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Oxidation-reduction (redox) reactions are important in drinking water treatment and distribution. Oxidation-reduction potential (ORP) measurements of water reflect the tendency of major constituents in the water to accept or lose electrons. Although ORP measurements are valuable...
The generation and inactivation mechanism of oxidation¢reduction potential of electrolyzed oxidizing water
The Nernst equations between the oxidation¢reduction potential (ORP), the concentration of hypochlorous acid and chlorine and the value of pH in electrolyzed oxidizing water (EOW) were developed in three parts, which were in agreement in the measured values. The role of ORP in EOW for killing Escherichia coli O157:H7 was studied. The inactivation effect of EOW on E. coli O157:H7
Long B. Liao; Wei M. Chen; Xian M. Xiao
Effect of Estuarine Sediment pH and Oxidation-Reduction Potential on Microbial Hydrocarbon Degradation.
National Technical Information Service (NTIS)
Microbial mineralization rates of two petroleum hydrocarbons, as affected by pH and oxidation-reduction potential, were determined in a Barataria Bay, Louisiana, sediment using 14C-labeled hydrocarbons. Hydrocarbon mineralization rates were inferred from ...
G. A. Hambrick R. D. DeLaune W. H. Patrick
Characteristics of Volatile Fatty Acid and Oxidation Reduction Potential for Treating Municipal Wastewater in Modified EGSB
The traditional Expanded Granular Sludge Bed (EGSB) reactor was modified to treating municipal wastewater. The characteristics of Oxidation Reduction Potential (ORP) and Volatile Fatty Acid (VFA) concentration of effluent was studied to judge to the operation condition of anaerobic degradation process. The characteristics of ORP and VFA for treating municipal wastewater was studied in modified Expanded Granular Sludge Bed (EGSB).
Ma Limin; Sun Xiaojing; Ma Xiujuan
The reduction potential of nitric oxide (NO) and its importance to NO biochemistry
A potential of about ?0.8 (▒0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion (3NO?) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous electrochemical measurements involving NO. Reduction of NO to 1NO? is highly unfavorable, with a predicted reduction potential of about ?1.7 (▒0.2) V at 1 M versus normal hydrogen electrode. These results represent a substantial revision of the derived and widely cited values of +0.39 V and ?0.35 V for the NO/3NO? and NO/1NO? couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means. With such highly negative reduction potentials, NO is inert to reduction compared with physiological events that reduce molecular oxygen to superoxide. From these reduction potentials, the pKa of 3NO? has been reevaluated as 11.6 (▒3.4). Thus, nitroxyl exists almost exclusively in its protonated form, HNO, under physiological conditions. The singlet state of nitroxyl anion, 1NO?, is physiologically inaccessible. The significance of these potentials to physiological and pathophysiological processes involving NO and O2 under reductive conditions is discussed.
Bartberger, Michael D.; Liu, Wei; Ford, Eleonora; Miranda, Katrina M.; Switzer, Christopher; Fukuto, Jon M.; Farmer, Patrick J.; Wink, David A.; Houk, Kendall N.
Microbial reduction of crystalline iron(III) oxides: Influence of oxide surface area and potential for cell growth
Quantitative aspects of microbial crystalline iron(III) oxide reduction were examined using a dissimilatory iron(III) oxide-reducing bacterium (Shewanella alga strain BrY). The initial rate and long-term extent of reduction of a range of synthetic iron(III) oxides were linearly correlated with oxide surface area. Oxide reduction rates reached an asymptote at cell concentrations in excess of =1 x 10Ōü╣\\/m┬▓ of oxide surface.
Eric E. Roden; John M. Zachara
Monitored Environment System to Control Cell Growth, Morphology, and Metabolic Rate in Fungi by Oxidation-Reduction Potentials
A device for the adjustment, maintenance, and monitoring of a desired oxidation-reduction potential in a liquid environment is described. The filamentous species, Penicillium lilacinum and Trichophyton schoenleinii, and the dimorphic species, Histoplasma capsulatum, developed budding yeastlike cells when grown in a liquid medium with a low oxidation-reduction potential. When the organisms were inoculated into fresh medium, they returned to the filamentous condition as the oxidation-reduction potential was restored to a more positive (oxidizing) environment. Images Fig. 1 Fig. 6
Rippon, John W.
Stoichiometry of electron uptake and oxidation-reduction midpoint potentials of NADH:nitrate reductase.
