+) and Fe(3+), Fe3O4 promoted denitrification by serving as an electron donor. Finally, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirmed attachments of nZVI on the surface of the cell, and the formation of iron oxides. This study indicated that, as an electron donor source with minimal cellular toxicity, nZVI could be used to promote denitrification efficiency under biotic conditions. PMID:24630453
Liu, Yan; Li, Shibin; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi
Microwave-induced nanoscale zero-valent iron degradation of perchloroethylene and pentachlorophenol.
Microwave (MW) is applied to enhance perchloroethylene (PCE) or pentachlorophenol (PCP) removal using zero-valent iron (ZVI; Fe(0)) as the dielectric medium. ZVI has a much higher dielectric loss factor (39.5) than other media; it is capable of absorbing MW radiation rapidly to speed up the release of electrons, leading to rises of the ZVI particle surface temperature. If the MW power is continued, excessive electricity will accumulated inside ZVI particles, resulting in sparks. The results show that during the initial 5 sec (700 W), the linear aliphatic PCE has a faster decomposing rate than the ringed PCP (82.0% vs. 4.8%) because less energy is required for decomposing the linear-chlorine bond (90 kcal mol(-1)) than ring-chlorine bonds (95 kcal mol(-1)). Later the removal rate for either PCE or PCP remains the same when the exposure time is between 5 and 60 sec. Without MW irradiation, linear PCE molecules have larger surface area to contact ZVI, and hence they have better removal efficiencies than PCP molecules. Using Fe(0) as a microwave dielectric medium to treat PCE or PCP is a new and worthwhile treatment technology; it is environmentally friendly, and its use will eliminate the secondary pollution. Implications: Nanoscale iron particles are characterized by high surface-area-to-volume ratios, high specific surface area, and high surface reactivity. With a much higher dielectric loss factor, it is capable of absorbing MW radiation rapidly to speed up the release of electrons, leading to rise in temperature. The time needed to achieve a satisfactory treatment is also reduced, leading to significant saving of energy consumption to make this method cost-effective and also environmentally friendly for the industry to pursuit sustainable development. PMID:23362763
Lee, Chien-Li; Lin, Chitsan; Jou, Chih-Ju G
Straining of polyelectrolyte-stabilized nanoscale zero valent iron particles during transport through granular porous media.
In this study, the relevance of straining of nano-sized particles of zero valent iron coated with carboxymethyl cellulose (CMC-NZVI) during transport in model subsurface porous media is assessed. Although deposition of polyelectrolyte stabilized-NZVI on granular subsurface media due to physicochemical attachment processes has been reported previously, there is limited knowledge on the significance of the collector (sand) diameter on the deposition and spatial distribution of the retention of such nanoparticles. Experiments were conducted to assess the transport of CMC-NZVI in columns packed with four different-sized sands of mean diameter of 775 ?m, 510 ?m, 250 ?m and 150 ?m and at three different particle concentrations of 0.085 g L(-1), 0.35 g L(-1) and 1.70 g L(-1). CMC-NZVI effluent concentrations decreased with smaller sand diameters. High CMC-NZVI particle retention near the inlet, particularly for the finer sands was observed, even with a low ionic strength of 0.1 mM for the electrolyte medium. These observations are consistent with particle retention in porous media due to straining and/or wedging. Two colloid transport models, one considering particle retention by physicochemical deposition and detachment of those deposited particles, and the other considering particle retention by straining along with particle deposition and detachment, were fitted to the experimental data. The model accounting for straining shows a better fit, especially to the CMC-NZVI retention data along the length of the column. The straining rate coefficients decreased with larger sand diameters. This study demonstrates that CMC-NZVI particles, despite of their small size (hydrodynamic diameters of 167-185 nm and transmission electron microscopy imaged diameters of approximately 85 nm), may be removed by straining during transport, especially through fine granular subsurface media. The tailing effect, observed in the particle breakthrough curves, is attributed to detachment of deposited particles. PMID:24361705
Raychoudhury, Trishikhi; Tufenkji, Nathalie; Ghoshal, Subhasis
Rapid removal of flutriafol in water by zero-valent iron powder.
A study of the effect of zero-valent iron (ZVI) powder is carried out for the first time on the degradation of flutriafol ((RS)-2,4'-difluoro-alpha-(1H-1,2,4-triazol-1-ylmethyl)-benzhydryl alcohol, C(16)H(13)F(2)N(3)O), a bifluorinated soil and water persistent triazole pesticide using a laboratory scale device consisting of a 20 ml pyrex serum vials fixed to a Vortex agitator. Different amounts of ZVI powder (10-50 g l(-1)) at pH 6.6 and room temperature were investigated. Experiments showed an observed degradation rate k(obs) directly proportional to the surface of contact of flutriafol with ZVI. Flutriafol degradation reactions demonstrated first order kinetic with a half-live of about 10.8+/-0.5 min and 3.6+/-0.2 min when experiments were conducted at [ZVI]=10 g l(-1) into oxygenated and anoxic solutions, respectively. Three analytical techniques were employed to monitor flutriafol degradation and to understand solution and by-products behaviors: (1) A UV-Vis spectrophotometer; (2) a high performance liquid chromatography (HPLC) coupled with a photo diode array (PDA) and fluorescence detectors; (3) a similar HPLC coupled with a PDA and a mass spectrometer detectors equipped with an atmospheric pressure photoionization source. Results showed a complete disappearance of flutriafol after 20 min of contact with ZVI, the loss of fluorescence properties of the final by-products, the defluorination of the triazole pesticide via hydroxylation reaction and finally the hydrogenation of the triazole ring. PMID:18178235
Ghauch, Antoine
Effects of nano-scale zero-valent iron particles on a mixed culture dechlorinating trichloroethylene.
Nano-scale zero-valent iron particles (NZVI) are increasingly being used to treat sites contaminated with chlorinated solvents. This study investigated the effect of NZVI on dechlorinating microorganisms that participate in the anaerobic bioremediation of such sites. NZVI can have a biostimulatory effect associated with water-derived cathodic H(2) production during its anaerobic corrosion (730+/-30 micromol H(2) was produced in 166 h in abiotic controls with 1 g/L NZVI) or an inhibitory effect upon contact with cell surfaces (assessed by transmission electron microscopy). Methanogens, which are known to compete for H(2) with dechlorinators, were significantly biostimulated by NZVI and methane production increased relative to NZVI-free controls from 58+/-5 to 275+/-2 micromol. In contrast, bacteria dechlorinating TCE were inhibited by NZVI, and the first-order degradation rate coefficient decreased from 0.115+/-0.005 h(-1) (R(2)=0.99) for controls to 0.053+/-0.003 h(-1) (R(2)=0.98) for treatments with 1 g/L NZVI. Ethene production from TCE was initially inhibited by NZVI, but after 331 h increased to levels observed for an NZVI-free system (7.6+/-0.3 micromol ethene produced in 502 h compared to 11.6+/-0.5 mmol in the NZVI-free system and 3.8+/-0.3 micromol ethene for NZVI alone). Apparently, cathodic H(2) was utilized as electron donor by dechlorinating bacteria, which recovered following the partial oxidation and presumably passivation of the NZVI. Overall, these results suggest that reductive treatment of chlorinated solvent sites with NZVI might be enhanced by the concurrent or subsequent participation of bacteria that exploit cathodic depolarization and reductive dechlorination as metabolic niches. PMID:19819128
Xiu, Zong-Ming; Jin, Zhao-Hui; Li, Tie-Long; Mahendra, Shaily; Lowry, Gregory V; Alvarez, Pedro J J
Reducing the mobility of arsenic in brownfield soil using stabilised zero-valent iron nanoparticles.
The use of nanoscale zero-valent iron (nZVI) as a new tool for the treatment of polluted soils and groundwater has received considerable attention in recent years due to its high reactivity, in situ application and cost-effectiveness. The objectives of this study were to investigate the effectiveness of using a commercial stabilised suspension of nZVI to immobilise As in brownfield soil and to investigate its impact on Fe availability in the treated soil. The phytotoxicities of the soil samples were also evaluated using a germination test with two plant species: barley (Hordeum vulgare L) and common vetch (Vicia sativa L). Two doses of the commercial nZVI suspension were studied, 1% and 10%, and two soil-nanoparticle interaction times, 72 h and 3 mo, were used to compare the stabilities of the soils treated with nZVI. The As availability was evaluated using a sequential extraction procedure and the toxicity characteristics leaching procedure (TCLP) test. The application of nZVI significantly decreased the availability of As in the soil. The immobilisation of As was more effective and more stable over time with the 10% dose than with the 1% dose of the commercial nZVI suspension. The application of nZVI did not induce an important increase in Fe mobility because the Fe leachability was less than 2 mg L(-1) over the time period studied. The lower availability of As in the soil led to a decrease in the phytotoxicity of the soil to barley and vetch germination. Thus, the proposed nanotechnology could be a potential alternative for the in situ remediation of As-polluted soils and could be combined with remediation processes where plants are involved. PMID:25072767
Gil-Díaz, Mar; Alonso, Juan; Rodríguez-Valdés, Eduardo; Pinilla, Paloma; Lobo, Maria Carmen
Impact of nano zero valent iron (NZVI) on methanogenic activity and population dynamics in anaerobic digestion.
Nano zero valent iron (NZVI), although being increasingly used for environmental remediation, has potential negative impact on methanogenesis in anaerobic digestion. In this study, NZVI (average size = 55 ± 11 nm) showed inhibition of methanogenesis due to its disruption of cell integrity. The inhibition was coincident with the fast hydrogen production and accumulation due to NZVI dissolution under anaerobic conditions. At the concentrations of 1 mM and above, NZVI reduced methane production by more than 20%. At the concentration of 30 mM, NZVI led to a significant increase in soluble COD (an indication of cell disruption) and volatile fatty acids in the mixed liquor along with an accumulation of H2, resulting in a reduction of methane production by 69% (±4% [standard deviation]). By adding a specific methanogenesis inhibitor-sodium 2-bromoethanesulfonate (BES) to the anaerobic sludge containing 30 mM NZVI, the amount of H2 produced was only 79% (±1%) of that with heat-killed sludge, indicating the occurrence of bacterially controlled hydrogen utilization processes. Quantitative PCR data was in accordance with the result of methanogenesis inhibition, as the level of methanogenic population (dominated by Methanosaeta) in the presence of 30 mM NZVI decreased significantly compared to that of the control. On the contrary, ZVI powder (average size <212 ?m) at the same concentration (30 mM) increased methane production presumably due to hydrogenotrophic methanogenesis of hydrogen gas that was slowly released from the NZVI powder. While it is a known fact that NZVI disrupts cell membranes, which inhibited methanogenesis described herein, the results suggest that the rapid hydrogen production due to NZVI dissolution also contribute to methanogenesis inhibition and lead to bacterially controlled hydrogenotrophic processes. PMID:24112628
Yang, Yu; Guo, Jialiang; Hu, Zhiqiang
A Case Study of Using Zero-Valent Iron Nanoparticles for Groundwater Remediation
Zero-valent iron nanoparticle (nZVI) is a promising technology for rapid in situ remediation of numerous contaminants, including chlorinated solvents, in groundwater and soil. Because of the high specific surface area of nZVI particles, this technology achieves treatment rates that are significantly faster than micron-scale and granular ZVI. However, a key technical challenge facing this technology involves agglomeration of nZVI particles. To improve nZVI mobility/deliverability and reactivity, an innovative method was recently developed using a low-cost and bio-degradable organic polymer as a stabilizer. This nZVI stabilization strategy offers unique advantages including: (1) the organic polymer is cost-effective and "green" (completely bio-compatible), (2) the organic polymer is highly effective in stabilizing nZVI particles; and (3) the stabilizer is applied during particle preparation, making nZVI particles more stable. Through a funding from the U.S. Air Force Center for Engineering and the Environment (AFCEE), AMEC performed a field study to test the effectiveness of this innovative technology for degradation of chlorinated solvents in groundwater at a military site. Laboratory treatability tests were conducted using groundwater samples collected from the test site and results indicated that trichloroethene (main groundwater contaminant at the site) was completely degraded within four hours by nZVI particles. In March and May 2011, two rounds of nZVI injection were performed at the test site. Approximately 700 gallons of nZVI suspension with palladium as a catalyst were successfully prepared in the field and injected into the subsurface. Before injection, membrane filters with a pore size of 450 nm were used to check the nZVI particle size and it was observed that >85% of nZVI particles were passed through the filter based on total iron measurement, indicating particle size of <450 nm. During field injections, nZVI particles were observed in a monitoring well located 5 feet downgradient from the injection well. Chlorinated solvent degradation products, e.g. ethane and ethene, increased significantly in monitoring wells following nZVI injections. Groundwater monitoring will be continued for approximately eight months following the last sampling event in July 2011 to demonstrate the performance of nZVI particles.
Xiong, Z.; Kaback, D.; Bennett, P. J.
The main objectives of the present study were to investigate the chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization. This work also exemplifies the utilization of field emission-scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD) to reveal the speciation and possible reaction pathway in a very complex adsorption and redox reaction process. Experimentally, ZVIN of this study was prepared by sodium borohydride reduction method at room temperature and ambient pressure. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20-50 nm were observed with FE-SEM or TEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65-83% and 51-68%, respectively, based on three different initial concentrations. Based on the XRD pattern analyses, it is found that the quantitative relationship between nitrite and Fe(III) or Fe(II) is similar to the one between nitrate and Fe(III) in the ZVIN study. The possible reason is due to the faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The extended x-ray absorption fine structure (EXAFS) or x-ray absorption near edge structure (XANES) spectra show that the nitrites or nitrates reduce to N2 or NH3 while oxidizing the ZVIN to Fe2O3 or Fe3O4 electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive.
Lin, Kuen-Song; Chang, Ni-Bin; Chuang, Tien-Deng
The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted to evaluate the effect of different arrangements of electrodes and ZVI barriers in the column on the TCE removal capacity (RC). In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved up to six times with simultaneous application of ZVI and DC compared to that using ZVI only. The most effective arrangement of electrode and ZVI for TCE removal was the column set with ZVI and a cathode installed at the down gradient. Based on the electrokinetic study for the column systems with only DC input, single acid front movement could explain different RCs. An enhanced dechlorination rate of TCE using E2PRB systems, compared to a conventional PRB system, was observed, and is considered to be attributed to more electron sources: (1) external DC, (2) electrolysis of water, (3) oxidation of ZVI, (4) oxidation of dissolved Fe2+, (5) oxidation of molecular hydrogen at the cathode, and (6) oxidation of Fe2+ in mineral precipitates. Each of these electron sources was evaluated for their potential influencing the TCE RC through the electron competition model and energy consumption. A strong correlation between the quantity of electrons generated, RC, and the energy-effectiveness was found.
Moon, Ji-Won; Moon, Hi-Soo; Kim, Heonki; Roh, Yul
Treatment of chemical warfare agents by zero-valent iron nanoparticles and ferrate(VI)/(III) composite.
Nanoscale zero-valent iron (nZVI) particles and a composite containing a mixture of ferrate(VI) and ferrate(III) were prepared by thermal procedures. The phase compositions, valence states of iron, and particle sizes of iron-bearing compounds were determined by combination of X-ray powder diffraction, Mössbauer spectroscopy and scanning electron microscopy. The applicability of these environmentally friendly iron based materials in treatment of chemical warfare agents (CWAs) has been tested with three representative compounds, sulfur mustard (bis(2-chlorethyl) sulfide, HD), soman ((3,3'-imethylbutan-2-yl)-methylphosphonofluoridate, GD), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX). Zero-valent iron, even in the nanodimensional state, had a sluggish reactivity with CWAs, which was also observed in low degrees of CWAs degradation. On the contrary, ferrate(VI)/(III) composite exhibited a high reactivity and complete degradations of CWAs were accomplished. Under the studied conditions, the estimated first-order rate constants (? 10(-2)s(-1)) with the ferrate(VI)/(III) composite were several orders of magnitude higher than those of spontaneous hydrolysis of CWAs (10(-8)-10(-6)s(-1)). The results demonstrated that the oxidative technology based on application of ferrate(VI) is very promising to decontaminate CWAs. PMID:22119195
Zboril, Radek; Andrle, Marek; Oplustil, Frantisek; Machala, Libor; Tucek, Jiri; Filip, Jan; Marusak, Zdenek; Sharma, Virender K
Degradation of Perchloroethene by zero-valent iron evaluated by carbon isotope fractionation
Perchloroethene (PCE) is a widely spread groundwater contaminant in formally used industrial sites. Zero valent iron (ZVI) is used for in situ chemical reduction (ISCR) of PCE contaminants in the groundwater. A key factor in the application of in situ remediation technologies is a proper monitoring of contaminant reduction. The measurement of the stable isotope ratio is a promising method that is already used for quantifying microbial degradation of chlorinated contaminants. The carbon isotope ratio of PCE, measured by - isotope ratio mass spectrometry coupled to a gas chromatograph via a combustion interface (GC-C-IRMS), increases during degradation of PCE and can be directly related to the degree of degradation. It can be used to directly quantify chemical degradation and thus serves as a useful monitoring tool for groundwater remediation. An experiment to determine the carbon isotopic fractionation factor was performed as a lab experiment using Nanofer Star (NANOIRON). Two different PCE concentrations (c1: 220mgL-1, c2: 110mgL-1) mixed with 0.5 g of ZVI were sealed under deoxygenated conditions in 250 ml glas bottles locked with mininert caps. The bottles were incubated on a shaker for 865 h. Samples were taken weekly to measure the change in the carbon isotopic ratio of PCE as well as its concentration. Results showed a strong increase in the carbon isotope ratio (?-value) of PCE (start: -27 o end: -4 ), which indicates a significant dechlorination process of PCE. Beside PCE also one degradation product (Trichloroethylene - TCE) was measured. TCE was further dechlorinated as indicated by the ?-value change of TCE from -26 o to -4 oȦn unexpected intermediate value of -45 o for TCE was observed in the experiment. This fluctuation could be induced by the time depending concentration due to degradation and conversation processes. Furthermore, it seems that the progress of the ?-value is affected by the starting concentration of PCE (?-value of c1 < c2) as there is a higher ratio of PCE to ZVI.
Leitner, Simon; Watzinger, Andrea; Reichenauer, Thomas G.
More on sonolytic and sonocatalytic decomposition of Diclofenac using zero-valent iron.
The study is an extension of our previous work on sonolytic and sonocatalytic decomposition of Diclofenac-Na (DCF) to depict and highlight further operation parameters of significance, and to assess the effect of a novel home-made catalyst made of magnetic nanoparticles of zero-valent iron (ZVI). It was found that high-frequency was more effective than power ultrasound (20 kHz), and the efficiency was a maximum at 861 kHz, acetate-buffered pH 3.0 and air bubbling provided that samples were prepared from a pre-heated stock solution to enhance solubility of the compound. As such, 40-min sonication rendered nearly complete transformation of DCF to intermediate products that were more biodegradable than itself, but with little mineralization of organic carbon. Catalytic sono-treatment showed that the effect of the catalyst was largest in a non-buffered acidic solution and the rate of DCF elimination increased with increasing concentrations of solids up to a "critical" mass, above which it declined via the coalescence of particles and bubbles. Sonocatalysis using the "effective" solid mass also enhanced the overall degradation or mineralization of the compound as portrayed by the accumulation of chloride and nitrate ions in solution after prolonged contact. The production of excess H(2)O(2) during catalysis with ZVI was attributed to the presence of additional and major routes of (·)OH and/or H(2)O(2) formation (other than water pyrolysis). The initial rate of DCF degradation in the presence of nanoparticles was found highly sensitive to the mass of solids in solution, declining sharply as the mass exceeded a "critical" effective level. A catalyst efficacy factor was defined as a function of the initial mass ratio of Fe(0) to DCF and found to be one order of magnitude larger than that obtained by using commercial microparticles with a threefold larger Fe content. The result signifies that the role of aqueous Advanced Fenton reactions (Fe(0)/H(2)O(2)) was less significant in the presence of nanoparticles relative to that of heterogeneous reactions with reactive Fe and oxygen species on the massive surface areas with enriched reaction/adsorption and nucleation sites. PMID:22738831
Ziylan, Asu; Koltypin, Yuri; Gedanken, Aharon; Ince, Nilsun H
Effectiveness of nanoscale zero-valent iron for treatment of a PCE-DNAPL source zone
Nanoscale zero-valent iron (nZVI) has received considerable attention as a potential in situ remediation technology for treating chlorinated solvent source zones. Experimental and mathematical modeling studies were conducted to investigate the performance of nZVI in the transformation of tetrachloroethene (PCE) entrapped as a dense nonaqueous phase liquid (DNAPL). Injection of a 60 g/L suspension of nZVI into a column containing 20-30 mesh Ottawa sand and PCE-DNAPL at a residual saturation of 5.5% resulted in a uniform distribution of nZVI and minimal displacement of PCE. Subsequent flushing with 267 pore volumes of water containing 3 mM CaCl 2 at a Darcy velocity of 0.75 m/day resulted in steady-state effluent concentrations of PCE near the solubility limit (ca. 200 mg/L) and production of dissolved-phase ethene (10-30 mg/L). Over the duration of the experiment, approximately 30% of the initial PCE-DNAPL mass reacted to form ethene, 50% was eluted as dissolved-phase PCE, and 20% remained in the column as PCE-DNAPL. To further explore the implications of the nZVI column results, a multiphase transport model was developed that incorporated rate-limited PCE-DNAPL dissolution and reactions with nZVI. Using a fitted pseudo first-order transformation rate coefficient of 1.42 1/h, the model accurately captured observed trends in effluent concentrations of PCE and ethene and overall mass balance. A model sensitivity study reveals a strong dependence of treatment effectiveness on system characteristics. The sensitivity analysis suggests that an increase in the extent of PCE transformation is facilitated by decreasing flow rate, emplacement of nZVI down-gradient of the DNAPL source zone, and decreasing length of the DNAPL source zone. These findings indicate that, although emplacement of high concentrations of nZVI within a PCE-DNAPL source zone can result in substantial transformation of the parent compound, careful attention to design parameters (e.g. flow rate, location and amount nZVI delivered) will be required to achieve complete conversion to benign reaction products.
Taghavy, Amir; Costanza, Jed; Pennell, Kurt D.; Abriola, Linda M.
Effectiveness of nanoscale zero-valent iron for treatment of a PCE-DNAPL source zone.
Nanoscale zero-valent iron (nZVI) has received considerable attention as a potential in situ remediation technology for treating chlorinated solvent source zones. Experimental and mathematical modeling studies were conducted to investigate the performance of nZVI in the transformation of tetrachloroethene (PCE) entrapped as a dense nonaqueous phase liquid (DNAPL). Injection of a 60 g/L suspension of nZVI into a column containing 20-30 mesh Ottawa sand and PCE-DNAPL at a residual saturation of 5.5% resulted in a uniform distribution of nZVI and minimal displacement of PCE. Subsequent flushing with 267 pore volumes of water containing 3mM CaCl(2) at a Darcy velocity of 0.75 m/day resulted in steady-state effluent concentrations of PCE near the solubility limit (ca. 200mg/L) and production of dissolved-phase ethene (10-30 mg/L). Over the duration of the experiment, approximately 30% of the initial PCE-DNAPL mass reacted to form ethene, 50% was eluted as dissolved-phase PCE, and 20% remained in the column as PCE-DNAPL. To further explore the implications of the nZVI column results, a multiphase transport model was developed that incorporated rate-limited PCE-DNAPL dissolution and reactions with nZVI. Using a fitted pseudo first-order transformation rate coefficient of 1.421/h, the model accurately captured observed trends in effluent concentrations of PCE and ethene and overall mass balance. A model sensitivity study reveals a strong dependence of treatment effectiveness on system characteristics. The sensitivity analysis suggests that an increase in the extent of PCE transformation is facilitated by decreasing flow rate, emplacement of nZVI down-gradient of the DNAPL source zone, and decreasing length of the DNAPL source zone. These findings indicate that, although emplacement of high concentrations of nZVI within a PCE-DNAPL source zone can result in substantial transformation of the parent compound, careful attention to design parameters (e.g. flow rate, location and amount nZVI delivered) will be required to achieve complete conversion to benign reaction products. PMID:20888664
Taghavy, Amir; Costanza, Jed; Pennell, Kurt D; Abriola, Linda M
Nanoscale zero-valent iron supported on mesoporous silica: characterization and reactivity for Cr(VI) removal from aqueous solution.
MCM-41-supported nanoscale zero-valent iron (nZVI) was sytnhesized by impregnating the mesoporous silica martix with ferric chloride, followed by chemical reduction with NaHB4. The samples were studied with a combination of characterization techniques such as powder X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Mössbauer spectroscopy, N2 adsorption measurements, transmission electron microscopy (TEM), magnetization measurements, and thermal analysis methods. The experimental data revealed development of nanoscale zero-valent iron particles with an elliptical shape and a maximum size of ?80 nm, which were randomly distributed and immobilized on the mesoporous silica surface. Surface area measurements showed that the porous MCM-41 host matrix maintains its hexagonal mesoporous order structure and exhibits a considerable high surface area (609 m(2)/g). Mössbauer and magnetization measurements confirmed the presence of core-shell iron nanoparticles composed of a ferromagnetic metallic core and an oxide/hydroxide shell. The kinetic studies demonstrated a rapid removal of Cr(VI) ions from the aqueous solutions in the presence of these stabilized nZVI particles on MCM-41, and a considerably increased reduction capacity per unit mass of material in comparison to that of unsupported nZVI. The results also indicate a highly pH-dependent reduction efficiency of the material, whereas their kinetics was described by a pseudo-first order kinetic model. PMID:23959249
Petala, Eleni; Dimos, Konstantinos; Douvalis, Alexios; Bakas, Thomas; Tucek, Jiri; Zbo?il, Radek; Karakassides, Michael A
Investigation into the potential toxicity of zero-valent iron nanoparticles to a trichloroethylene-degrading groundwater microbial community
The microbiological impact of zero-valent iron remediation of groundwater was investigated by exposing a trichloroethylene-degrading anaerobic microbial community to bare and coated iron nanoparticles. Changes in population numbers and metabolic activity were analyzed using qPCR and were compared to those of a blank, negative, and positive control to assess for microbial toxicity. Additionally, these results were compared to those of samples exposed to an equal concentration of iron filings in an attempt to discern the source of toxicity. Statistical analysis revealed that the three iron treatments were equally toxic to total Bacteria and Archaea populations, as compared with the controls. Therefore, toxicity appears to result either from the release of iron ions and the generation of reactive oxygen species, or from alteration of the redox system and the disruption of microbial metabolisms. There does not appear to be a unique nanoparticle-based toxicity.
Zabetakis, Kara M.
Transport of zero-valent iron nanoparticles in carbonate-rich porous aquifers
Use of nanoscale zero-valent iron (nZVI) for in situ dechlorination of chlorinated solvents in groundwater is a promising remediation technology, due to a high dechlorination efficiency of nZVI and possible applications in e.g., great depth or under above-ground infrastructure. The success of the in situ nZVI dechlorination strongly depends on the particle delivery to the contaminants. Previous studies reported a limited transport of nZVI through porous media (cm- to dm-range) and this has been recognized as one of the major obstacles in a widespread utilization of this technology (TRATNYEK & JOHNSON, 2006). Factors that limit the transport are particle aggregation and deposition onto the aquifer solids. Both depend on particle properties (e.g., size, shape, iron content, surface coating, surface charge), on concentrations of suspensions, and on site-specific parameters, such as the groundwater chemistry and the properties and inhomogeneity of the aquifer material. Adsorbed anionic polyelectrolyte coatings provide electrostatic double layer repulsions between negatively charged nZVI particles (SALEH ET AL., 2007), hindering their aggregation and also deposition on the negatively charged quartz surfaces (usually prevailing in aquifers). However, it is shown that the presence of surface charge heterogeneities in the aquifer effects the particle transport (JOHNSON ET AL., 1996). Carbonates, iron oxides, and the edges of clay minerals, for instance, carry a positive surface charge at neutral pH (often encountered in groundwater). This leads to a favorable deposition of negatively charged nZVI particles onto carbonates, metal oxide impurities or clay edges, and finally to a decreased particle transport. Considering the high proportion of carbonates commonly encountered in Alpine porous aquifers, in this study we aimed to evaluate the transport of commercially available polyelectrolyte coated nZVI (polyacrylic acid coated-nZVI, NANOIRON s.r.o., CZ) in both quartz and carbonate-rich porous media and to quantify alteration in travel distances with the increasing proportion of carbonate sands. Transport studies using Nanofer 25S are carried out in 1 D columns filled with different proportions of quartz and carbonate sands at a pH typically encountered in groundwater. Column experiments demonstrated that the travel distance of coated-nZVI systematically decreases with increasing portion of carbonate sand. The transportability of Nanofer 25S was reduced by ~45% in pure carbonate sand, compared to that in pure quartz sand. These results demonstrated different attachment affinities of coated-nZVI for the investigated solids. Current experiments are carried out in order to provide a mechanistic understanding of the observed nanoparticle-solid matrix interactions. Furthermore, the effects of varying groundwater chemistry, size and shape of the packing material, as well as the presence of metal oxides and natural organic matter on the nZVI transport will be investigated. The project is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW). Management by Kommunalkredit Public Consulting GmbH. Literature TRATNYEK, P.G., JOHNSON, R.L., (2006): Nano Today 1, 44-48. SALEH, N. ET AL., (2007): Environmental Engineering Science24, 45-57. JOHNSON, P.R. ET AL., (1996): Environmental Science & Technology 30, 3284-3293.
Laumann, S.; Micic, V.; Hofmann, T.
Advantages of low pH and limited oxygenation in arsenite removal from water by zero-valent iron.
The removal of toxic arsenic species from contaminated waters by zero-valent iron (ZVI) has drawn considerable attention in recent years. In this approach, arsenic ions are mainly removed by adsorption to the iron corrosion products. Reduction to zero-valent arsenic on the ZVI surface is possible in the absence of competing oxidants and can reduce arsenic mobility and sludge formation. However, associated removal rates are relatively low. In the current study, simultaneous high reduction and removal rates of arsenite (H3AsO3), the more toxic and mobile environmentally occurring arsenic species, was demonstrated by reacting it with ZVI under limited aeration and relatively low pH. 90% of the removed arsenic was attached to the ZVI particles and 60% of which was in the elemental state. Under the same non-acidic conditions, only 40-60% of the removed arsenic was attached to the ZVI with no change in arsenic oxidation state. Under anaerobic conditions, reduction occurred but total arsenic removal rate was significantly lower and ZVI demand was higher. The effective arsenite removal under acidic oxygen-limited conditions was explained by formation of Fe(II)-solid intermediate on the ZVI surface that provided high surface area and reducing power. PMID:23500792
Klas, Sivan; Kirk, Donald W
Recent studies of contaminant reduction by zero-valent iron metal (Fe0) have highlighted the role of iron oxides at the metal–water interface and the effect that sorption has at the oxide–water interface on contaminant reduction kinetics. The results s...
Coupling of zero valent iron and biobarriers for remediation of trichloroethylene in groundwater.
This study attempted to construct a three series barrier system to treat high concentrations of trichloroethylene (TCE; 500 mg/L) in synthetic groundwater. The system consisted of three reactive barriers using iron fillings as an iron-based barrier in the first column, sugarcane bagasse mixed with anaerobic sludge as an anaerobic barrier in the second column, and a biofilm coated on oxygen carbon inducer releasing material as an aerobic barrier in the third column. In order to evaluate the extent of removal of TCE and its metabolites in the aquifer down gradient of the barrier system, a fourth column filled with sand was applied. Residence time of the system was investigated by a bromide tracer test. The results showed that residence time in the column system of the control set and experimental set were 23.62 and 29.99 days, respectively. The efficiency of the three series barrier system in removing TCE was approximately 84% in which the removal efficiency of TCE by the iron filling barrier, anaerobic barrier and aerobic barrier were 42%, 16% and 25%, respectively, cis-Dichloroethylene (cis-DCE), vinyl chloride (VC), ethylene and chloride ions were observed as metabolites following TCE degradation. The presence of chloride ions in the effluent from the column system indicated the degradation of TCE. However, cis-DCE and VC were not fully degraded by the proposed barrier system which suggested that another remediation technology after the barrier treatment such as air sparging and adsorption by activated carbon should be conducted. PMID:21793396
Teerakun, Mullika; Reungsang, Alissara; Lin, Chien-Jung; Liao, Chih-Hsiang
Carbonate minerals in porous media decrease mobility of polyacrylic acid modified zero-valent iron nanoparticles used for groundwater remediation.
The limited transport of nanoscale zero-valent iron (nZVI) in porous media is a major obstacle to its widespread application for in situ groundwater remediation. Previous studies on nZVI transport have mainly been carried out in quartz porous media. The effect of carbonate minerals, which often predominate in aquifers, has not been evaluated to date. This study assessed the influence of the carbonate minerals in porous media on the transport of polyacrylic acid modified nZVI (PAA-nZVI). Increasing the proportion of carbonate sand in the porous media resulted in less transport of PAA-nZVI. Predicted travel distances were reduced to a few centimeters in pure carbonate sand compared to approximately 1.6 m in quartz sand. Transport modeling showed that the attachment efficiency and deposition rate coefficient increased linearly with increasing proportion of carbonate sand. PMID:23644276
Laumann, Susanne; Mici?, Vesna; Lowry, Gregory V; Hofmann, Thilo
Relevance study of bare and coated zero valent iron nanoparticles for lindane degradation from its by-product monitorization.
Zero-valent iron nanoparticles (NZVI) as well as polymer-stabilized nanoparticles were synthesized and used for lindane (?-hexachlorocyclohexane) degradation in aqueous solution. To study the effectiveness of the different coated nanoparticles, simple and rapid analytical methods have been developed to measure and to detect lindane and its by-products. For the monitorization of lindane degradation solid-phase extraction (SPE) was used, while volatile by-products formation measurement was carried out by headspace-solid phase microextraction (HS-SPME) followed by GC/MS. The SPE-GC/MS method provides low detection limits (0.2 ?g L(-1)), high recovery (above 95%) and it is a valuable tool for kinetic studies of the degradation process for each polymer used, while HS-SPME-GC/MS has proved to be an effective tool for the extraction and evaluation of volatile degradation by-products. PMID:23972910
San Román, I; Alonso, M L; Bartolomé, L; Galdames, A; Goiti, E; Ocejo, M; Moragues, M; Alonso, R M; Vilas, J L
Characterization of nanoscale zero valent iron modified by nonionic surfactant for trichloroethylene removal in the presence of humic acid: A research note
Trichloroethylene (TCE) is a common contaminant in water and groundwater, known as suspected carcinogens, and its presence in the environment is of significant concern. Nano-scale zero-valent iron (NZVI) has emerged as an excellent reduction catalyst due to fast degradation of chlorinated solvents. However aggregation of NZVI is a serious limitation. In this study, NZVI was coated with nonionic surfactant to
Young-Chul Lee; Chul-Woong Kim; Jae-Young Lee; Hyun-Jae Shin; Ji-Won Yang
The reaction of zero-valent iron (ZVI) with oxygen can lead to the formation of oxidants, which may be used to transform recalcitrant contaminants including non-polar organics and certain metals. Nanoparticulate iron might provide a practical mechanism of remediating oxygen-containing groundwater and contaminated soil. To gain insight into the reaction mechanism and to quantify the yield of oxidants, experiments were performed with model organic compounds in the presence of nanoparticulate zero-valent iron and oxygen. At pH values below 5, ZVI nanoparticles were oxidized within 30 minutes with a stoichiometry of approximately two Fe0 oxidized per O2 consumed. Using the oxidation of methanol and ethanol to formaldehyde and acetaldehyde, respectively, we found that less than 2% of the consumed oxygen was converted to reactive oxidants under acidic conditions. The yield of aldehydes increased with pH up to pH 7, with maximum oxidant yields of around 5% relative to the mass of ZVI added. The increase of aldehyde yield with pH was attributable to changes in the processes responsible for oxidant production. At pH values below 5, the corrosion of ZVI by oxygen produces hydrogen peroxide, which subsequently reacts with ferrous iron [Fe(II)] via the Fenton reaction. At higher pH values, the aldehydes are produced when Fe(II), the initial product of ZVI oxidation, reacts with oxygen. The decrease in oxidant yield at pH values above 7 may be attributable to precipitation of Fe(II). The oxidation of benzoic acid and 2-propanol to para-hydroxybenzoic acid and acetone, respectively, followed a very different trend compared to the primary alcohols. In both cases, the highest product yields (approximately 2% with respect to ZVI added) were observed at pH 3. Yields decreased with increasing pH, with no oxidized product detected at neutral pH. These results suggest that two different oxidants may be produced by the system: hydroxyl radical (OH-·) at acidic pH and a more selective oxidant such as the ferryl ion [Fe(IV)] at neutral pH. This provides insight into the type of compounds that may be oxidized using the zero-valent iron and oxygen system. The addition of certain compounds such as oxalate and polyoxometalate (POM) may improve contaminant remediation efficiencies by enhancing oxidant yields. The introduction of 1 mM oxalate improved the formaldehyde yield by approximately 20% at neutral pH. Oxalate accelerates the Fenton reaction and limits the passivation of the ZVI surface by increasing iron solubility. The presence of excess POM greatly enhanced the yield of formaldehyde, with maximum yields of 60 and 35% with respect to ZVI added at pH 2 and 7, respectively. The mechanism of POM enhancement is a function of solution pH. At acidic pH, POM acts an electron shuttle by directly transferring electrons from ZVI to oxygen to increase the hydrogen peroxide production. At neutral pH, POM may act by forming soluble iron-complexes and preventing the build-up of an iron oxide layer on the ZVI surface.
Keenan, C. R.; Lee, C.; Sedlak, D. L.
Comparisons of the reactivity, reusability and stability of four different zero-valent iron-based nanoparticles.
Our previous reports showed that nano zero-valent iron (nZVI), steel pickle liquor for the synthesis of nZVI (S-nZVI), nZVI immobilised in mesoporous silica microspheres (SiO2@FeOOH@Fe) and nano Ni/Fe bimetallic particles (Ni/Fe) have been proved to show good property for elimination of polybrominated diphenyl ethers (PBDEs). However, it is necessary to compare their reactivity, reusability and stability when applied to in situ remediation. In this study, the performances of different iron-based nanoparticles were compared through reusability, sedimentation and iron dissolution experiments. The SiO2@FeOOH@Fe and Ni/Fe nanoparticles were shown to have higher reusability and stability, as they could be reused more than seven times, and that the SiO2@FeOOH@Fe can effectively avoid leaching iron ions into the solution and causing secondary pollution in the reaction. This study may serve as a reference for PBDE remediation in the future. PMID:24582360
Xie, Yingying; Fang, Zhanqiang; Qiu, Xinhong; Tsang, Eric Pokeung; Liang, Bin
Application of Zero-Valent Iron Nanoparticles for the Removal of Aqueous Zinc Ions under Various Experimental Conditions
Application of zero-valent iron nanoparticles (nZVI) for Zn2+ removal and its mechanism were discussed. It demonstrated that the uptake of Zn2+ by nZVI was efficient. With the solids concentration of 1 g/L nZVI, more than 85% of Zn2+ could be removed within 2 h. The pH value and dissolved oxygen (DO) were the important factors of Zn2+ removal by nZVI. The DO enhanced the removal efficiency of Zn2+. Under the oxygen-contained condition, oxygen corrosion gave the nZVI surface a shell of iron (oxy)hydroxide, which could show high adsorption affinity. The removal efficiency of Zn2+ increased with the increasing of the pH. Acidic condition reduced the removal efficiency of Zn2+ by nZVI because the existing H+ inhibited the formation of iron (oxy)hydroxide. Adsorption and co-precipitation were the most likely mechanism of Zn2+ removal by nZVI. The FeOOH-shell could enhance the adsorption efficiency of nZVI. The removal efficiency and selectivity of nZVI particles for Zn2+ were higher than Cd2+. Furthermore, a continuous flow reactor for engineering application of nZVI was designed and exhibited high removal efficiency for Zn2+.