Microcoulometric titrations of NADH:nitrate reductase at 25 degrees C in Mops buffer, pH 7.0, showed that the native enzyme, containing functional FAD, haem and Mo, required addition of five electrons for complete reduction. Reduction of the native enzyme occurred in three waves corresponding to addition of reducing equivalents to the centres in the order: Mo, haem, FAD. Oxidation-reduction midpoint potentials (E'0) for the various redox couples were calculated to be as follows: MoVI/MoV, +16 mV; MoV/MoIV, -27 mV; haemoxidized/haemreduced, -172 mV; FAD/FADH2, -283 mV. The values for the haem and flavin are in excellent agreement with those obtained by visible titrations, namely -164 mV and -288 mV respectively. In contrast, the results for the Mo centre are 28-50 mV more positive than the values previously determined by e.p.r. analysis of frozen enzyme samples poised at defined potentials at 25 degrees C and suggest different pH-dependencies or entropies of reduction for the Mo couples.
Spence, J T; Barber, M J; Solomonson, L P
Chapter A6. Section 6.5. Reduction-Oxidation Potential (Electrode Method)
Reduction-oxidation (redox) potential--also referred to as Eh--is a measure of the equilibrium potential, relative to the standard hydrogen electrode, developed at the interface between a noble metal electrode and an aqueous solution containing electroactive chemical species. Measurements of Eh are used to evaluate geochemical speciation models, and Eh data can provide insights on the evolution and status of water chemistry in an aqueous system. Nevertheless, the measurement is fraught with inherent interferences and limitations that must be understood and considered to determine applicability to the aqueous system being studied. For this reason, Eh determination is not one of the field parameters routinely measured by the U.S. Geological Survey (USGS). This section of the National Field Manual (NFM) describes the equipment and procedures needed to measure Eh in water using a platinum electrode. Guidance as to the limitations and interpretation of Eh measurement also is included.
Nordstrom, Darrell Kirk; Wilde, Franceska D.
Computation of equilibrium oxidation and reduction potentials for reversible and dissociative electron-transfer reactions in solution
Equilibrium free-energy cycles relating oxidation and reduction potentials in solution to ionization potentials and electron affinities in the gas phase are constructed and the utilities of various levels of theory for computing particular free-energy changes within these cycles are discussed within the context of several examples. Emphasis is placed on the use of quantum-mechanical continuum solvation models to compute free
P. Winget; C. J. Cramer; D. G. Truhlar
NSDL National Science Digital Library
Created by team members from Kapi'olani Community College and Leeward Community College, this site provides educators and students with a colorful background lesson in oxidation and reduction. The site is divided into concepts, exercises, and everyday examples of oxidation and reduction. Each exercise allows users to check all answers.
1Methyl4-phenylpyridinium (MPP +) Decreases Mitochondrial Oxidation-Reduction (REDOX) Activity and Membrane Potential (?? m) in Rat Striatum
Mitochondrial dysfunction has long been implicated in the death of nigrostriatal dopaminergic neurons in Parkinson's disease (PD) and its experimental models. Here we further analyzed changes in the mitochondrial oxidation-reduction (REDOX) activity and membrane potential (??m) of striatal synaptosomes after the infusion of 1-methyl-4-phenylpyridinium (MPP+) into rat striatum. MPP+ (40 nmol) treatment produced decreases in mitochondrial REDOX activity and ??m
Masami Nakai; Atsushi Mori; Akihito Watanabe; Yasuhide Mitsumoto
Gamma radiation interacts with melanin to alter its oxidation-reduction potential and results in electric current production.
The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials. PMID:21632287
Turick, Charles E; Ekechukwu, Amy A; Milliken, Charles E; Casadevall, Arturo; Dadachova, Ekaterina
The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials.
Turick, C.; Ekechukwu, A.; Milliken, C.
Oxidation-Reduction Equilibria
NSDL National Science Digital Library
This 11-page PDF document is part of an environmental geochemistry course taught by Dr. David Sherman at the University of Bristol. Topics include oxidation-reduction reactions and oxidation states, the Nerst Equation, Eh-pH diagrams, and redox environments in nature. Also included are the calculation of Eh from concentrations and the prediction of stable oxidation states. Helpful diagrams accompany the text.
Sherman, David M.; Bristol, University O.
Effects of oxidation reduction potential in the bypass micro-aerobic sludge zone on sludge reduction for a modified oxic-settling-anaerobic process.
Batch experiments were conducted to determine the effect of oxidation reduction potential (ORP) on sludge reduction in a bypass micro-aerobic sludge reduction system. The system was composed of a modified oxic-settling-anaerobic process with a sludge holding tank in the sludge recycle loop. The ORPs in the micro-aerobic tanks were set at approximately +350, -90, -150, -200 and -250 mV, by varying the length of aeration time for the tanks. The results show that lower ORP result in greater sludge volume reduction, and the sludge production was reduced by 60% at the lowest ORP. In addition, low ORP caused extracellular polymer substances dissociation and slightly reduced sludge activity. Comparing the sludge backflow characteristics of the micro-aerobic tank's ORP controlled at -250 mV with that of +350 mV, the average soluble chemical oxygen (SCOD), TN and TP increased by 7, 0.4 and 2 times, median particle diameter decreased by 8.5 ?m and the specific oxygen uptake rate (SOUR) decreased by 0.0043 milligram O2 per gram suspended solids per minute. For the effluent, SCOD and TN and TP fluctuated around 30, 8.7 and 0.66 mg/L, respectively. Therefore, the effective assignment of ORP in the micro-aerobic tank can remarkably reduce sludge volume and does not affect final effluent quality. PMID:24845332
Li, Kexun; Wang, Yi; Zhang, Zhongpin; Liu, Dongfang
Effect of reducing agents on oxidation-reduction potential and the outgrowth of Clostridium botulinum type E spores.
Oxidation-reduction potential (Eh) levels were measured and standardized to pH (Eh7) for Trypticase soy broth containing various concentrations of reducing agents. Prereduced Trypticase soy broth with no added reducing agents exhibited a potential of -141 mV. Ascorbic acid at 0.2 to 0.005% and sodium thioglycolate at concentrations below 0.05% produced an Eh7 higher than the prereduced Trypticase soy broth containing no added reducing agents. The addition of cysteine hydrochloride,2-mercaptoethanol, and sodium formaldehyde sulfoxylate to prereduced Trypticase soy broth resulted in a reduction of Eh7 compared to the system without added reducing agents. The order of relative reducing intensity (from highest to lowest) for the reducing agents when comparing molar concentration was: sodium formaldehyde sulfoxylate,2-mercaptoethanol, cysteine hydrochloride, sodium thioglycolate, and ascorbic acid. Optimal growth of the test organism occurred at low Eh7 and low concentration of the reducing agents. A direct correlation existed between growth of the test organism and -Eh7 x -log concentration of the reducing agent.
Smith, M V; Pierson, M D
Twenty-five oxidation-reduction indicators were injected in oxidized or reduced form into Amoeba dubia and Am£ba proteus under controlled conditions of oxygen access. (1) Under anaerobiosis the ameba was able to reduce completely all the reversible oxidation-reduction indicators down to and including indigo disulfonate. (2) Under anaerobiosis the ameba was unable to reoxidize six of the most easily oxidizable indicators. (3) Under aerobiosis the ameba was able to reduce completely all the indicators down to and including 1-naphthol-2-sulfonate indo-2, 6-dichlorophenol. Toluylene blue, methylene blue and indigo tetrasulfonate were sometimes completely and sometimes only partly reduced, depending on the quantity of indicator injected and the duration of observation. (4) The time of reduction varied approximately with the size of the injection. Reduction was more rapid under anaerobiosis than under aerobiosis, more rapid in active than in sluggish cells and was retarded by toxic compounds. (5) Sulfonated compounds were somewhat toxic, as a rule. In interpreting reduction phenomena of micro injection, it is necessary to take into consideration the intensity, capacity and rate factors. It then becomes apparent that the ameba has a high reducing potential lying on the rH scale below the zone of indigo disulfonate. The reducing capacity of the ameba seems to be relatively great in the region of the simple indophenols and of a progressively diminishing magnitude as the zone of the indigos is approached. Material of high reduction potential appears to be generated within the ameba at a measurable rate. These phenomena, observed in the interior of the cell with the aid of indicators, parallel very closely those found in reduction electrode studies on bacterial cultures.
Cohen, Barnett; Chambers, Robert; Reznikoff, Paul
Effect of sediment pH and oxidation-reduction potential on PCB mineralization
Microbial mineralization rates of a 14C-labelled PCB mixture were determined in PCB-contaminated Capitol Lake, LA, sediment under controlled pH and redox conditions. Mineralization rates were inferred from the activity of 14CO2 evolved from the sediment suspensions. Sediment pH and redox potential significantly affected PCB mineralization. Mineralization rates were higher under moderately aerobic conditions (microaerophilic) ( + 250 mV) than under
John H. Pardue; Ronald D. Delaune; William H. Patrick
The influence of oxidation reduction potential and water treatment processes on quartz lamp sleeve fouling in ultraviolet disinfection reactors.