Liang, Wen; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei
Biodegradable surfactant stabilized nanoscale zero-valent iron for in situ treatment of vinyl chloride and 1,2-dichloroethane.
Nanoscale zero-valent iron (NZVI) stabilized with dispersants is a promising technology for the remediation of contaminated groundwater. In this study, we demonstrated the use of biodegradable surfactant stabilized NZVI slurry for successful treatment of vinyl chloride (VC) and 1,2-dichloroethane (1,2-DCA) in a contaminated site in Taiwan. The biodegradable surfactant stabilized NZVI was coated with palladium and synthesized on-site. From monitoring the iron concentration breakthrough and distribution, it was found that the stabilized NZVI is capable of transporting in the aquifer at the test plot (200 m(2)). VC was effectively degraded by NZVI while the 1,2-DCA degradation was relatively sluggish during the 3-month field test. Nevertheless, as 1,2-DCA is known to resist abiotic reduction by NZVI, the observation of 1,2-DCA degradation and hydrocarbon production suggested a bioremediation took place. ORP and pH results revealed that a reducing condition was achieved at the testing area facilitating the biodegradation of chlorinated organic hydrocarbons. The bioremediation may be attributed to the production of hydrogen gas as electron donor from the corrosion of NZVI in the presence of water or the added biodegradable surfactant serving as the carbon source as well as electron donor to stimulate microbial growth. PMID:22118849
Wei, Yu-Ting; Wu, Shian-chee; Yang, Shi-wei; Che, Choi-Hong; Lien, Hsing-Lung; Huang, De-Huang
Rapid and complete destruction of perchlorate in water and ion-exchange brine using stabilized zero-valent iron nanoparticles.
Perchlorate has emerged as a widespread contaminant in groundwater and surface water. Because of the unique chemistry of perchlorate, it has been challenging to destroy perchlorate. This study tested the feasibility of using a new class of stabilized zero-valent iron (ZVI) nanoparticles for complete transformation of perchlorate in water or ion-exchange brine. Batch kinetic tests showed that at an iron dosage of 1.8 g L(-1) and at moderately elevated temperatures (90-95 degrees C), approximately 90% of perchlorate in both fresh water and a simulated ion-exchange brine (NaCl=6% (w/w)) was destroyed within 7h. An activation energy (Ea) of 52.59+/-8.41 kJ mol(-1) was determined for the reaction. Kinetic tests suggested that Cl(VII) in perchlorate was rapidly reduced to chloride without accumulation of any intermediate products. Based on the surface-area-normalized rate constant k(SA), starch- and CMC-stabilized ZVI nanoparticles degraded perchlorate 1.8 and 3.3 times, respectively, faster than non-stabilized ZVI particles. Addition of a metal catalyst (Al, Cu, Co, Ni, Pd, or Re) did not show any reaction improvement. This technology provides an effective method for complete destruction of perchlorate in both contaminated water and brine. PMID:17597179
Xiong, Zhong; Zhao, Dongye; Pan, Gang
The application of zero-valent iron nanoparticles for the remediation of a uranium-contaminated waste effluent.
Zero-valent iron nanoparticles (INP) were investigated as a remediation strategy for a uranium-contaminated waste effluent from AWE, Aldermaston. Nanoparticles were introduced to the effluent, under both oxic and anoxic conditions, and allowed to react for a 28-d period during which the liquid and nanoparticle solids were periodically sampled. Analysis of the solution indicated that under both conditions U was removed to <1.5% of its initial concentration within 1h of introduction and remained at similar concentrations until approximately 48 h. A rapid release of Fe into solution was also recorded during this initial period; attributed to the limited partial dissolution of the INP. XPS analyses of the reacted nanoparticulate solids between 1 and 48 h showed an increased Fe(III):Fe(II) ratio, consistent with the detection of iron oxidation products (akaganeite and magnetite) by XRD and FIB. XPS analysis also recorded uranium on the recovered particulates indicating the chemical reduction of U(VI) to U(IV) within 1h. Following the initial retention period U-dissolution of U was recorded from 48 h, and attributed to reoxidation. The efficient uptake and retention of U on the INP for periods up to 48 h provide proof that INP may be effectively used for the remediation of complex U-contaminated effluents. PMID:20129731
Dickinson, Michelle; Scott, Thomas B
Simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewater by zero-valent iron.
The zero-valent iron (ZVI) wastewater treatment has been applied to simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewaters. The simultaneous removal occurs by the reactions performed due to the sequential transformation of ZVI under the acidic condition. Fortunately the solution pH of semiconductor acidic wastewaters is low which is effective for the sequential transformation of ZVI. Firstly the reduction of nitrate is taken place by electrons generated by the corrosion of ZVI under acidic conditions. Secondly the ferrous ion generated by the corrosion of ZVI reacts with hydrogen peroxide and generates ·OH radical (Fenton reaction). The Fenton reaction consists of the degradation of hydrogen peroxide and the generation of ferric ion. Finally phosphate precipitates out with iron ions. In the simultaneous removal process, 1.6 mM nitrate, 9.0 mM hydrogen peroxide and 1.0 mM phosphate were completely removed by ZVI within 100, 15 and 15 min, respectively. The synergy among the reactions for the removal of nitrate, hydrogen peroxide and phosphate was found. In the individual pollutant removal experiment, the removal of phosphate by ZVI was limited to 80% after 300 min. Its removal rate was considerably improved in the presence of hydrogen peroxide and the complete removal of phosphate was achieved after 15 min. PMID:24798898
Yoshino, Hiroyuki; Tokumura, Masahiro; Kawase, Yoshinori
Oxidation of Orange G by persulfate activated by Fe(II), Fe(III) and zero valent iron (ZVI).
Persulfate (PS) was employed in the oxidation of Orange G (OG), an azo dye commonly found in textile wastewaters. Activation of PS was conducted with iron to generate sulfate free radicals (SO4(-)) with high redox potential capable to oxidize most of the organics in water. Identification of oxidation intermediates was carried out by analyzing at different times organic by-products generated from treatment of a concentrate dye solution (11.6 mM) with 153 mM of PS and 20 mM of Fe(II) at 20 °C. Intermediate reaction products (mainly phenol (PH) and benzoquinone (BQ), and in less extent aniline, phenolic compounds and naphthalene type compounds with quinone groups) were identified by GC/MS and HPLC, and an oxidation pathway was proposed for the oxidation of OG with iron activated PS. The effect of iron valence (0, II and III) in the oxidation of an aqueous solution of OG (containing 0.1 mM) was studied in a 0.5 L batch reactor at 20 °C. Initial activator and PS concentrations employed were both 1 mM. Complete pollutant removal was achieved within the first 30 min when iron II or III were employed as activators. Quinone intermediates generated during pollutant oxidation may act as electron shuttles, allowing the reduction of Fe(III) into Fe(II) in the redox cycling of iron. Therefore, activation of PS by Fe(III) allowed complete OG removal. When zero valent iron (ZVI) was employed (particle diameter size 0.74 mm) the limiting step in SO4(-) generation was the surface reaction between ZVI and the oxidant yielding a lower oxidation rate of the dye. An increase in the oxidant dosage (0.2 mM OG, 2 mM Fe(III) and 6 mM PS) allowed complete pollutant and ecotoxicity removal, as well as mineralization close to 75%. PMID:24439838
Rodriguez, S; Vasquez, L; Costa, D; Romero, A; Santos, A
Treatment of phenol-containing wastewater by photoelectro-Fenton method using supported nanoscale zero-valent iron.
This study presents the degradation of phenol by the photoelectro-Fenton method using nano zero-valent iron (nZVI) immobilized in polyvinyl alcohol-alginate beads. The effect of nZVI loading, H(2)O(2) concentration, pH, and initial phenol concentration on phenol degradation and chemical oxygen demand reduction was studied. The scanning electron microscope images of the nZVI beads were used to analyze their morphology, and their diameters were in the range of 500-600 ?m. The concentration of nZVI in the beads was varied from 0.1 to 0.6 g/L. Fe(2+) leakage of 1 and 3 % was observed with 0.5 and 0.6 g/L of nZVI, respectively, and the observed beads' fracture frequency was 2 %, which confirmed the stability of the beads. The optimum operating conditions that arrived for better degradation were 0.5 g/L of nZVI, pH 6.2, and 400 mg H(2)O(2)/L. The treatment of effluent by this method increased the biodegradability index of the effluent, and the degradation data were found to follow pseudo first-order kinetics. PMID:22711016
Babuponnusami, Arjunan; Muthukumar, Karuppan
Synthesis and characterization of porous zero-valent iron nanoparticles for remediation of chromium-contaminated wastewater.
The physical and chemical properties of porous zero-valent iron nanoparticles (ZVINs) have highly been acknowledged in the decontamination of heavy metal containing wastes and groundwater. In the present work, the treatment of Cr-contaminant through adsorption onto the ZVINs has been studied. The morphology, crystal structure, and surface composition of Fe(O) nanoparticles were investigated by field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. X-ray absorption near edge structure (XANES) revealed that the Cr(VI) species reduce to Cr(III) while oxidizing the ZVINs to Fe2O3, Fe3O4 or FeO electrochemically. Furthermore, the nitrogen adsorption-desorption isotherm of the porous nanoparticles was similar to a type IV curve with an obvious mesopore-characteristic H3 hysteresis loop, whereas the sizes of mesopores were in the range of 30-50 nm. Experimentally, the efficiency for Cr(VI) removal in the range of 150-300 ppm was found to be > 99.9%. Remarkably, the reduction reaction was completed within 10 min in the absence of additional pH controls. This work also highlights the utility of X-ray absorption spectroscopy (XAS) coupled with conventional characterization methods to comprehensively study the speciation and possible reaction pathway in adsorption process. PMID:23763143
Lin, Kuen-Song; Dehvari, Khalilalrahman; Liu, Yeu-Jye; Kuo, Hua; Hsu, Pei-Ju
Background species effect on aqueous arsenic removal by nano zero-valent iron using fractional factorial design.
This study describes the removal of arsenic species in groundwater by nano zero-valent iron process, including As(III) and As(V). Since the background species may inhibit or promote arsenic removal. The influence of several common ions such as phosphate (PO4(3-)), bicarbonate (HCO3-)), sulfate (SO4(2-)), calcium (Ca2+), chloride (Cl-), and humic acid (HA) were selected to evaluate their effects on arsenic removal. In particular, a 2(6-2) fractional factorial design (FFD) was employed to identify major or interacting factors, which affect arsenic removal in a significant way. As a result of FFD evaluation, PO4(3-) and HA play the role of inhibiting arsenic removal, while Ca2+ was observed to play the promoting one. As for HCO3- and Cl-, the former one inhibits As(III) removal, whereas the later one enhances its removal; on the other hand, As(V) removal was affected only slightly in the presence of HCO3- or Cl-. Hence, it was suggested that the arsenic removal by the nanoiron process can be improved through pretreatment of PO4(3-) and HA. In addition, for the groundwater with high hardness, the nanoiron process can be an advantageous option because of enhancing characteristics of Ca2+. PMID:22245511
Tanboonchuy, Visanu; Grisdanurak, Nurak; Liao, Chih-Hsiang
Nitrate and ammonium ions removal from groundwater by a hybrid system of zero-valent iron combined with adsorbents.
Nitrate (NO(3)(-)) is a commonly found contaminant in groundwater and surface water. It has created a major water quality problem worldwide. The laboratory batch experiments were conducted to investigate the feasibility of HCl-treated zero-valent iron (Fe(0)) combined with different adsorbents as hybrid systems for simultaneous removal of nitrate (NO(3)(-)) and ammonium (NH(4)(+)) ions from aqueous solution. The maximum NO(3)(-) removal in combined Fe(0)-granular activated carbon (GAC), Fe(0)-filtralite and Fe(0)-sepiolite systems was 86, 96 and 99%, respectively, at 45 °C for 24 h reaction time. The NO(3)(-) removal rate increased with the increase in initial NO(3)(-) concentration. The NO(3)(-) removal efficiency by hybrid systems was in the order of sepiolite > filtralite > GAC. The NH(4)(+) produced during the denitrification process by Fe(0) was successfully removed by the adsorbents, with the removal efficiency in the order of GAC > sepiolite > filtralite. Results of the present study suggest that the use of a hybrid system could be a promising technology for achieving simultaneous removal of NO(3)(-) and NH(4)(+) ions from aqueous solution. PMID:22344042
Ji, Min-Kyu; Park, Won-Bae; Khan, Moonis Ali; Abou-Shanab, Reda A I; Kim, Yongje; Cho, Yunchul; Choi, Jaeyoung; Song, Hocheol; Jeon, Byong-Hun
Nonionic surfactant greatly enhances the reductive debromination of polybrominated diphenyl ethers by nanoscale zero-valent iron: Mechanism and kinetics.
Nanoscale zero-valent iron (nZVI) has been considered as an effective agent for reductive debromination of polybrominated diphenyl ethers (PBDEs). But the high lipophilicity of PBDEs will hinder their debromination owing to the inefficient contact of PBDEs with nZVI. In this study, different ionic forms of surfactants were investigated aiming to promote PBDE debromination, and the beneficial effects of surfactant were found to be: nonionic polyethylene glycol octylphenol ether (Triton X-100, TX)>cationic cetylpyridinium chloride (CPC)>anionic sodium dodecyl benzenesulfonate (SDDBS). Except for with SDDBS, the promotion effect for PBDE debromination was positively related to the surfactant concentrations until a critical micelle concentration (CMC). The debromination process of octa-BDE and its intermediates could be described as a consecutive reaction. The corresponding rate constants (k) for the debromination of parent octa-BDE (including nona- to hepta-BDEs), the intermediates hexa-, penta-, and tetra-BDEs are 1.24×10(-1)h(-1), 8.97×10(-2)h(-1), 6.50×10(-2)h(-1) and 2.37×10(-3)h(-1), respectively. PMID:25019577
Liang, Da-Wei; Yang, Yu-Han; Xu, Wei-Wei; Peng, Si-Kan; Lu, Shan-Fu; Xiang, Yan
Coupled effects of aging and weak magnetic fields on sequestration of selenite by zero-valent iron.
The sequestration of Se(IV) by zero-valent iron (ZVI) is strongly influenced by the coupled effects of aging ZVI and the presence of a weak magnetic field (WMF). ZVI aged at pH 6.0 with MES as buffer between 6 and 60 h gave nearly constant rates of Se(IV) removal with WMF but with rate constants that are 10- to 100-fold greater than without. XANES analysis showed that applying WMF changes the mechanism of Se(IV) removal by ZVI aged for 6-60 h from adsorption followed by reduction to direct reduction. The strong correlation between Se(IV) removal and Fe2+ release suggests direct reduction of Se(IV) to Se(0) by Fe0, in agreement with the XANES analysis. The numerical simulation of ZVI magnetization revealed that the WMF influence on Se(IV) sequestration is associated mainly with the ferromagnetism of ZVI and the paramagnetism of Fe2+. In the presence of the WMF, the Lorentz force gives rise to convection in the solution, which narrows the diffusion layer, and the field gradient force, which tends to move paramagnetic ions (esp. Fe2+) along the higher field gradient at the ZVI particle surface, thereby inducing nonuniform depassivation and eventually localized corrosion of the ZVI surface. PMID:24804570
Liang, Liping; Guan, Xiaohong; Shi, Zhong; Li, Jialing; Wu, Yinan; Tratnyek, Paul G
Evaluation of the effects of nanoscale zero-valent iron (nZVI) dispersants on intrinsic biodegradation of trichloroethylene (TCE).
In this study, the biodegradability of nanoscale zero-valent iron (nZVI) dispersants and their effects on the intrinsic biodegradation of trichloroethylene (TCE) were evaluated. Results of a microcosm study show that the biodegradability of three dispersants followed the sequence of: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A) > polyoxyethylene (20) sorbitan monolaurate (Tween 20) > polyacrylic acid (PAA) under aerobic conditions, and PV3A > Tween 20 > PAA under anaerobic conditions. Natural biodegradation of TCE was observed under both aerobic and anaerobic conditions. No significant effects were observed on the intrinsic biodegradation of TCE under aerobic conditions with the presence of the dispersants. The addition of PAA seemed to have a slightly adverse impact on anaerobic TCE biodegradation. Higher accumulation of the byproducts of anaerobic TCE biodegradation was detected with the addition of PV3A and Tween 20. The diversity of the microbial community was enhanced under aerobic conditions with the presence of more biodegradable PV3A and Tween 20. The results of this study indicate that it is necessary to select an appropriate dispersant for nZVI to prevent a residual of the dispersant in the subsurface. Additionally, the effects of the dispersant on TCE biodegradation and the accumulation of TCE biodegrading byproducts should also be considered. PMID:24901632
Chang, Y C; Huang, S C; Chen, K F
Effect of anions and humic acid on the performance of nanoscale zero-valent iron particles coated with polyacrylic acid.
Effects of anions (NO3(-), HCO3(-), Cl(-), SO4(2-)) and humic acid on the reactivity and core/shell chemistries of polyacrylic acid-coated nanoscale zero-valent iron (PAA-NZVI) and inorganically modified NZVI (INORG-NZVI) particles were investigated. The reactivity tests under various ion concentrations (0.2-30mN) revealed the existence of a favorable molar ratio of anion/NZVI that increased the reactivity of NZVI particles. The presence of a relatively small amount of humic acid (0.5mgL(-1)) substantially decreased the INORG-NZVI reactivity by 76%, whereas the reactivity of PAA-NZVI decreased only by 12%. The XRD and TEM results supported the role of the PAA coating of PAA-NZVI in impeding the oxidation of the Fe(0) core by groundwater solutes. This protective role provided by the organic coating also resulted in a 2.3-fold increase in the trichloroethylene (TCE) reduction capacity of PAA-NZVI compared to that of INORG-NZVI in the presence of anions/humic acid. Ethylene and ethane were simultaneously produced as the major reduction products of TCE in both NZVI systems, suggesting that a hydrodechlorination occurred without the aid of metallic catalysts. The PAA coating, originally designed to improve the mobility of NZVI, enhanced TCE degradation performances of NZVI in the presence of anions and humic acid. PMID:25065795
Kim, Hong-Seok; Ahn, Jun-Young; Kim, Cheolyong; Lee, Seockheon; Hwang, Inseong
Mobility enhancement of nanoscale zero-valent iron in carbonate porous media through co-injection of polyelectrolytes.
The mobility of nanoscale zero-valent iron (nZVI), which is used for in situ groundwater remediation, is affected by chemical and physical heterogeneities within aquifers. Carbonate minerals in porous aquifers and the presence of divalent cations reduce nZVI mobility. This study assesses the potential for enhancing the mobility of polyacrylic acid coated nZVI (PAA-nZVI) in such aquifers through the co-injection of polyelectrolytes (natural organic matter, humic acid, carboxymethyl cellulose, and lignin sulfonate). When applied at the same concentration, all of the polyelectrolytes produced similar enhancement of PAA-nZVI mobility in carbonate porous media. This increase in mobility was a result of increased repulsion between PAA-nZVI and the carbonate matrix. Lignin sulfonate, an environmentally friendly and inexpensive agent, was identified as the most suitable polyelectrolyte for field applications. The greatest increase in PAA-nZVI mobility was achieved with co-injection of lignin sulfonate at concentrations ?50 mg L(-1); at these concentrations the maximum PAA-nZVI travel distance in carbonate porous media was twice of that in the absence of lignin sulfonate. PMID:24361704
Laumann, Susanne; Mici?, Vesna; Hofmann, Thilo
Effects of nanoscale zero-valent iron particles on biological nitrogen and phosphorus removal and microorganisms in activated sludge.
The use of nanoscale zero-valent iron (NZVI) particles in environmental remediation and wastewater treatment has recently increased. The effects of NZVI on nitrogen and phosphorus removal were examined under continuous aerobic/anaerobic conditions by employing activated sludge. NZVI did not display any measurable effect on nitrogen removal at the concentration of 50mg/L and below. However, 200mg/L of NZVI inhibited NH4(+)-N removal. The addition of NZVI at 20mg/L and above significantly (p<0.05) improved the phosphorous removal. The microbial activities were inhibited upon exposure to NZVI according to the ATP and reactive oxygen species (ROS) results. In comparison to control, the ATP content decreased by around 13%, 31% and 43% at the NZVI doses of 20, 50, and 200mg/L, respectively, probably due to ROS production under NZVI exposure. Lactate dehydrogenase (LDH) release assay suggested that NZVI concentration of 200mg/L cast adverse effects on microorganisms. Interestingly, lower concentrations of NZVI (20 and 50mg/L) boosted the dehydrogenase activity; however, approximately 19% depression in dehydrogenase activity was detected at 200mg/L. The high throughput 16S rDNA pyrosequencing results indicated that uncultured bacterial genera Sinobacteraceae, Xanthomonadaceae, Alcaligenaceae and Propionivibrio were sensitive to NZVI particles. PMID:24121637
Wu, Donglei; Shen, Yanhong; Ding, Aqiang; Mahmood, Qaisar; Liu, Shuai; Tu, Qiaoping
Enhance the photocatalytic activity for the degradation of organic contaminants in water by incorporating TiO 2 with zero-valent iron
Titanium dioxide (TiO2) has become the most popular photocatalyst in treating persistent organic pollutants. The main disadvantage of TiO2 is the diminishing photocatalytic activity over time due to the electron–hole pair recombination. Many studies have aimed to prolong the photocatalytic life of TiO2. Among them, incorporation of zero-valent iron (ZVI) is one of the approaches. In this study, a novel
Wen-Pin Hsieh; Jill Ruhsing Pan; Chihping Huang; Yu-Chun Su; Ya-Ju Juang
Influences of humic acid, bicarbonate and calcium on Cr(VI) reductive removal by zero-valent iron.
The influences of various geochemical constituents, such as humic acid, HCO(3)(-), and Ca(2+), on Cr(VI) removal by zero-valent iron (Fe(0)) were investigated in a batch setting. The collective impacts of humic acid, HCO(3)(-), and Ca(2+) on the Cr(VI) reduction process by Fe(0) appeared to significantly differ from their individual impacts. Humic acid introduced a marginal influence on Fe(0) reactivity toward Cr(VI) reduction, whereas HCO(3)(-) greatly enhanced Cr(VI) removal by maintaining the solution pH near neutral. The Cr(VI) reduction rate constants (k(obs)) were increased by 37.8% and 78.3%, respectively, with 2 mM and 6 mM HCO(3)(-) in solutions where humic acid and Ca(2+) were absent. Singly present Ca(2+) did not show a significant impact to Cr(VI) reduction. However, probably due to the formation of passivating CaCO(3), further addition of Ca(2+) to HCO(3)(-) containing solutions resulted in a decrease of k(obs) compared to solutions containing HCO(3)(-) alone. Ca(2+) enhanced humic acid adsorption led to a minor decrease of Cr(VI) reduction rates. In Ca(2+)-free solutions, humic acid increased the amount of total dissolved iron to 25 mg/l due to the formation of soluble Fe-humate complexes and stably dispersed fine Fe (oxy)hydroxide colloids, which appeared to suppress iron precipitation. In contrast, the coexistence of humic acid and Ca(2+) significantly promoted the aggregation of Fe (oxy)hydroxides, with which humic acid co-aggregated and co-precipitated. These aggregates would progressively be deposited on Fe(0) surfaces and impose long-term impacts on the permeability of PRBs. PMID:19232679
Liu, Tongzhou; Rao, Pinhua; Lo, Irene M C
Degradation of trinitroglycerin (TNG) using zero-valent iron nanoparticles/nanosilica SBA-15 composite (ZVINs/SBA-15).
Trinitroglycerin (TNG) is an industrial chemical mostly known for its clinical use in treating angina and manufacturing dynamite. The wide manufacture and application of TNG has led to contamination of vast areas of soil and water. The present study describes degradation of TNG with zero-valent iron nanoparticles (ZVINs) in water either present alone or stabilized on nanostructured silica SBA-15 (Santa Barbara Amorphous No. 15). The BET surface areas of ZVINs/SBA-15 (275.1 m2 g(-1)), as determined by nitrogen adsorption-desorption isotherms, was much larger than the non-stabilized ZVINs (82.0 m2 g(-1)). X-ray diffraction (XRD) showed that iron in both ZVINs and ZVINs/SBA-15 was present mostly in the ?-Fe0 crystalline form considered responsible for TNG degradation. Transmission Electron Microscopy (TEM) showed that iron nanoparticles were well dispersed on the surface of the nanosilica support. Both ZVINs and ZVINs/SBA-15 degraded TNG (100%) in water to eventually produce glycerol and ammonium. The reaction followed pseudo-first-order kinetics and was faster with ZVINs/SBA-15 (k1 0.83 min(-1)) than with ZVINs (k1 0.228 min(-1)). The corresponding surface-area normalized rate constants, knorm, were 0.36 and 0.33 L h(-1) m(-2) for ZVINs/SBA-15 and ZVINs, respectively. The ZVINs/SBA-15 retained its original degradation efficiency of TNG after repeatedly reacting with fresh nitrate ester for five successive cycles. The rapid and efficient transformation of TNG with ZVINs/SBA-15, combined with excellent sustained reactivity, makes the nanometal an ideal choice for the clean up of water contaminated with TNG. PMID:20801482
Saad, Rabih; Thiboutot, Sonia; Ampleman, Guy; Dashan, Wang; Hawari, Jalal
Carbothermal synthesis of carbon-supported nanoscale zero-valent iron particles for the remediation of hexavalent chromium.
Nanoscale, zero-valent iron is a promising reagent for in situ reduction of a variety of subsurface contaminants, but its utility in full-scale remediation projects is limited by material costs. Iron nanoparticles (20-100 nm diameter) supported on carbon (C-Fe0) were synthesized by reacting iron salts, adsorbed or impregnated from aqueous solutions onto 80 m2/g carbon black, at 600-800 degrees C under Ar. Similar products were obtained by heating the reactants under air in a covered alumina crucible. X-ray powder diffraction patterns show that Fe3O4 particles are formed at 300-500 degrees C in the initial stage of the reaction and that these particles are reduced to a mixture of alpha- and gamma-Fe nanoparticles above 600 degrees C. When C-Fe0 was combined with carboxymethylcellulose in a 5:1 weight ratio in water, the resulting material had similar transport properties to previously optimized nanoiron/polyanion suspensions in water-saturated sand columns. At a 10:3 Fe/Cr mole ratio, C-Fe0 reduced a 10 ppm Cr(VI) solution to approximately 1 ppm within three days. The surface area normalized first-order Cr removal rate was 1.2 h(-1) m(-2) under these conditions. These results demonstrate that reactive nanoiron with good transport properties in water-saturated porous media can be made in a scalable process from inexpensive starting materials by carbothermal reduction. PMID:18505003
Hoch, Laura B; Mack, Elizabeth J; Hydutsky, Bianca W; Hershman, Jessica M; Skluzacek, Joanna M; Mallouk, Thomas E
Rapid treatment of water contamined with atrazine and parathion with zero-valent iron
The utility of fine-grained iron metal in the remediation of water contamined with Atrazine and Parathion was investigated. Batch procedures under water treatment conditions (ambient temperature and pH of ?7) indicated that these pesticides degrade rapidly in the presence of iron powder (40–60 mesh, 40 g\\/l). The decline in the concentration of pesticide was monitored by HPLC. Experiments with unbuffered
Antoine Ghauch; Jamil Rima; Charbel Amine; Michel Martin-Bouyer
Deployment of an innovative thermally enhanced soil mixing process augmented with zero-valent iron.
An innovative in-situ soil treatment process, referred to as soil mixing/thermally enhanced soil vapor extraction (SM/TESVE), was used to remediate the 317 Area of Argonne National Laboratory-East (i.e., Argonne), which is contaminated with volatile organic compounds (VOCs). Following the initial soil treatment, polishing was required to reduce residual concentrations of contaminants. A study of polishing methods was conducted. It determined that injecting metallic iron particles into the soil, in conjunction with soil mixing, would reduce residual VOC concentrations more effectively than the original conventional soil ventilation approach. After the effectiveness of iron injection was verified, it replaced the soil ventilation step. The modified process involved mixing the soil while hot air and steam were injected into it. Off-gases were captured in a hood over the treatment area. During this process, an iron slurry, consisting of up to 50% iron particles in water with guar gum added as a thickening agent, was injected and mixed into the soil by the mixing equipment. Approximately 6,246 m{sup 3} (8, 170 yd{sup 3}) of soil was treated during this project. Confirmatory samples were then collected. In these samples, VOC concentrations were usually reduced by more than 80%.
Lynch, P. L.
High Precision Measurements of 235U/238U Isotopic Fractionations Resulting From Uranium Reduction Induced by Zero Valent Iron
Uranium is a widespread natural and anthropogenic contaminant in surface and subsurface waters. Like several other inorganic contaminants, uranium is mobile under oxidizing conditions but may be immobilized by chemical reduction. U(VI) moves with groundwater as (UO2)2+ and as soluble complexes with carbonate, phosphate, and fluoride. In many groundwater systems, uranium undergoes chemical reduction to U(IV), which is insoluble and immobile. Therefore, understanding the extent of reduction is essential for predicting the mobility of uranium in groundwater. Mass dependent isotopic fractionations of redox sensitive contaminants frequently found in groundwater (including chromate, selenate, and nitrate) have proven exceptionally useful for estimating the rate and extent of reduction and immobilization. Until recently, however, analytical limitations have prevented these techniques from being applied to heavier redox sensitive elements, such as uranium. The advent of highly sensitive multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS) enables high precision measurements of previously undetected variations in many elements. Laboratory reduction experiments with zero valent iron (ZVI) were performed in a controlled environment to test the hypothesis that uranium isotopes, specifically 235U/238U, behave similarly to other redox sensitive contaminants and produce a mass dependent fractionation during the transformation between valence states. Because of the large abundance differences between 235U and 238U, initial experiments used U500, an enriched uranium standard with approximately equal parts 235U and 238U. Results suggest that the highly sensitive MC-ICP-MS distinguishes 235U/238Uvariations to approximately + 0.02per mil. Measured isotopic fractionations between the 235U/238U of the initial and final experimental solutions (~70% reduced) are approximately 1.1 per mil, and increase with decreasing concentration. Measured variations in 235U/238U suggest that uranium isotopic ratios could also prove to be valuable indicators of contaminant immobilization and paleoenvironmental conditions.
Rademacher, L.; Lundstrom, C.; Johnson, T.
Nanoscale zero-valent iron application for in situ reduction of hexavalent chromium and its effects on indigenous microorganism populations.
Because of its high toxicity and mobility, hexavalent chromium is considered to be a high priority pollutant. This study was performed to carry out a pilot-scale in-situ remediation test in the saturated zone of a historically Cr(VI)-contaminated site using commercially available nanoscale zero-valent iron (nZVI). The site was monitored before and after the nZVI application by means of microbial cultivation tests, phospholipid fatty acid analysis (PLFA) and toxicological tests with Vibrio fischeri. Injection of nZVI resulted in a rapid decrease in the Cr(VI) and total Cr concentrations in the groundwater without any substantial effect on its chemical properties. The ecotoxicological test with V. fischeri did not indicate any negative changes in the toxicity of the groundwater following the application of nZVI and no significant changes were observed in cultivable psychrophilic bacteria densities and PLFA concentrations in the groundwater samples during the course of the remediation test. However, PLFA of soil samples revealed that the application of nZVI significantly stimulated the growth of Gram-positive bacteria. Principle component analysis (PCA) was applied to the PLFA results for the soil samples from the site in order to explain how Cr(VI) reduction and the presence of Fe influence the indigenous populations. The PCA results clearly indicated a negative correlation between the Cr concentrations and the biota before the application of nZVI and a significant positive correlation between bacteria and the concentration of Fe after the application of nZVI. PMID:24369106
N?me?ek, Jan; Lhotský, Ond?ej; Cajthaml, Tomáš
PCE dissolution and simultaneous dechlorination by nanoscale zero-valent iron particles in a DNAPL source zone
While the capability of nanoscale zero-valent iron (NZVI) to dechlorinate organic compounds in aqueous solutions has been demonstrated, the ability of NZVI to remove dense non-aqueous phase liquid (DNAPL) from source zones under flow-through conditions similar to a field scale application has not yet been thoroughly investigated. To gain insight on simultaneous DNAPL dissolution and NZVI-mediated dechlorination reactions after direct placement of NZVI into a DNAPL source zone, a combined experimental and modeling study was performed. First, a DNAPL tetrachloroethene (PCE) source zone with emplaced NZVI was built inside a small custom-made flow cell and the effluent PCE and dechlorination byproducts were monitored over time. Second, a model for rate-limited DNAPL dissolution and NZVI-mediated dechlorination of PCE to its three main reaction byproducts with a possibility for partitioning of these byproducts back into the DNAPL was formulated. The coupled processes occurring in the flow cell were simulated and analyzed using a detailed three-dimensional numerical model. It was found that subsurface emplacement of NZVI did not markedly accelerate DNAPL dissolution or the DNAPL mass-depletion rate, when NZVI at a particle concentration of 10 g/L was directly emplaced in the DNAPL source zone. To react with NZVI the DNAPL PCE must first dissolve into the groundwater and the rate of dissolution controls the longevity of the DNAPL source. The modeling study further indicated that faster reacting particles would decrease aqueous contaminant concentrations but there is a limit to how much the mass removal rate can be increased by increasing the dechlorination reaction rate. To ensure reduction of aqueous contaminant concentrations, remediation of DNAPL contaminants with NZVI should include emplacement in a capture zone down-gradient of the DNAPL source.
Fagerlund, F.; Illangasekare, T. H.; Phenrat, T.; Kim, H.-J.; Lowry, G. V.
Polyelectrolyte multilayer-assisted immobilization of zero-valent iron nanoparticles onto polymer nanofibers for potential environmental applications.
We report a facile approach to synthesizing and immobilizing zero-valent iron nanoparticles (ZVI NPs) onto polyelectrolyte (PE) multilayer-assembled electrospun polymer nanofibers for potential environmental applications. In this approach, negatively charged cellulose acetate (CA) nanofibers fabricated by electrospinning were assembled with multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and polyacrylic acid (PAA) through electrostatic layer-by-layer assembly. The formed PAA/PDADMAC multilayers onto CA nanofibers were then used as a nanoreactor to complex Fe(II) ions through the binding with the free carboxyl groups of PAA for subsequent reductive formation of ZVI NPs. Combined scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetry analysis studies demonstrate that the ZVI NPs are successfully synthesized and uniformly distributed into the PE multilayers assembled onto the CA nanofibers. The produced hybrid nanofibrous mats containing ZVI NPs were found to exhibit superior capability to decolorize acid fuchsin, an organic dye in dyeing wastewater. We show that the loading capacity of ZVI NPs can be tuned by changing the number of PE layers and the cycles of binding/reduction process. Increasing the number of the binding/reduction cycles leads to a slight bigger size of the ZVI NPs, which is not beneficial for improving the reactivity of ZVI NPs. The present approach to synthesizing and immobilizing ZVI NPs onto polymer nanofibers opens a new avenue to fabricating various fiber-based composite materials with a high surface area to volume ratio for environmental, catalytic, and sensing applications. PMID:20356166
Xiao, Shili; Wu, Siqi; Shen, Mingwu; Guo, Rui; Huang, Qingguo; Wang, Shanyuan; Shi, Xiangyang
Transformation of chlorinated hydrocarbons using aquocobalamin or coenzyme F{sub 430} in combination with zero-valent iron
More effective methods are necessary for the remediation of soils, sediments, and ground waters contaminated with halogenated organic compounds. The authors objective was to determine the feasibility and utility of using a tetrapyrrole-Fe(0) mixture for reductive dehalogenation of synthetic organic contaminants. Aquocobalamin or coenzyme F{sub 430} was combined with Fe(0) in aqueous systems containing either a single chlorinated compound or mixtures of chlorinated compounds, and substrate disappearance was monitored using gas chromatography-mass spectrometry (GC-MS). Zero-valent iron effectively dehalogenated CCl{sub 4} at low to neutral pH values, while increases in CCl{sub 4} dehalogenation resulting from inclusion of tetrapyrrole catalysts along with Fe(0) occurred only at basic pH values. Rates of CCl{sub 4} disappearance increased with additional aquocobalamin, but reached a maximum and decreased at higher aquocobalamin concentrations. overall dehalogenation rates may thus be a function of Fe(0)'s limited reactive surface area. There was a trend for both tetrapyrrole catalysts to promote the disappearance of halogenated compounds in a mixed substrate containing 20 compounds. Studies with five individual substrates likewise showed trends for increased substrate removal with F{sub 430} beyond that for Fe(0) alone. This increase is most important for compounds such as 1,2-dichloroethane and 1,4-dichlorobenzene that are not readily dehalogenated by Fe(0). Chloride concentrations in the reaction mixtures indicated that reductive dehalogenation was the dominant process responsible for substrate disappearance. Use of a combination of aquocobalamin or coenzyme F{sub 430} and Fe(0) may effectively promote dehalogenation, thus producing fewer products and more complete dehalogenation of the target substrates than can be achieved using only one of the abiotic reductants alone.
Morra, M.J.; Borek, V.; Koolpe, J.
PCE dissolution and simultaneous dechlorination by nanoscale zero-valent iron particles in a DNAPL source zone.
While the capability of nanoscale zero-valent iron (NZVI) to dechlorinate organic compounds in aqueous solutions has been demonstrated, the ability of NZVI to remove dense non-aqueous phase liquid (DNAPL) from source zones under flow-through conditions similar to a field scale application has not yet been thoroughly investigated. To gain insight on simultaneous DNAPL dissolution and NZVI-mediated dechlorination reactions after direct placement of NZVI into a DNAPL source zone, a combined experimental and modeling study was performed. First, a DNAPL tetrachloroethene (PCE) source zone with emplaced NZVI was built inside a small custom-made flow cell and the effluent PCE and dechlorination byproducts were monitored over time. Second, a model for rate-limited DNAPL dissolution and NZVI-mediated dechlorination of PCE to its three main reaction byproducts with a possibility for partitioning of these byproducts back into the DNAPL was formulated. The coupled processes occurring in the flow cell were simulated and analyzed using a detailed three-dimensional numerical model. It was found that subsurface emplacement of NZVI did not markedly accelerate DNAPL dissolution or the DNAPL mass-depletion rate, when NZVI at a particle concentration of 10g/L was directly emplaced in the DNAPL source zone. To react with NZVI the DNAPL PCE must first dissolve into the groundwater and the rate of dissolution controls the longevity of the DNAPL source. The modeling study further indicated that faster reacting particles would decrease aqueous contaminant concentrations but there is a limit to how much the mass removal rate can be increased by increasing the dechlorination reaction rate. To ensure reduction of aqueous contaminant concentrations, remediation of DNAPL contaminants with NZVI should include emplacement in a capture zone down-gradient of the DNAPL source. PMID:22326687
Fagerlund, F; Illangasekare, T H; Phenrat, T; Kim, H-J; Lowry, G V
Reductive dechlorination of trichloroethylene by combining autotrophic hydrogen-bacteria and zero-valent iron particles
The objective of this study was to evaluate the dechlorination rate (from an initial concentration of 180?moll?1) and synergistic effect of combining commercial Fe0 and autotrophic hydrogen-bacteria in the presence of hydrogen, during TCE degradation process. In the batch test, the treatment using Fe0 in the presence of hydrogen (Fe0\\/H2), showed more effective dechlorination and less iron consumption than Fe0
Shang-Ming Wang; Szu-kung Tseng
Influence of riboflavin on nanoscale zero-valent iron reactivity during the degradation of carbon tetrachloride.
Experiments were conducted to investigate the effect of riboflavin on the reactivity of nanoscale zerovalent iron (NZVI) during three reaction cycles of carbon tetrachloride (CT) degradation. The degradation kinetics of CT by NZVI without riboflavin (0.556 ± 0.044 h(-1)) was 1.5 times higher than that with riboflavin (0.370 ± 0.012 h(-1)) in the first cycle. Riboflavin was rapidly reduced (65.0 ± 7.0 h(-1)) by NZVI during CT degradation, resulting in the slow degradation kinetics of CT in the first cycle due to competition for electrons from NZVI between riboflavin and CT. These results indicate that riboflavin is not effective as an electron shuttle for reduction of CT by NZVI. On the other hand, the degradation kinetics of CT by NZVI without riboflavin decreased to 0.122 ± 0.033 h(-1) in the third cycle, while that with riboflavin was significantly enhanced (0.663 ± 0.005 h(-1)). The results from X-ray analyses and transmission electron microscopy suggest that the decline in reactivity of NZVI without riboflavin in the third cycle resulted from continuous Fe(0) oxidation to iron oxides on the NZVI surface. In contrast, riboflavin enhanced the reactivity of NZVI by reductive dissolution of passive iron oxides on NZVI surface by reduced riboflavin. The experimental results suggest that riboflavin can play a pivotal role in the prolongation of NZVI reactivity in long-term in situ and ex situ applications of NZVI. PMID:24479987
Bae, Sungjun; Lee, Woojin
Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions
Calcium carbonate is a major secondary mineral precipitate that influences PRB reactivity and hydraulic performance. In this study, we conducted column experiments to investigate electrical signatures resulting from concurrent CaCO3 and iron oxides precipitation in two simulated PRB media. Solid phase analysis identified CaCO3 (calcite and aragonite) as a major mineral phase throughout the columns, with magnetite being another major phase present close to the influent. Electrical measurements revealed a consistent decrease in conductivity and polarization magnitude of both columns, suggesting that the electrically insulating CaCO3 dominates the electrical response despite the presence of both electrically conductive iron oxides and CaCO3 precipitates. SEM/EDX imaging suggests that the electrical properties result from the geometrical arrangement of the mineral phases. The CaCO3 forms an insulating film on ZVI/magnetite surfaces, which we assume restricts redox-driven transfer of electric charge between the pore electrolyte and ZVI particles, as well as across interconnected ZVI particles. As surface reactivity also depends on the ability of the surface to engage in redox reactions, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss.
Yuxin Wu; Roelof Versteeg; Lee Slater; Doug Labrecque
Diversity of Contaminant Reduction Reactions by Zero-Valent Iron: Role of the Reductate
The reactions of 8 model contaminants with 9 types of granular Fe(0) were studied in batch experiments using consistent experimental conditions. The model contaminants (herein referred to as reductates because they were reduced by the iron metal) included cations (Cu2+), anions (CrO42-; NO3-; and 5,5,7,7-indigotetrasulfonate), and neutral species (2-chloroacetophenone; 2,4,6-trinitrotoluene; carbon tetrachloride; and trichloroethene). The diversity of this range of reductates offers a uniquely broad perspective on the reactivity of Fe(0). Rate constants for disappearance of the reductates vary over as much as 4 orders of magnitude for particular reductates (due to differences in the 9 types of iron) but differences among the reductates were even larger, ranging over almost 7 orders of magnitude. Various ways of summarizing the data all suggest that relative reactivities with Fe(0) varies in the order: Cu2, I4S > 2CAP, TNT > CT, Cr6 > TCE > NO3. Although the reductate h as the largest effect on disappearance kinetics, more subtle differences in reactivity due to the type of Fe(0) suggests that removal of Cr6 and NO3 (the inorganic anions) involves adsorption to oxides on the Fe(0), whereas the disappearance kinetics of all other types of reductants is favored by reduction on comparatively oxide-free metal. Correlation analysis of the disappearance rate constants using descriptors of the reductates calculated by molecular modeling (energies of the lowest unoccupied molecular orbitals, LUMO, highest occupied molecular orbitals, HOMO, and HOMO-LUMO gaps) showed that reactivities generally increase with decreasing ELUMO and increasing EGAP (and, therefore, increasing chemical hardness h).
Miehr, R; Tratnyek, Paul G.; Bandstra, J; Scherer, Michelle; Alowitz, M; Bylaska, Eric J.
Reduction and immobilization of radionuclides and toxic metal ions using combined zero valent iron and anaerobic bacteria. 1998 annual progress report
'Previous research findings indicate that both zero valent iron and sulfate reducing bacteria (SRB) can yield significant decreases in Cr(VI) or U(VI) concentrations due to abiotic and microbial reduction, respectively. The major hypothesis associated with this research project is that a combined abiotic-biological system can synergistically combine both processes to maximize metal ion reduction in an engineered permeable reactive barrier. The overall goal of this project is to design a combined abiotic/microbial, reactive, permeable, in-situ barrier with sufficient reductive potential to prevent downgradient migration of toxic metal ions. The field-scale application of this technology would utilize anaerobic digester sludge, Fe(O) particles for supporting anaerobic biofilms, and suitable aquifer material for construction of the barrier. Successful completion of this goal requires testing of the two hypotheses listed above by evaluating: (1) the rates of abiotic metal ion reduction, and (2) the rates of microbial metal ion reduction in microbial and combined abiotic/microbial reduction systems under a range of environmental conditions. This report summarizes work after one and one-half years of a three year project. Abiotic studies: The thrust of the abiotic research conducted to date has been to determine the rates of Cr(VI) reduction in batch reactors and to evaluate the role of aquifer materials on those rates. Experiments have been conducted to determine the rates of reduction by Fe(II) and Fe(O). The parameters that have been evaluated are the effect of pH and the presence of sulfide and aquifer material.'
Weathers, L.
Treatment of 1,2-dibromo-3-chloropropane and nitrate-contaminated water with zero-valent iron or hydrogen\\/palladium catalysts
The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2\\/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compared. DBCP reacted with iron powder (100–200 mesh, 36 g\\/l) in HEPES-buffered water (pH = 7.0) with a t12 of 2.5 min and in different groundwaters (pH = 8.2–8.7) with a
Darsa P. Siantar; Cindy G. Schreier; Chi-Su Chou; Martin Reinhard
Environmental benefits and risks of zero-valent iron nanoparticles (nZVI): risk mitigation or trade-off?
The use of nanoscaled particles in environmental remediation is gaining increasing amounts of attention in recent years, including the use of zero-valent iron nanoparticles (nZVI) for soil and groundwater remediation. The main advantages of its use include high degrees of reactivity towards a wide range of contaminants, enhanced mobility of the often coated particles, and its cost-effective in situ applications. Numerous studies have shown that compared to larger sized iron particles nZVI may have some superior properties, due to high surface areas and small sizes associated with nanoscale dimensions. While the use and further development of nZVI is understandably heralded as an environmentally-beneficial technology, the potentials risks of introducing these nanoparticles into the environment also needs to be considered. To date most research has focused on the potential benefits of nZVI and very little research has investigated its potential health and environmental risks. Nonetheless, some recent studies have documented adverse effects from its exposure including the generation of reactive oxygen species (ROS), oxidative stress, bactericidal effects, DNA damage, and inflammatory responses. Moreover, field site injections often involve the use of large quantities of nZVI (10-50 g/L) which may be directly injected into groundwater flow. Combined with the pursuit of designing more mobile and reactive particles, this may potentially lead to risks related to environmental exposures of substantial concentrations. In this study, we provide a brief synopsis of the expected environmental benefits and potential risks of nZVI, particularly focusing on its environmental fate and behavior and potential role as contaminant carrier. These are some areas of primary concern for risk assessors. Furthermore, we estimate and compare the span between probable environmental concentrations from its use in the field and concentrations which have been shown to cause adverse effects in laboratory settings. This is in light of the challenges that quantitative risk assessments face for nZVI and other nanoparticles, in part due to extensive and fundamental uncertainties. These data may provide a starting point to more thoroughly investigate the potential risks of nZVI and ultimately help scientists, engineers, and decision makers make better informed decisions regarding the use of nZVI for environmental remediation.
Grieger, K.; Fjordbøge, A.; Hartmann, N.; Eriksson, E.; Baun, A.
Effects of zero-valent iron (Fe 0) and temperature on the transformation of DDT and its metabolites in lake sediment
Zero-valent iron improves the transformation of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and its metabolites in aged and highly contaminated lake sediment under biotic conditions. The addition of Fe0 has a strong effect on transformation rates at 22°C and 9°C, the most enhanced degradation being obtained for DDT and DDOH [2,2-bis(p-chlorophenyl)ethanol]. At 22°C and 10 weeks' incubation, the DDT concentration is reduced from 2.75?molg?1
Trine Eggen; Andrzej Majcherczyk
Mechanism of 5-amino-2-formylbenzene sulfonic acid formation during reduction of 4,4?-dinitrostilbene-2,2?-disulfonic acid by Zero-Valent Iron
5-Amino-2-formylbenzene sulfonic acid (ABAS) as a by-product during reduction of 4,4?-dinitrostilbene-2,2?-disulfonic acid (DNS) by Zero-Valent Iron has been detected. Experiments show that the pH and temperature are the most important factors controlling the formation of ABAS. In addition, diluted solution of DNS (<0.001mol\\/L) favors the formation of ABAS other than 4,4?-diaminostilbene-2,2?-disulfonic acid (DSD). Competitive oxidative reactions in dark with the
Xiaobin Fan; Fengbao Zhang; Guoliang Zhang; Junxia Du
Iron-mediated oxidation of arsenic(III) by oxygen and hydrogen peroxide: Dispersed versus resin-supported zero-valent iron.
The goal of this study is to assess the differences in As(III) removal kinetics and mechanisms between dispersed zero-valent iron (d-ZVI) and resin-supported zero-valent iron (D201-ZVI) in the presence of dissolved oxygen and hydrogen peroxide. Experimental results show that As(III) could be removed by all the studied systems (d-ZVI/O2, d-ZVI/H2O2, D201-ZVI/O2, D201-ZVI/H2O2). The d-ZVI/H2O2 system was more efficient than D201-ZVI/H2O2 for the oxidation of As(III). Similar trends were observed in O2 system for both solids. The kinetic behaviors as well as the influence of a hydroxyl radical scavenger (2-propanol) on the oxidation of As(III) at different pH suggest that the oxidation of As(III) in the d-ZVI/O2 and d-ZVI/H2O2 systems occurred mainly through Fenton-like reactions. The oxidation of As(III) in the D201-ZVI/O2 and D201-ZVI/H2O2 systems might be expected as follows: As(III) was firstly adsorbed onto the surface of the D201-ZVI, and then oxidation may proceed mainly through a non-Fenton mechanism that directly converts H2O2 into O2 and H2O. In addition, certain iron oxides in the D201-ZVI could also serve as oxidants for As(III) oxidation. The significant differences between the dispersed and supported ZVIs suggest that the supporting matrix interfered in the removal process, which deserves a further investigation. PMID:24910051
Du, Qiong; Zhou, Lixia; Zhang, Shujuan; Pan, Bingcai; Lv, Lu; Zhang, Weiming; Zhang, Quanxing
Simulating the reactive transport of organic solutes and zero valent iron nano particles in 1-D column experiments
This research investigates the reactive transport of nano Zero Valent Iron (nZVI) particles and organic solutes in a two fluid phase system. A hybrid model for the simultaneous simulation of reactive transport of ZVI particles and solutes is presented. This simulator couples a Lagrangian Random Walk-based Particle Tracking (RWPT) method for ZVI transport with a conventional Eulerian Finite Differencing (FD) scheme for the reactive transport of solutes. The RWPT module accounts for particle deposition using two stochastic particle capture methods. The first method is consistent with the Classic Filtration Theory for irreversible interception of nano-particles by soil grains, while the second method is based on the assumption of a maximum collector capacity. In the conceptual model, the pore space may contain two fluid phases, the aqueous phase and NAPL. Rate limited mass transfer between the aqueous-NAPL phases is incorporated using a linear driving force expression, while a local equilibrium assumption is assumed for aqueous-solid phase mass transfer. Unlike many particle transport modeling approaches that treat particles as a component of the aqueous phase, nZVI particles are treated here as a separate solid phase. This enables the simulator to track iron particles and their reactive content. nZVI reactivity is modeled separately for each individual particle using 1st-order kinetics with respect to the iron content of the particle. The iron oxidation reaction rate is considered to be a function of concentrations of organic reactants which are linearly interpolated at the location of individual particles from the solute concentrations at the two contiguous nodes. The computed corrosion of nZVI particles contained within each numerical element is then used to estimate the lumped consumption/production rates of reactant/product solutes at the node locations. These rates are then incorporated into the advective-dispersive-reactive transport (ADR) expression as a source/sink term. The utility of simulator is demonstrated by modeling experimental results obtained from a series of nZVI column studies. In the first phase of these experiments, nZVI particles were introduced to ~15cm long water-saturated sand columns containing a uniform distribution of residual tetrachloroethene (PCE) and the nZVI distribution profile was monitored over time. Preliminary modeling results indicate that classical filtration theory fails to describe RNIP transport in the column experiments, while the RWPT model is able to capture the particle deposition profile within the column. In the second phase of the column studies, water was introduced into sand columns containing nZVI and residual PCE. Column effluent samples were analyzed for PCE, TCE, and ethene. Model predictions of PCE transformation, based upon batch measured rates, are compared with the observed consumption rates of ZVI under these column experimental conditions.
Taghavy, A.; Costanza, J.; Pennell, K. D.; Abriola, L.
Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell: reaction progress modeling.
Three treatment cells were operated at a site near Durango, CO. One treatment cell operated for more than 3 years. The treatment cells were used for passive removal of contamination from groundwater at a uranium mill tailings repository site. Zero-valent iron [Fe(0)] that had been powdered, bound with aluminosilicate and molded into plates was used as a reactive material in one treatment cell. The others used granular Fe(0) and steel wool. The treatment cells significantly reduced concentrations of As, Mn, Mo, Se, U, V and Zn in groundwater that flowed through it. Zero-valent iron [Fe(0)], magnetite (Fe3O4), calcite (CaCO3), goethite (FeOOH) and mixtures of contaminant-bearing phases were identified in the solid fraction of one treatment cell. A reaction progress approach was used to model chemical evolution of water chemistry as it reacted with the Fe(0). Precipitation of calcite, ferrous hydroxide [Fe(OH)2] and ferrous sulfide (FeS) were used to simulate observed changes in major-ion aqueous chemistry. The amount of reaction progress differed for each treatment cell. Changes in contaminant concentrations were consistent with precipitation of reduced oxides (UO2, V2O3), sulfides (As2S3, ZnS), iron minerals (FeSe2, FeMoO4) and carbonate (MnCO3). Formation of a free gas phase and precipitation of minerals contributed to loss of hydraulic conductivity in one treatment cell. PMID:12076025
Morrison, Stan J; Metzler, Donald R; Dwyer, Brian P
Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell: reaction progress modeling
Three treatment cells were operated at a site near Durango, CO. One treatment cell operated for more than 3 years. The treatment cells were used for passive removal of contamination from groundwater at a uranium mill tailings repository site. Zero-valent iron [Fe(0)] that had been powdered, bound with aluminosilicate and molded into plates was used as a reactive material in one treatment cell. The others used granular Fe(0) and steel wool. The treatment cells significantly reduced concentrations of As, Mn, Mo, Se, U, V and Zn in groundwater that flowed through it. Zero-valent iron [Fe(0)], magnetite (Fe 3O 4), calcite (CaCO 3), goethite (FeOOH) and mixtures of contaminant-bearing phases were identified in the solid fraction of one treatment cell. A reaction progress approach was used to model chemical evolution of water chemistry as it reacted with the Fe(0). Precipitation of calcite, ferrous hydroxide [Fe(OH) 2] and ferrous sulfide (FeS) were used to simulate observed changes in major-ion aqueous chemistry. The amount of reaction progress differed for each treatment cell. Changes in contaminant concentrations were consistent with precipitation of reduced oxides (UO 2, V 2O 3), sulfides (As 2S 3, ZnS), iron minerals (FeSe 2, FeMoO 4) and carbonate (MnCO 3). Formation of a free gas phase and precipitation of minerals contributed to loss of hydraulic conductivity in one treatment cell.
Morrison, Stan J.; Metzler, Donald R.; Dwyer, Brian P.
Carboxymethyl Cellulose Stabilized Nano-scale Zero Valent Iron Transport in Porous Media: An Experimental and Modeling Study
An experimental and modeling study is being conducted to evaluate carboxymethyl cellulose (CMC) stabilized nano-scale zero valent iron (nZVI) transport in porous media. A two-dimensional water-saturated glass-walled sandbox (55 cm x 45 cm x 1.3 cm in size) is being used for the study. The sandbox was packed uniformly with silica sand (600 ?m to 425 ?m grain diameter) under water-saturated conditions. From a series of hydraulic tests permeability of the system was calculated to be 1.0 x 10-12 m2. The transport tests are being conducted at pore-water velocities of 3, 5, and 10 m.d-1 to identify any shear-thinning effects associated with the CMC (MW = 90,000) solution, and effects of velocity on nZVI attachment to the porous media. A set of transport tests is being carried out using LissamineTM Green B (LGB) dye and CMC mixtures to characterize the CMC transport without nZVI. The transport tests are being conducted at various CMC concentrations ranging from 0.2% to 0.8% (w/v) to determine the effect of CMC concentration on nZVI transport under flowing conditions. For the CMC stabilized nZVI transport tests, nZVI is synthesized freshly in CMC solution before each experiment using sodium borohydride and ferrous sulfate. The synthesized nZVI concentrations range from 0.1 to 2.5 g.L-1. While higher nZVI concentration is desired for higher contaminant degradation, the higher nZVI concentration may cause greater aggregation and attachment to the porous media limiting the delivery distance for nZVI. In each transport experiment, the LGB-CMC solution or nZVI-CMC solution is injected into the sandbox as a pulse of 0.25 pore volume (PV). For LGB, the mass recovery was calculated to be ~ 96.5% indicating non-reactive transport in silica sand. The preliminary results also show that increased concentration of CMC (from 0.2% to 0.4 %) causes higher pressure drop across the sandbox, indicating that use of high CMC concentrations will limit injection rates with a corresponding effect on velocity and nZVI attachment. The transport experiments are being modeled using a two-dimensional multiphase flow and transport model. The sandbox is being discretized into 55 by 45 grid blocks (1 cm x 1 cm x 1.3 cm in size). LGB and CMC are modeled as soluble components, while nZVI is being considered as a colloid. In case of nZVI transport, attachment coefficients are being fitted to match the experimental breakthrough curves. The estimated attachment coefficients can be used to predict the CMC stabilized nZVI transport in field scale applications.
Mondal, P.; Rrokaj, E.; Sleep, B. E.
Injection of polyelectrolytes enhances mobility of zero-valent iron nanoparticles in carbonate-rich porous media
The application of nanoscale zero-valent iron (nZVI) for in situ groundwater remediation has received increased attention as a beneficial and novel remediation technique. A precondition for effective nZVI field applications is its delivery to the contaminated source zones. This has proved to be difficult due to the limited mobility of nZVI, which remains one major obstacle to widespread utilization of this remediation approach (O'CAROLL ET AL., 2012). One important factor that controls mobility of nZVI is physical and chemical heterogeneity within the subsurface, such as mineralogical variations (KIM ET AL., 2012). In our previous study we showed that the nZVI transport in carbonate-rich porous media is significantly reduced compared to that in quartz porous media (LAUMANN ET AL., 2012). This is caused by favorable nZVI deposition onto carbonate sand and is attributed to the less negative surface charge of carbonate compared to that of quartz sand under the range of water chemical conditions typically encountered in aquifers. New strategies are therefore required to improve nZVI mobility in carbonate-rich porous media. One approach can be the injection of polyelectrolytes in the subsurface, which are expected to adsorb onto aquifer grains and provide greater repulsion between nZVI and the porous media. In this study the effect of co-injected polyelectrolytes on the transport of polyacrylic acid (PAA) coated nZVI in two model porous media, quartz and carbonate sands was evaluated. Column experiments were carried out aiming to evaluate mobility of PAA-nZVI co-injected with four polyelectrolytes, including natural organic matter (NOM), humic acid, carboxymethyl cellulose (CMC), and lignin sulfonate. The results demonstrated that the co-injection of the chosen polyelectrolytes does not influence mobility of PAA-nZVI in quartz sand; the breakthrough with co-injected polyelectrolytes was similar to that of the pure PAA-nZVI dispersion. This observation can be explained by the strong negative surface charge of the quartz sand, which was apparently not changed in the presence of polyelectrolytes. Conversely, the co-injected polyelectrolytes affected the breakthrough in carbonate sand, increasing nZVI mobility for approximately 15%. This can be explained by the attachment of the polyelectrolytes to the less negatively charged carbonate sand, which then promoted the PAA-nZVI mobility. Even though there are structural differences among the polyelectrolytes applied in this study, our results showed no significant variations in the PAA-nZVI mobility when these polyelectrolytes are present at concentration of 50 mg L-1. Lignin sulfonate was furthermore selected to investigate the effect of different polyelectrolyte concentrations (0, 10, 25, 50, 250, and 500 mg L-1) on the PAA-nZVI mobility. The results showed that higher lignin sulfonate concentrations (250 and 500 mg L-1) do not affect the transport of PAA-nZVI in quartz sand. In carbonate sand, on contrary, increasing mobility due to co-injected lignin sulfonate was observed at concentrations above 25 mg L-1, having the highest value with 500 mg L-1 co-injected with the PAA-nZVI dispersion. Overall, the results demonstrated that lignin sulfonate adsorption onto the carbonate sand reduce PAA-nZVI deposition onto aquifer grains and promote its mobility, the effect which is more pronounced at higher polyelectrolyte concentrations co-injected with the PAA-nZVI dispersion. The project is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW). Management by Kommunalkredit Public Consulting GmbH. Literature O'CAROLL, D. ET AL., (2012): Advances in Water Resources, in press. KIM, H.-J. ET AL., (2012): Journal of Colloid and Interface Science 370, 1-10. LAUMANN, S. ET AL., (2012): Environmental Pollution, submitted.
Laumann, Susanne; Mici?, Vesna; Schmid, Doris; Hofmann, Thilo
Application of ultrasound to enhance the zero-valent iron-initiated abiotic degradation of halogenated aliphatic compounds
Permeable iron barriers, while effective as a near-passive in situ remediation technology for halogenated organic solvents, are susceptible to the loss of reactivity over time, most probably due to a build up of corrosion products or other precipitates on the iron surface. If such material can be removed, a barrier's lifetime can be significantly extended. This proof-of-concept project employed ultrasonic
Nancy Elaine Ruiz
Abstract The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compa...
Effects of hardness and alkalinity on the removal of arsenic(V) from humic acid-deficient and humic acid-rich groundwater by zero-valent iron.
The effects of hardness (Ca(2+)) and alkalinity (HCO(3)(-)) on arsenic(V) removal from humic acid (HA)-deficient and HA-rich groundwater by zero-valent iron (Fe(0)) were investigated using batch experiments. Arsenic, in general, is removed from groundwater possibly by adsorption and co-precipitation with the iron corrosion products. However, in the co-presence of HCO(3)(-) and Ca(2+), the removal rate of arsenic increased with increasing concentrations of either Ca(2+) or HCO(3)(-). It was observed that the removal of arsenic was significantly enhanced by the formation of CaCO(3) as a nucleation seed for the growth of large iron (hydr)oxide particles. In the co-existence of Ca(2+), HCO(3)(-) and HA, the presence of HA diminished the positive role of Ca(2+) due to the formation of Fe-humate complexes in solution and delaying of the formation of CaCO(3). As a result, the formation of the large iron (hydr)oxide particles was inhibited in the earlier stage which, in turn, affected the removal of arsenic. However, after the formation of CaCO(3) and the subsequent growth of such particles, the presence of large iron (hydr)oxide particles resulted in the rapid removing of arsenic and Fe-humate by adsorption and/or co-precipitation. PMID:19580986
Mak, Mark S H; Rao, Pinhua; Lo, Irene M C
[Effects of pH value on the adsorption and degradation of 2, 4-DCP by nanoscale zero-valent iron].
To evaluate the effect of pH on the degradation of 2,4-DCP by zero-valent iron nanoparticles (with the particle size of 30-40 nm in diameter) samples were taken for TEM, SEM-EDX, and ICP-OES analysis and investigated on the particle morphology changes and 2,4-DCP removal under different pH conditions. It is shown that iron nanoparticles agglomerate from individual particles and tiny clusters into massive aggregate assemblies with their surfaces oxidized and coated by the needle-like rotten iron oxide products (FeOOH) in the degradation process, which will block up a further reaction of 2,4-DCP dechlorination, while the low pH value condition in acidic system can effectively suppress particles aggregation and the surface oxidation, although iron loss in the solid phase is somehow inevitable. Large quantity of Fe2+ ions soaked out from iron nanoparticles significantly promote 2,4-DCP removal by reduction, and the solution pH tends to go up in the reaction process. Acidic conditions facilitate 2,4-DCP dechlorination, and the removal efficiency became higher with the pH reduced, in which 90% of 2,4-DCP removal is reached in 24 h under the pH value of 3. PMID:22452195
Feng, Li; Ge, Xiao-Peng; Wang, Dong-Sheng; Tang, Hong-Xiao
Enhanced degradation of ortho-nitrochlorobenzene by the combined system of zero-valent iron reduction and persulfate oxidation in soils.
ortho-Nitrochlorobenzene (o-NCB) in soil poses significant health risks to human because of its persistence and high toxicity. The removal of o-NCB by both zero-valent iron (ZVI) and chemical oxidation (persulfate) was investigated by batch experiments. The o-NCB removal rate increases significantly from 15.1 to 97.3 % with an increase of iron dosage from 0.1 to 1.0 mmol g(-1). The o-NCB removal rate increases with the decrease of the initial solution pH, and a removal efficiency of 90.3 % is obtained at an initial pH value of 6.8 in this combined system. It is found that temperature and soil moisture could also increase the o-NCB removal rate. The o-NCB degradation rate increases from 83.9 to 96.2 % and from 41.5 to 82.4 % with an increase of temperature (15 to 35 °C) and soil moisture (0.25 to 1.50 mL g(-1)), respectively. Compared to the persulfate oxidation system and ZVI system, the persulfate-iron system shows high o-NCB removal capacity. o-NCB removal rates of 41.5 and 62.4 % are obtained in both the persulfate oxidation system and the ZVI system, while the removal rate of o-NCB is 90.3 % in the persulfate-iron system. PMID:24385185
Xu, Hai-bo; Zhao, Dao-yuan; Li, Yu-jiao; Liu, Pei-ya; Dong, Chang-xun
Effects of humic acid on arsenic(V) removal by zero-valent iron from groundwater with special references to corrosion products analyses.
The effects of humic acid (HA) on As(V) removal by zero-valent iron (Fe(0)) from groundwater, associated with corrosion products analyses, were investigated using batch experiments. It was found that arsenic was rapidly removed from groundwater possibly due to its adsorption and co-precipitation with the corrosion products of Fe(0). The removal rate of arsenic by Fe(0) was inhibited in the presence of HA probably because of the formation of soluble Fe-humate in groundwater which hindered the production of iron precipitates. A longer reaction time was then required for arsenic removal. Such an influence of HA on arsenic removal increased with increasing HA concentration from 5 to 25mgL(-1). The binding capacity of HA for dissolved Fe was estimated to be about 0.75mg Femg(-1) HA. When the complexation of HA with dissolved Fe was saturated, further corrosion of Fe(0) would produce precipitates, which significantly accelerated the removal of arsenic from groundwater via adsorption and co-precipitation with the corrosion products. Iron (hydr)oxides such as maghemite, lepidocrocite, and magnetite were characterized by XRD analyses as the corrosion products, while As(V) was found on the surface of these corrosion products as detected by fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. PMID:19157491
Rao, Pinhua; Mak, Mark S H; Liu, Tongzhou; Lai, Keith C K; Lo, Irene M C
Preparation of stabilized nano zero-valent iron particles via a rheological phase reaction method and their use in dye decolourization.
In this study, sodium carboxymethyl cellulose (NaCMC)-stabilized nano zero-valent iron (C-nZVI) was synthesized using a rheological phase reaction method. The orthogonal method was used to evaluate the factors influencing C-nZVI properties and this showed that the reaction time, solid-liquid ratio (w/v), grinding time and NaCMC concentration were all important factors. Characterization with scanning electron microscopy validated the hypothesis that the introduction of CMC led to a decrease in aggregation of iron nanoparticles. X-ray diffraction confirmed the existence of Fe(0) and the strong antioxidant activity of the iron particles. Batch decolourization experiments exhibited that solution pH, C-nZVI dosage and reaction time have significant effects on dye decolourization. A high decolourization efficiency (94.5%) was obtained within 30 min for 100 mg/L of reactive blue-19 at the optimal pH value of 5 and C-nZVI loading of 6 g/L at room temperature. The decolourization rates followed modified pseudo-first-order kinetic equations with respect to dye concentration. The observed removal rate constant was 0.0447 min(-1) for the C-nZVI loading of 6 g/L. PMID:23530358
Cheng, Yue; Lu, Mang; Jiao, Chuang; Liu, Hai-Jiang
Phenol removal using zero-valent iron powder in the presence of dissolved oxygen: roles of decomposition by the Fenton reaction and adsorption/precipitation.
The mechanism for removal of phenol by zero-valent iron (ZVI) was quantitatively evaluated in the presence of dissolved oxygen by varying the pH from 2 to 8.1 (natural). The measurement of OH radical concentration suggests that the removal of phenol by ZVI was occurred due to the decomposition by the Fenton reaction besides the adsorption/precipitation to the iron surface. From the measurements of dissolved organic carbon (DOC) in the filtrate with the 0.45 ?m syringe filter and the solution obtained from acidification of suspended precipitates, the roles of decomposition by the Fenton reaction and adsorption/precipitation were separately evaluated. At solution pH 3, 91% of phenol removal was achieved and 24% of TOC (total organic carbon) decreased. The contribution of the Fenton reaction was found to be 77% of overall TOC reduction. When the pH values were 4 and 5, the overall TOC removal was found to be mainly due to the adsorption/precipitation. At pH 2 and 8.1, the reduction of TOC was very small. The pH and dissolved oxygen significantly affected the dissolution of iron and the production of OH radicals and changed the roles of phenol removal by the Fenton reaction and adsorption/precipitation. PMID:22119308
Shimizu, Ayana; Tokumura, Masahiro; Nakajima, Koshiro; Kawase, Yoshinori
Environmental benefits and risks of zero-valent iron nanoparticles (nZVI) for in situ remediation: Risk mitigation or trade-off?
The use of nanoscaled zero-valent iron particles (nZVI) to remediate contaminated soil and groundwater has received increasing amounts of attention within the last decade, primarily due to its potential for broader application, higher reactivity, and cost-effectiveness compared to conventional zero-valent iron applications and other in situ methods. However, the potential environmental risks of nZVI in in situ field scale applications are largely unknown at the present and traditional environmental risk assessment approaches are not yet able to be completed. Therefore, it may not yet be fully clear how to consider the environmental benefits and risks of nZVI for in situ applications. This analysis therefore addresses the challenges of comprehensively considering and weighing the expected environmental benefits and potential risks of this emerging environmentally-beneficial nanotechnology, particularly relevant for environmental engineers, scientists, and decision makers. We find that most of the benefits of using nZVI are based on near-term considerations, and large data gaps currently exist within almost all aspects of environmental exposure and effect assessments. We also find that while a wide range of decision support tools and frameworks alternative to risk assessment are currently available, a thorough evaluation of these should be undertaken in the near future to assess their full relevancy for nZVI at specific sites. Due to the absence of data in environmental risk evaluations, we apply a 'best' and 'worst' case scenario evaluation as a first step to qualitatively evaluate the current state-of-knowledge regarding the potential environmental risks of nZVI. The result of this preliminary qualitative evaluation indicates that at present, there are no significant grounds on which to form the basis that nZVI currently poses a significant, apparent risk to the environment, although the majority of the most serious criteria (i.e. potential for persistency, bioaccumulation, toxicity) are generally unknown. We recommend that in cases where nZVI may be chosen as the 'best' treatment option, short and long-term environmental monitoring is actively employed at these sites. We furthermore recommend the continued development of responsible nZVI innovation and better facilitated information exchange between nZVI developers, nano-risk researchers, remediation industry, and decision makers.
Grieger, Khara D.; Fjordbøge, Annika; Hartmann, Nanna B.; Eriksson, Eva; Bjerg, Poul L.; Baun, Anders
Conversion of mill-scale waste to nanoscale zero valent iron (nZVI) for 'green' hydrogen generation via metal-steam reforming
The Proton Exchange Membrane Fuel Cells (PEMFCs) are the most preferred and efficient energy conversion devices for automotive applications but demand high purity hydrogen which comes at a premium price. The currently pursued hydrogen generation methods suffer from issues such as, low efficiency, high cost, environmental non-benignity, and, in some cases, commercial non-viability. Many of these drawbacks including the CO contamination and, storage and delivery can be overcome by resorting to metal-steam reforming (MSR) using iron from steel industry's mill-scale waste. A novel solution-based room temperature technique using sodium borohydride (NaBH4) as the reducing agent has been developed that produces highly active nanoscale (30-40 nm) iron particles. A slightly modified version of this technique using a surfactant and water oil microemulsion resulted in the formation of 5 nm Fe particles. By using hydrazine (N2H4) as an inexpensive and more stable (compared to NaBH4) reductant, body centered cubic iron particles with edge dimensions ˜5 nm were obtained under mild solvothermal conditions in ethanol. The nanoscale zero valent iron (nZVI) powder showed improved kinetics and greater propensity for hydrogen generation than the coarser microscale iron obtained through traditional reduction techniques. To initiate and sustain the somewhat endothermic MSR process, a solar concentrator consisting of a convex polyacrylic sheet with aluminum reflective coating was fabricated. This unique combination of mill-scale waste as iron source, hydrazine as the reductant, mild process conditions for nZVI generation and solar energy as the impetus for actuating MSR, obviates several drawbacks plaguing the grand scheme of producing, storing and delivering pure and humidified H2 to a PEMFC stack.
Kesavan, Sathees Kumar
Degradation of 4-Chloro-3,5-Dimethylphenol by a Heterogeneous Fenton-Like Reaction Using Nanoscale Zero-Valent Iron Catalysts.
Degradation of 4-chloro-3,5-dimethylphenol (PCMX) by a heterogeneous Fenton-like process using nanoparticulate zero-valent iron (nZVI) and hydrogen peroxide (H2O2) at pH 6.3 was investigated. Interactive effects of three factors-initial PCMX concentration, nZVI dosage, and H2O2 concentration-were investigated using the response surface method based on the Box-Behnken design. Experimental results showed that complete decomposition of PCMX and 65% of total organic carbon removal were observed after 30?min of reaction at neutral pH under recommended reaction conditions: nZVI, 1.0?g/L; H2O2, 18?mM; and initial PCMX concentration, 0.15?g/L. Based on the effects of scavengers n-butanol and KI, removal of PCMX was mainly attributed to the attack of •OH, especially the surface-bonded •OH. A possible degradation pathway of PCMX was proposed. PMID:23781127
Xu, Lejin; Wang, Jianlong
Degradation of 4-Chloro-3,5-Dimethylphenol by a Heterogeneous Fenton-Like Reaction Using Nanoscale Zero-Valent Iron Catalysts
Abstract Degradation of 4-chloro-3,5-dimethylphenol (PCMX) by a heterogeneous Fenton-like process using nanoparticulate zero-valent iron (nZVI) and hydrogen peroxide (H2O2) at pH 6.3 was investigated. Interactive effects of three factors—initial PCMX concentration, nZVI dosage, and H2O2 concentration—were investigated using the response surface method based on the Box–Behnken design. Experimental results showed that complete decomposition of PCMX and 65% of total organic carbon removal were observed after 30?min of reaction at neutral pH under recommended reaction conditions: nZVI, 1.0?g/L; H2O2, 18?mM; and initial PCMX concentration, 0.15?g/L. Based on the effects of scavengers n-butanol and KI, removal of PCMX was mainly attributed to the attack of •OH, especially the surface-bonded •OH. A possible degradation pathway of PCMX was proposed.
SBA-15-incorporated nanoscale zero-valent iron particles for chromium(VI) removal from groundwater: mechanism, effect of pH, humic acid and sustained reactivity.
Nanoscale zero-valent iron particles (NZVIs) were incorporated inside the channels of SBA-15 rods by a "two solvents" reduction technique and used to remove Cr(VI) from groundwater. The resulting NZVIs/SBA-15 composites before and after reaction were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Results helped to propose the mechanism of Cr(VI) removal by NZVIs/SBA-15, where Cr(VI) in aqueous was firstly impregnated into the channels of the silica, then adsorbed on the surfaces of the incorporated NZVIs and reduced to Cr(III) directly in the inner pores of the silica. Corrosion products included Fe2O3, FeO(OH), Fe3O4 and Cr2FeO4. Batch experiments revealed that Cr(VI) removal decreased from 99.7% to 92.8% when the initial solution pH increased from 5.5 to 9.0, accompanied by the decrease of the kobs from 0.600 to 0.024 min(-1). Humic acid (HA) had a little effect on the removal efficiency of Cr(VI) by NZVIs/SBA-15 but could decrease the reduction rate. The stable reduction of NZVIs/SBA-15 was observed within six cycles. NZVIs/SBA-15 composites offer a promising alternative material to remove heavy metals from groundwater. PMID:24374562
Sun, Xia; Yan, Yubo; Li, Jiansheng; Han, Weiqing; Wang, Lianjun
Kinetics and mechanism study on the preparation of 4,4?-diaminostilbene-2,2?-disulfonic acid by reduction of 4,4?-dinitrostilbene-2,2?-disulfonic acid with zero-valent iron
This research is aimed at improving the understanding of the reduction of 4,4?-dinitrostilbene-2,2?-disulfonic acid (DNS) by zero-valent iron for the manufacture of 4,4?-diaminostilbene-2,2?-disulfonic acid (DSD). The formation of 5-amino-2-formylbenzene sulfonic acid (ABAS) during the process indicates that oxidation with the cleavage of CC double bond does occur besides the principle nitro-group reduction processes. The kinetics of the reduction of DNS
Xiaobin Fan; Fengbao Zhang; Guoliang Zhang; Guozhu Li
Iron Nanoparticles in Reactive Environmental Barriers
Zero-valent iron is cheap, environmentally innocuous, and effective at reducing chlorinated organics. It has, as a result, become a popular candidate for remediating aquifers contaminated with trichloroethylene and other halogenated pollutants. In this paper, we discuss one such system, where iron nanoparticles are synthesized and incorporated into polyvinyl alcohol membranes, forming water-permeable barriers to these pollutants. These barriers are tested against a variety of contaminants, including carbon tetrachloride, copper, and chromate.
Nuxoll, Eric E.; Shimotori, Tsutomu; Arnold, William A.; Cussler, Edward L.
The effects of operational parameters and common anions on the reactivity of zero-valent iron in bromate reduction
Bromate reduction by Fe(0) was investigated under various conditions in batch tests. The bromate was primarily reduced to bromide ions with possible adsorption onto iron. Bromate reduction by Fe(0) can be described by pseudo-first-order kinetics. The differences in surface areas, numbers of reactive sites, impurities, pretreatment methods and numbers of repeated uses of iron affected the rates of bromate reduction
Li Xie; Chii Shang
Dechlorination of PCBs in the simulative transformer oil by microwave-hydrothermal reaction with zero-valent iron involved
The conventional hydrothermal reaction with iron powder, NaOH and H2O as reactants was reported to occur at temperature above 423K, and iron oxides (Fe3O4 and NaFeO2) and hydrogen were produced. In this study, microwave heating was adopted to take the place of conventional heating to induce the hydrothermal reaction. Under microwave irradiation, NaOH and H2O absorbed microwave energy by space
Xitao Liu; Wei Zhao; Ke Sun; Guixiang Zhang; Ye Zhao
Degradation of bromothymol blue by 'greener' nano-scale zero-valent iron synthesized using tea polyphenols
A green single-step synthesis of iron nanoparticles using tea (Camellia sinensis) polyphenols is described that uses no added surfactants/polymers as a capping or reducing agents. The expeditious reaction between polyphenols and ferric nitrate occurs within few minutes at room te...
Organic-coated nanoparticulate zero valent iron for remediation of chemical oxygen demand (COD) and dissolved metals from tropical landfill leachate.
The use of nanoparticulate zero valent iron (NZVI) in the treatment of inorganic contaminants in landfill leachate and polluted plumes has been the subject of many studies, especially in temperate, developed countries. However, NZVI's potential for reduction of chemical oxygen demand (COD) and treatment of metal ion mixtures has not been explored in detail. We investigated the efficiency of NZVI synthesized in the presence of starch, mercaptoacetic, mercaptosuccinic, or mercaptopropenoic acid for the reduction of COD, nutrients, and metal ions from landfill leachate in tropical Sri Lanka. Synthesized NZVI were characterized with X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller. Of the samples tested, Starch-NZVI (S-NZVI) and mercaptoacetic-NZVI (MA-NZVI) performed well for treatment both COD and metal mixture. The removal percentages for COD, nitrate-nitrogen, and phosphate from S-NZVI were 50, 88, and 99 %, respectively. Heavy metal removal was higher in S-NZVI (>95 %) than others. MA-NZVI, its oxidation products, and functional groups of its coating showed the maximum removal amounts for both Cu (56.27 mg g(-1)) and Zn (28.38 mg g(-1)). All mercapto-NZVI showed well-stabilized nature under FTIR and XRD investigations. Therefore, we suggest mercapto acids as better agents to enhance the air stability for NZVI since chemically bonded thiol and carbonyl groups actively participation for stabilization process. PMID:24535668
Wijesekara, S S R M D H R; Basnayake, B F A; Vithanage, Meththika
Integration of nanosized zero-valent iron particles addition with UV/H2O2 process for purification of azo dye Acid Black 24 solution.
The challenging national effluent standards for color and organic concentration enforce the industrial concern most the techniques providing fast and efficient solution for the strenuous dye wastewater treatment before outflow. The best remediation technique pursuit is urgently demand for the industrial, government, academia and community. In this study, a di-azo dye, C.I. Acid Black 24, synthesized wastewater was successfully removed synchronously its total color and total organic carbon (TOC) using an integrated innovation technology by coupling the zero-valent iron (ZVI) nanoparticles with UV/H(2)O(2) oxidation process. The nanosized ZVI (NZVI) primarily reduced color successfully following coupling UV/H(2)O(2) oxidation process for the residual organic mineralization resulting reduction with oxidation process (Re-Ox) for total color removal and organic mineralization. From the experimental data, the Re-Ox process consumed shorter time than UV/H(2)O(2) oxidation process alone to obtain total color removal of dye wastewater. Moreover, the residual TOC of dye wastewater after NZVI reduction from 45 to 100% was effectively mineralized by UV/H(2)O(2) process. By using proposed processes integration with NZVI dosage of 0.3348 g l(-1) and hydrogen peroxide concentration of 23.2 mM, in only 10 min the AB24 color was complete eliminated and in 90 min the TOC was 93.9% removed. Thus, the coupling Re-Ox process was developed to provide a superior solution for dye wastewater treatment. PMID:19250743
Shu, Hung-Yee; Chang, Ming-Chin; Chang, Chi-Chen
Identification of degradation products of ionic liquids in an ultrasound assisted zero-valent iron activated carbon micro-electrolysis system and their degradation mechanism.
Ionic liquids (ILs) have potential applications in many areas of chemical industry because of their unique properties. However, it has been shown that the ILs commonly used to date are toxic and not biodegradable in nature, thus development of efficient chemical methods for the degradation of ILs is imperative. In this work, degradation of imidazolium, piperidinium, pyrrolidinium and morpholinium based ILs in an ultrasound and zero-valent iron activated carbon (ZVI/AC) micro-electrolysis system was investigated, and some intermediates generated during the degradation were identified. It was found that more than 90% of 1-alkyl-3-methylimidazolium bromide ([Cnmim]Br, n = 2, 4, 6, 8, 10) could be degraded within 110 min, and three intermediates 1-alkyl-3-methyl-2,4,5-trioxoimidazolidine, 1-alkyl-3-methylurea and N-alkylformamide were detected. On the other hand, 1-butyl-1-methylpiperidinium bromide ([C4mpip]Br), 1-butyl-1-methylpyrrolidinium bromide ([C4mpyr]Br) and N-butyl-N-methylmorpholinium bromide ([C4mmor]Br) were also effectively degraded through the sequential oxidization into hydroxyl, carbonyl and carboxyl groups in different positions of the butyl side chain, and then the N-butyl side chain was broken to form the final products of N-methylpiperidinium, N-methylpyrrolidinium and N-methylmorpholinium, respectively. Based on these intermediate products, degradation pathways of these ILs were suggested. These findings may provide fundamental information on the assessment of the factors related to the environmental fate and environmental behavior of these commonly used ILs. PMID:23623468
Zhou, Haimei; Lv, Ping; Shen, Yuanyuan; Wang, Jianji; Fan, Jing
Removal of organic compounds and trace metals from oil sands process-affected water using zero valent iron enhanced by petroleum coke.
The oil production generates large volumes of oil sands process-affected water (OSPW), referring to the water that has been in contact with oil sands or released from tailings deposits. There are concerns about the environmental impacts of the release of OSPW because of its toxicity. Zero valent iron alone (ZVI) and in combination with petroleum coke (CZVI) were investigated as environmentally friendly treatment processes for the removal of naphthenic acids (NAs), acid-extractable fraction (AEF), fluorophore organic compounds, and trace metals from OSPW. While the application of 25 g/L ZVI to OSPW resulted in 58.4% removal of NAs in the presence of oxygen, the addition of 25 g petroleum coke (PC) as an electron conductor enhanced the NAs removal up to 90.9%. The increase in ZVI concentration enhanced the removals of NAs, AEF, and fluorophore compounds from OSPW. It was suggested that the electrons generated from the oxidation of ZVI were transferred to oxygen, resulting in the production of hydroxyl radicals and oxidation of NAs. When OSPW was de-oxygenated, the NAs removal decreased to 17.5% and 65.4% during treatment with ZVI and CZVI, respectively. The removal of metals in ZVI samples was similar to that obtained during CZVI treatment. Although an increase in ZVI concentration did not enhance the removal of metals, their concentrations effectively decreased at all ZVI loadings. The Microtox(®) bioassay with Vibrio fischeri showed a decrease in the toxicity of ZVI- and CZVI-treated OSPW. The results obtained in this study showed that the application of ZVI in combination with PC is a promising technology for OSPW treatment. PMID:24681364
Pourrezaei, Parastoo; Alpatova, Alla; Khosravi, Kambiz; Drzewicz, Przemys?aw; Chen, Yuan; Chelme-Ayala, Pamela; Gamal El-Din, Mohamed
Batch tests were performed utilizing four zerovalent iron (Fe0) filings (Fisher, Peerless, Master Builders, and Aldrich) to remove As(V) and As(III) from water. One gram of metal was reacted headspace-free at 23 °C for up to 5 days in the dark with 41.5 mL of 2 mg L-1 As(V), or A...
Removal of tetracycline from aqueous solutions using polyvinylpyrrolidone (PVP-K30) modified nanoscale zero valent iron
The interactions of tetracycline (TC) with nanoscale zerovalent iron (NZVI) modified by polyvinylpyrrolidone (PVP-K30) were investigated using batch experiments as a function of reactant concentration, pH, temperature, and competitive anions. Transmission electron micrographs (TEM), BET surface area and Zeta (?)-potential analyses indicated that the mean particle size was 10–40nm with a surface area of 36.90m2\\/g, and a iso-electric point of
Hua Chen; Hanjin Luo; Yuecun Lan; Tingting Dong; Bingjie Hu; Yiping Wang
Removal of co-present chromate and arsenate by zero-valent iron in groundwater with humic acid and bicarbonate.
The interactions of co-present Cr(VI) and As(V), and the influences of humic acid and bicarbonate in the process of Cr(VI) and As(V) removal by Fe(0) were investigated in a batch setting using simulated groundwater with 5 mM NaCl, 1 mM Na(2)SO(4), and 0.8 mM CaCl(2) as background electrolytes at an initial pH value of 7. Cr(VI) and As(V) were observed to be subject to different impacts induced by co-existing As(V) or Cr(VI), humic acid and bicarbonate, originating from their distinct removal mechanisms by Fe(0). Cr(VI) removal is a reduction-dominated process, whereas As(V) removal principally involves adsorption onto iron corrosion products. Experimental results showed that Cr(VI) removal was not affected by the presence of As(V) and humic acid. However, As(V) removal appeared to be inhibited by co-present Cr(VI). When the Cr(VI) concentration was 2, 5, and 10 mg/L, in the absence of humic acid and bicarbonate, As(V) removal rate constants were decreased by 27.9%, 49.0%, and 61.2%, respectively, which probably resulted from competition between Cr(VI) and As(V) for adsorption sites of the iron corrosion products. Furthermore, the presence of humic acid significantly varied As(V) removal kinetics by delaying the formation and aggregation of iron hydroxides due to the formation of soluble Fe-humate complexes and stably dispersed fine iron hydroxides colloids. In the presence of bicarbonate, both Cr(VI) and As(V) removal was increased and the inhibitory effect of Cr(VI) on As(V) removal was suppressed, resulting from the buffering effects and the promoted iron corrosion induced by bicarbonate, and the formation of CaCO(3) in solution, which enhanced As(V) adsorption. PMID:19321187
Liu, Tongzhou; Rao, Pinhua; Mak, Mark S H; Wang, Peng; Lo, Irene M C
Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose.
In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed?~?36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 ?g/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7?±?0.1. The maximum removal efficiency of both arsenic species was obtained at pH?=?5?±?0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe(0) nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660
Mosaferi, Mohammad; Nemati, Sepideh; Khataee, Alireza; Nasseri, Simin; Hashemi, Ahmad Asl
Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose
In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed?~?36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 ?g/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7?±?0.1. The maximum removal efficiency of both arsenic species was obtained at pH?=?5?±?0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water.
Removal of uranium (VI) from aqueous systems by nanoscale zero-valent iron particles suspended in carboxy-methyl cellulose
Carboxy-methyl-cellulose (CMC), a common "delivery vehicle" for the subsurface deployment of iron nanoparticles (INP) has been tested in the current work for the removal of aqueous uranium from synthetic water samples. A comparison of the removal of aqueous uranium from solutions using carboxy-methyl-cellulose with and without iron nanoparticles (CMC-INP and CMC, respectively) was tested over a 48 h reaction period. Analysis of liquid samples using spectrophotometry determined a maximum sorption capacity of uranium, Qmax, of 185.18 mg/g and 322.58 mg/g for CMC and CMC-INP respectively, providing strong evidence of an independent aqueous uranium removal ability exhibited by CMC. The results point out that CMC provides an additional capacity for aqueous uranium removal. Further tests are required to determine whether similar behaviour will be observed for other aqueous contaminant species and if the presence of CMC within a INP slurry inhibits or aids the reactivity, reductive capacity and affinity of INP for aqueous contaminant removal.
Popescu (Ho?tuc), Ioana-Carmen; Filip, Petru; Humelnicu, Doina; Humelnicu, Ionel; Scott, Thomas Bligh; Crane, Richard Andrew
U.S. EPA (Environmental Protection Agency) staff developed a field procedure to measure hydraulic conductivity using a direct-push system to obtain vertical profiles of hydraulic conductivity. Vertical profiles were obtained using an in situ field device-composed of a Geopr...
The Use of Ultrasound to Restore the Dehalogenation Activity of Iron in Permeable Reactive Barriers
In situ permeable reactive barriers (PRBs) containing iron as the reactive agent have gained popularity in the past decade as a near-passive, in situ groundwater remediation technology for halogenated solvents. Although zero-valent iron has been shown to be effective for this purpose, a continuing problem is the loss of system reactivity over time. This loss is due, at least in
Cherie L. Geiger; Christian A. Clausen; Debra R. Reinhart; Nancy Ruiz
Chromium(VI) reduction kinetics by zero-valent iron in moderately hard water with humic acid: iron dissolution and humic acid adsorption.
In zerovalent iron treatment systems, the presence of multiple solution components may impose combined effects that differ from corresponding individual effects. The copresence of humic acid and hardness (Ca2+/Mg2+) was found to influence Cr(VI) reduction by Feo and iron dissolution in a way different from their respective presence in batch kinetics experiments with synthetic groundwater at initial pH 6 and 9.5. Cr(VI) reduction rate constants (k(obs)) were slightly inhibited by humic acid adsorption on iron filings (decreases of 7-9% and 10-12% in the presence of humic acid alone and together with hardness, respectively). The total amount of dissolved Fe steadily increased to 25 mg L(-1) in the presence of humic acid alone because the formation of soluble Fe-humate complexes appeared to suppress iron precipitation. Substantial amounts of soluble and colloidal Fe-humate complexes in groundwater may arouse aesthetic and safety concerns in groundwater use. In contrast, the coexistence of humic acid and Ca2+/Mg2+ significantly promoted aggregation of humic acid and metal hydrolyzed species, as indicated by XPS and TEM analyses, which remained nondissolved (>0.45 microm) in solution. These metal-humate aggregates may impose long-term impacts on PRBs in subsurface settings. PMID:18409642
Liu, Tongzhou; Tsang, Daniel C W; Lo, Irene M C
Reactive iron barriers: a niche enabling microbial dehalorespiration of 1,2-dichloroethane
A reactive iron barrier in a contaminated aquifer with low pH was found to dechlorinate 1,2-dichloroethane (1,2-DCA) in situ.\\u000a This chlorinated ethane is known to resist abiotic reduction by zero valent iron. Samples taken up-gradient and within the\\u000a barrier were used to inoculate anaerobic batch cultures amended with various electron donors. Cultures inoculated with groundwater\\u000a from within the reactive iron
Olivier Zemb; Matthew Lee; Adrian Low; Mike Manefield
A two and half-year-performance evaluation of a field test on treatment of source zone tetrachloroethene and its chlorinated daughter products using emulsified zero valent iron nanoparticles.
A field test of emulsified zero valent iron (EZVI) nanoparticles was conducted at Parris Island, SC, USA and was monitored for two and half years to assess the treatment of subsurface-source zone chlorinated volatile organic compounds (CVOCs) dominated by tetrachloroethene (PCE) and its chlorinated daughter products. Two EZVI delivery methods were used: pneumatic injection and direct injection. In the pneumatic injection plot, 2180 L of EZVI containing 225 kg of iron (Toda RNIP-10DS), 856 kg of corn oil, and 22.5 kg of surfactant were injected to remedy an estimated 38 kg of CVOCs. In the direct injection plot, 572 L of EZVI were injected to treat an estimated 0.155 kg of CVOCs. After injection of the EZVI, significant reductions in PCE and trichloroethene (TCE) concentrations were observed in downgradient wells with corresponding increases in degradation products including significant increases in ethene. In the pneumatic injection plot, there were significant reductions in the downgradient groundwater mass flux values for PCE (>85%) and TCE (>85%) and a significant increase in the mass flux of ethene. There were significant reductions in total CVOC mass (86%); an estimated reduction of 63% in the sorbed and dissolved phases and 93% reduction in the PCE DNAPL mass. There are uncertainties in these estimates because DNAPL may have been mobilized during and after injection. Following injection, significant increases in dissolved sulfide, volatile fatty acids (VFA), and total organic carbon (TOC) were observed. In contrast, dissolved sulfate and pH decreased in many wells. The apparent effective remediation seems to have been accomplished by direct abiotic dechlorination by nanoiron followed by biological reductive dechlorination stimulated by the corn oil in the emulsion. PMID:22868086
Su, Chunming; Puls, Robert W; Krug, Thomas A; Watling, Mark T; O'Hara, Suzanne K; Quinn, Jacqueline W; Ruiz, Nancy E
Effect of pH on the dissolution kinetics of zero-valent iron in the presence of EDDHA and EDTA
The effect of environmental factors (e.g., pH, solution composition, and temperature) that affect the longevity of Fe(0) barriers in the subsurface are difficult to quantify independently from changes that occur to the passivating layer. Therefore, to quantify the rate of Fe(0) dissolution under conditions which maintain the pO2 at a relatively constant level and minimize the formation of a passivating layer on the metal surface, a series of experiments have been conducted with the single-pass flow-through (SPFT) apparatus. These experiments were conducted over the pH range from 7.0 to 12.0 at 90°C in the presence of 5 mM EDDHA or 5 mM EDTA. The organic acids, EDDHA and EDTA, helped to maintain the aqueous Fe concentration below saturation with respect to Fe-bearing alteration phases and minimize the formation of a partially oxidized surface film. Results suggest the corrosion of Fe(0) is relatively insensitive to pH and the forward or maximum dissolution rate is 3 to 4 orders of magnitude higher than when a passive film and corrosion products are present.
Lodge, Alexander M.; Pierce, Eric M.; Wellman, Dawn M.; Cordova, Elsa A.
Impact of peroxydisulfate in the presence of zero valent iron on the oxidation of cyclohexanoic acid and naphthenic acids from oil sands process-affected water.
Large volumes of oil sands process-affected water (OSPW) are produced during the extraction of bitumen from oil sands in Alberta, Canada. The degradation of a model naphthenic acid, cyclohexanoic acid (CHA), and real naphthenic acids (NAs) from OSPW were investigated in the presence of peroxydisulfate (S(2)O(8)(2-)) and zerovalent iron (ZVI). For the model compound CHA (50 mg/L), in the presence of ZVI and 500 mg/L S(2)O(8)(2-), the concentration decreased by 45% after 6 days of treatment at 20 °C, whereas at 40, 60, and 80 °C the concentration decreased by 20, 45 and 90%, respectively, after 2 h of treatment. The formation of chloro-CHA was observed during ZVI/S(2)O(8)(2-) treatment of CHA in the presence of chloride. For OSPW NAs, in the presence of ZVI alone, a 50% removal of NAs was observed after 6 days of exposure at 20 °C. The addition of 100 mg/L S(2)O(8)(2-) to the solution increased the removal of OSPW NAs from 50 to 90%. In absence of ZVI, a complete NAs removal from OSPW was observed in presence of 2000 mg/L S(2)O(8)(2-) at 80 °C. The addition of ZVI increased the efficiency of NAs oxidation by S(2)O(8)(2-) near room temperature. Thus, ZVI/S(2)O(8)(2-) process was found to be a viable option for accelerating the degradation of NAs present in OSPW. PMID:22799739
Drzewicz, Przemys?aw; Perez-Estrada, Leonidas; Alpatova, Alla; Martin, Jonathan W; Gamal El-Din, Mohamed
Nanoscale Zero-Valent Iron (NZVI) supported on sineguelas waste for Pb(II) removal from aqueous solution: Kinetics, thermodynamic and mechanism.
In this study, the synthesis and characterization of a new adsorbent containing nanoscale zerovalent iron particles (NZVI) decorated sineguelas waste (S-NaOH-NZVI) from agriculture biomass was investigated for the adsorption/reduction of inorganic pollution such as Pb(II) ions. The combination of ZVI particles on the surface of sineguelas waste can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. The synthesized materials were characterized with different methods such as FT-IR, BET, XRD, TEM and pHPZC. Good dispersion of NZVI particles (ca. 10-70nm) on the sineguelas waste was observed. The effects of various parameters, such as contact time, pH, concentration, adsorbent dosage and temperature were studied. The adsorption of Pb(II) ions has been studied in terms of pseudo-first- and second-order kinetics, and the Freundlich, Langmuir and Langmuir-Freundlich isotherms models have also been used to the equilibrium adsorption data. The adsorption kinetics followed the mechanism of the pseudo-second-order equation. The thermodynamic parameters (?G, ?H and ?S) indicated that the adsorption of Pb(II) ions were feasible, spontaneous and endothermic at 25-80°C. XRD analysis indicated the presence of Pb(0) on the S-NaOH-NZVI surface. This study suggests that the modified sineguelas waste by NZVI particles can be prepared at low cost and the materials are environmentally benign for the removal of Pb(II) ions, and likely many other heavy metal ions, from water. PMID:24863789
Arshadi, M; Soleymanzadeh, M; Salvacion, J W L; SalimiVahid, F
Remediation of Perchloroethylene Contaminated Groundwater by Permeable Reactive Barrier Using Iron, Granular Activated Carbon, and Soil
The objective of this study is to evaluate the effects of zero-valent iron (ZVI), granular activated carbon (GAC) and soil as materials to build permeable reactive barrier (PRB). Flow-through Column experiments were conducted to evaluate the reactivity and adsorptive capacity of various materials for Perchloroethylene(PCE) contaminated groundwater. Columns were packed with various materials such as ZVI, GAC, and Soil. A
L. Jeon; D. Lee; H. Chang
The transport of organic contaminants down the soil profile constitutes a serious threat to the quality of ground water. Zero-valent metals are considered innocuous abiotic agents capable of mediating decontamination processes in terrestrial systems. In this investigation, ze...
Oxidative degradation of organic pollutants in aqueous solution using zero valent copper under aerobic atmosphere condition.
Oxidative degradation of organic pollutants and its mechanism were investigated in aqueous solution using zero valent copper (ZVC) under aerobic atmosphere condition. Diethyl phthalate (DEP) was completely oxidized after 120min reaction by ZVC at initial pH 2.5 open to the air. DEP degradation followed the pseudo-first-order kinetics after the lag period, and the degradation rate of DEP increased gradually with the increase of ZVC dosage, and the decrease of initial pH from 5.8 to 2.0. ZVC required a shorter induction time and exhibited persistent oxidation capacity compared to that of zero valent iron and zero valent aluminium. The mechanism investigation showed that remarkable amount of Cu(+)/Cu(2+) and H2O2 were formed in ZVC acidic system, which was due to the corrosive dissolution of ZVC and the concurrent reduction of oxygen. The addition of tert-butanol completely inhibited the degradation of DEP and the addition of Fe(2+) greatly enhanced the degradation rate, which demonstrated that hydroxyl radical was mainly responsible for the degradation of DEP in ZVC acidic system under aerobic atmosphere condition, and the formation of hydroxyl radical was attributed to the Fenton-like reaction of in situ formed Cu(+) with H2O2. PMID:24857902
Wen, Gang; Wang, Sheng-Jun; Ma, Jun; Huang, Ting-Lin; Liu, Zheng-Qian; Zhao, Lei; Xu, Jin-Lan
DEEP REACTIVE BARRIERS FOR REMEDIATION OF VOCs AND HEAVY METALS
Azimuth controlled vertical hydraulic fracturing technology has constructed full scale in situ iron reactive permeable barriers at moderate to significant depth for remediation of groundwater contaminated with chlorinated hydrocarbons and metals. Zero valent iron reactive permeable barriers have been installed to remediate chlorinated solvent contaminated groundwater by abiotic degradation of the halogenated volatile organic compounds into harmless daughter products. Alternatively
Grant Hocking; Samuel L. Wells; Rafael I. Ospina
Chemical denitrification of water by zero-valent magnesium powder
A laboratory-scale study was conducted in batch mode to investigate the feasibility of using zero-valent magnesium (Mg0), for removal of nitrate from aqueous solution. Reaction pH, dose of Mg0, initial nitrate concentration and temperature were considered variable parameters during the study. Strong acidic condition enhanced nitrate reduction and in absence of external proton addition, reaction pH increased rapidly above ten
Manish Kumar; Saswati Chakraborty
Field Studies of the Electrical Properties of Permeable Reactive Barriers for Monitoring Barrier Aging
Permeable reactive barriers (PRB) are a promising technology for the remediation of groundwater containing a range of organic and inorganic contaminants. Although there are number of different types of reactive barriers, some of the most important are constructed from granular zero valent iron (ZVI). One challenge in the large- scale, long-term implementation of PRBs is to monitor the change in
R. Sharpe; D. J. Labrecque; L. Slater
Zero-valent aluminum for oxidative degradation of aqueous organic pollutants.
Oxidative degradation of aquatic organic contaminants using zero-valent aluminum (ZVAl) in the presence of dissolved oxygen (O2) was investigated. The metal corrosion process in acidic conditions (pH < 4) was accompanied by electron transfer from ZVAl to O2, which led to the simultaneous generation of Al3+ and hydrogen peroxide (H2O2). The oxidation of 4-chlorophenol (4-CP), a model substrate, was initiated by the generation of hydroxyl radicals (HO*) via electron transfer from Al0 to H2O2. Degradation was initiated after an induction period of about 2 h, during which the native oxide layer was dissoluted. The HO*(-) mediated oxidation reaction was completely quenched by adding methanol as a radical scavenger. Systematic studies on the effects of ZVAl loading, pH, and surface oxide content revealed that the oxide layer dissolution controlled the Al0-mediated oxidation of 4-CP. The proposed process is similarly compared with the zero-valent iron (ZVI) system, but the ZVAl/O2 system showed a higher oxidation capacity compared with ZVI/O2 because of the stability of aquo-complexed Al3+ ions over a wider pH range. The degradation of phenol, nitrobenzene, and dichloroacetate was also successfully achieved with ZVAl. The present study proposes the ZVAl/O2 process as a viable method of oxidative water treatment. PMID:19806753
Bokare, Alok D; Choi, Wonyong
Construction and Performance Monitoring of In Situ Reactive Barriers
In situ reactive barriers have been constructed by a variety of means and with a range of reactive materials. Zero valent iron reactive permeable barriers have been installed to remediate chlorinated solvent contaminated groundwater by abiotic degradation of the halogenated volatile organic compounds into harmless daughter products. Alternative reactive materials are used for precipitation, sorption or biodegradation of various groundwater
Grant Hocking; Rafael I. Ospina
Fundamental Studies of the Removal of Contaminants from Ground and Waste Waters via Reduction by Zero-Valent Metals
Contaminated groundwater and surface waters are a problem throughout the United States and the world. In many instances, the types of contamination can be directly attributed to man's actions. For instance, the burial of chemical wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater and surface water contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements (including radioisotopes) that are soluble and mobile in soils and aquifers. Oxyanions of uranium, selenium, chromium, arsenic, technetium, and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. Uranium is a particularly widespread contaminant at most DOE sites including Oak Ridge, Rocky Flats, Hanford, Idaho (INEEL), and Fernald. The uranium contamination is associated with mining and milling of uranium ore (UMTRA sites), isotope separation and enrichment, and mixed waste and TRU waste burial. In addition, the careless disposal of halogenated solvents, such as carbon tetrachloride and trichloroethylene, has further contaminated many groundwaters at these sites. A potential remediation method for many of these oxyanions and chlorinated-solvents is to react the contaminated water with zero-valent iron. In this reaction, the iron serves as both an electron source and as a catalyst. Elemental iron is already being used on an experimental basis at many DOE sites. Both in situ reactive barriers and above-ground reactors are being developed for this purpose. However, the design and operation of these treatment systems requires a detailed process-level understanding of the interactions between the contaminants and the iron surfaces. We are performing fundamental investigations of the interactions of the relevant chlorinated solvents and trace element-containing compounds with single- and poly-crystalline Fe surfaces. The aim of this work is to develop th e fundamental physical and chemical understanding that is necessary for the development of cleanup techniques and procedures.
Yarmoff, Jory A.; Amrhein, Christopher
The generation and release of acidic drainage from mine wastes is an environmental problem of international scale. The use of zero-valent iron and/or iron mixtures in subsurface Permeable Reactive Barriers (PRB) presents a possible passive alternative for remediating acidic grou...
Accumulation Rate of Microbial Biomass at Two Permeable Reactive Barrier Sites
Accumulation of mineral precipitates and microbial biomass are key factors that impact the long term performance of in situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero valent iron reactivity and permeability. Results are presented from solid phase and groundwater monitoring studies conducted at two Permeable Reactive Barrier sites, U.S. Coast Guard
R. Wilkin; G. Sewell; R. Puls
Reaction of 1,1,1-trichloroethane with zero-valent metals and bimetallic reductants
Information concerning the pathways and products of reaction of 1,1,1-trichloroethane (1,1,1-TCA) with zero-valent metals may be critical to the success of in situ treatment techniques. Many researchers assume that alkyl polyhalides undergo reduction via stepwise hydrogenolysis (replacement of halogen by hydrogen). Accordingly, 1,1,1-TCA should react to 1,1-dichloroethane (1,1-DCA), to chloroethane, and finally to ethane. Experiments conducted in laboratory-scale batch reactors indicate, however, that with zinc, iron, and two bimetallic reductants (nickel-plated iron and copper-plated iron) this simplistic stepwise scheme cannot explain observed results. 1,1,1-TCA was found to react rapidly with zinc to form ethane and 1,1-DCA. Independent experiments confirmed that 1,1-DCA reacts too slowly to represent an intermediate in the formation of ethane. In reactions with iron, nickel/iron, and copper/iron, cis-2-butene, ethylene, and 2-butyne were also observed as minor products. Product ratios were dependent on the identity of the metal or bimetallic reductant, with zinc resulting in the lowest yield of chlorinated product. For reactions with iron and bimetallic reductants, a scheme involving successive one-electron reduction steps to form radicals and carbenoids can be invoked to explain the absence of observable intermediates, as well as the formation of products originating from radical or possibly from carbenoid coupling.
Fennelly, J.P.; Roberts, A.L. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Geography and Environmental Engineering] [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Geography and Environmental Engineering
The primary objective of this research is to select an effective reductant for detoxification and immobilization of hexavalent chromium present in the soils/sediments collected from the old plating shop of the U.S. Coast Guard Air Support Center, Elizabeth City, North Carolina. ...
Optimization of Cr(VI) reduction by zero-valent bimetallic nanoparticles using the response surface modeling approach
Bimetallic iron–silver zero-valent nanoparticles were synthesized, characterised and studied for reduction of Cr(VI) in water solution. A four-factor, central composite design (CCD) combined with response surface modeling (RSM) and optimization was employed for maximizing the Cr(VI) reduction by the bimetallic system. Four independent variables, viz., temperature (10–50°C), pH of solution (2–8), Cr(VI) concentration (30–70mg\\/l), and particles dose (0.4–1.6g\\/l) were transformed
Kunwar P. Singh; Arun K. Singh; Shikha Gupta; Sarita Sinha
Reductive denitrification kinetics of nitrite by zero-valent iron
The objective of this current work was to investigate different factors that may affect the denitrification of nitrite in the presence of Fe0 and the denitrification kinetics. Our results show that nitrite can be effectively reduced to innocuous N2 gas and NH4+ by Fe0, no other intermediates were generated during the denitrification of NO2?. The reduction efficiency of nitrite decreased
Zhen Zhang; Zhiwei Hao; Yueping Yang; Jinghui Zhang; Qian Wang; Xinhua Xu
Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of in-situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero-valent iron reactivity...
Stability of Multi-Permeable Reactive Barriers for Long Term Removal of Mixed Contaminants
The Permeable Reactive Barriers (PRBs) are relatively simple, promising technology for groundwater remediation. A PRBs consisting\\u000a of two reactive barriers (zero valent iron-barrier and bio-barrier) were designed to evaluate the application and feasibility\\u000a of the barriers for the removal of wide range of pollutants from synthetic water. After 470 days of Multi-PRBs column operation,\\u000a the pH level in the water sample
Jai-Young LeeKui-Jae; Kui-Jae Lee; Sun Young Youm; Mi-Ran Lee; Seralathan Kamala-Kannan; Byung-Taek Oh
Remediation of trichloroethylene and monochlorobenzene contaminated groundwater by Iron and activated carbon
Batch tests were conducted to investigate the performance of various material remediation systems for the degradation and sorption of aqueous-phase trichloroethylene (TCE) and monochlorobenzene (MCB). The objective of this study was to evaluate the effects of zero-valent iron (ZVI) and granular activated carbon (GAC) as useful materials to build permeable reactive barriers (PRBs). ZVI is conventionally used as PRB material
L. Jeon; S. Jeen; D. Koh; H. Chang
Catalytic transformation of persistent contaminants using a new composite material based on nanosized zero-valent metal - field experiment results
A new composite material based on deposition of nanosized zero valent iron (ZVI) particles and cyanocobalamine (vitamin B12) on a diatomite matrix is presented. Cyanocobalamine is known to be an effective electron mediator, having strong synergistic effects with ZVI for reductive dehalogenation reactions. This composite material also improves the reducing capacity of nanosized ZVI by preventing agglomeration of iron particles, thus increasing their active surface area. The porous structure of the diatomite matrix allows high hydraulic conductivity, which favors channeling of contaminated water to the reactive surface of the composite material and in turn faster rates of remediation. The ability of the material to degrade or transform rapidly and completely a large spectrum of water pollutants will be demonstrated, based on results from two field site experiments where polluted groundwater containing a mixture of industrial and agricultural persistent pollutants was treated. In addition a set of laboratory experiments using individual contaminant solutions to analyze chemical transformations under controlled conditions will be presented.
Dror, I.; Merom Jacov, O.; Berkowitz, B.
The objective of this study is to evaluate the effects of zero-valent iron (ZVI), granular activated carbon (GAC) and soil as materials to build permeable reactive barrier (PRB). Flow-through Column experiments were conducted to evaluate the reactivity and adsorptive capacity of various materials for Perchloroethylene(PCE) contaminated groundwater. Columns were packed with various materials such as ZVI, GAC, and Soil. A peristaltic pump was used to feed this medium at 2.5mL/h resulting in a hydraulic retention time of approximately 70h. The column which packed only the soil shows PCE contamination came out passing after 10 pore volumes. But the other columns are continued purification effect.
Jeon, L.; Lee, D.; Chang, H.
Liquid-liquid Extraction Methods to Determine Reductive Dechlorination of 2,4,6-trichlorophenol by Zero-valent Metals and Zero-valent Bimetals
The reductive dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) was studied using zero-valent metals (ZVMs) and bimetals. A reliable extraction method was required to distinguish the removal by chemical transformation from the removal by physical adsorption on the ZVMs or bimetal. Three liquid–liquid extraction methods with ethyl acetate were evaluated by conducting mass recovery tests in the ZVM-chlorophenol systems. A typical liquid–liquid extraction
Jeong-Hak Choi; Sang June Choi; Young-Hun Kim
Polychlorinated ethane reaction with zero-valent zinc: pathways and rate control
Efficient design of zero-valent metal permeable `barriers' for the reduction of organohalides requires information regarding the pertinent reaction rates as well as an understanding of the resultant distribution of products. In this study, the pathways and kinetics for reaction of polychlorinated ethanes with Zn(0) have been examined in batch reactors. Reductive ?-elimination was the only route through which hexachloroethane (HCA), 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), 1,1,2-trichloroethane (1,1,2-TCA) and 1,2-dichloroethane (1,2-DCA) reacted. Pentachloroethane (PCA) reacted via concurrent reductive ?-elimination (93%) and hydrolysis (7%). As previously demonstrated, 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethane (1,1-DCA) reacted predominantly via reductive ?-elimination. Attempts to correlate BET surface area-normalized rate constants ( kSA-BET) with one-electron reduction potential ( E1) met with limited success, as HCA, PCA, 1,1,1,2-TeCA, and 1,1,1-TCA reacted at nearly identical rates despite substantial differences in E1 values. Comparison of the pseudo-first-order rate constants ( kobs) for these species with rate constants ( kLa) obtained from a correlation for mass transfer to suspended particles revealed that the reaction of these species was mass transfer limited even though reaction rates were unaffected by mixing speed. Calculations suggest that mass transfer limitations may also play a role in the design of treatment systems for highly reactive species, with overall rate constants predicted to increase with flow velocity.
Arnold, William A.; Ball, William P.; Roberts, A. Lynn
Fundamental studies of the removal of contaminants from ground and waste waters via reduction by zero-valent metals. 1998 annual progress report
'Contaminated groundwater and surface waters are a problem throughout the US and the world. In many instances, the types of contamination can be directly attributed to man''s actions. For instance, the burial of wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater and surface water contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements that are soluble and mobile in soils and aquifers. Oxyanions of selenium, chromium, uranium, arsenic, and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. In addition, the careless disposal of cleaning solvents, such as carbon tetrachloride and trichloroethylene, has further contaminated many groundwaters at these sites. Oxyanions of selenium, nitrogen, arsenic, vanadium, uranium, chromium, and molybdenum are contaminants in agricultural areas of the Western US. The management of these waters requires treatment to remove the contaminants before reuse or surface water disposal. In one instance in the Central Valley of California, the discharge of selenate-contaminated shallow groundwater to a wildlife refuge caused catastrophic bird deaths and deformities of embryos. A potential remediation method for many of these oxyanions and chlorinated-solvents is to react the contaminated water with zero-valent iron. In this reaction, the iron serves as both an electron source and as a catalyst. Elemental iron is already being used on an experimental basis. Both in-situ reactive barriers and above-ground reactors are being developed for this purpose. However, the design and operation of these treatment systems requires a detailed process-level understanding of the interactions between the contaminants and the iron surfaces. Only limited success has been achieved in the field, partly because the basic surface chemical reactions are not well understood. The authors are performing fundamental investigations of the interactions of the relevant chlorinated solvents, and trace element-containing compounds with single- and poly-crystalline Fe surfaces. The aim of this work is to develop the fundamental physical and chemical understanding that is necessary for the development of cleanup techniques and procedures. As of May 1998, they have performed both bulk chemical measurements of the reduction reactions and surface science studies of model chemical systems. During these first two years of funding, the authors have made significant progress in both areas. Initially, they focused primarily on the reduction of selenate by elemental iron. They also performed some work with chromate, perchlorate, uranyl, and carbon tetrachloride. In the following sections some of the progress is described.'
Yarmoff, J.A.; Amrhein, C.
Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron
Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for
António Fiúza; Aurora Silva; Goreti Carvalho; António V. de la Fuente; Cristina Delerue-Matos
Perchlorate reduction during electrochemically induced pitting corrosion of zero-valent titanium (ZVT).
Zero-valent metals and ionic metal species are a popular reagent for the abatement of contaminants in drinking water and groundwater and perchlorate is a contaminant of increasing concern. However, perchlorate degradation using commonly used reductants such as zero-valent metals and soluble reduced metal species is kinetically limited. Titanium in the zero-valent and soluble states has a high thermodynamic potential to reduce perchlorate. Here we show that perchlorate is effectively reduced to chloride by soluble titanium species in a system where the surface oxide film is removed from ZVT and ZVT is oxidized during electrochemically induced pitting corrosion to produce reactive soluble species. The pitting potential of ZVT was measured as 12.77±0.04 V (SHE) for a 100 mM solution of perchlorate. The rate of perchlorate reduction was independent of the imposed potential as long as the potential was maintained above the pitting potential, but it was proportional to the applied current. Solution pH and surface area of ZVT electrodes showed negligible effects on rates of perchlorate reduction. Although perchlorate is effectively reduced during electrochemically induced corrosion of ZVT, this process may not be immediately applicable to perchlorate treatment due to the high potentials needed to produce active reductants, the amount of titanium consumed, the inhibition of perchlorate removal by chloride, and oxidation of chloride to chlorine. PMID:21993148
Lee, Chunwoo; Batchelor, Bill; Park, Sung Hyuk; Han, Dong Suk; Abdel-Wahab, Ahmed; Kramer, Timothy A
Reactive transport modeling of an in situ reactive barrier for the treatment of hexavalent chromium and trichloroethylene in groundwater
Multicomponent reactive transport modeling was conducted for the permeable reactive barrier at the Coast Guard Support Center near Elizabeth City, North Carolina. The zero-valent iron barrier was installed to treat groundwater contaminated by hexavalent chromium and chlorinated solvents. The simulations were performed using the reactive transport model MIN3P, applied to an existing site-specific conceptual model. Reaction processes controlling the geochemical
K. Ulrich Mayer; David W. Blowes; Emil O. Frind
Electro-enhanced Permeable Reactive Barrier : Optimal Design of PRB System With External Current for Effective TCE Removal From Groundwater
The objective of this study was to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC). A series of column experiments were conducted to evaluate the location of Fe0 permeable reactive barrier (PRB) and the effects of electrode arrangement in the column on the TCE
J. Moon; H. Moon; Y. Roh; H. Kim; Y. Song
Performance Evaluation of In-Situ Iron Reactive Barriers at the Oak Ridge Y-12 Site
In November 1997, a permeable iron reactive barrier trench was installed at the S-3 Ponds Pathway 2 Site located at the Y-12 Plant, Oak Ridge, Tennessee. The overall goal of the project is to evaluate the ability of permeable reactive barrier technology to remove uranium, nitrate, and other inorganic contaminants in groundwater and to assess impacts of biogeochemical interactions on long-term performance of the treatment system. Zero-valent iron (Fe0) was used as the reactive medium, which creates a localized zone of reduction or low oxidation reduction potential (ORP), elevated pH, and dissolved H{sub 2} as Fe{sup 0} corrodes in groundwater. These conditions favor the removal of metals and radionuclides (such as uranium and technetium) through redox-driven precipitation and/or sorption to iron corrosion byproducts, such as iron oxyhydroxides. The technology is anticipated to be economical and low in maintenance as compared with conventional pump-and-treat technology. Groundwater monitoring results indicate that the iron barrier is effectively removing uranium and technetium, the primary contaminants of concern, as anticipated from our previous laboratory studies. In addition to uranium and technetium, nitrate, sulfate, bicarbonate, calcium, and magnesium are also found to be removed, either partially or completely by the iron barrier. Elevated concentrations of ferrous ions and sulfide, and pH were observed within the iron barrier. Although ferrous iron concentrations were initially very high after barrier installation, ferrous ion concentrations have decreased to low to non-detectable levels as the pH within the iron has increased over time (as high as 9 or 10). Iron and soil core samples were taken in February 1999 and May 2000 in order to evaluate the iron surface passivation, morphology, mineral precipitation and cementation, and microbial activity within and in the vicinity of the iron barrier. Results indicate that most of the iron filings collected in cores were still loose and not clogged after approximately 2.5 years of barrier installation. However, significant amounts of cemented iron filings were observed in the upgradient portion of the iron. In particular, the cementation appeared to have increased significantly over time from the 1999 to 2000 coring events in both the upgradient and downgradient portions of the iron. Minerals identified by scanning electron microscope (SEM), energy dispersive x-ray (EDX), and x-ray diffraction (XRD) that have precipitated in the iron include iron sulfide, calcium carbonate (aragonite), iron oxyhydroxides (goethite, akagneite, amorphous), siderite (iron carbonate), makinawite, and green rusts. These mineral precipitants are responsible for the cementation observed within the iron barrier. Elevated microbial activity and increased diversity within and in the vicinity of the iron barrier were also observed, particularly denitrifiers and sulfate-reducers, which may have been responsible or partially responsible for the removal of nitrate and sulfate in groundwater and the formation of ferrous sulfide minerals within the iron barrier. Hydraulic gradients across the Pathway 2 site have remained relatively stable and consistent from east to west. Increases and decreases in the gradients across the site observed over the past 2.5 years appear to be primarily related to recharge during precipitation events and seasonal fluctuations. However, closer inspection of gradient fluctuations within the iron appear to indicate that cementation within the iron may be starting to impact groundwater flow through the iron. Since the spring of 1999, recharge events have had a more pronounced impact on hydraulic gradients observed between wells located upgradient, within, and downgradient of the iron. This data suggests that the connectivity of the iron and gravel in the upgradient portion of the trench to the iron and gravel in the downgradient portion of the trench may be decreasing over time due to cementation in the iron.
Watson, D.B.
Laboratory study on sequenced permeable reactive barrier remediation for landfill leachate-contaminated groundwater
Permeable reactive barrier (PRB) was a promising technology for groundwater remediation. Landfill leachate-polluted groundwater riches in various hazardous contaminants. Two lab-scale reactors (reactors A and B) were designed for studying the feasibility of PRB to remedy the landfill leachate-polluted groundwater. Zero valent iron (ZVI) and the mixture of ZVI and zeolites constitute the first section of the reactors A and
Dong Jun; Zhao Yongsheng; Zhang Weihong; Hong Mei
Field Monitoring of a Permeable Reactive Barrier for Removal of Chlorinated Organics
The application of zero-valent iron Fe0 in the funnel-and-gate permeable reactive barrier PRB installed at the Vapokon site, Denmark, was conducted in 1999 to remediate the groundwater contaminated by chlorinated aliphatic hydrocarbons CAHs. Over the past 4 years, except in September 2002 and January 2003, about 92.4-97.5% CAH removal could be achieved with the PRB. Although there was a continuous
Keith C. K. Lai; Irene M. C. Lo; Vibeke Birkelund; Peter Kjeldsen
High-density chemical intercalation of zero-valent copper into Bi2Se3 nanoribbons.
A major goal of intercalation chemistry is to intercalate high densities of guest species without disrupting the host lattice. Many intercalant concentrations, however, are limited by the charge of the guest species. Here we have developed a general solution-based chemical method for intercalating extraordinarily high densities of zero-valent copper metal into layered Bi(2)Se(3) nanoribbons. Up to 60 atom % copper (Cu(7.5)Bi(2)Se(3)) can be intercalated with no disruption to the host lattice using a solution disproportionation redox reaction. PMID:22524598
Koski, Kristie J; Cha, Judy J; Reed, Bryan W; Wessells, Colin D; Kong, Desheng; Cui, Yi
Long-term efficiency and kinetic evaluation of ZVI barriers during clean-up of copper containing solutions
Sixteen continuous column experiments were carried out under dynamic flow conditions in order to study the efficiency of zero-valent iron (ZVI) permeable reactive barriers (PRBs) to remove copper from solutions. The effect of various operational parameters, such as pH of the feed solution (2.5 and 4.5), initial copper concentration (5 and 50mg\\/L), pore water velocity (30.48 and 152.40cm\\/day) and residence
K. Komnitsas; G. Bartzas; K. Fytas; I. Paspaliaris
Hydrogeochemical and biological processes affecting the long-term performance of an iron-based permeable reactive barrier.
Despite the wide diffusion of zero-valent iron (Fe(0)) permeable reactive barriers (PRBs), there is still a great uncertainty about their longevity and long-term performance. The aim of this study is to investigate the biological and the hydrogeochemical processes that take place at a Fe(0) installation located in Avigliana, Italy, and to derive some general considerations about long-term performance of PRBs.The examined PRB was installed in November 2004 to remediate a chlorinated solvents plume (mainly trichloroethene and 1,2-dichloroethene). The investigation was performed during the third year of operation and included: (1) groundwater sampling and analysis for chlorinated solvents, dissolved CH(4), dissolved H(2) and major inorganic constituents; (2) Fe(0) core sampling and analysis by SEM-EDS, XRD, and FTIR spectroscopy for the organic fraction; (3) in situ permeability tests and flow field monitoring by water level measurements.The study revealed that iron passivation is negligible, as the PRB is still able to effectively treat the contaminants and to reduce their concentrations below target values. Precipitation of several inorganic compounds inside the PRB was evidenced by SEM-EDS and XRD analysis conducted on iron samples. Groundwater sampling evidenced heavy sulfate depletion and the highest reported CH(4) concentration (>5,000 microg/L) at zero-valent iron PRB sites. These are due to the intense microbial activity of sulfate-reducers and methanogens, whose proliferation was most likely stimulated by the use of a biopolymer (i.e. guar gum) as shoring fluid during the excavation of the barrier. Slug tests within the barrier evidenced an apparent hydraulic conductivity two orders of magnitude lower than the predicted value. This occurrence can be ascribed to biofouling and/or accumulation of CH(4)(g) inside the iron filings.This experience suggests that when biopolymer shoring is planned to be used, long-term column tests should be performed beforehand with initial bacterial inoculation and organic substrate dosing, in order to predict the effects of bacterial overgrowth and gas generation. During construction particular care should be taken in order to minimize the amount of used biopolymer so that complete breakdown can be achieved. PMID:19329678
Zolla, Valerio; Freyria, Francesca Stefania; Sethi, Rajandrea; Di Molfetta, Antonio
Thallium(I) as a coordination site protection agent: preparation of an isolable zero-valent nickel tris-isocyanide.
Blocking the pass: Low-valent Ni centers readily bind Tl(I) ions in a synthetically reversible fashion. The Tl units, in turn, serve as coordination site protection agents for Ni with respect to incoming Lewis basic ligands. This synthetic sequence allows for the isolation of a reactive zero-valent Ni tris-isocyanide complex. PMID:19173272
Fox, Brian J; Millard, Matthew D; DiPasquale, Antonio G; Rheingold, Arnold L; Figueroa, Joshua S
Fundamental studies of the removal of contaminants from ground and waste waters via reduction by zero-valent metals. Annual progress report, September 1, 1996--August 31, 1997
'Contaminated groundwater is a problem throughout the US and the world. In many instances the tvpes of contamination can be directly attributed to man''s actions. For instance, the burial of wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements that are soluble and mobile in soils and aquifers. Oxyanions of selenium. chromium. uranium. arsenic. and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. In addition. the careless disposal of cleaning solvents. such as carbon tetrachloride and trichloroethylene. has further contaminated many groundwaters at these sites. In agricultural areas of the western US, shallow groundwaters have become contaminated with high levels of selenate, chromate, and uranyl. The management of these waters requires treatment to remove the contaminants before reuse or surface water disposal. In one instance in the Central Valley of California. the discharge of selenate-contaminated shallow groundwater to a wildlife refuge caused catastrophic bird deaths and deformities of embryos. At sites where solid-propellant rocket motors were tested or disposed of, high concentrations of perchlorate and trichloroethylene are being found in the groundwater. A potential remediation method for many of these oxyanions and chlorinated-solvents is to react the contaminated water with zero-valent iron. In this reaction, the iron serves as both an electron source and as a catalyst. Elemental iron is already being used, on an experimental basis, for the reductive dechlorination of solvents and the removal of toxic trace elements. Both in situ reactive barriers and above-ground reactors are being developed for this purpose. However, the design and operation of these treatment systems requires a detailed process-level understanding of the interactions between the contaminants and the iron surfaces. Only limited success has been achieved in the field, partly because the basic surface chemical reactions are not well understood. The authors are performing fundamental investigations of the interactions of the relevant chlorinated solvents, trace elements, and trace element-containing compounds with single- and poly-crystalline Fe surfaces. The aim of this work is to develop the fundamental physical and chemical understanding that is necessary for the development of cleanup techniques and procedures. The authors are perforrming both bulk chemical measurements of the reduction reactions and surface science studies of model chemical systems. During this first year of funding, the authors have already made significant progress in both areas. Initially, they have focused primarily on the reduction of selenate by elemental iron. They have also performed some work with chromate, perchlorate, uranyl, and carbon tetrachloride, as well. In the following sections, some of the progress is described.'
EPA/ITRC-RTDF permeable reactive barrier short course. Permeable reactive barriers: Application and deployment
This report focuses on the following: Permeable Reactive Barriers: Application and Deployment; Introduction to Permeable Reactive Barriers (PRBs) for Remediating and Managing Contaminated Groundwater in Situ; Collection and Interpretation of Design Data 1: Site Characterization for PRBs; Reactive Materials: Zero-Valent Iron; Collection and Interpretation of Design Data 2: Laboratory and Pilot Scale Tests; Design Calculations; Compliance Monitoring, Performance Monitoring and Long-Term Maintenance for PRBs; PRB Emplacement Techniques; PRB Permitting and Implementation; Treatment of Metals; Non-Metallic Reactive Materials; Economic Considerations for PRB Deployment; and Bibliography.
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Reaction of zero-valent magnesium with water: Potential applications in environmental remediation
This study examined the dissolution kinetics of granular zero-valent Mg (ZVMg) at pH 7 in water that was open to the atmosphere and buffered with 50 mM Na-MOPS. The oxidative dissolution of ZVMg was rapid; the initial amount of ZVMg (10-50 mg/L) dissolved completely within 200 min. The rate and extent of ZVMg dissolution was not affected by atmospheric oxygen. Although the oxidation of ZVMg is thermodynamically more feasible by dissolved oxygen or proton ions (H+), the primary oxidants are water molecules. The initial rate of ZVMg dissolution obeys first order kinetics with respect to ZVMg concentration with an observed rate constant, kMg,7 = 1.05 ± 0.06 × 10-2 min-1. Model calculations using the rate constant perfectly predict the extent of ZVMg dissolution for an extended time period at lower [Mg0]0 but underestimate at 50 mg/L [Mg0]0. The offset is likely attributed to the rapid dissolution of ZVMg particles, which could cause a substantial increase in the specific surface area. As to the reactivity of Mg-water system, we suggest that the hydrated electron (eaq-), the most powerful reducing agent, would probably be the major reactive entity under neutral and alkaline conditions. In addition, we discuss briefly the factors affecting the rate and extent of the Mg-water reaction such as background electrolytes, ZVMg impurities, surface passivation, solution pH and temperature based on literature review.
Lee, Giehyeon; Park, Jaeseon
The remediation performance of a specific electrokinetics integrated with zero-valent metals for perchloroethylene contaminated soils
This research was conducted to evaluate an integrated technique, combination of the electrokinetics (EK) and zero-valent metal (ZVM), for remediation of the perchloroethylene (PCE) contaminated soils. Various experimental conditions were controlled such as different voltage gradients, the position of ZVM, and ZVM species. The appropriate operational parameters are concluded as follows: (1) 0.01M sodium carbonate serves as the working solution;
Jih-Hsing Chang; Shu-Fen Cheng
Iron Sulfide as a Sustainable Reactive Material for Permeable Reactive Barriers
Permeable reactive barriers (PRBs) are gaining acceptance for groundwater remediation, as they operate in situ and do not require continuous energy input. The majority of PRBs use zero-valent iron (ZVI). However, some ZVI PRBs have hydraulically failed [1,2], due to the fact that ZVI may reduce not only contaminants but also water and non-contaminant solutes. These reactions may form precipitates or gas phases that reduce permeability. Therefore, there is a need to assess the hydraulic suitability of possible alternatives, such as iron sulfide (FeS). The capability of FeS to remove both metals and halogenated organics from aqueous systems has been demonstrated previously [3,4], and FeS formed in situ within a ZVI PRB has been linked to contaminant removal [5]. These results suggest possible applications in groundwater remediation as a permeable reactive barrier (PRB) material. However, the propensity of FeS for permeability loss, due to solids and gas production, must be evaluated in order to address its suitability for PRBs. The reduction in permeability for FeS-coated sands under the anoxic conditions often encountered at contaminated groundwater sites was examined through column experiments and geochemical modeling under conditions of high calcium and nitrate, which have been previously shown to cause significant permeability reduction in zero-valent iron (ZVI) systems [6]. The column experiments showed negligible production of both solids and gases. The geochemical model was used to estimate solid and gas volumes generated under conditions of varying FeS concentration. Then, the Kozeny-Carman equation and a power-law relationship was used to predict permeability reduction, with a maximum reduction in permeability of 1% due to solids and about 30% due to gas formation under conditions for which a complete loss of permeability was predicted for ZVI systems. This difference in permeability reduction is driven by the differences in thermodynamic stability of ZVI and FeS in aqueous solutions. The results suggest that geochemical conditions that result in high permeability losses for ZVI systems will necessarily not be problematic, from a permeability perspective, for FeS-based reactive materials. Therefore, this research represents an important advance for sustainable groundwater remediation. References: [1] Mushovic, P., Bartlett, T. R., Morrison, S. (2006) Tech. News & Trends 23, 1-3. [2] Kiilerich, O., Larsen, J. W., Nielsen, C., Deigaard, L. D. (2000) In: Wickramanayake, G.B., et al. (Eds.), Chemical Oxidation and Reactive Barriers: Remediation of Chlorinated and Recalcitrant Compounds, Battelle Press, Columbus, OH, 377-384. [3] Han, Y., Gallegos, T. J., Demond, A. H., Hayes, K. F. (2011) Water Res. 45(2), 593-604. [4] Jeong, H. Y. and Hayes, K. F. (2007) Environ. Sci. Technol. 41(18), 6390-6396. [5] Beak, D. G. and Wilkin, R. T. (2009) J. Contam. Hydrol. 106(1-2), 15-28. [6] Henderson, A. D. and Demond, A. H. (2007) Environ. Eng. Sci. 24(4), 401-423.
Henderson, A. D.; Demond, A. H.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
Azo dye degradation by recycled waste zero-valent iron powder
Neste trabalho é apresentado um método eficiente para a degradação de corantes, usando uma fonte de pó de ferro zero ambientalmente amigável (resíduo de um processo industrial). A influência de vários fatores experimentais (tais como: pH, massa de ferro, tamanho de partícula, concentração do substrato, atmosfera inerte ou oxidante) sobre a eficiência do ferro zero em reduzir o grupo cromóforo
Wellington S. Pereira; Renato S. Freire
In field arsenic removal from natural water by zero-valent iron assisted by solar radiation
An in situ arsenic removal method applicable to highly contaminated water is presented. The method is based in the use of steel wool, lemon juice and solar radiation. The method was evaluated using water from the Camarones River, Atacama Desert in northern Chile, in which the arsenic concentration ranges between 1000 and 1300?gL?1. Response surface method analysis was used to
Lorena Cornejo; Hugo Lienqueo; María Arenas; Jorge Acarapi; David Contreras; Jorge Yáñez; Héctor D. Mansilla
This pilot test has been carried out as part of a RCRA Corrective Measure Study (CMS) at a facility located in Research Triangle Park, North Carolina. The study area is located in the Durham subbasin of the Deep River Triassic Basin and is underlain by interbedded siltstone and sandstone sequences. Groundwater underlying portions of the site has been impacted by
Robert Glazier; Florin Gheorghiu; Lindsey Walata; Ramesh Venkatakrishnan
An innovative in-situ soil treatment process, referred to as soil mixing/thermally enhanced soil vapor extraction (SM/TESVE), was used to remediate the 317 Area of Argonne National Laboratory-East (i.e., Argonne), which is contaminated with volatile organ...
P. L. Lynch
The generation and release of acidic, metal-rich water from mine wastes continues to be an intractable environmental problem. Although the effects of acid mine drainage (AMD) are most evident in surface waters, there is an obvious need for developing cost-effective approaches fo...
Effects of zero-valent metals together with quartz sand on the mechanochemical destruction of dechlorane plus coground in a planetary ball mill.
Mechanochemical destruction by grinding with additives in high energy ball milling has been identified as a good alternative to traditional incineration for the disposal of wastes containing halogenated organic pollutants. Despite CaO normally used as an additive, recently Fe+SiO2 has been used to replace CaO for a faster destruction. In the present study, zero-valent metals (Al, Zn, besides Fe) together with SiO2 were investigated for their efficiencies of prompting the destruction of dechlorane plus (DP). Aluminum was found of be the best with a destruction percentage of nearly 99% for either syn- or anti-DP after 2.5h milling. In comparison, only 88/85% and 37/32% of syn-/anti-DP were destroyed when using zinc and iron after the same time, respectively. The detected water soluble chloride was lower than the stoichiometric amount containing in the original DP samples, due to the Si-Cl bond formed during the process. The potential fate of C and Cl present in DP is in the form of inorganic carbon, inorganic Cl and formation of Si-Cl bonds, respectively. The results suggested that Al+SiO2 is promising in the mechanochemical destruction of chlorinated organic pollutants like DP. PMID:24295775
Wang, Haizhu; Huang, Jun; Zhang, Kunlun; Yu, Yunfei; Liu, Kai; Yu, Gang; Deng, Shubo; Wang, Bin
Changes in Ground-Water Quality near Two Granular-Iron Permeable Reactive Barriers in a Sand and Gravel Aquifer, Cape Cod, Massachusetts, 1997-2000
Two experimental permeable reactive barriers (PRBs) of granular zero-valent iron were emplaced in the path of a tetrachloroethene plume (the Chemical Spill-10 plume) at the Massachusetts Military Reservation, Cape Cod, Massachusetts, in June 1998. The goal of the field experiment was to achieve emplacement of a granular-iron PRB deeper than attempted before. The PRBs were expected to create a reducing environment and degrade the tetrachloroethene by reductive dechlorination. The goal of the work presented in this report was to observe temporary and sustained changes to the ground-water chemistry downgradient from the PRBs. A hydraulic-fracturing method involving injection of the granular iron with a guar-biopolymer and enzyme slurry was used to install the parallel 30- to 33-foot-wide wall-shaped barriers at a depth of 82 to 113 feet below land surface. An acetic acid and enzyme mixture was subsequently injected in wells near the barriers to degrade the guar biopolymer. Prior to the emplacement, tetrachloroethene concentrations in the Chemical Spill-10 plume at the study area were as high as 250 micrograms per liter. Other water properties in the plume generally were similar to the properties of uncontaminated ground water in the area, which typically has dissolved oxygen concentrations of 250 to 375 micromoles per liter, pH of 5.5 to 6.0, and specific conductance of 60 to 90 microsiemens per centimeter. Water-quality samples were collected periodically from monitoring wells near the PRBs to determine how the emplacement of the granular-iron walls altered the ground-water quality. In addition, an automated well-sampling device measured temperature, specific conductance, pH, and dissolved oxygen every 1?4 days for 16 months in a well downgradient from the two parallel PRBs. Temporary increases (lasting about 5 to 6 months) in specific conductance were observed downgradient from the PRBs as a result of the sodium chloride, potassium carbonate, and other salts included in the slurry and the acetic acid and enzyme mixture that was subsequently injected to degrade the guar biopolymer. Temporary increases in the concentrations of major cations (sodium, potassium, magnesium, and calcium) were observed downgradient from the PRBs, as were temporary but substantial increases in the dissolved and total organic carbon concentrations. Methane was detected, sulfate concentrations decreased temporarily, and concentrations of dissolved inorganic carbon increased in samples from wells downgradient from the PRBs. A sustained (longer than 12 months) reducing environment, in which dissolved oxygen concentrations decreased to zero, the pH increased to about 6.8, and dissolved iron concentrations increased substantially, developed as a result of the oxidation (corrosion) of the granular iron; this zone persisted at least 65 feet downgradient from the PRBs. The pH and dissolved iron concentrations increased with distance from the granular-iron walls. Concentrations of arsenic, cobalt, manganese, and phosphorus increased, and nitrate concentrations were reduced to below the detection limit downgradient from the walls. A sustained decrease of tetrachloroethene concentrations was not observed; however, reductive dechlorination products were observed at wells downgradient from the PRBs during several rounds of sampling. The emplacement of zero-valent iron in the aquifer to remove tetrachloroethene from the ground water caused changes in the water chemistry that persisted farther downgradient from the PRBs than has been observed at other sites because of the low chemical reactivity of the quartz-dominated aquifer sediments and the low ambient dissolved chemical concentrations in the ground water. The small transverse dispersion in the aquifer and the probable long-term persistence of the iron indicate that the chemically altered zone probably will extend a substantial distance downgradient from the PRBs for a substantial period of time (years); fur
Savoie, Jennifer G.; Kent, Douglas B.; Smith, Richard L.; LeBlanc, Denis R.; Hubble, David W.
Preparation of spherical iron nanoclusters in ethanol–water solution for nitrate removal
In this study, a higher surface area spherical nanoscale zero valent iron (HNZVI) cluster (80nm, 54.25m2g?1) was synthesized in ethanol–water mixed solvent in the presence of dispersion agent of polyglycol (PEG). At the same time, a lower surface area nanoscale zero valent iron (LNZVI) particle (80nm, 8.08m2g?1) was also prepared with only de-ioned water as reaction media. Their structures, compositions
Wei Wang; Zhao-hui Jin; Tie-long Li; Huan Zhang; Si Gao
Removal of Cr(VI) from simulative contaminated groundwater by iron metal
The Cr(VI) removal from simulative contaminated groundwater using zero-valent iron (Fe0) filings, Fe0 powder and nanoscale Fe0 in batch experimental mode was studied. Cr(VI) is a primary pollutant of some soils and groundwater. Zero-valent iron, an important natural reductant, could transform Cr(VI) to Cr(III) which is much less toxic and immobile. The Cr(VI) removal percentage was 87% at a metal
Naman Cissoko; Zhen Zhang; Jinghui Zhang; Xinhua Xu
Cysteine-induced modifications of zero-valent silver nanomaterials: implications for particle surface chemistry, aggregation, dissolution, and silver speciation.
The persistence of silver nanoparticles in aquatic environments and their subsequent impact on organisms depends on key transformation processes, which include aggregation, dissolution, and surface modifications by metal-complexing ligands. Here, we studied how cysteine, an amino acid representative of thiol ligands that bind monovalent silver, can alter the surface chemistry, aggregation, and dissolution of zero-valent silver nanoparticles. We compared nanoparticles synthesized with two coatings, citrate and polyvinylpirrolidone (PVP), and prepared nanoparticle suspensions (approximately 8 ?M total Ag) containing an excess of cysteine (400 ?M). Within 48 h, up to 47% of the silver had dissolved, as indicated by filtration of the samples with a 0.025-?m filter. Initial dissolution rates were calculated from the increase of dissolved silver concentration when particles were exposed to cysteine and normalized to the available surface area of nanoparticles in solution. In general, the rates of dissolution were almost 3 times faster for citrate-coated nanoparticles relative to PVP-coated nanoparticles. Rates tended to be slower in solutions with higher ionic strength in which the nanoparticles were aggregating. X-ray absorption spectroscopy analysis of the particles suggested that cysteine adsorbed to silver nanoparticles surfaces through the formation of Ag(+I)--sulfhydryl bonds. Overall, the results of this study highlight the importance of modifications by sulfhydryl-containing ligands that can drastically influence the long-term reactivity of silver nanoparticles in the aquatic environment and their bioavailability to exposed organisms. Our findings demonstrate the need to consider multiple interlinked transformation processes when assessing the bioavailability, environmental risks, and safety of nanoparticles, particularly in the presence of metal-binding ligands. PMID:22448900
Gondikas, Andreas P; Morris, Amanda; Reinsch, Brian C; Marinakos, Stella M; Lowry, Gregory V; Hsu-Kim, Heileen
Experimental design and response surface modelling for optimization of vat dye from water by nano zero valent iron (NZVI).
In this study, NZVI particles was prepared and studied for the removal of vat green 1 dye from aqueous solution. A four-factor central composite design (CCD) combined with response surface modeling (RSM) to evaluate the combined effects of variables as well as optimization was employed for maximizing the dye removal by prepared NZVI based on 30 different experimental data obtained in a batch study. Four independent variables, viz. NZVI dose (0.1-0.9 g/L), pH (1.5-9.5), contact time (20-100 s), and initial dye concentration (10-50 mg/L) were transform to coded values and quadratic model was built to predict the responses. The significant of independent variables and their interactions were tested by the analysis of variance (ANOVA). Adequacy of the model was tested by the correlation between experimental and predicted values of the response and enumeration of prediction errors. The ANOVA results indicated that the proposed model can be used to navigate the design space. Optimization of the variables for maximum adsorption of dye by NZVI particles was performed using quadratic model. The predicted maximum adsorption efficiency (96.97%) under the optimum conditions of the process variables (NZVI dose 0.5 g/L, pH 4, contact time 60 s, and initial dye concentration 30 mg/L) was very close to the experimental value (96.16%) determined in batch experiment. In the optimization, R2 and R2adj correlation coefficients for the model were evaluated as 0.95 and 0.90, respectively. PMID:24362989
Arabi, Simin; Sohrabi, Mahmoud Reza
Removal of Nitrate and Ammonium ions from Livestock Wastewater by Hybrid Systems Composed of Zero-Valent Iron and Adsorbents
The feasibility of hybrid systems for simultaneous removal of nitrate (NO) and ammonium ions (NH) from livestock wastewater was examined in batch experiments. As a part of efforts to remove nitrate and ammonium simultaneously, Fe and adsorbents including coconut-based granular activated carbon (GAC), sepiolite and filtralite were used. Various parameters such as adsorbent dosages and temperature were studied. Removal of
Min-Kyu Ji; Yong-Tae Ahn; Moonis Ali Khan; Reda A. I. Abou-Shanab; Yunchul Cho; Jae-Young Choi; Yong Je Kim; Hocheol Song; Byong-Hun Jeon
Removal of high concentration p-nitrophenol in aqueous solution by zero valent iron with ultrasonic irradiation (US-ZVI).
In this study, the US-ZVI system was used to produce the strong reductants including H and nascent Fe(2+) ions to eliminate the toxicity of the high concentration p-nitrophenol (PNP) wastewater. The effect of the reactor structure, initial pH, ZVI dosage, ultrasonic power and initial PNP concentration on the removal efficiency of PNP from water was investigated intensively. The results show that a higher removal rate can be obtained by using a conical structure reactor, and the lower initial pH can aid the acceleration of PNP removal rate by using US-ZVI system. Furthermore, the removal efficiencies of PNP increased obviously with the increase of initial ZVI concentration from 0 to 15 gL(-1). Also, the treatment capacity of ZVI was enhanced remarkably by the ultrasonic irradiation, and the US-ZVI system can maintain high treatment efficiency for the high concentration PNP wastewater (500-10,000 mgL(-1)). Meanwhile, the high removal efficiency of PNP was mainly resulted from the synergistic reaction of ZVI and US. At last, the main degradation product (i.e., p-aminophenol) was detected by gas chromatography-mass spectrum (GC-MS). Thus, the reaction pathway of PNP in the US-ZVI system is proposed as a reducing process by the H and nascent Fe(2+) ions. PMID:23454461
Lai, Bo; Chen, Zhaoyu; Zhou, Yuexi; Yang, Ping; Wang, Juling; Chen, Zhiqiang
Investigating the potential for long-term permeable reactive barrier (PRB) monitoring from the electrical signatures associated with the reduction in reactive iron performance
The objective of this work was to conduct laboratory and field experiments to determine the sensitivity of low frequency electrical measurements (resistivity and induced polarization) to the processes of corrosion and precipitation that are believed to limit permeable reactive barrier (PRB) performance. The research was divided into four sets of experiments that were each written up and submitted to a peer-reviewed journal: [1] A laboratory experiment to define the controls of aqueous chemistry (electrolyte activity; pH; valence) and total zero valent iron (Fe0) available surface area on the electrical properties of Fe0 columns. [2] A laboratory experiment to determine the impact of corrosion and precipitation on the electrical response of synthetic Fe0 columns as a result of geochemical reactions with NaSO4 and NaCO3 electrolytes. [3] Laboratory experiments on a sequence of cores retrieved from the Kansas City PRB to determine the magnitude of electrical and geochemical changes within a field active PRB after eight years of operation [4] Field-scale cross borehole resistivity and induced polarization monitoring of the Kansas City PRB to evaluate the potential of electrical imaging as a technology for non-invasive, long-term monitoring of indicators of reduced PRB performance This report first summarizes the findings of the four major experiments conducted under this research. The reader is referred to the four papers in Appendices 1-4 for a full description of each experiment, including motivation and significance, technical details, findings and implications. The deliverables of the project, including the publications, conference papers and new collaborative arrangements that have resulted are then described. Appendices 5-6 contain two technical reports written by co-PI Korte describing (1) supporting geochemical measurements, and (2) the coring procedure, conducted at the Kansas City PRB as part of this project.
Slater, Lee D.; Korte, N.; Baker, J.
Groundwater Performance Monitoring of an Iron Permeable Reactive Barrier
Azimuth controlled vertical hydraulic fracturing technology constructed a full scale in situ iron permeable reactive barrier (PRB) at moderate depth at a Superfund site for remediation of groundwater contaminated with chlorinated solvents, primarily trichloroethene (TCE). The iron permeable reactive barrier was completed in late 1999 and was two hundred and forty (240) feet in length, three (3) inches in average
Grant Hocking; Samuel L. Wells
Selected hydrologic data for the field demonstration of three permeable reactive barriers near Fry Canyon, Utah, 1996-2000
Three permeable reactive barriers (PRBs) were installed near Fry Canyon, Utah, in August 1997 to demonstrate the use of PRBs to control the migration of uranium in ground water. Reactive material included (1) bone-char phosphate, (2) zero-valent iron pellets, and (3) amorphous ferric oxyhydroxide coated gravel. An extensive monitoring network was installed in and around each PRB for collection of water samples, analysis of selected water-quality parameters, and monitoring of water levels. Water temperature, specific conductance, pH, Eh (oxidation-reduction potential), and dissolved oxygen were measured continuously within three different barrier materials, and in two monitoring wells. Water temperature and water level below land surface were electronically recorded every hour with pressure transducers. Data were collected from ground-water monitoring wells installed in and around the PRBs during 1996-98 and from surface-water sites in Fry Creek.
Wilkowske, Chris D.; Rowland, Ryan C.; Naftz, David L.
Stabilization of Zero-Valent Hydrazido Complexes by Phosphine Ligands. Crystal Structure of fac-(CO)3(DPPE)W=NNMe2, a Nitrene Analogue to Fischer Carbenes. (Reannouncement with New Availability Information).
The generation of zero-valent transition metal nitrene (or imido) and hydrazido complexes of the form L5M=NR (1) has been the subject of several reports in recent years, but in all cases these compounds have proven too labile for isolation. Interest in th...
B. A. Arndtsen T. K. Schoch L. McElwee-White
Catalytic gasification of carbon using iron
Iron is an active catalyst for the steam gasification of carbon provided the reaction environment is controlled to maintain the zero valent state. It is also active for the hydrogasification of carbon. When graphite is gasified with steam and hydrogen at atmospheric pressure and temperatures around 500° to 700°C the only products which are formed in appreciable quantities are carbon
C. R. F. Lund; R. T. K. Baker
Iron Hydroxy Carbonate Formation in Zerovalent Iron Permeable Reactive Barriers: Characterization and Evaluation of Phase Stability
Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently obs...
Mineral precipitates in zero-valent iron PRBs can be classified by formation processes into three groups: 1) those that result from changes in chemical conditions (i.e., change in pH, e.g., calcite); 2) those that are a consequence of microbial activity (i.e., sulfate reduction, ...
Results are presented from laboratory batch tests using zero-valent iron to treat arsenic-contaminated groundwater. The laboratory tests were conducted using near- neutral pH groundwater from a contaminated aquifer located adjacent to a custom smelting facility. Experiments we...
Halogenated organic compounds are common pollutants in groundwater. Consequently, there is widespread interest in understanding the reactions of these compounds in the environment and developing remediation strategies. One area of ongoing research involves the reductive dechlo...
Use of Electrophoresis for Transporting Nano-Iron in Porous Media
Research was conducted to evaluate if electrophoresis could transport surface stabilized nanoscale zero-valent iron (nZVI) through fine grained sand with the intent of remediating a contaminant in situ. The experimental procedure involved determining the transport rates of poly...
Iron(II,III)-polyphenol complex nanoparticles derived from green tea exhibit a high ecotoxicological hazard
There are several greener methods exist to synthesize zero–valent iron nanoparticles (nZVI) using different bio-based reducing agents. Although their useful properties in degradation of organic dyes, chlorinated organics, or arsenic have been described earlier, their charac...
Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of PRBs. Both processes can impact remedial performance by affecting zero-valent iron reactivity and permeability. Results will be presented from solid-phase and gro...
Monitoring the removal of phosphate from ground water discharging through a pond-bottom permeable reactive barrier
Installation of a permeable reactive barrier to intercept a phosphate (PO4) plume where it discharges to a pond provided an opportunity to develop and test methods for monitoring the barrier's performance in the shallow pond-bottom sediments. The barrier is composed of zero-valent-iron mixed with the native sediments to a 0.6-m depth over a 1100-m2 area. Permanent suction, diffusion, and seepage samplers were installed to monitor PO 4 and other chemical species along vertical transects through the barrier and horizontal transects below and near the top of the barrier. Analysis of pore water sampled at about 3-cm vertical intervals by using multilevel diffusion and suction samplers indicated steep decreases in PO4 concentrations in ground water flowing upward through the barrier. Samples from vertically aligned pairs of horizontal multiport suction samplers also indicated substantial decreases in PO4 concentrations and lateral shifts in the plume's discharge area as a result of varying pond stage. Measurements from Lee-style seepage meters indicated substantially decreased PO4 concentrations in discharging ground water in the treated area; temporal trends in water flux were related to pond stage. The advantages and limitations of each sampling device are described. Preliminary analysis of the first 2 years of data indicates that the barrier reduced PO4 flux by as much as 95%. ?? 2009 National Ground Water Association.
McCobb, T. D.; LeBlanc, D. R.; Massey, A. J.
Reductive denitrification of nitrate by scrap iron filings*
Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.
Hao, Zhi-wei; Xu, Xin-hua; Wang, Da-hui
Investigating dominant processes in ZVI permeable reactive barriers using reactive transport modeling
The reactive and hydraulic efficacy of zero valent iron permeable reactive barriers (ZVI PRBs) is strongly affected by geochemical composition of the groundwater treated. An enhanced version of the geochemical simulation code MIN3P was applied to simulate dominating processes in chlorinated hydrocarbons (CHCs) treating ZVI PRBs including geochemical dependency of ZVI reactivity, gas phase formation and a basic formulation of degassing. Results of target oriented column experiments with distinct chemical conditions (carbonate, calcium, sulfate, CHCs) were simulated to parameterize the model. The simulations demonstrate the initial enhancement of anaerobic iron corrosion due to carbonate and long term inhibition by precipitates (chukanovite, siderite, iron sulfide). Calcium was shown to enhance long term corrosion due to competition for carbonate between siderite, chukanovite, and aragonite, with less inhibition of iron corrosion by the needle like aragonite crystals. Application of the parameterized model to a field site (Bernau, Germany) demonstrated that temporarily enhanced groundwater carbonate concentrations caused an increase in gas phase formation due to the acceleration of anaerobic iron corrosion.
Weber, Anne; Ruhl, Aki S.; Amos, Richard T.
CO hydrogenation over carbon-supported iron-cobalt and potassium-iron-cobalt carbonyl cluster-derived catalysts
FeCo and K-promoted Fe-Co CO hydrogenation catalysts were prepared by dispersing iron, cobalt, and iron-cobalt carbonyl clusters on a clean, high-surface-area carbon support. High dispersions were achieved as indicated by chemisorption and XRD measurements. Because of their zero-valent state and the absence of oxygen functional groups on the carbon surface, these catalysts required no high-temperature reduction for activation. The Coâ(CO)â\\/C
A. A. Chen; M. Kaminsky; G. L. Geoffroy; M. A. Vannice
Phosphate Barriers for Immobilization of Uranium Plumes
Uranium contamination of the subsurface remains a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB?s) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB's, such as zero-valent iron, may be a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorous amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain sodium polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is paramount to preventing fouling of wells at the point of injection.
Icenhower, Jonathan P.; Burns, Peter C.
Uranium contamination of the subsurface remains a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB?s) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB?s, such as zero-valent iron, may be a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorus amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain sodium polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is paramount to preventing fouling of wells at the point of injection.
Burns, Peter C.
The Proton Exchange Membrane Fuel Cells (PEMFCs) are the most preferred and efficient energy conversion devices for automotive applications but demand high purity hydrogen which comes at a premium price. The currently pursued hydrogen generation methods suffer from issues such as, low efficiency, high cost, environmental non-benignity, and, in some cases, commercial non-viability. Many of these drawbacks including the CO
Sathees Kumar Kesavan
Reduction of Contaminant Mobility at the TNX Outfall Delta Through the Use of Apatite and Zero-Valent Iron as Soil Amendments.
The TNX pilot-scale research facility released processed waste, containing high concentrations of several metals and radionuclides into an unlined seepage basin between 1958 and 1980. The contents of this basin have entered the nearby swamp, the TNX Outfa...
D. Kaplan A. Knox C. Coffey
Performance of a Deep Iron Permeable Reactive Barrier for Groundwater Remediation of VOCs
Azimuth controlled vertical hydraulic fracturing technology constructed a full scale in situ iron permeable reactive barrier (PRB) at moderate depth at a Superfund site in south eastern Iowa for remediation of groundwater contaminated with chlorinated solvents, primarily trichlorooethene (TCE). The iron permeable reactive barrier was completed in late 1999 and was two hundred and forty (240) feet in length, three
Grant Hocking; Samuel L. Wells; Rafael I. Ospina; Golder Sierra; LLC Atlanta
Iron hydroxy carbonate formation in zerovalent iron permeable reactive barriers: Characterization and evaluation of phase stability
Predicting the long-term potential of permeable reactive barriers for treating contaminated groundwater relies on understanding the endpoints of biogeochemical reactions between influent groundwater and the reactive medium. Iron hydroxy carbonate (chukanovite) is frequently observed as a secondary mineral precipitate in granular iron PRBs. Mineralogical characterization was carried out using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and X-ray absorption spectroscopy on materials collected from three field-based PRBs in the US (East Helena, MT; Elizabeth City, NC; Denver Federal Center, CO). These PRBs were installed to treat a range of contaminants, including chlorinated organics, hexavalent chromium, and arsenic. Results obtained indicate that chukanovite is a prevalent secondary precipitate in the PRBs. Laboratory experiments on high-purity chukanovite separates were carried out to constrain the room-temperature solubility for this mineral. An estimated Gibbs energy of formation (? fG°) for chukanovite is - 1174.4 ± 6 kJ/mol. A mineral stability diagram is consistent with observations from the field. Water chemistry from the three reactive barriers falls inside the predicted stability field for chukanovite, at inorganic carbon concentrations intermediate to the stability fields of siderite and ferrous hydroxide. These new data will aid in developing better predictive models of mineral accumulation in zerovalent iron PRBs.
Lee, Tony R.; Wilkin, Richard T.
Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface
Dehalogenation of chlorinated aliphatic contaminants at the surface of zero-valent iron metal (Fe0) is mediated by the thin film of iron (hydr)oxides found on Fe0 under environmental conditions. To evaluate the role this oxide film plays in the reduction of chlorinated methanes, carbon tetrachloride (CCl4) degradation by Fe0 was studied under the influence of various anions, ligands, and initial CCl4
Timothy L. Johnson; William Fish; Yuri A. Gorby; Paul G. Tratnyek
Impact of Copper on an Alkali Promoted Iron Fischer–Tropsch Catalyst
Copper has traditionally been added to precipitated iron Fischer–Tropsch (FT) catalysts to facilitate reduction of Fe2O3 to zero valent iron during activation [M.E. Dry, in: J.R. Anderson and M. Boudart (eds), Catalysis Science and Technology, Vol. 1 (Springer-Verlag, New York, 1981) p. 179] by lowering the reduction temperature when activating with hydrogen, carbon monoxide or syngas [R.J. O'Brien et al.,
Robert J. O'Brien; Burtron H. Davis
Geomicrobiological Regeneration of Iron Sulfides in Engineered barrier Systems
The reactive capacity of iron sulfide-based permeable reactive barriers (PRB) to complex and co-precipitate heavy metal ions from groundwater will depend on the potential for regeneration of reactive FeS during the expected lifetime of the PRB. FeS reactivity may decrease in a PRB in time as the result of the following processes: (i) oxidation of FeS and the formation of ferric iron (Fe(III)) oxide solids in the presence of oxygenated groundwater at the entrance of the PRB, (ii) oxidation of FeS in the presence of redox active metals like As(V) with the formation of ferric solids, (iii) co-precipitation of heavy metals within the PRB with the reactive FeS leading to the formation of insoluble metal sulfides co-precipitates with the concomitant release of ferrous iron and formation of ferrous (Fe(II) oxide, hydroxide, or carbonate solids, (iv) clogging of the PRB structure due to formation of precipitate products from processes (i) - (iii).. We have demonstrated the formation of triolite in the presence of an oxidized form of hydrous ferric oxide (HFO), various sulfate concentrations, and biomass densities for the sulfate reducing bacterium (SRB) Desulfovibrio vulgaris. This result has allowed us to demonstrate the feasibility of regeneration of FeS from the ferric oxide and hydroxide solids that may be produced under scenarios (i) and (ii) above as well as to establish the electron donor and acceptor requirements for this SRB. Using Desulfobacterium autotrophicum, both HFO and soluble complexed forms of ferric iron gave rise to the formation of mackinawite. The latter have been shown to react with As (V) and Cd (II) to form ferric solids. Both organisms will be used to generate FeS solids in the presence of crystalline forms of ferric solids expected to form from scenarios (i) and (ii) (e.g., goethite and the mixed Fe(II)/(Fe(III) magnetite, and green rusts) and ferrous iron solids from scenarios (iii) and (iv) (Fe(II) oxides and siderite). Similar to the study completed on HFO and ferric citrate, the FeS solids will be characterized in terms of structure (XRD), conversion efficiency to FeS, and subsequent reactivity in batch systems to As and Cd.
Vannela, R.; Adriaens, P.; Hayes, K. F.
Effects of Mineral Precipitation on the Long-term Performance of Granular Iron Permeable Reactive Barriers
Granular iron permeable reactive barriers (PRBs) have received considerable attention as long term, low-maintenance remediation solutions for groundwater contaminated with chlorinated organics, heavy metals, and radionuclides. However, the long-term effects of mineral precipitation on the performance of the iron still remain uncertain. Laboratory column experiments and numerical simulations were conducted to evaluate the effects of mineral precipitation on the permeability
S. Jeen; D. W. Blowes; R. W. Gillham
Microwave-hydrothermal decomposition of perfluorooctanoic acid in water by iron-activated persulfate oxidation
The microwave-hydrothermal decomposition of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in aqueous solution using persulfate activated by zero-valent iron (ZVI) at 60 and 90°C was examined. The results of laboratory study reveal that when PFOA is treated with 5mM persulfate (PS) and ZVI at 90°C for 2h, 67.6% of PFOA is effectively decomposed to form shorter-chain perfluorinated carboxylic acids (PFCAs)
Yu-Chi Lee; Shang-Lien Lo; Pei-Te Chiueh; Yau-Hsuan Liou; Man-Li Chen
Uranium contamination of the subsurface has remained a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of fissile uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB's) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB?s, such as zero-valent iron, are a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorus amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is key to preventing fouling of wells at the point of injection. Our other fundamental objective is to synthesize and correctly characterize the uranyl phosphate phases that form in the geochemical conditions under consideration. This report summarizes work conducted at the University of Notre Dame through November of 2003 under DOE grant DE-FG07-02ER63489, which has been funded since September, 2002. The objectives at Notre Dame are development of synthesis techniques for uranyl phosphate phases, together with detailed structural and chemical characterization of the myriad of uranyl phosphate phases that may form under geochemical conditions under consideration.
Uranium contamination of the subsurface has remained a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of fissile uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB?s) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB?s, such as zero-valent iron, are a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorous amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is key to preventing fouling of wells at the point of injection. Our other fundamental objective is to synthesize and correctly characterize the uranyl phosphate phases that form in the geochemical conditions under consideration. This report summarizes work conducted at the University of Notre Dame through November of 2003 under DOE grant DE-FG07-02ER63489, which has been funded since September, 2002. The objectives at Notre Dame are development of synthesis techniques for uranyl phosphate phases, together with detailed structural and chemical characterization of the myriad of uranyl phosphate phases that may form under geochemical conditions under consideration.
Chelation of intracellular iron enhances endothelial barrier function: A Role for Vitamin C?
Ascorbic acid improves endothelial barrier function by decreasing the permeability of endothelial cells cultured on semi-porous membrane filters. This decrease was not due to enhanced collagen synthesis and was mimicked by the collagen synthesis inhibitor ethyl-3, 4-dihydroxybenzoic acid (EDHB). Since EDHB is known to chelate intracellular free iron, the effects of two membrane-permeant iron chelators were tested on endothelial permeability. Both 2,2?-dipyridyl and desferrioxamine decreased trans-endothelial permeability in a concentration-dependent manner. Increasing intracellular iron with a chelate of 8-hydroxyquinoline and ferric iron prevented effects of both EDHB and intracellular ascorbate. That EDHB and ascorbate did in fact chelate intracellular iron was supported by finding that they both decreased the cellular fluorescence quenching of the iron-sensitive dye Phen green SK. These results show that chelation of intracellular iron decreases endothelial barrier permeability and implicate this mechanism in the ability of EDHB and possibly intracellular ascorbate to tighten the endothelial barrier.
May, James M.; Qu, Zhi-chao
Effect of Geochemical and Physical Heterogeneity on the Hanford 100D Area In Situ Redox Manipulation Barrier Longevity
The purpose of this study was to quantify the influence of physical and/or geochemical heterogeneities in the Hanford 100D area In Situ Redox Manipulation (ISRM) barrier, which may be contributing to the discontinuous chromate breakthrough locations along the 65-well (2,300 ft long) barrier. Possible causes of chromate breakthrough that were investigated during this study include: (1) high hydraulic conductivity zones; (2) zones of low reducible iron; and (3) high hydraulic conductivity zones with low reducible iron. This laboratory-scale investigation utilized geochemical and physical characterization data collected on 0.5 to 1 foot intervals from four borehole locations. Results of this laboratory study did not provide definitive support any of the proposed hypotheses for explaining chromate breakthrough at the Hanford 100-D Area ISRM barrier. While site characterization data indicate a significant degree of vertical variability in both physical and geochemical properties in the four boreholes investigated, lateral continuity of high conductivity/low reductive capacity zones was not observed. The one exception was at the water table, where low reductive capacity and high-K zones were observed in 3 of four boreholes. Laterally continuous high permeability zones that contain oxic sediment near the water table is the most likely explanation for high concentration chromium breakthrough responses observed at various locations along the barrier. A mechanism that could explain partial chromate breakthrough in the ISRM barrier is the relationship between the field reductive capacity and the rate of chromate oxidation. Subsurface zones with low reductive capacity still have sufficient ferrous iron mass to reduce considerable chromate, but the rate of chromate reduction slows by 1 to 2 orders of magnitude relative to sediments with moderate to high reductive capacity. The original barrier longevity estimate of 160 pore volumes for homogeneous reduced sediment, or approximately 20 years, (with 5 mg/L dissolved oxygen and 2 ppm chromate) is reduced to 85 pore volumes (10 years) when the wide spread 60 ppm nitrate plume is included in the calculation. However, this reduction in barrier lifetime is not as great for high permeability channels, as there is insufficient time to reduce nitrate (and consume ferrous iron). If the cause of laterally discontinuous breakthrough of chromate along the ISRM barrier is due to oxic transport of chromate near the water table, additional dithionite treatment in these zones will not be effective. Treatment near the water table with a technology that emplaces considerable reductive capacity is needed, such as injectable zero valent iron.
Szecsody, Jim E.; Vermeul, Vince R.; Fruchter, Jonathan S.; Williams, Mark D.; Phillips, Jerry L.; Devary, Brooks J.; Rockhold, Mark L.; Liu, Ying
The purpose of this study was to quantify the influence of physical and/or geochemical heterogeneities in the Hanford 100D area In Situ Redox Manipulation (ISRM) barrier, which may be contributing to the discontinuous chromate breakthrough locations along the 65-well (2,300 ft long) barrier. Possible causes of chromate breakthrough that were investigated during this study include: i) high hydraulic conductivity zones; ii) zones of low reducible iron; and iii) high hydraulic conductivity zones with low reducible iron. This laboratory-scale investigation utilized geochemical and physical characterization data collected on 0.5 to 1 foot intervals from four borehole locations.Results of this laboratory study did not provide definitive support any of the proposed hypotheses for explaining chromate breakthrough at the Hanford 100-D Area ISRM barrier. While site characterization data indicate a significant degree of vertical variability in both physical and geochemical properties in the four boreholes investigated, lateral continuity of high conductivity / low reductive capacity zones was not observed. The one exception was at the water table, where low reductive capacity and high-K zones were observed in 3 of four boreholes.Laterally continuous high permeability zones that contain oxic sediment near the water table is the most likely explanation for high concentration chromium breakthrough responses observed at various locations along the barrier. A mechanism that could explain partial chromate breakthrough in the ISRM barrier is the relationship between the field reductive capacity and the rate of chromate oxidation. Subsurface zones with low reductive capacity still have sufficient ferrous iron mass to reduce considerable chromate, but the rate of chromate reduction slows by 1 to 2 orders of magnitude relative to sediments with moderate to high reductive capacity.The original barrier longevity estimate of 160 pore volumes for homogeneous reduced sediment, or approximately 20 years, (with 5 mg/L dissolved oxygen and 2 ppm chromate) is reduced to 85 pore volumes (10 years) when the wide spread 60 ppm nitrate plume is included in the calculation. However, this reduction in barrier lifetime is not as great for high permeability channels, as there is insufficient time to reduce nitrate (and consume ferrous iron). If the cause of laterally discontinuous breakthrough of chromate along the ISRM barrier is due to oxic transport of chromate near the water table, additional dithionite treatment in these zones will not be effective. Treatment near the water table with a technology that emplaces considerable reductive capacity is needed, such as injectable zero valent iron.
Szecsody, Jim E.; Fruchter, Jonathan S.; Phillips, Jerry L.; Rockhold, Mark L.; Vermeul, Vince R.; Williams, Mark D.; Devary, Brooks J.; Liu, Ying
The in situ application of granular iron (Fe0) has become popular for the destruction of halogenated organic compounds for the immobilization of specific metals in groundwater. However, a knowledge gap exists concerning the long-term performance of the Fe0-barriers. The corrosi...
Transformation of Reactive Iron Minerals in a Permeable Reactive Barrier (Biowall) Used to Treat TCE in Groundwater
Abstract: Iron and sulfur reducing conditions are generally created in permeable reactive barrier (PRB) systems constructed for groundwater treatment, which usually leads to formation of iron sulfide phases. Iron sulfides have been shown to play an important role in degrading ch...
Regulation of Brain Iron and Copper Homeostasis by Brain Barrier Systems: Implication in Neurodegenerative Diseases
Iron (Fe) and copper (Cu) are essential to neuronal function; excess or deficiency of either is known to underlie the pathoetiology of several commonly known neurodegenerative disorders. This delicate balance of Fe and Cu in the central milieu is maintained by the brain barrier systems, i.e., the blood-brain barrier (BBB) between the blood and brain interstitial fluid and the blood- cerebrospinal fluid barrier (BCB) between the blood and cerebrospinal fluid (CSF). This review provides a concise description on the structural and functional characteristics of the brain barrier systems. Current understanding of Fe and Cu transport across the brain barriers is thoroughly examined, with major focuses on whether the BBB and BCB coordinate the direction of Fe and Cu fluxes between the blood and brain/CSF. In particular, the mechanism by which pertinent metal transporters in the barriers, such as the transferrin receptor (TfR), divalent metal transporter (DMT1), copper transporter (CTR1), ATP7A/B, and ferroportin (FPN), regulate metal movement across the barriers is explored. Finally, the detrimental consequences of dysfunctional metal transport by brain barriers, as a result of endogenous disorders or exogenous insults, are discussed. Understanding the regulation of Fe and Cu homeostasis in the central nervous system aids in the design of new drugs targeted on the regulatory proteins at the brain barriers for the treatment of metal's deficiency or overload-related neurological diseases.
Zheng, Wei; Monnot, Andrew D.
Schottky barrier formation using composite of polyaniline containing iron oxides
A composite of polyaniline (PANI) containing iron oxides (Fe3O4) with nanometer size was prepared by a chemical method. The electrical properties of (PANI-Fe3O4) sandwich structure using ohmic gold and blocking aluminium electrodes were studied. The current density - voltage (J-V) characteristics for the device resemble the typical dark current versus applied voltage characteristic for conventional Schottky diode. Electronic parameters have been calculated using J-V and capacitance-voltage (C-V) measurements.
Motaweh, H. A.; Abdel-Malik, T. G.
Comparison study of ferrofluid and powder iron oxide nanoparticle permeability across the blood-brain barrier
In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood–brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood–brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood–brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood–brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood–brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood–brain barrier, and deserve further investigation for a wide range of applications.
Hoff, Dan; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J
Comparison study of ferrofluid and powder iron oxide nanoparticle permeability across the blood-brain barrier.
In the present study, the permeability of 11 different iron oxide nanoparticle (IONP) samples (eight fluids and three powders) was determined using an in vitro blood-brain barrier model. Importantly, the results showed that the ferrofluid formulations were statistically more permeable than the IONP powder formulations at the blood-brain barrier, suggesting a role for the presently studied in situ synthesized ferrofluid formulations using poly(vinyl) alcohol, bovine serum albumin, collagen, glutamic acid, graphene, and their combinations as materials which can cross the blood-brain barrier to deliver drugs or have other neurological therapeutic efficacy. Conversely, the results showed the least permeability across the blood-brain barrier for the IONP with collagen formulation, suggesting a role as a magnetic resonance imaging contrast agent but limiting IONP passage across the blood-brain barrier. Further analysis of the data yielded several trends of note, with little correlation between permeability and fluid zeta potential, but a larger correlation between permeability and fluid particle size (with the smaller particle sizes having larger permeability). Such results lay the foundation for simple modification of iron oxide nanoparticle formulations to either promote or inhibit passage across the blood-brain barrier, and deserve further investigation for a wide range of applications. PMID:23426527
Reactive Membrane Barriers for Containment of Subsurface Contamination
The overall goal of this project was to develop reactive membrane barriers--a new and flexible technique to contain and stabilize subsurface contaminants. Polymer membranes will leak once a contaminant is able to diffuse through the membrane. By incorporating a reactive material in the polymer, however, the contaminant is degraded or immobilized within the membrane. These processes increase the time for contaminants to breakthrough the barrier (i.e. the lag time) and can dramatically extend barrier lifetimes. In this work, reactive barrier membranes containing zero-valent iron (Fe{sup 0}) or crystalline silicotitanate (CST) were developed to prevent the migration of chlorinated solvents and cesium-137, respectively. These studies were complemented by the development of models quantifying the leakage/kill time of reactive membranes and describing the behavior of products produced via the reactions within the membranes. First, poly(vinyl alcohol) (PVA) membranes containing Fe{sup 0} and CST were prepared and tested. Although PVA is not useful in practical applications, it allows experiments to be performed rapidly and the results to be compared to theory. For copper ions (Cu{sup 2+}) and carbon tetrachloride, the barrier was effective, increasing the time to breakthrough over 300 times. Even better performance was expected, and the percentage of the iron used in the reaction with the contaminants was determined. For cesium, the CST laden membranes increased lag times more than 30 times, and performed better than theoretical predictions. A modified theory was developed for ion exchangers in reactive membranes to explain this result. With the PVA membranes, the effect of a groundwater matrix on barrier performance was tested. Using Hanford groundwater, the performance of Fe{sup 0} barriers decreased compared to solutions containing a pH buffer and high levels of chloride (both of which promote iron reactivity). For the CST bearing membrane, performance improved by a factor of three when groundwater was used in place of deionized water. The performance of high density polyethylene (HDPE) membranes containing Fe{sup 0} was then evaluating using carbon tetrachloride as the target contaminant. Only with a hydrophilic additive (glycerol), was the iron able to extend lag times. Lag times were increased by a factor of 15, but only 2-3% of the iron was used, likely due to formation of oxide precipitates on the iron surface, which slowed the reaction. With thicker membranes and lower carbon tetrachloride concentrations, it is expected that performance will improve. Previous models for reactive membranes were also extended. The lag time is a measurement of when the barrier is breached, but contaminants do slowly leak through prior to the lag time. Thus, two parameters, the leakage and the kill time, were developed to determine when a certain amount of pollutant has escaped (the kill time) or when a given exposure (concentration x time) occurs (the leakage). Finally, a model was developed to explain the behavior of mobile reaction products in reactive barrier membranes. Although the goal of the technology is to avoid such products, it is important to be able to predict how these products will behave. Interestingly, calculations show that for any mobile reaction products, one half of the mass will diffuse into the containment area and one half will escape, assuming that the volumes of the containment area and the surrounding environment are much larger than the barrier membrane. These parameters/models will aid in the effective design of barrier membranes.
William A. Arnold; Edward L. Cussler
Automated Impedance Tomography for Monitoring Permeable Reactive Barrier Health
The objective of this research was the development of an autonomous, automated electrical geophysical monitoring system which allows for near real-time assessment of Permeable Reactive Barrier (PRB) health and aging and which provides this assessment through a web-based interface to site operators, owners and regulatory agencies. Field studies were performed at four existing PRB sites; (1) a uranium tailing site near Monticello, Utah, (2) the DOE complex at Kansas City, Missouri, (3) the Denver Federal Center in Denver, Colorado and (4) the Asarco Smelter site in East Helena, Montana. Preliminary surface data over the PRB sites were collected (in December, 2005). After the initial round of data collection, the plan was modified to include studies inside the barriers in order to better understand barrier aging processes. In September 2006 an autonomous data collection system was designed and installed at the EPA PRB and the electrode setups in the barrier were revised and three new vertical electrode arrays were placed in dedicated boreholes which were in direct contact with the PRB material. Final data were collected at the Kansas City, Denver and Monticello, Utah PRB sites in the fall of 2007. At the Asarco Smelter site in East Helena, Montana, nearly continuous data was collected by the autonomous monitoring system from June 2006 to November 2007. This data provided us with a picture of the evolution of the barrier, enabling us to examine barrier changes more precisely and determine whether these changes are due to installation issues or are normal barrier aging. Two rounds of laboratory experiments were carried out during the project. We conducted column experiments to investigate the effect of mineralogy on the electrical signatures resulting from iron corrosion and mineral precipitation in zero valent iron (ZVI) columns. In the second round of laboratory experiments we observed the electrical response from simulation of actual field PRBs at two sites: the Kansas City barrier and the East Helena barrier. As these sites are also used for our field monitoring efforts, this allowed for a comparison between field and laboratory. In column studies with high concentrations of calcium and carbonate/bicarbonate, we observed that the increase of electrical resistivity and decrease of polarization magnitude is significant and is mainly controlled by the precipitation of calcium carbonates. In general, the electrical properties of all of the barriers studied follow a pattern. New barriers are fairly resistive with in-situ conductivity only a few times background (outside the barrier) values. Older barriers get increasingly conductive, with failed barriers showing values of over 100 S/m. The induced polarization response is more complicated. Chargeability values increase over time for young barriers, are largest for healthy barriers in the middle of their lifespan, and decrease as the barrier ages These results suggest that normalized IP appears promising as a measure of barrier age.
LaBrecque, D J; Adkins, P L
Chromium-Removal Processes during Groundwater Remediation by a Zerovalent Iron Permeable Reactive Barrier
Solid-phase associations of chromium were examined in core materials collected from a full-scale, zerovalent iron permeable reactive barrier (PRB) at the U.S. Coast Guard Support Center located near Elizabeth City, NC. The PRB was installed in 1996 to treat groundwater contaminated with hexavalent chromium. After eight years of operation, the PRB remains effective at reducing concentrations of Cr from average
Richard T. Wilkin; Chunming Su; Robert G. Ford; Cynthia J. Paul
Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers
A study was conducted to assess key factors to include when modeling porosity reductions caused by mineral fouling in permeable reactive barriers (PRBs) containing granular zero valent iron. The public domain codes MODFLOW and RT3D were used and a geochemical algorithm was developed for RT3D to simulate geochemical reactions occurring in PRBs. Results of simulations conducted with the model show that the largest porosity reductions occur between the entrance and mid-plane of the PRB as a result of precipitation of carbonate minerals and that smaller porosity reductions occur between the mid-plane and exit face due to precipitation of ferrous hydroxide. These findings are consistent with field and laboratory observations, as well as modeling predictions made by others. Parametric studies were conducted to identify the most important variables to include in a model evaluating porosity reduction. These studies showed that three minerals (CaCO 3, FeCO 3, and Fe(OH) 2 (am)) account for more than 99% of the porosity reductions that were predicted. The porosity reduction is sensitive to influent concentrations of HCO 3-, Ca 2+, CO 32-, and dissolved oxygen, the anaerobic iron corrosion rate, and the rates of CaCO 3 and FeCO 3 formation. The predictions also show that porosity reductions in PRBs can be spatially variable and mineral forming ions penetrate deeper into the PRB as a result of flow heterogeneities, which reflects the balance between the rate of mass transport and geochemical reaction rates. Level of aquifer heterogeneity and the contrast in hydraulic conductivity between the aquifer and PRB are the most important hydraulic variables affecting porosity reduction. Spatial continuity of aquifer hydraulic conductivity is less significant.
Li, Lin; Benson, Craig H.; Lawson, Elizabeth M.
Backfill barriers: the use of engineered barriers based on geologic materials to assure isolation of radioactive wastes in a repository. [Nickel-iron alloys
A preliminary assessment is made to show that canisters fabricated of nickel-iron alloys, and surrounded by a suitable backfill, may produce an engineered barrier where the canister material is thermodynamically stable with respect to its environment. As similar conditions exist in nature, the performance of such systems as barriers to isolate radionuclides can be predicted over very long periods, of the order of 10/sup 6/ years.
Apps, J.A.; Cook, N.G.W.
C–S, C–H, and N–H bond cleavage of heterocycles by a zero-valent iron complex, Fe(N 2)(depe) 2 [depe=1,2-bis(diethylphosphino)ethane
Treatment of Fe(N2)(depe)2 [depe=1,2-bis(diethylphosphino)ethane] (1) with benzo[b]thiophene at room temperature results in the regioselective C–S and C–H bond cleavages giving Fe(SC6H4CH?CH)(depe)2 (2a) and trans-FeH(C?CHC6H4S)(depe)2 (3a) in 72 and 19% yields, respectively. Complex 1 also reacts with thiophene, 2- and 3-acetylthiophenes and 2- and 3-methylthiophenes to give both C–S and C–H bond oxidative addition products: Fe(SCH?CHCH?CH)(depe)2 (2b) and trans-FeH(C?CHCH?CHS)(depe)2 (3b), Fe[SC(COMe)?CHCH?CH](depe)2
Takashi Morikita; Masafumi Hirano; Akito Sasaki; Sanshiro Komiya
Impact of Mineral Fouling on the Long-Term Performance of Permeable Reactive Barriers
A modeling study was conducted to investigate the impact of mineral fouling on the long-term performance of permeable reactive barriers (PRBs) using zero-valent iron. MODFLOW was used to simulate flow in an aquifer containing a PRB. RT3D was used to simulate geochemical reactions and to predict mineral fouling in the PRB. A geochemical algorithm including kinetic expressions of oxidation-reduction and mineral precipitation-dissolution was developed for RT3D. Predictions made with the model after calibration were in general agreement with field measurements reported for PRBs at Moffett Field, CA and Elizabeth City, NC. Mineral precipitation and related porosity reductions were simulated for different scenarios. Porosity reduction in PRB is found to be spatially variable as a result of flow heterogeneity. The largest porosity reductions occur between the entrance face and the mid-plane. Carbonate minerals precipitate in this region, and the amount of precipitated carbonates is closely related to the Darcy velocities. The relationship between mineral precipitation and Darcy velocity reflects the balance between the rate of mass transport and the geochemical reaction rates. Porosity reductions decrease and then level out as carbonates precipitates in front half of the PRB. Porosity reductions in the rear half of the PRB are primarily due to precipitation of ferrous hydroxide, and are not related to the Darcy velocity. The analysis shows that reduction of hydraulic conductivity and porosity by mineral fouling causes seepage velocities through the PRB to increase over time, which reduces the residence time. Shorter residence times make a PRB less effective because less time is available for contaminants to be treated. When precipitation in the reactive medium is so extensive that very large reductions in hydraulic conductivity occur in the PRB, changes in the flow paths occur, along with flow bypassing. Both the reduction in residence times caused by mineral fouling and bypassing may have a significant impact on the long-term effectiveness of PRBs.
Li, L.; Craig, B.
Simulation of Two Strategies to Enhance Permeable Reactive Barriers in Heterogeneous Aquifer
Ground water flow (MODFLOW) and geochemical reactive transport models (RT3D) were used to assess the effectiveness of two strategies in limiting mineral fouling and its impact on hydraulic behavior of continuous-wall permeable reactive barriers (PRBs) employing granular zero valent iron (ZVI). A geochemical algorithm including kinetic expressions of oxidation-reduction and mineral precipitation-dissolution was developed for RT3D. The two strategies that were evaluated are (i) adding pea gravel equalization zones upgradient and down gradient of the reactive zone and (ii) placement of sacrificial pretreatment zones upgradient of the reactive zone. The PRB locates at a three-dimensional heterogeneous sandy aquifer. The sacrificial pretreatment zone contains mixtures of pea gravel and ZVI. Results of simulations show that installation of pea gravel zones provides a more conductive path for ground water flow through the ZVI, which enhances preferential flow and causes greater porosity reductions and shorter residence time in the PRB. After installation of pea gravel zones, the esidence time decreases which is caused by short travel distances in the ZVI due to short circuit of preferential flow. Sacrificial pretreatment zones can be used to elevate the ground water pH and consume many of the mineral forming ions to form secondary minerals in before the reactive zone is reached. The remaining mineral forming ions that pass into the reactive zone cause less mineral fouling. However, mineral fouling by Fe(OH)2 still occurs, and this mineral is formed regardless of the influent mineral forming ions. Addition of the sacrificial pretreatment zone slightly decreases the initial median residence time. However, the pretreatment zone retains higher residence time after 30 yrs due to less mineral fouling in the pure ZVI zone.
Li, L.; Benson, C.
Simulation of Two Strategies to Limit the Impact of Fouling in Permeable Reactive Barriers
Ground water flow (MODFLOW) and geochemical reactive transport models (RT3D) were used to assess the effectiveness of two strategies in limiting mineral fouling and its impact on hydraulic behavior of continuous- wall permeable reactive barriers (PRBs) employing granular zero valent iron (ZVI). A geochemical algorithm including kinetic expressions of oxidation-reduction and mineral precipitation-dissolution was developed for RT3D. The two strategies that were evaluated are (i) adding pea gravel equalization zones upgradient and down gradient of the reactive zone and (ii) placement of sacrificial pretreatment zones upgradient of the reactive zone. The PRB locates at a three-dimensional heterogeneous sandy aquifer. The sacrificial pretreatment zone contains mixtures of pea gravel and ZVI. Results of simulations show that installation of pea gravel zones provides a more conductive path for ground water flow through the ZVI, which enhances preferential flow and causes greater porosity reductions and shorter residence time in the PRB. After installation of pea gravel zones, the residence time decreases which is caused by short travel distances in the ZVI due to short circuit of preferential flow. Sacrificial pretreatment zones can be used to elevate the ground water pH and consume many of the mineral forming ions to form secondary minerals in before the reactive zone is reached. The remaining mineral forming ions that pass into the reactive zone cause less mineral fouling. However, mineral fouling by Fe(OH)2 still occurs, and this mineral is formed regardless of the influent mineral forming ions. Addition of the sacrificial pretreatment zone slightly decreases the initial median residence time. However, the pretreatment zone retains higher residence time after 30 yrs due to less mineral fouling in the pure ZVI zone.
Verification and monitoring of deep granular iron permeable reactive barriers emplaced by vertical hydraulic fracturing and injection for groundwater remediation
This study evaluated the use of vertical hydraulic fracturing and injection (VHFI) to emplace granular iron as a deep passive treatment system to remove organic contaminants from groundwater at the Massachusetts Military Reservation on Cape Cod, Massachusetts. It was the first permeable reactive barrier (PRB) constructed at a depth greater than 15 m below the ground surface. VHFI propagates a
David Wallace Hubble
Enhanced chitosan beads-supported Fe(0)-nanoparticles for removal of heavy metals from electroplating wastewater in permeable reactive barriers.
The removal of heavy metals from electroplating wastewater is a matter of paramount importance due to their high toxicity causing major environmental pollution problems. Nanoscale zero-valent iron (NZVI) became more effective to remove heavy metals from electroplating wastewater when enhanced chitosan (CS) beads were introduced as a support material in permeable reactive barriers (PRBs). The removal rate of Cr (VI) decreased with an increase of pH and initial Cr (VI) concentration. However, the removal rates of Cu (II), Cd (II) and Pb (II) increased with an increase of pH while decreased with an increase of their initial concentrations. The initial concentrations of heavy metals showed an effect on their removal sequence. Scanning electron microscope images showed that CS-NZVI beads enhanced by ethylene glycol diglycidyl ether (EGDE) had a loose and porous surface with a nucleus-shell structure. The pore size of the nucleus ranged from 19.2 to 138.6 ?m with an average aperture size of around 58.6 ?m. The shell showed a tube structure and electroplating wastewaters may reach NZVI through these tubes. X-ray photoelectron spectroscope (XPS) demonstrated that the reduction of Cr (VI) to Cr (III) was complete in less than 2 h. Cu (II) and Pb (II) were removed via predominant reduction and auxiliary adsorption. However, main adsorption and auxiliary reduction worked for the removal of Cd (II). The removal rate of total Cr, Cu (II), Cd (II) and Pb (II) from actual electroplating wastewater was 89.4%, 98.9%, 94.9% and 99.4%, respectively. The findings revealed that EGDE-CS-NZVI-beads PRBs had the capacity to remediate actual electroplating wastewater and may become an effective and promising technology for in situ remediation of heavy metals. PMID:24075723
Liu, Tingyi; Yang, Xi; Wang, Zhong-Liang; Yan, Xiaoxing
Mineralogical characteristics and transformations during long-term operation of a zerovalent iron reactive barrier.
Design and operation of Fe0 permeable reactive barriers (PRBs) can be improved by understanding the long-term mineralogical transformations that occur within PRBs. Changes in mineral precipitates, cementation, and corrosion of Fe0 filings within an in situ pilot-scale PRB were examined after the first 30 months of operation and compared with results of a previous study of the PRB conducted 15 months earlier using X-ray diffraction and scanning electron microscopy employing energy dispersive X-ray and backscatter electron analyses. Iron (oxy)hydroxides, aragonite, and maghemite and/or magnetite occurred throughout the cores collected 30 mo after installation. Goethite, lepidocrocite, mackinawite, aragonite, calcite, and siderite were associated with oxidized and cemented areas, while green rusts were detected in more reduced zones. Basic differences from our last detailed investigation include (i) mackinawite crystallized from amorphous FeS, (ii) aragonite transformed into calcite, (iii) akaganeite transformed to goethite and lepidocrocite, (iv) iron (oxy)hydroxides and calcium and iron carbonate minerals increased, (v) cementation was greater in the more recent study, and (vi) oxidation, corrosion, and disintegration of Fe0 filings were greater, especially in cemented areas, in the more recent study. If the degree of corrosion and cementation that was observed from 15 to 30 mo after installation continues, certain portions of the PRB (i.e., up-gradient entrance of the ground water to the Fe0 section of the PRB) may last less than five more years, thus reducing the effectiveness of the PRB to mitigate contaminants. PMID:14674525
Phillips, D H; Watson, D B; Roh, Y; Gu, B
Understanding pH Effects on Trichloroethylene and Perchloroethylene Adsorption to Iron in Permeable Reactive Barriers for Groundwater Remediation
Metallic iron filings are becoming increasing used in permeable reactive barriers for remediating groundwater contaminated by chlorinated solvents. Understanding solution pH effects on rates of reductive dechlorination in permeable reactive barriers is essential for designing remediation systems that can meet treatment objectives under conditions of varying groundwater properties. The objective of this research was to investigate how the solution pH value affects adsorption of trichloroethylene (TCE) and perchloroethylene (PCE) on metallic iron surfaces. Because adsorption is first required before reductive dechlorination can occur, pH effects on halocarbon adsorption energies may explain pH effects on dechlorination rates. Adsorption energies for TCE and PCE were calculated via molecular mechanics simulations using the Universal force field and a self-consistent reaction field charge equilibration scheme. A range in solution pH values was simulated by varying the amount of atomic hydrogen adsorbed on the iron. The potential energies associated TCE and PCE complexes were dominated by electrostatic interactions, and complex formation with the surface was found to result in significant electron transfer from the iron to the adsorbed halocarbons. Adsorbed atomic hydrogen was found to lower the energies of TCE complexes more than those for PCE. Attractions between atomic hydrogen and iron atoms were more favorable when TCE versus PCE was adsorbed to the iron surface. These two findings are consistent with the experimental observation that changes in solution pH affect TCE reaction rates more than those for PCE.
Luo, Jing; Farrell, James
Molecular mechanism of distorted iron regulation in the blood-CSF barrier and regional blood-brain barrier following in vivo subchronic manganese exposure
Previous studies in this laboratory indicated that manganese (Mn) exposure in vitro increases the expression of transferrin receptor (TfR) by enhancing the binding of iron regulatory proteins (IRPs) to iron responsive element-containing RNA. The current study further tested the hypothesis that in vivo exposure to Mn increased TfR expression at both blood–brain barrier (BBB) and blood–cerebrospinal fluid (CSF) barrier (BCB), which contributes to altered iron (Fe) homeostasis in the CSF. Groups of rats (10–11 each) received oral gavages at doses of 5 mg Mn/kg or 15 mg Mn/kg as MnCl2 once daily for 30 days. Blood, CSF, and choroid plexus were collected and brain capillary fractions were separated from the regional parenchyma. Metal analyses showed that oral Mn exposure decreased concentrations of Fe in serum (?66%) but increased Fe in the CSF (+167%). Gel shift assay showed that Mn caused a dose-dependent increase of binding of IRP1 to iron responsive element-containing RNA in BCB in the choroid plexus (+70%), in regional BBB of capillaries of striatum (+39%), hippocampus (+56%), frontal cortex (+49%), and in brain parenchyma of striatum (+67%), hippocampus (+39%) and cerebellum (+28%). Real-time RT-PCR demonstrated that Mn exposure significantly increased the expression of TfR mRNA in choroid plexus and striatum with concomitant reduction in the expression of ferritin (Ft) mRNA. Collectively, these data indicate that in vivo Mn exposure results in Fe redistribution in body fluids through regulating the expression of TfR and ferritin at BCB and selected regional BBB. The disrupted Fe transport by brain barriers may underlie the distorted Fe homeostasis in the CSF.
Li, G. Jane; Choi, Byung-Sun; Wang, Xueqian; Liu, Jie; Waalkes, Michael P.; Zheng, Wei
Iron is an active catalyst for the steam gasification of carbon provided the reaction environment is controlled to maintain the zero valent state. It is also active for the hydrogasification of carbon. When graphite is gasified with steam and hydrogen at atmospheric pressure and temperatures around 500/sup 0/ to 700/sup 0/C the only products which are formed in appreciable quantities are carbon monoxide, carbon dioxide, and methane. However, when a real coal char is gasified there may be significant quantities of higher hydrocarbons evolved resulting from the continued decomposition of the parent coal. In this study the gasification of graphite was studied in a feed of ethane and steam to probe what effects higher hydrocarbons in the gas phase might have upon the course of the gasification reaction.
Lund, C.R.F.; Baker, R.T.K.
The objective of this study was to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC). A series of column experiments were conducted to evaluate the location of Fe0 permeable reactive barrier (PRB) and the effects of electrode arrangement in the column on the TCE removal efficiency and iron corrosion processes. In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved with simultaneous application of both ZVI and DC compared to that used ZVI only to evaluate the synergistic effect (SE). The most effective arrangement of electrode and ZVI for TCE removal from simulated groundwater was a column set with ZVI and cathode installed at the down gradient (outlet side). Based on the electrochemical study in the E2PRB system, application of direct current provided external electrons to the system so that the system did not depend entirely on the oxidation of the medium for the reductive dechlorination of TCE. The enhanced dechlorination rate of TCE in ZVI-DC systems is considered to attributed to more generation and fast formation kinetic of electron by following reactions: (1) direct supply of electrons from external DC source (2) the electrolysis of water generating additional electrons at the vicinity of the anode (3) the electro-reduction of the compound by released electrons on the ZVI surfaces by oxidation (4) released electron through oxidation of dissolved ferrous iron, and (5) oxidation of atomic hydrogen at the cathode. The competition between five different electron sources generated from five sources evidently influenced on the TCE removal efficiency, valid lifetime of E2PRB system, and reduction of energy expenditure in both of electrochemical and electrokinetic aspects. The results from a series of experiments with twelve columns showed a trend that removal efficiency was more related to the electrode arrangement, but longevity of ZVI PRB and reduction of energy expenditure to location of ZVI installation.
Moon, J.; Moon, H.; Roh, Y.; Kim, H.; Song, Y.
Recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite clay by electrokinetics coupled with a permeable reactive barrier.
Zero-valent iron (Fe(0)) and magnetite (Fe3O4) were investigated as potential reductants in an electrokinetic/permeable reactive barrier hybrid system (EK/PRB) for the recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite. For the EK/Fe(0) PRB, regardless of the pH in the anode well, the system facilitated the reduction of Cr(VI) into Cr(III), but the recovery of the Cr(III) in the PRB was low. Conversely, the reduction of Cr(VI) occurred only in the PRB for the EK/Fe3O4 PRB. However, when the anode pH was not controlled and the soil pH values correspondingly decreased gradually from the anode side, a greater fraction of Cr(VI) sorbed onto the kaolinite; as a result, a lower amount of Cr(VI) migrated to the Fe3O4 PRB. In addition, it was found that the majority of Cr(VI) migrating to the Fe3O4 PRB retained its oxidation state without being converted into Cr(III). These two adverse effects were mitigated by maintaining the soil pH values at 6.8, but at the same time, 18% of Cr(VI) penetrated through the Fe3O4 PRB. The penetration of Cr(VI) through the Fe3O4 PRB was successfully prevented by increasing the reaction time through the introduction of a cation exchange membrane between the Fe3O4 PRB and the anode well. PMID:24981681
Suzuki, Tasuma; Kawai, Katsunori; Moribe, Mai; Niinae, Masakazu
Uranium precipitation in a permeable reactive barrier by progressive irreversible dissolution of zerovalent iron.
A permeable reactive barrier (PRB) containing zerovalent iron [Fe(O)] was installed at a former uranium milling site in Monticello, UT. A large-scale column experiment was conducted at the site to test the feasibility of Fe(O) to treat U prior to installing the PRB. Effluents from the field column experiment had pH values near 7.34, moderate decreases in C(IV) and Ca concentrations, and an elevated Fe concentration (27.1 mg/L). In contrast, groundwater exiting the PRB had a pH value of 9.82, decreases in C(IV) and Ca concentrations, and a low concentration of Fe (0.17 mg/L). A geochemical model was used to explain the chemical changes that occurred in both the field column experiment and the PRB. The model simulated the systems by the progressive irreversible dissolution of Fe(O). Modeling results indicated that a longer residence time in the PRB compared with the shorter residence time in the column contributed to the disparate effluent qualities. Prior to modeling, a controlled laboratory column experiment was conducted to help evaluate the dominant chemical mechanisms by which Fe(O) removes U from aqueous solutions. Results of the laboratory column experiment indicated that only a small amount of U could be adsorbed to ferric minerals, and, therefore, this mechanism was not considered in the model. PMID:11347614
Morrison, S J; Metzler, D R; Carpenter, C E
Geophysical Monitoring of Two types of Subsurface Injection
Nano-scale particles of zero-valent iron (ZVI) were injected into the subsurface at the 100-D area of the DOE Hanford facility. The intent of this iron injection was to repair a gap in the existing in-situ redox manipulation barrier located at the site. A number of geophysical me...
In the past ten years, passive reactive barriers (PRBs) have found widespread application to treat chlorinated solvent contamination in ground water. The traditional PRB commonly uses granular zero-valent iron and/or iron alloys as filling materials for treatment of chlorinated ...
Pyrite formation by reactions of iron monosulfides with dissolved inorganic and organic sulfur species
Pyrite formation has been investigated at 70°C and pH 6-8 by aging precipitated, disordered mackinawite, Fe 9S 8, and greigite, Fe 3S 4, in solutions containing aqueous H 2S, HS -, S x2-, S 2O 32-, SO 32-, colloidal elemental sulfur, and the organic sulfur species thiol, disulfide, and sulfonate. Pyrite formed in all experiments where unoxidized iron monosulfides were aged with species containing zero-valent sulfur, i.e., polysulfides and colloidal elemental sulfur, but not with hydrogen sulfide (or bisulfide), the sulfoxy anions, or the organic sulfur species. Pyrite formation also occurred in experiments where the starting monosulfides were air-exposed prior to aging in sulfide solutions, or when air was bubbled through a reaction vessel containing iron monosulfides suspended in a sulfid sulfide solution. The experiments indicate the rate of conversion from iron monosulfides to pyrite is not only a function of solution chemistry (i.e., pH and aqueous speciation), but also depends on the surface oxidation state of the precursor iron monosulfides. Measurements of ?34S of reactants and products from pyrite-forming experiments suggest that the conversion from iron monosulfides to pyrite may proceed via loss of ferrous iron from, rather than via addition of zero-valent sulfur to, the precursor monosulfides. The sulfur isotopic composition of pyrite in sedimentary environments should reflect the sulfur isotopic composition of the precursor iron monosulfide plus sulfur sources incorporated during surface-controlled growth processes. Pyrite forms produced in this study ranged from poorly developed octahedral grains, in experiments where initial pyritization rates were the slowest, to framboidal aggregates in experiments where initial pyritization rates were the fastest. Although greigite formation occurred in experiments that produced framboids, not all experiments that produced greigite led to framboid formation. The formation of pyrite with framboidal texture is apparently favored when iron monosulfides rapidly convert to pyrite.
Wilkin, R. T.; Barnes, H. L.
Advanced hydraulic fracturing methods to create in situ reactive barriers
This article describes the use of hydraulic fracturing to increase permeability in geologic formations where in-situ remedial action of contaminant plumes will be performed. Several in-situ treatment strategies are discussed including the use of hydraulic fracturing to create in situ redox zones for treatment of organics and inorganics. Hydraulic fracturing methods offer a mechanism for the in-situ treatment of gently dipping layers of reactive compounds. Specialized methods using real-time monitoring and a high-energy jet during fracturing allow the form of the fracture to be influenced, such as creation of assymmetric fractures beneath potential sources (i.e. tanks, pits, buildings) that should not be penetrated by boring. Some examples of field applications of this technique such as creating fractures filled with zero-valent iron to reductively dechlorinate halogenated hydrocarbons, and the use of granular activated carbon to adsorb compounds are discussed.
Murdoch, L. [FRX Inc., Cincinnati, OH (United States)]|[Clemson Univ., SC (United States). Dept. of Geological Sciences; Siegrist, B.; Meiggs, T. [Oak Ridge National Lab., TN (United States)] [and others
Heterogeneous Fenton oxidation of Direct Black G in dye effluent using functional kaolin-supported nanoscale zero iron.
This study investigated kaolin-supported nanoscale zero-valent iron (nZVI/K) as a heterogeneous Fenton-like catalyst for the adsorption and oxidation of an azo dye, Direct Black G (DBG). New findings suggest that kaolin as a support material not only reduced the aggregation of nanoscale zero-valent iron (nZVI) but also improved the adsorption of DBG. It consequently improved Fenton oxidation by increasing the local concentration of DBG in the vicinity of nZVI. This was confirmed by scanning electron microscopy and X-ray diffraction for the surface morphology of nZVI/K before and after the Fenton-like reaction. Furthermore, nZVI/K proved to be a catalyst for the heterogeneous Fenton-like oxidation of the DBG process in the neutral pH range. More than 87.22 % of DBG was degraded, and 54.60 % of total organic carbon was removed in the optimal conditions: 0.6 g/L dosage of nZVI/K, 33 mM H2O2, 100 mg/L initial DBG concentration, temperature of 303 K and pH of 7.06. Finally, it was demonstrated that nZVI/K removed DBG from dye wastewater through the processes of adsorption and oxidation. PMID:24014200
Liu, Xinwen; Wang, Feifeng; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra
Implementation of fluidized granulated iron reactors in a chromate remediation process.
A new approach concerning in-situ remediation on source ('hot-spot') decontamination of a chromate damage in connection with an innovative pump-and-treat-technique has been developed. Iron granulates show significant higher reduction rates, using fluidized bed conditions, than a literature study with a fixed bed installation of small-sized iron granules. First results from an abandoned tannery site concerning injections of sodium dithionite as a chromate reductant for the vadose zone in combination with a pump-and-treat-method, allying the advantages of granulated zero valent iron (ZVI), are reported. Reduction amounts of chromate have been found up to 88% compared with initial values in the soil after a soil water exchange of 8 pore volumes within 2.5months. Chromate concentrations in the pumped effluent have been reduced to under the detection limit of 0.005mg/L by treatment with ZVI in the pilot plant. PMID:24530188
Müller, P; Lorber, K E; Mischitz, R; Weiß, C
Laboratory Evaluation of Sulfur Modified Iron for Use as a Filter Material to Treat Agricultural Drainage Waters
Where subsurface drainage practices are employed, fertilizer nutrients and pesticides applied on farm fields and municipal locations are commonly intercepted by the buried drainage pipes and then discharged into local streams and lakes, oftentimes producing adverse environmental impacts on these surface water bodies. On-site water filter treatment systems can be employed to prevent the release of agricultural nutrients/pesticides into adjacent waterways. Sulfur modified iron is a relatively unknown industrial product that may have promise for use as a filter material to remove contaminants from subsurface drainage waters. Sulfur modified iron (SMI) is a high surface area iron powder (zero valent iron) that has been altered via chemical reaction with pure sulfur to produce a sulfur/iron surface coating on the iron particles. A laboratory investigation was conducted with contaminant removal batch tests, saturated falling-head hydraulic conductivity tests, and saturated solute transport column experiments to evaluate the feasibility for using SMI to treat subsurface drainage waters. Contaminant removal batch tests showed that three SMI samples were much more effective removing nitrate (> 94% nitrate removed) than three zero valent iron samples (< 10% nitrate removed). Batch test results additionally showed that SMI removed greater that 94% of dissolved phosphate, but was not particularly effective removing the pesticide, atrazine (< 37% atrazine removed). Hydraulic conductivity tests indicated that all three SMI samples that were evaluated had sufficient hydraulic conductivity, much greater than the 1 x 10-3 cm/s standard used for stormwater sand filters. The saturated solute transport tests confirmed that SMI can be effective removing nitrate and phosphate from drainage waters. Analysis of column effluent also showed that the large majority of nitrate removed by SMI was converted to ammonium. Consequently, these laboratory findings support the use of SMI in agricultural drainage water filter treatment systems, particularly when nitrate and phosphate pollution are major environmental concerns.
Allred, B. J.
Iron poisoning causes its metabolic effects in proportion to the concentrations of free iron. Toxicity is therefore related to dose ingested. The amount of iron in different salts varies, and iron concentrations may rise and fall, making plasma concentrations difficult to interpret in acute poisoning. Clinical features include severe gastrointestinal irritation, cardiovascular collapse and direct organ damage to liver and
D. Nicholas Bateman
A pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI), limestone and pea gravel was installed at a former phosphate fertilizer manufacturing facility in Charleston, S.C. in September 2002. The PRB is designed to treat arsenic an...
A pilot permeable reactive barrier (PRB) consisting of a mixture of 30% yard waste compost, 20% zero-valent iron (ZVI), 5% limestone and 45% pea gravel by volume was installed at a former phosphate fertilizer manufacturing facility in Charleston, S.C. in September 2002. The pilo...
Treatment of Arsenic, Heavy Metals, and Acidity Using a Mixed ZVI-Compost PRB
A 30-month performance evaluation of a pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI), limestone and pea gravel installed at a former phosphate fertilizer manufacturing facility was conducted. The PRB is designed to remove ...
Iron monosulfide as a scavenger for dissolved hexavalent chromium and cadmium.
Iron sulfide minerals are common components of soil/sedimentary environments. Reactions near the surfaces of iron sulfides play important roles in metal retention, mobility, and bioavailability. A series of batch experiments was conducted to study the removal of aqueous chromium and cadmium by iron monosulfide. Hexavalent chromium was reduced to Cr(III) by iron monosulfide with simultaneous precipitation of chromium and iron oxyhydroxide. In contrast to chromium, the primary retention mechanism of cadmium by iron monosulfide was lattice exchange. Surface adsorption to iron monosulfide and precipitation with sulfide on the iron monosulfide surface also contributed to the removal of aqueous cadmium. New phases of both chromium and cadmium were confirmed with transmission electron microscopy. The solution pH was an important factor in this research; it can change particle surface charge and metal species, hence affecting the removal of chromium, but not cadmium. Ferrous ions without FeS exhibited less Cr(VI) removal than with FeS, which might be owing to sulfides from FeS and the existence of the solid phase. Iron monosulfide exhibited higher removal efficiency for chromium and cadmium than zero valent iron and other iron oxide minerals, and the synergistic effect of ferrous iron and sulfide appeared to cause this result. PMID:18844124
Jo, S; Lee, J Y; Kong, S H; Choi, J; Park, J W
Dehalogenation of Polybrominated Diphenyl Ethers and Polychlorinated Biphenyl by Bimetallic, Impregnated, and Nanoscale Zerovalent Iron
Nanoscale zerovalent iron particles (nZVI), bimetallic nanoparticles (nZVI/Pd), and nZVI/Pd impregnated activated carbon (nZVI/Pd-AC) composite particles were synthesized and investigated for their effectiveness to remove polybrominated diphenyl ethers (PBDEs) and/or polychlorinated biphenyls (PCBs). Palladization of nZVI promoted the dehalogenation kinetics for mono- to tri-BDEs and 2,3,4-trichlorobiphenyl (PCB 21). Compared to nZVI, the iron-normalized rate constants for nZVI/Pd were about 2-, 3-, and 4-orders of magnitude greater for tri-, di-, and mono-BDEs, respectively, with diphenyl ether as a main reaction product. The reaction kinetics and pathways suggest an H-atom transfer mechanism. The reaction pathways with nZVI/Pd favor preferential removal of para-halogens on PBDEs and PCBs. X-ray fluorescence mapping of nZVI/Pd-AC showed that Pd mainly deposits on the outer part of particles, while Fe was present throughout the activated carbon particles. While BDE 21 was sorbed onto activated carbon composites quickly, debromination was slower compared to reaction with freely dispersed nZVI/Pd. Our XPS and chemical data suggest about 7% of the total iron within the activated carbon was zero-valent, which shows the difficulty with in-situ synthesis of a significant fraction of zero-valent iron in the micro-porous material. Related factors that likely hinder the reaction with nZVI/Pd-AC are the heterogenous distribution of nZVI and Pd on activated carbon and/or immobilization of hydrophobic organic contaminants at the adsorption sites thereby inhibiting contact with nZVI.
Zhuang, Yuan; Ahn, Sungwoo; Seyfferth, Angelia L.; Masue-Slowey, Yoko; Fendorf, Scott; Luthy, Richard G.
Thermally Evaporated Iron (Oxide) on an Alumina Barrier Layer, by XPS
We report the XPS characterization of a thermally evaporated iron thin film (6 nm) deposited on an Si/SiO_2/Al_2O_3 substrate using Al Ka X-rays. An XPS survey spectrum, narrow Fe 2p scan, narrow O 1s, and valence band scan are shown.
Madaan, Nitesh; Kanyal, Supriya S.; Jensen, David S.; Vail, Michael A.; Dadson, Andrew; Engelhard, Mark H.; Linford, Matthew R.
Surface Reactivity of Core Shell Iron-Iron Oxide Nanoclusters towards Breakdown of Carbon Tetrachloride
Zero-valent iron (ZVI) is one of the technologies for groundwater remediation to reduce contaminants by removal of mobile chlorinated hydrocarbons. Iron-Iron oxide (Fe/Fe3O4) nanoclusters (NCs) made in our laboratory using cluster deposition technique have enhanced reactivity towards targeted contaminants due to the presence of ZVI protected by a passivated oxide shell. Here, we investigate the effectiveness of the Fe/Fe3O4 NCs in reducing carbon tetrachloride (CT) under laboratory conditions. The reactivity of the NCs was investigated by conducting unbuffered aqueous batch experiments to reduce CT at room temperature. Initial results show that 80% of the degradation of CT resulted in the formation of dichloromethane (DCM) and chloroform (CF); the remainder likely followed a competing pathway to yield nonhazardous products such as CO. The production of undesirable hydrogenated products such as DCM and CF suggests that the dominant reaction pathway occurs through hydrogen (H) atom transfer via H atoms generated by corrosion of the iron. Comparative experiments with ZVI NCs prepared by other methods are underway and the results will be reported. Future work is to analyze and understand factors that control the reaction pathways between desirable and undesirable products.
Tarsem S., Maninder K.; Qiang, You; Kim, Hongseok; Amonette, James E.; Baer, Donald R.
Mechanism of copper transport at the blood-cerebrospinal fluid barrier: influence of iron deficiency in an in vitro model
Copper (Cu) is an essential trace element that requires tight homeostatic regulation to ensure appropriate supply while not causing cytotoxicity due to its strong redox potential. Our previous in vivo study has shown that iron deficiency (FeD) increases Cu levels in brain tissues, particularly in the choroid plexus, where the blood–cerebrospinal fluid (CSF) barrier resides. This study was designed to elucidate the mechanism by which FeD results in excess Cu accumulation at the blood–CSF barrier. The effect of FeD on cellular Cu retention and transporters Cu transporter-1 (Ctr1), divalent metal transporter 1 (DMT1), antioxidant protein-1 (ATOX1) and ATP7A was examined in choroidal epithelial Z310 cells. The results revealed that deferoximine treatment (FeD) resulted in 70% increase in cellular Cu retention (P < 0.05). A significant increase in the mRNA levels of DMT1, but not Ctr1, was also observed after FeD treatment, suggesting a critical role of DMT1 in cellular Cu regulation during FeD. Knocking down Ctr1 or DMT1 resulted in significantly lower Cu uptake by Z310 cells, whereas the knocking down of ATOX1 or ATP7A led to substantial increases of cellular retention of Cu. Taken together, these results suggest that Ctr1, DMT1, ATOX1 and ATP7A contribute to Cu transport at the blood–CSF barrier, and that the accumulation of intracellular Cu found in the Z310 cells during FeD appears to be mediated, at least in part, via the upregulation of DMT1 after FeD treatment.
Monnot, Andrew D; Zheng, Gang; Zheng, Wei
Characterization and Performance of Granular Iron as Reactive Media for TCE degradation by Permeable Reactive Barriers
The application of Permeable Reactive Barriers (PRBs), an innovative clean-up technology for in-situ groundwater remediation, represents an effective alternative to traditional pump-and-treat systems and has raised strong interest during recent years. From recent statistics of the Italian Water Research Institute (IRSA), trichloroethylene (TCE) from industrial activities is the most widespread contaminant in groundwater. The goal of the research was to
Renato Baciocchi; Maria Rosaria Boni; Laura D'Aprile
Reduction of aqueous perchlorate by iron surfaces in batch and column studies
The rate and extent of perchlorate reduction on several types of iron metal was studied in batch and column reactors. Mass balances performed on the batch experiments indicate that perchlorate is reduced to chloride. Perchlorate reduction was proportional to the iron dosage in the batch reactors, with up to 66 percent removal in the highest dosage system. Surface normalized reaction rates among three commercial sources of iron filings were very similar for acid washed samples. The most significant perchlorate transformation occurred in solutions with near neutral initial pH values. Surface mediation of the reaction is supported by the absence of reduction in batch experiments with soluble Fe(II). Elevated chloride concentrations significantly inhibited perchlorate reduction, and lower removal rates were observed for iron samples with higher amounts of background chloride contamination. Perchlorate reduction was not observed on electrolytic sources of iron or on a pure mixed phase oxide (Fe2O3), suggesting that the reactive iron phase is not pure zero valent iron but is instead a combination of the elemental metal coated by a mixed valence iron hydr(oxide) phase. The observed reaction rates are too slow for direct use in remediation system design, but the findings may provide a basis for future development of cost-effective abiotic perchlorate reduction techniques. Further work to elucidate the mechanism of perchlorate reduction on iron media is in progress.
Moore, A. M.; de Leon, C. H.; Young, T. M.
Evaluating Trichloroethylene Degradation Using Differing Nano- and Micro-Scale Iron Particles
Trichioroethylene, or TCE, is a central nervous system depressant and possible carcinogen, as well as a persistent groundwater pollutant. TCE exists in the aquifer either as free product in the form of a dense non-aqueous phase liquid (DNAPL) or as a dissolved-phase constituent. It is only slightly soluble in water, so dissolution of the contaminant is a long-term process and in-situ remediation is difficult. To remedy this, NASA and the University of Central Florida developed Emulsified Zero-Valent Iron, or EZVI. The emulsion droplet contains ZVI particles and water encapsulated by an oil/surfactant membrane, and effectively penetrates to degrade DNAPL-phase TCE. To maximize the efficiency of this process, several commercially available ZVIs of radically different particle sizes and morphologies both in emulsion and as neat (unemulsified) metal were evaluated for relative effectiveness at TCE degradation.
Berger, Cristina M.; Geiger, Cherie L.; Clausen, Christian A.; Billow, Alexa M.; Quinn, Jacqueline W.; Brooks, Kathleen B.
Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 2. Geochemical modeling and solid phase studies
Arsenic uptake processes were evaluated in a zerovalent iron reactive barrier installed at a lead smelting facility using geochemical modeling, solid-phase analysis, and X-ray absorption spectroscopy techniques. Aqueous speciation of arsenic is expected to play a key role in directing arsenic uptake processes. Geochemical modeling reveals contrasting pH-dependencies for As(III) and As(V) precipitation. At the moderately alkaline pH conditions typically encountered in zerovalent iron reactive barriers, As(III) is unlikely to precipitate as an oxide or a sulfide phase. Conversely, increasing pH is expected to drive precipitation of metal arsenates including ferrous arsenate. Bacterially mediated sulfate reduction plays an important role in field installations of granular iron. Neoformed iron sulfides provide surfaces for adsorption of oxyanion and thioarsenic species of As(III) and As(V) and are expected to provide enhanced arsenic removal capacity. X-ray absorption near edge structure (XANES) spectra indicate that arsenic is sequestered in the solid phase as both As(III) and As(V) in coordination environments with O and S. Arsenic removal in the PRB probably results from several pathways, including adsorption to iron oxide and iron sulfide surfaces, and possible precipitation of ferrous arsenate. Corrosion of granular iron appears to result in some As(III) oxidation to As(V) as the proportion of As(V) to As(III) in the solid phase is greater compared to influent groundwater. As(0) was not detected in the PRB materials. These results are broadly comparable to laboratory based studies of arsenic removal by zerovalent iron, but additional complexity is revealed in the field environment, which is largely due to the influence of subsurface microbiota.
Beak, Douglas G.; Wilkin, Richard T.
Dielectric barrier formation and tunneling magnetoresistance effect in strontium iron molybdate
A comparative X-ray diffraction study of the initial single-phase metal-oxide compound-strontium iron molybdate Sr2FeMoO6 - ? (SFMO)-and that subjected to additional isothermal annealing shows that this heat treatment leads to the appearance of a SrMoO4 (SMO) phase. Small-angle neutron scattering measurements indicate that the SMO phase forms a dielectric shell surrounding SFMO grains, which has a characteristic thickness of 2-4 nm and extends above 120 nm. The character of the temperature dependence of the electric resistance corresponds to the metal-type conduction in single-phase SFMO and changes to a semiconductor type in the material with SMO dielectric shells, which is evidence of a tunneling mechanism of charge transfer. This conclusion is confirmed by an increase in the absolute value of the negative magnetoresistance of SFMO due to the appearance of a tunneling magnetoresistance component of the same sign.
Dem'yanov, S. E.; Kalanda, N. A.; Kovalev, L. V.; Avdeev, M. V.; Zheludkevich, M. L.; Garamus, V. M.; Willumeit, R.
Investigating the Effect of Implementing Heating Rods within a ZVI-PRB to Enhance Performance, Improve Design and Reduce Costs
This paper presents a study performed to evaluate the feasibility of implementing a series of heating rods within a zero-valent\\u000a iron permeable reactive barrier (ZVI-PRB) to enhance the conventional design of PRBs, and thus to improve the barrier's removal\\u000a efficiency, and reduce construction and reactive material costs. A numerical modeling approach is undertaken where a hypothetical\\u000a case is introduced and
F. Fatemi; L. Liu; O. Khajeh Mahabadi; M. Satish
Corrosion and environmental-mechanical characterization of iron-base nuclear waste package structural barrier materials. Annual report, FY 1984
Disposal of high-level nuclear waste in deep underground repositories may require the development of waste packages that will keep the radioisotopes contained for up to 1000 y. A number of iron-base materials are being considered for the structural barrier members of waste packages. Their uniform and nonuniform (pitting and intergranular) corrosion behavior and their resistance to stress-corrosion cracking in aqueous environments relevant to salt media are under study at Pacific Northwest Laboratory. The purpose of the work is to provide data for a materials degradation model that can ultimately be used to predict the effective lifetime of a waste package overpack in the actual repository environment. The corrosion behavior of the candidate materials was investigated in simulated intrusion brine (essentially NaCl) in flowing autoclave tests at 150/sup 0/C, and in combinations of intrusion/inclusion (high-Mg) brine environments in moist salt tests, also at 150/sup 0/C. Studies utilizing a /sup 60/Co irradiation facility were performed to determine the corrosion resistance of the candidate materials to products of brine radiolysis at dose rates of 2 x 10/sup 3/ and 1 x 10/sup 5/ rad/h and a temperature of 150/sup 0/C. These irradiation-corrosion tests were ''overtests,'' as the irradiation intensities employed were 10 to 1000 times as high as those expected at the surface of a thick-walled waste package. With the exception of the high general corrosion rates found in the tests using moist salt containing high-Mg brines, the ferrous materials exhibited a degree of corrosion resistance that indicates a potentially satisfactory application to waste package structural barrier members in a salt repository environment.
Westerman, R.E.; Haberman, J.H.; Pitman, S.G.; Pulsipher, B.A.; Sigalla, L.A.
Pulsed Magnetic Field Improves the Transport of Iron Oxide Nanoparticles through Cell Barriers
Understanding how a magnetic field affects the interaction of magnetic nanoparticles (MNPs) with cells is fundamental to any potential downstream applications of MNPs as gene and drug delivery vehicles. Here, we present a quantitative analysis of how a pulsed magnetic field influences the manner in which MNPs interact with, and penetrate across a cell monolayer. Relative to a constant magnetic field, the rate of MNP uptake and transport across cell monolayers was enhanced by a pulsed magnetic field. MNP transport across cells was significantly inhibited at low temperature under both constant and pulsed magnetic field conditions, consistent with an active mechanism (i.e. endocytosis) mediating MNP transport. Microscopic observations and biochemical analysis indicated that, in a constant magnetic field, transport of MNPs across the cells was inhibited due to the formation of large (>2 ?m) magnetically-induced MNP aggregates, which exceeded the size of endocytic vesicles. Thus, a pulsed magnetic field enhances the cellular uptake and transport of MNPs across cell barriers relative to a constant magnetic field by promoting accumulation while minimizing magnetically-induced MNP aggregates at the cell surface.
Min, Kyoung Ah; Shin, Meong Cheol; Yu, Faquan; Yang, Meizhu; David, Allan E.; Yang, Victor C.; Rosania, Gus R.
The ultimate objective of this project is to quantify the ability of the electrical induced polarization (IP) method to non-invasively monitor the reduction in reactive iron performance that is known to reduce the effectiveness of the permeable reactive barrier (PRB) with time. The primary scientific goals include: (1) fundamental laboratory studies to evaluate the sensitivity of the IP method to physical/chemical changes to the iron surface resulting from oxidation, precipitation and clogging (2) monitoring of the electrical tomographic response of an installed PRB over a three-year period and assessment, via correlation with aqueous geochemical data and extracted iron cores, of whether electrical signatures associated with reduced PRB performance are resolvable in field studies (3) optimization of a three-dimensional tomographic imaging algorithm for application to highly conductive, high electrical contrast environments as represented by a PRB IP theory and empirical data resulting from the original development of the method for mineral exploration suggests that the method is highly relevant in the study of reactive iron barriers. Laboratory and field IP studies on mineral deposits illustrate the sensitivity of IP parameters to metal concentration, particle size and metal surface chemistry. IP theory, based on electrical (Warburg) impedance associated with diffusive ion transfer to/from the electrolyte to electron exchange sites on the metal surface, provides a framework for interpreting IP signatures of PRBs as a function of redox chemistry.
Slater, Lee; Choi, Jaeyoung
Corrosion resistance of cast irons and titanium alloys as reference engineered metal barriers for use in basalt geologic storage: a literature assessment
A survey and assessment of the literature on the corrosion resistance of cast irons and low-alloy titanium are presented. Selected engineering properties of cast iron and titanium are briefly described; however, the corrosion resistance of cast iron and titanium in aqueous solutions or in soils and their use in a basalt repository are emphasized. In evaluating the potential use of cast iron and titanium as structural barrier materials for long-lived nuclear waste packages, it is assumed that titanium has the general corrosion resistance to be used in relatively thin cross sections whereas the cost and availability of cast iron allows its use even in very thick cross sections. Based on this assumption, the survey showed that: The uniform corrosion of low-alloy titanium in a basalt environment is expected to be extremely low. A linear extrapolation of general corrosion rates with an added corrosion allowance suggests that a 3.2- to 6.4-mm-thick wall may have a life of 1000 yr. Pitting and crevice corrosion are not likely corrosion modes in basalt ground waters. It is also unlikely that stress corrosion cracking (SCC) will occur in the commercially pure (CP) titanium alloy or in palladiumor molybdenum-alloyed titanium materials. Low-alloy cast irons may be used as barrier metals if the environment surrounding the metal keeps the alloy in the passive range. The solubility of the corrosion product and the semipermeable nature of the oxide film allow significant uniform corrosion over long time periods. A linear extrapolation of high-temperature corrosion rates on carbon steels and corrosion rates of cast irons in soils gives an estimated metal penetration of 51 to 64 mm after 1000 yr. A corrosion allowance of 3 to 5 times that suggests that an acceptable cast iron wall may be from 178 to 305 mm thick. Although they cannot be fully assessed, pitting and crevice corrosion should not affect cast iron due to the ground-water chemistry of basalt.
Charlot, L.A.; Westerman, R.E.
Efflux of Iron from the Cerebrospinal Fluid to the Blood at the Blood-CSF Barrier: Effect of Manganese Exposure
The blood-cerebrospinal fluid (CSF) barrier (BCB) resides within the choroid plexus, with the apical side facing the CSF and the basolateral side towards the blood. Previous studies demonstrate that manganese (Mn) exposure in rats disrupts iron (Fe) homeostasis in the blood and CSF. The present study used a primary culture of rat choroidal epithelial cells grown in the two-chamber Transwell system to investigate the transepithelial transport of Fe across the BCB. Free, unbound Fe as [59Fe] was added to the donor chamber and the radioactivity in the acceptor chamber was quantified to determine the direction of Fe fluxes. Under the normal condition, the [59Fe] efflux (from the CSF to the blood) was 128% higher than that of the influx (P < 0.01). Mn exposure significantly increased the efflux rate of [59Fe] (P < 0.01) and the effect was inhibited when the cells were pre-incubated with the antibody against divalent metal transport 1 (DMT1). Moreover, when the siRNA knocked down the cellular DMT1 expression, the elevated Fe uptake caused by Mn exposure in the choroidal epithelial Z310 cells was completely abolished, indicating that Mn may facilitate Fe efflux via a DMT1-mediated transport mechanism. In vivo subchronic exposure to Mn in rats reduced Fe clearance from the CSF, as demonstrated by the ventriculo-cisternal brain perfusion, along with up-regulated mRNAs encoding DMT1 and transferrin receptor (TfR) in the same animals. Taken together, these data suggest that free Fe appears to be favorably transported from the CSF toward the blood by DMT1 and this process can be facilitated by Mn exposure. Enhanced TfR-mediated influx of Fe from the blood and ferroportin-mediated expelling Fe toward the CSF may compromise DMT1-mediated efflux, leading to an increased Fe concentration in the CSF as seen in Mn-exposed animals.
Wang, Xueqian; Li, G. Jane; Zheng, Wei
Fe(o)-based bioremediation of aquifers contaminated with mixed wastes
US Patent & Trademark Office Database
Disclosed are methods, devices and apparatus for bioremediation of mixed waste aquifers, based on a synergistic combination of reductive treatment using zero-valent iron and anaerobic biotransformations. Also disclosed are methods for in situ and ex situ remediation of groundwater and wastewater via these iron-bacterial compositions in a variety of devices including batch reactors, permeable and semipermeable reactive barriers, flow-through reactors, fluidized bed reactors, and sediment tanks.
Formulation design for target delivery of iron nanoparticles to TCE zones
Nanoparticles of zero-valent iron (NZVI) are effective reducing agents for some dense non-aqueous phase liquid (DNAPL) contaminants such as trichloroethylene (TCE). However, target delivery of iron nanoparticles to DNAPL zones in the aquifer remains an elusive feature for NZVI technologies. This work discusses three strategies to deliver iron nanoparticles to DNAPL zones. To this end, iron oxide nanoparticles coated with oleate (OL) ions were used as stable analogs for NZVI. The OL-coated iron oxide nanoparticles are rendered lipophilic via (a) the addition of CaCl2, (b) acidification, or (c) the addition of a cationic surfactant, benzethonium chloride (BC). Mixtures of OL and BC show promise as a target delivery strategy due to the high stability of the nanoparticles in water, and their preferential partition into TCE in batch experiments. Column tests show that while the OL-BC coated iron oxide nanoparticles remain largely mobile in TCE-free columns, a large fraction of these particles are retained in TCE-contaminated columns, confirming the effectiveness of this target delivery strategy.
Wang, Ziheng; Acosta, Edgar
Formulation design for target delivery of iron nanoparticles to TCE zones.
Nanoparticles of zero-valent iron (NZVI) are effective reducing agents for some dense non-aqueous phase liquid (DNAPL) contaminants such as trichloroethylene (TCE). However, target delivery of iron nanoparticles to DNAPL zones in the aquifer remains an elusive feature for NZVI technologies. This work discusses three strategies to deliver iron nanoparticles to DNAPL zones. To this end, iron oxide nanoparticles coated with oleate (OL) ions were used as stable analogs for NZVI. The OL-coated iron oxide nanoparticles are rendered lipophilic via (a) the addition of CaCl2, (b) acidification, or (c) the addition of a cationic surfactant, benzethonium chloride (BC). Mixtures of OL and BC show promise as a target delivery strategy due to the high stability of the nanoparticles in water, and their preferential partition into TCE in batch experiments. Column tests show that while the OL-BC coated iron oxide nanoparticles remain largely mobile in TCE-free columns, a large fraction of these particles are retained in TCE-contaminated columns, confirming the effectiveness of this target delivery strategy. PMID:24096200
Removal of hexavalent chromium from aqueous solution by iron nanoparticles*
Groundwater remediation by nanoparticles has received increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe0) nanoparticles. Cr(VI) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(VI), is an option in the remediation of contaminated sites, transforming Cr(VI) to essentially nontoxic Cr(III). At a dose of 0.4 g/L, 100% of Cr(VI) (20 mg/L) was degraded. The Cr(VI) removal efficiency decreased significantly with increasing initial pH. Different Fe0 type was compared in the same conditions. The reactivity was in the order starch-stabilized Fe0 nanoparticles>Fe0 nanoparticles>Fe0 powder>Fe0 filings. Electrochemical analysis of the reaction process led to the conclusion that Cr(OH)3 should be the final product of Cr(VI). Iron nanoparticles are good choice for the remediation of heavy metals in groundwater.
Niu, Shao-feng; Liu, Yong; Xu, Xin-hua; Lou, Zhang-hua
Investigating the Potential for Long-Term Permeable Reactive Barrier (PRB) Monitoring from the Electrical Signatures Associated with the Reduction in Reactive Iron Performance
The objective of this project is to quantify the ability of the electrical induced polarization (IP) method to non-invasively monitor the reduction in reactive iron performance that is known to reduce the effectiveness of the permeable reactive barrier (PRB) with time. The primary scientific goals include: (1) fundamental laboratory studies to evaluate the sensitivity of the IP method to: Fe0 total surface area Fe0 surface chemistry physical/chemical changes to the Fe0 surface resulting from oxidation and precipitation (2) monitoring of the electrical tomographic response of the Kansas City PRB over a three-year period and assessment, via correlation with aqueous geochemical data and extracted iron cores, of whether electrical signatures associated with reduced PRB performance are resolvable in field studies (3) optimization of a three-dimensional tomographic imaging algorithm for application to highly conductive, high electrical contrast environments as represented by a PRB IP theory and empirical data resulting from the original development of the method for mineral exploration suggests that the method is highly relevant in the study of reactive iron barriers. Laboratory and field IP studies on mineral deposits illustrate the sensitivity of IP parameters to metal concentration, particle size and metal surface chemistry. IP theory, based on electrical (Warburg) impedance associated with diffusive ion transfer to/from the electrolyte to electron exchange sites on the metal surface, provides a framework for interpreting IP signatures of PRBs as a function of redox chemistry.
Slater, Lee
The objective of this project is to quantify the ability of the electrical induced polarization (IP) method to noninvasively monitor the reduction in reactive iron performance that is known to reduce the effectiveness of the permeable reactive barrier (PRB) with time. The primary scientific goals include: (1) fundamental laboratory studies to evaluate the sensitivity of the IP method to: Fe0 total surface area Fe0 surface chemistry physical/chemical changes to the Fe0 surface resulting from oxidation and precipitation (2) monitoring of the electrical tomographic response of the Kansas City PRB over a three-year period and assessment, via correlation with aqueous geochemical data and extracted iron cores, of whether electrical signatures associated with reduced PRB performance are resolvable in field studies (3) optimization of a three-dimensional tomographic imaging algorithm for application to highly conductive, high electrical contrast environments as represented by a PRB IP theory and empirical data resulting from the original development of the method for mineral exploration suggests that the method is highly relevant in the study of reactive iron barriers. Laboratory and field IP studies on mineral deposits illustrate the sensitivity of IP parameters to metal concentration, particle size and metal surface chemistry. IP theory, based on electrical (Warburg) impedance associated with diffusive ion transfer to/from the electrolyte to electron exchange sites on the metal surface, provides a framework for interpreting IP signatures of PRBs as a function of redox chemistry.
Behaviour of uranium in iron-bearing permeable reactive barriers: investigation with 237U as a radioindicator
This study was undertaken to investigate the long-term performance of elemental iron as reactive material for the removal of uranium in passive groundwater remediation systems. By using 237U as a radioindicator it was possible to track the movement of the contamination front through a test column without taking samples or dismantling the apparatus. The stoichiometric ratio between uranium and iron
Franz-Georg Simon; Christian Segebade; Martina Hedrich
Advanced thermal barrier system bond coatings for use on nickel-, cobalt- and iron-base alloy substrates
New and improved Ni-, Co-, and Fe-base bond coatings have been identified for the ZrO2-Y2O3 thermal barrier coatings to be used on Ni-, Co-, and Fe-base alloy substrates. These bond coatings were evaluated in a cyclic furnace between 1120 and 1175 C. It was found that MCrAlYb (where M = Ni, Co, or Fe) bond coating thermal barrier systems have significantly longer lives than MCrAlY bond coating thermal barrier systems. The longest life was obtained with the FeCrAlYb thermal barrier system followed by NiCrAlYb and CoCrAlYb thermal barrier systems in that order.
Stecura, S.
Performance of a zerovalent iron reactive barrier for the treatment of arsenic in groundwater: Part 1. Hydrogeochemical studies
Developments and improvements of remedial technologies are needed to effectively manage arsenic contamination in groundwater at hazardous waste sites. In June 2005, a 9.1 m long, 14 m deep, and 1.8 to 2.4 m wide (in the direction of groundwater flow) pilot-scale permeable reactive barrier (PRB) was installed at a former lead smelting facility, located near Helena, Montana (USA). The reactive barrier was
Richard T. Wilkin; Steven D. Acree; Randall R. Ross; Douglas G. Beak; Tony R. Lee
A 30-month performance evaluation of a pilot permeable reactive barrier (PRB) consisting of a mixture of leaf compost, zero-valent iron (ZVI), limestone, and pea gravel was conducted at a former phosphate fertilizer manufacturing facility in Charleston, SC. The PRB is designed to remove heavy metals and arsenic from groundwater by promoting microbially mediated sulfate reduction and sulfide-mineral precipitation and arsenic
Ralph D. Ludwig; David J. A. Smyth; David W. Blowes; Laura E. Spink; Richard T. Wilkin; David G. Jewett; Christopher J. Weisener
Volatilization and sorption of dissolved mercury by metallic iron of different particle sizes: Implications for treatment of mercury contaminated water effluents.
Batch experiments were conducted to investigate the interactions between metallic iron particles and mercury (Hg) dissolved in aqueous solutions. The effect of bulk zero valent iron (ZVI) particles was tested by use of (i) granular iron and (ii) iron particles with diameters in the nano-size range and referred to herein as nZVI. The results show that the interactions between Hg(n+) and Fe(0) are dominated by Hg volatilization and Hg adsorption; with Hg adsorption being the main pathway for Hg removal from solution. Hg adsorption kinetic studies using ZVI and nZVI resulted in higher rate constants (k) for nZVI when k values were expressed as a function of mass of iron used (day(-1)g(-1)). In contrast, ZVI showed higher rates of Hg removal from solution when k values were expressed as a function iron particles' specific surface area (gm(-2)day(-1)). Overall, nZVI particles had a higher maximum sorption capacity for Hg than ZVI, and appeared to be an efficient adsorbent for Hg dissolved in aqueous solutions. PMID:24929302
Vernon, Julianne D; Bonzongo, Jean-Claude J
In-situ method to remove iron and other metals from solution in groundwater down gradient from permeable reactive barrier
This invention is directed to a process for treating the flow of anaerobic groundwater through an aquifer with a primary treatment media, preferably iron, and then passing the treated groundwater through a second porous media though which an oxygenated gas is passed in order to oxygenate the dissolved primary treatment material and convert it into an insoluble material thereby removing the dissolved primary treatment material from the groundwater.
Carpenter, Clay E. (Grand Junction, CO); Morrison, Stanley J. (Grand Junction, CO)
Ambient iron-mediated aeration (IMA) for water reuse.
Global water shortages caused by rapidly expanding population, escalating water consumption, and dwindling water reserves have rendered water reuse a strategically significant approach to meet current and future water demand. This study is the first to our knowledge to evaluate the technical feasibility of iron-mediated aeration (IMA), an innovative, potentially economical, holistic, oxidizing co-precipitation process operating at room temperature, atmospheric pressure, and neutral pH, for water reuse. In the IMA process, dissolved oxygen (O?) was continuously activated by zero-valent iron (Fe?) to produce reactive oxygen species (ROS) at ambient pH, temperature, and pressure. Concurrently, iron sludge was generated as a result of iron corrosion. Bench-scale tests were conducted to study the performance of IMA for treatment of secondary effluent, natural surface water, and simulated contaminated water. The following removal efficiencies were achieved: 82.2% glyoxylic acid, ~100% formaldehyde as an oxidation product of glyoxylic acid, 94% of Ca²? and associated alkalinity, 44% of chemical oxygen demand (COD), 26% of electrical conductivity (EC), 98% of di-n-butyl phthalate (DBP), 80% of 17?-estradiol (E2), 45% of total nitrogen (TN), 96% of total phosphorus (TP), 99.8% of total Cr, >90% of total Ni, 99% of color, 3.2 log removal of total coliform, and 2.4 log removal of E. Coli. Removal was attributed principally to chemical oxidation, precipitation, co-precipitation, coagulation, adsorption, and air stripping concurrently occurring during the IMA treatment. Results suggest that IMA is a promising treatment technology for water reuse. PMID:23232032
Deng, Yang; Englehardt, James D; Abdul-Aziz, Samer; Bataille, Tristan; Cueto, Josenrique; De Leon, Omar; Wright, Mary E; Gardinali, Piero; Narayanan, Aarthi; Polar, Jose; Tomoyuki, Shibata
Iron oxide nanotube layer fabricated with electrostatic anodization for heterogeneous Fenton like reaction.
Iron oxide nanotubes (INT) were fabricated with potentiostatic anodization of zero valent iron foil in 1M Na2SO4 containing 0.5wt% NH4F electrolyte, holding the potential at 20, 40, and 60V for 20min, respectively. Field emission scanning electron microscopy and X-ray diffractometry were used to evaluate the morphology and crystalline structure of the INT film. The potential of 40V for 20min was observed to be optimal to produce an optimal catalytic film. Cyanide dissolved in water was degraded through the Fenton-like reaction using the INT film with hydrogen peroxide (H2O2). In case of INT-40V in the presence of H2O2 3%, the first-order rate constant was found to be 1.7×10(-2)min(-1), and 1.2×10(-2)min(-1) with commercial hematite powder. Degradation of cyanide was much less with only H2O2. Therefore, this process proposed in this work can be an excellent alternative to traditional catalysts for Fenton-like reaction. PMID:24704548
Jang, Jun-Won; Park, Jae-Woo
Modeling the effects of methanol on iron dechlorination of a complex chlorinated NAPL.
Research was conducted to examine the effects of various fractions of cosolvent solutions on dechlorination of toxaphene by zero-valent iron (Fe(0)). Experimental results showed that toxaphene degradation in solution was found to be the result of dechlorination at the Fe(0) surface. The rate of toxaphene dechlorination was also found to reduce with the increase of cosolvent in solution, as the cosolvent presence caused a reduction in toxaphene adsorption to Fe(0) surfaces. Toxaphene sorption to Fe(0) was found to correspond to a Freundlich nonlinear sorption equation and indicated that the linearity of this isotherm in the presence of cosolvent was related to the saturation of solution, which was the ratio of aqueous concentration to the solubility (C(a)/S(c)). When C(a)/S(c)>0.2, the sorption isotherm was almost linear and the concept of cosolvency power can be applied mathematically to describe this process. A mathematical model detailing the sorption and dechlorination of toxaphene by Fe(0) was developed, and showed that experimental data agreed with the theoretically derived data. Overall, results indicated that dechlorination of complex chlorinated substances, such as toxaphene, by Fe(0) can be greatly dependent upon adsorption to the iron surface. PMID:18848392
Chen, Xiaosong; Clark, Clayton J
Evaluating the Mobility of Arsenic in Synthetic Iron-containing Solids Using a Modified Sequential Extraction Method
Many water treatment technologies for arsenic removal that are used today produce arsenic-bearing residuals which are disposed in non-hazardous landfills. Previous works have established that many of these residuals will release arsenic to a much greater extent than predicted by standard regulatory leaching tests (e.g. the toxicity characteristic leaching procedure, TCLP) and, consequently, require stabilization to ensure benign behavior after disposal. In this work, a four-step sequential extraction method was developed in an effort to determine the proportion of arsenic in various phases in untreated as well as stabilized iron-based solid matrices. The solids synthesized using various potential stabilization techniques included: amorphous arsenic-iron sludge (ASL), reduced ASL via reaction with zero valent iron (RASL), amorphous ferrous arsenate (PFA), a mixture of PFA and SL (M1), crystalline ferrous arsenate (HPFA), and a mixture of HPFA and SL (M2). The overall arsenic mobility of the tested samples increased in the following order: ASL > RASL > PFA > M1 > HPFA > M2.
Shan, Jilei; Saez, A. Eduardo; Ela, Wendell P.
Magnetic field enhanced convective diffusion of iron oxide nanoparticles in an osmotically disrupted cell culture model of the blood-brain barrier
Purpose The present study examines the use of an external magnetic field in combination with the disruption of tight junctions to enhance the permeability of iron oxide nanoparticles (IONPs) across an in vitro model of the blood–brain barrier (BBB). The feasibility of such an approach, termed magnetic field enhanced convective diffusion (MFECD), along with the effect of IONP surface charge on permeability, was examined. Methods The effect of magnetic field on the permeability of positively (aminosilane-coated [AmS]-IONPs) and negatively (N-(trimethoxysilylpropyl)ethylenediaminetriacetate [EDT]-IONPs) charged IONPs was evaluated in confluent monolayers of mouse brain endothelial cells under normal and osmotically disrupted conditions. Results Neither IONP formulation was permeable across an intact cell monolayer. However, when tight junctions were disrupted using D-mannitol, flux of EDT-IONPs across the bEnd.3 monolayers was 28%, increasing to 44% when a magnetic field was present. In contrast, the permeability of AmS-IONPs after osmotic disruption was less than 5%. The cellular uptake profile of both IONPs was not altered by the presence of mannitol. Conclusions MFECD improved the permeability of EDT-IONPs through the paracellular route. The MFECD approach favors negatively charged IONPs that have low affinity for the brain endothelial cells and high colloidal stability. This suggests that MFECD may improve IONP-based drug delivery to the brain.
Sun, Zhizhi; Worden, Matthew; Wroczynskyj, Yaroslav; Yathindranath, Vinith; van Lierop, Johan; Hegmann, Torsten; Miller, Donald W
Nano-scale metallic iron for the treatment of solutions containing multiple inorganic contaminants.
Although contaminant removal from water using zero-valent iron nanoparticles (INP) has been investigated for a wide array of chemical pollutants, the majority of studies to date have only examined the reaction of INP in simple single-contaminant systems. Such systems fail to reproduce the complexity of environmental waters and consequently fail as environmental analogues due to numerous competitive reactions not being considered. Consequently there is a high demand for multi-elemental and site-specific studies to advance the design of INP treatment infrastructure. Here INP are investigated using batch reactor systems over a range of pH for the treatment of water containing multi-element contaminants specifically U, Cu, Cr and Mo, selected to provide site-specific analogues for leachants collected from the Li?ava mine, near Oravi?a in South West Romania. Concurrently, a U-only solution was also analysed as a single-system for comparison. Results confirmed the suitability of nano-Fe(0) as a highly efficient reactive material for the aqueous removal of Cr(IV), Cu(II) and U(VI) over a range of pH applicable to environmental waters. Insufficient Mo(VI) removal was observed at pH >5.7, suggesting that further studies were necessary to successfully deploy INP for the treatment of geochemically complex mine water effluents. Results also indicated that uranium removal in the multi-element system was less than for the comparator containing only uranium. PMID:21115222
Scott, T B; Popescu, I C; Crane, R A; Noubactep, C
Cellular management of iron in the brain
All organs including the brain contain iron, and the proteins involved in iron uptake (transferrin and transferrin receptor) and intracellular storage (ferritin). However, because the brain resides behind a barrier and has a heterogeneous population of cells, there are aspects of its iron management that are unique. Iron management, the timely delivery of appropriate amounts of iron, is crucial to
James R. Connor; Sharon L. Menzies
Performance Optimization of Metallic Iron and Iron Oxide Nanomaterials for Treatment of Impaired Water Supplies
Iron nanomaterials including nanoscale zero valent iron (NZVI), NZVI-based bimetallic reductants (e.g., Pd/NZVI) and naturally occurring nanoscale iron mineral phases represent promising treatment tools for impaired water supplies. However, questions pertaining to fundamental and practical aspects of their reactivity may limit their performance during applications. For NZVI treatment of pollutant source zones, a major hurdle is its limited reactive lifetime. In Chapter 2, we report the longevity of NZVI towards 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and hexavalent chromium [Cr(VI)] in oxygen-free systems with various anionic co-solutes (e.g., Cl-, SO4 2-, ClO4-, HCO3 -, NO3-). Trends in longevity provide evidence that surface-associated Fe(II) species are responsible for Cr(VI) reduction, whereas 1,1,1,2-TeCA reduction depends on the accessibility of Fe(0) at the NZVI particle surface. In Chapter 3, we show that dithionite, previously utilized for in situ redox manipulation, can restore the reducing capacity of passivated NZVI treatment systems. Air oxidation of NZVI at pH ? 8 quickly exhausted reactivity despite a significant fraction of Fe(0) persisting in the particle core. Reduction of this passive layer by low dithionite concentrations restored suspension reactivity to levels of unaged NZVI, with multiple dithionite additions further improving pollutant removal. In Chapter 4, measurements of solvent kinetic isotope effects reveals that optimal Pd/NZVI reactivity results from accumulation of atomic hydrogen, which only occurs in NZVI-based systems due to their higher rates of corrosion. However, atomic hydrogen formation only occurs in aged Pd/NZVI suspensions for ˜2 weeks, after which any reactivity enhancement likely results from galvanic corrosion of Fe(0). Finally, the activity of hybrid nanostructures consisting of multi-walled carbon nanotubes decorated with of hematite nanoparticles (alphaFe 2O3/MWCNT) is explored in Chapter 5. Sorption of Cu(II) and Cr(VI) is enhanced in hybrid nanostructure systems beyond what would be expected from simple additive sorption capacities of their building blocks. The enhanced sorption capacity is in part derived from the greater surface area of hematite nanoparticles immobilized on MWCNTs relative to aggregated hematite suspensions. The hybrid alphaFe2O3/MWCNT may also exhibit unique surface chemistry, as supported by the tunable values of zeta potential measured as a function of the mass of alphaFe2O 3 deposited on the MWCNTs.
Xie, Yang
Monitoring engineered remediation with borehole radar
The success of engineered remediation is predicated on correct emplacement of either amendments (e.g., vegetable-oil emulsion, lactate, molasses, etc.) or permeable reactive barriers (e.g., vegetable oil, zero-valent iron, etc.) to enhance microbial or geochemical breakdown of contaminants and treat contaminants. Currently, site managers have limited tools to provide information about the distribution of injected materials; the existence of gaps or holes in barriers; and breakdown or transformation of injected materials over time. ?? 2007 Society of Exploration Geophysicists.
Lane, Jr. , J. W.; Day-Lewis, F. D.; Joesten, P. K.
Enhanced formation of oxidants from bimetallic nickel-iron nanoparticles in the presence of oxygen.
Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants capable of transforming organic contaminants in water. However,the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not increase the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4-9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values. PMID:19068843
Lee, Changha; Sedlak, David L
Enhanced Formation of Oxidants from Bimetallic Nickel-Iron Nanoparticles in the Presence of Oxygen
Nanoparticulate zero-valent iron (nZVI) rapidly reacts with oxygen to produce strong oxidants, capable of transforming organic contaminants in water. However, the low yield of oxidants with respect to the iron added normally limits the application of this system. Bimetallic nickel-iron nanoparticles (nNi-Fe; i.e., Ni-Fe alloy and Ni-coated Fe nanoparticles) exhibited enhanced yields of oxidants compared to nZVI. nNi-Fe (Ni-Fe alloy nanoparticles with [Ni]/[Fe] = 0.28 and Ni-coated Fe nanoparticles with [Ni]/[Fe] = 0.035) produced approximately 40% and 85% higher yields of formaldehyde from the oxidation of methanol relative to nZVI at pH 4 and 7, respectively. Ni-coated Fe nanoparticles showed a higher efficiency for oxidant production relative to Ni-Fe alloy nanoparticles based on Ni content. Addition of Ni did not enhance the oxidation of 2-propanol or benzoic acid, indicating that Ni addition did not enhance hydroxyl radical formation. The enhancement in oxidant yield was observed over a pH range of 4 – 9. The enhanced production of oxidant by nNi-Fe appears to be attributable to two factors. First, the nNi-Fe surface is less reactive toward hydrogen peroxide (H2O2) than the nZVI surface, which favors the reaction of H2O2 with dissolved Fe(II) (the Fenton reaction). Second, the nNi-Fe surface promotes oxidant production from the oxidation of ferrous ion by oxygen at neutral pH values.
Lee, Changha; Sedlak, David L.
Effect of geochemical properties on degradation of trichloroethylene by stabilized zerovalent iron nanoparticle with Na-acrylic copolymer.
Stable nanoscale zero-valent iron (NZVI) particles have been developed to remediate chlorinated compounds. The degradation kinetics and efficiency of trichloroethylene (TCE) by a commercial stabilized NZVI with Na-acrylic copolymer (acNZVI) were investigated and compared with those by laboratory-synthesized NZVI and carboxymethyl cellulose (CMC)-stabilized NZVI particles. Results show that the degradation of TCE by acNZVI was faster than that by NZVI and CMC-NZVI. Increase in temperature enhanced the degradation rate and efficiency of TCE with acNZVI. The activation energy of TCE degradation by acNZVI was estimated to be 23 kJ/mol. The degradation rate constants of TCE decreased from 0.064 to 0.026 min(-1) with decrease in initial pH from 9.03 to 4.23. Common groundwater anions including NO3(-), Cl(-), HCO3(-), and SO4(2-) inhibited slightly the degradation efficiencies of TCE by acNZVI. The Na-acrylic copolymer-stabilized NZVI, which exhibited high degradation kinetics and efficiency, could be a good remediation agent for chlorinated organic compounds. PMID:24929499
Chen, Meng-Yi; Su, Yuh-Fan; Shih, Yang-Hsin
Reductive transformation and sorption of cis- and trans-1,2-dichloroethene in a metallic iron-water system
Reductive transformation kinetic and sorption coefficients were determined for both cis- and trans-1,2-dichloroethene (DCE) in batch systems with zero-valent iron and water. Sorption quasi-equilibrium occurred rapidly for both compounds. Freundlich-type isotherms adequately described sorption over the measured concentration range. The magnitude of sorption was greater for trans-1,2-DCE than for the more soluble cis-1,2-DCE, indicating a possible influence of hydrophobicity. The trans-isomer was more reactive than the cis-isomer. The reaction order for trans-1,2-DCE was 1.22 and for cis-1,2-DCE was 1.77 and 1.64 in relatively high and low initial concentration experiments, respectively. The fact that the reaction order for the cis-isomer could not be reduced to unity by assuming that the bulk of observed sorption was to nonreactive sorption sites suggests that either the assumption may not be valid or that a more complex process exists for this isomer. Chloride was produced by the transformation reaction and chlorine mass balances for the batch systems were 80 to 85%. Other products observed were acetylene, ethene, ethane, C{sub 3}-C{sub 5} alkanes, and vinyl chloride.
Allen-King, R.M.; Halket, R.M. [Washington State Univ., Pullman, WA (United States). Dept. of Geology; Burris, D.R. [Armstrong Lab., Tyndall AFB, FL (United States)
Zero-valent metals such as bulk iron and zinc are known to dechlorinate toxicorganic compounds. Enhancement in reaction rates has been achieved through bimetallicnanosized particles such as nickel\\/iron (Ni\\/Fe) and palladium\\/iron (Pd\\/Fe). Batchdegradation of model compounds, trichlroethylene (TCE) and 2,2'-dichlorobiphenyls(DCB), were conducted using bimetallic Ni\\/Fe and Pd\\/Fe nanoparticles. Completedegradation of TCE and DCB is achieved at room temperature. Zero-valent iron, as
Yit-Hong Tee
Characterization and Properties of Metallic Iron and Iron-Oxide Nanoparticles: Spectroscopy, Electrochemistry, and Kinetics
There are reports that nano-sized zero-valent iron (Fe0) exhibits greater reactivity than micro-sized particles of Fe0, and it has been suggested that the higher reactivity of nano-Fe0 may impart advantages for groundwater remediation or other environmental applications. However, most of these reports are preliminary in that they leave a host of potentially significant (and often challenging) material or process variables either uncontrolled or unresolved. In an effort to better understand the reactivity of nano-Fe0, we have used a variety of complementary techniques to characterize two widely studied nano-Fe0 preparations:�¢���� one synthesized by reduction of goethite with heat and H2 (FeH2) and the other by reductive precipitation with borohydride (FeBH). FeH2 is a two-phase material consisting of 40 nm ���±-Fe0 (made up of crystals approximately the size of the particles) and Fe3O4 particles of similar size or larger containing reduced sulfur; whereas FeBH is mostly 20�¢����80 nm metallic Fe particles (aggregates of <1.5 nm grains) with an oxide shell/coating that is high in oxidized boron. The FeBH particles further aggregate into chains. Both materials exhibit corrosion potentials that are more negative than nano-sized Fe2O3, Fe3O4, micro-sized Fe0, or a solid Fe0 disk, which is consistent with their rapid reduction of oxygen, benzoquinone, and carbon tetrachloride. Benzoquinonewhich presumably probes inner-sphere surface reactionsreacts more rapidly with FeBH than FeH2, whereas carbon tetrachloride reacts at similar rates with FeBH and FeH2, presumably by outer-sphere electron transfer. Both types of nano-Fe0 react more rapidly than micro-sized Fe0 based on mass-normalized rate constants, but surface area-normalized rate constants do not show a significant nano-size effect. The distribution of products from reduction of carbon tetrachloride is more favorable with FeH2, which produces less chloroform than reaction with FeBH.
JT Nurmi; PG Tratnyek; V Sarathy; DR Baer; JE Amonette; K Pecher; CM Wang; JC Linehan; DW Matson; RL Penn; MD Driessen
Comparison of biotic and abiotic treatment approaches for co-mingled perchlorate, nitrate, and nitramine explosives in groundwater
Biological and abiotic approaches for treating co-mingled perchlorate, nitrate, and nitramine explosives in groundwater were compared in microcosm and column studies. In microcosms, microscale zero-valent iron (mZVI), nanoscale zero-valent iron (nZVI), and nickel catalyzed the reduction of RDX and HMX from initial concentrations of 9 and 1 mg\\/L, respectively, to below detection (0.02 mg\\/L), within 2 h. The mZVI and
C. E. Schaefer; M. E. Fuller; C. W. Condee; J. M. Lowey; P. B. Hatzinger
Effective degradation of C.I. Acid Red 73 by advanced Fenton process
The degradation of C.I. Acid Red 73 (AR 73) was investigated by advanced Fenton process based on zero-valent iron and hydrogen peroxide. The effect of zero-valent iron dosage, hydrogen peroxide concentration, initial pH, initial dye concentration, mixing rate and temperature on the degradation of AR 73 was studied. The results showed that AR 73 removal efficiency increased with the increase
Fenglian Fu; Qi Wang; Bing Tang
Nanoscale Pd\\/Fe bimetallic particles: Catalytic effects of palladium on hydrodechlorination
Reported herein is a study on the catalytic properties of palladium for hydrodechlorination using nanoscale zero-valent iron particles. Temperature-dependent experiments and X-ray diffraction (XRD) are conducted to characterize reactions of chlorinated ethylenes with nanoscale Fe and Pd\\/Fe particles. XRD results suggest bimetallic structures are created as a result of Pd(II) reduction by zero-valent iron and the degree of surface palladium
Hsing-Lung Lien; Wei-Xian Zhang
Reductive Sequestration Of Pertechnetate (99TcO4–) By Nano Zerovalent Iron (nZVI) Transformed By Abiotic Sulfide
Under anoxic conditions, soluble 99TcO4– can be reduced to less soluble TcO2•nH2O, but the oxide is highly susceptible to reoxidation. Here we investigate an alternative strategy for remediation of Tc-contaminated groundwater whereby sequestration as Tc sulfide is favored by sulfidic conditions stimulated by nano zero-valent iron (nZVI). nZVI was pre-exposed to increasing concentrations of sulfide in simulated Hanford groundwater for 24 hrs to mimic the stages of aquifer sulfate reduction and onset of biotic sulfidogenesis. Solid-phase characterizations of the sulfidated nZVI confirmed the formation of nanocrystalline FeS phases, but higher S/Fe ratios (>0.112) did not result in the formation of significantly more FeS. The kinetics of Tc sequestration by these materials showed faster Tc removal rates with increasing S/Fe between S/Fe = 0–0.056, but decreasing Tc removal rates with S/Fe > 0.224. The more favorable Tc removal kinetics at low S/Fe could be due to a higher affinity of TcO4– for FeS (over iron oxides), and electron microscopy confirmed that the majority of the Tc was associated with FeS phases. The inhibition of Tc removal at high S/Fe appears to have been caused by excess HS–. X-ray absorption spectroscopy revealed that as S/Fe increased, Tc speciation shifted from TcO2•nH2O to TcS2. The most substantial change of Tc speciation occurred at low S/Fe, coinciding with the rapid increase of Tc removal rate. This agreement further confirms the importance of FeS in Tc sequestration.
Fan, Dimin; Anitori, Roberto; Tebo, Bradley M.; Tratnyek, Paul G.; Lezama Pacheco, Juan S.; Kukkadapu, Ravi K.; Engelhard, Mark H.; Bowden, Mark E.; Kovarik, Libor; Arey, Bruce W.
The effect of engineered iron nanoparticles on growth and metabolic status of marine microalgae cultures.
Synthetic zero-valent nano-iron (nZVI) compounds are finding numerous applications in environmental remediation owing to their high chemical reactivity and versatile catalytic properties. Studies were carried out to assess the effects of three types of industrially relevant engineered nZVI on phytoplankton growth, cellular micromorphology and metabolic status. Three marine microalgae (Pavlova lutheri, Isochrysis galbana and Tetraselmis suecica) were grown on culture medium fortified with the nano-Fe compounds for 23 days and subsequent alterations in their growth rate, size distribution, lipid profiles and cellular ultrastructure were assessed. The added nano Fe concentrations were either equimolar with the EDTA-Fe conventionally added to the generic f/2 medium (i.e. 1.17 × 10(-5)M), or factor 10 lower and higher, respectively. We provide evidence for the: (1) broad size distribution of nZVI particles when added to the nutrient rich f/2 media with the higher relative percentage of the smallest particles with the coated forms; (2) normal algal growth in the presence of all three types of nZVIs with standard growth rates, cellular morphology and lipid content comparable or improved when compared to algae grown on f/2 with EDTA-Fe; (3) sustained algal growth and normal physiology at nZVI levels 10 fold below that in f/2, indicating preference to nanoparticles over EDTA-Fe; (4) increased total cellular lipid content in T. suecica grown on media enriched with uncoated nZVI25, and in P. lutheri with inorganically coated nZVI(powder), when compared at equimolar exposures; (5) significant change in fatty acid composition complementing the nZVI(powder)-mediated increase in lipid content of P. lutheri; (6) a putative NP uptake mechanism is proposed for I. galbana via secretion of an extracellular matrix that binds nZVIs which then become bioavailable via phagocytotic membrane processes. PMID:23059967
Kadar, Eniko; Rooks, Paul; Lakey, Cara; White, Daniel A
In situ testing of metallic iron nanoparticle mobility and reactivity in a shallow granular aquifer
This paper describes the results of a series of single well push-pull tests conducted to evaluate the in situ transport of carboxymethyl cellulose (CMC) stabilized nanoscale zero-valent iron (ZVI) particles in saturated sediments and their reactivity toward chlorinated ethenes. CMC-stabilized nanoscale ZVI particles were synthesized on site by reducing ferrous ions with borohydride in water in the presence of CMC. Nanoscale ZVI and bimetallic ZVI-Pd nanoparticle suspensions were prepared and injected into depth-discrete aquifer zones during three push-pull tests. The injected nanoparticle suspensions contained a conservative tracer (Br -) and were allowed to reside in the aquifer pore space for various time periods prior to recovery by groundwater extraction. The comparison between Br - and Fe concentrations in extracted groundwater samples indicated that the CMC-stabilized nanoscale ZVI particles were mobile in the aquifer but appeared to lose mobility with time, likely due to the interactions between particles and aquifer sediments. After 13 h in the aquifer, the nanoscale ZVI particles became essentially immobilized. During the push-pull test with injection of Fe-Pd nanoparticles, ethane concentrations increased from non-detectable to 65 ?g/L in extracted groundwater within less than 2 h of reaction time, indicating the rapid abiotic degradation of chlorinated ethenes. The amount of total chlorinated ethene mass destroyed was low presumably because the injected solutions "pushed" the dissolved chlorinated ethenes away from the injection well, without substantial mixing, and because stationary (sorbed) chlorinated ethene mass on the aquifer sediments was low. In situ remediation programs using highly reactive metallic nanoparticles should incorporate delivery methods that maintain high groundwater pore velocities during injection to increase advective transport distances (e.g. groundwater circulation wells). Also, source zones with abundant stationary contaminant mass that is accessible by advective transport should be targeted for remediation with the nanoparticles, as opposed to portions of dissolved plumes, in order to maximize the in situ destruction of contaminants.
Bennett, Peter; He, Feng; Zhao, Dongye; Aiken, Brian; Feldman, Lester
Thermal barrier coating system
A high temperature oxidation resistant, thermal barrier coating system is disclosed for a nickel cobalt, or iron base alloy substrate. An inner metal bond coating contacts the substrate, and a thermal barrier coating covers the bond coating. NiCrAlR, FeCrAlR, and CoCrAlR alloys are satisfactory as bond coating compositions where R=Y or Yb. These alloys contain, by weight, 24.9-36.7% chromium, 5.4-18.5% aluminum, and 0.05 to 1.55% yttrium or 0.05 to 0.53% ytterbium. The coatings containing ytterbium are preferred over those containing yttrium. An outer thermal barrier coating of partial stabilized zirconium oxide (zirconia) which is between 6% and 8%, by weight, of yttrium oxide (yttria) covers the bond coating. Partial stabilization provides a material with superior durability. Partially stabilized zirconia consists of mixtures of cubic, tetragonal, and monoclinic phases.
Stecura, S. (inventor)
Zerovalent iron is being used in permeable reactive barriers (PRBs) to remediate groundwater arsenic contamination. Iron(II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron under anaerobic conditions. The interaction between arsenic and this green...
Abiotic transformation of high explosives by freshly precipitated iron minerals in aqueous Fe II solutions
Zerovalent iron barriers have become a viable treatment for field-scale cleanup of various ground water contaminants. While contact with the iron surface is important for contaminant destruction, the interstitial pore water within and near the iron barrier will be laden with aqueous, adsorbed and precipitated FeII phases. These freshly precipitated iron minerals could play an important role in transforming high
Hardiljeet K. Boparai; Steve D. Comfort; Tunlawit Satapanajaru; James E. Szecsody; Paul R. Grossl; Patrick J. Shea
Vehicle barrier
This patent describes a vehicle security barrier which can be conveniently placed across a gate opening as well as readily removed from the gate opening to allow for easy passage. The security barrier includes a barrier gate in the form of a cable\\/gate member in combination with laterally attached pipe sections fixed by way of the cable to the gate
China's Steel Imports: An Outline of Recent Trade Barriers
Since 1993, amounts of iron and steel imported into China have steadily declined. Coincidentally, ChinaÂ's State Council released an administrative circular aimed at controlling steel imports.This paper describes trade barriers applicable to iron and steel imports. These barriers fall under three categories: (1) Tariffs. (2) Licensing and registration. (3) Trading rights and \\
Ian Dickson
Reductive catalysis of novel TiO 2\\/Fe 0 composite under UV irradiation for nitrate removal from aqueous solution
Groundwater contaminated by nitrate has become a worldwide problem. Existing technologies for nitrate removal, including zero-valent iron reduction, can only transform nitrate ions to predominantly NH4+. As a result, many studies have concentrated on seeking a solution to convert nitrate to N2. In this study, the efficiencies of nitrate removal from aqueous solution by single (TiO2 and nano zero valent
Jill Ruhsing Pan; Chihpin Huang; Wen-Pin Hsieh; Bi-Ju Wu
Characterization of corrosion products in the permeable reactive barriers
The impact of geochemical processes and microbial activity has been a major concern for the long-term performance of reactive\\u000a iron barriers because corrosion products and precipitates during the water treatment with reactive materials will decrease\\u000a the reactivity and permeability of the iron bed. This study characterizes corrosion products in reactive iron barrier as well\\u000a as evaluates the effect of the
Y. Roh; S. Y. Lee; M. P. Elless
A vehicle security barrier which can be conveniently placed across a gate opening as well as readily removed from the gate opening to allow for easy passage. The security barrier includes a barrier gate in the form of a cable/gate member in combination with laterally attached pipe sections fixed by way of the cable to the gate member and lateral, security fixed vertical pipe posts. The security barrier of the present invention provides for the use of cable restraints across gate openings to provide necessary security while at the same time allowing for quick opening and closing of the gate areas without compromising security.
Hirsh, Robert A. (Bethel Park, PA)
Geotechnical techniques for the construction of reactive barriers
One of the newest and most promising remediation techniques for the treatment of contaminated groundwater and soil is the reactive barrier wall (commonly known as PRB for permeable reactive barrier or reactive barrier). Although a variety of treatment media and strategies are available, the most common technique is to bury granular iron in a trench so that contaminated groundwater passes
Steven R Day; Stephanie F O'Hannesin; Lloyd Marsden
Effects of Solution Chemistry on the Dechlorination of 1,2,3-Trichloropropane by Zero-Valent Zinc
The reactivity of zerovalent zinc (ZVZ) toward 1,2,3-trichloropropane (TCP) was evaluated under a variety of solution conditions, including deionized water, groundwater, and artificial groundwater, over a pH range of about 6.5-12. In deionized water, first-order rate constants for TCP disappearance (kobs) exhibit a broad minimum between pH 8 and 10, with increasing kobs observed at lower and higher pH. The similarity between this trend and zinc oxide (ZnO) solubility behavior suggests pH related changes to the ZnO surface layer strongly influence ZVZ reactivity. Values of kobs measured in acidic groundwater are similar to those measured in DI water, whereas values measured in alkaline groundwater are much smaller (>1 order of magnitude at pH values >10). Characterization of the surfaces of ZVZ exposed to deionized water, acidic groundwater, and alkaline groundwater suggests that the slower rates obtained in alkaline groundwater are related to the presence of a morphologically distinct surface film that passivates the ZVZ surface. TCP degradation rates in artificial groundwater containing individual solutes present in groundwater suggest that silicate anions contribute to the formation of this passivating film.
Salter-Blanc, Alexandra; Tratnyek, Paul G.
Iron (II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron that is being used in permeable reactive barriers to remediate groundwater arsenic contamination. To optimize the design of iron barriers, it is important to evaluate the influence of geoch...
Environmental Management Science Program (EMSP) Annual Report
The treatment or remediation of contaminants at some sites is neither technically nor economically feasible. Containment or stabilization of these subsurface contaminants, therefore, may be the only viable alternative for the protection of human and ecological health. The overall goal of the proposed research is the development of reactive membrane barriers which dramatically enhance containment. Reactive particles in these barriers serve to either immobilize or transform contaminants within the membrane, and thus increase the time to breakthrough. These membranes are a powerful, novel, and versatile technique to contain and stabilize subsurface contaminants. This work focuses on reactive membrane barriers containing either zero-valent iron (Fe0) particles (which can reduce metals and chlorinated solvents) or crystalline silicotitanate (CST, a selective ion exchanger of cesium and strontium) particles.
Arnold, William A.; Cussler, Edward L.
Clamshell excavation of a permeable reactive barrier
Nowadays, permeable reactive barriers (PRB) are one of the most widespread techniques for the remediation of contaminated aquifers. Over the past 10 years, the use of iron-based PRBs has evolved from innovative to accepted standard practice for the treatment of a variety of groundwater contaminants (ITRC in: Permeable reactive barriers: lessons learned\\/new directions. The Interstate Technology and Regulatory Council, Permeable Reactive
Antonio Di Molfetta; Rajandrea Sethi