Ultraviolet (UV) disinfection systems are incorporated into drinking water production facilities because of their broad-spectrum antimicrobial capabilities, and the minimal disinfection by-product formation that generally accompanies their use. Selection of an optimal location for a UV system within a drinking water treatment facility depends on many factors; a potentially important consideration is the effect of system location on operation and maintenance issues, including the potential for fouling of quartz surfaces. To examine the effect of system location on fouling, experiments were conducted at a groundwater treatment facility, wherein aeration, chlorination, and sand filtration were applied sequentially for treatment. In this facility, access to the water stream was available prior to and following each of the treatment steps. Therefore, it was possible to examine the effects of each of these unit operations on fouling dynamics within a UV system. Results indicated zero-order formation kinetics for the fouling reactions at all locations. Increases in oxidation reduction potential, caused by water treatment steps such as aeration and chlorination, increased the rate of sleeve fouling and the rate of irradiance loss within the reactor. Analysis of metals in the sleeve foulant showed that calcium and iron predominate, and relative comparisons of foulant composition to water chemistry highlighted a high affinity for incorporation into the foulant matrix for both iron and manganese, particularly after oxidizing treatment steps. Fouling behavior was observed to be in qualitative agreement with representations of the degree of saturation, relative to the metal:ligand combinations that are believed to comprise a large fraction of the foulants that accumulate on the surfaces of quartz jackets in UV systems used to treat water. PMID:17448518
Wait, Isaac W; Johnston, Cliff T; Blatchley, Ernest R
Reversible potentials for steps in methanol and formic acid oxidation to CO2; adsorption energies of intermediates on the ideal electrocatalyst for methanol oxidation and CO2 reduction.
Quantum chemical theory is used to identify the reasons for platinum's limitations as an electrocatalyst for oxidizing methanol at fuel cell anodes. The linear Gibbs energy relation (LGER) method is employed to predict reversible potentials for reaction steps for intermediates on the electrode surface. In this procedure, standard reversible potentials are calculated for the reactions in bulk solution phase and then they are perturbed using calculated adsorption bond strengths to the electrode surface, yielding the equilibrium potentials for each electron transfer step for adsorbed intermediates. Adsorption properties of ideal electrocatalysts for the methanol oxidation are found by imposing the condition that the reversible potential of each electron transfer step equals that for the overall reaction. The adsorption bond strengths that provide the ideal properties also apply to formic acid oxidation and carbon dioxide reduction. It is instructive to think of the ideal electrocatalyst as a lens that focusses the reversible potentials for the n individual electron transfer steps to the reversible potential for the n-electron process. It is found that the ideal catalyst will adsorb many intermediates, including HOOC, CO, OCH, HOC, HOCH, HOCH2, and OCH3 more weakly than platinum, and OOCH and OH more strongly. For example, for one possible pathway it is necessary to weaken adsorption bond strengths for HOCH2, HOCH, OCH, HOOC by about 0.5 eV, weaken adsorption CO by about 1.1 eV and strengthen OH adsorption by about 0.6 eV. These results imply a need for developing new multi-component catalysts. PMID:24741672
Anderson, Alfred B; Asiri, Haleema Aied
Determination of glucose oxidase oxidation-reduction potentials and the oxygen reactivity of fully reduced and semiquinoid forms.
The oxidation-reduction potential values for the two electron transfers to glucose oxidase were obtained at pH 5.3, where the neutral radical is the stable form, and at pH 9.3, where the anion radical is the stable form. The midpoint potentials at 25 degrees were: pH 5.3 EFl1ox + e- H+ equilibrium EFlH. Em1 = -0.063 +/- 0.011 V EFlH. + e- + H+ equilibrium EFlredH2 Em2 = -0.065 +/- 0.007 V pH 9.3 EFlox + e- EFi- Em1 = -0.200 +/- 0.010 V EFi- + e- + H+ equilibrium EFlredH- Em2 = -0.240 +/- 0.005 V All potentials were measured versus the standard hydrogen electrode (SHE). The potentials indicated that glucose oxidase radicals are stabilized by kinetic factors and not by thermodynamic energy barriers. The pK for the glucose oxidase radical was 7.28 from dead time stopped flow measurements and the extinction coefficient of the neutral semiquinone was 4140 M-1 cm-1 at 570 nm. Both radical forms reacted with oxygen in a second order fashion. The rate at 25 degrees for the neutral semiquinone was 1.4 X 10(4) M-1 s-1; that for the anion radical was 3.5 X 10(4) M-1 s-1. The rate of oxidation of the neutral radical changed by a factor of 9 for a temperature difference of 22 degrees. For the anion radical, the oxidation rate changed by a factor of 6 for a 22 degrees change in temperature. We studied the oxygen reactivity of the 2-electron reduced form of the enzyme over a wide wavelength range and failed to detect either oxygenated flavin derivatives or semiquinoid forms as intermediates. The rate of reoxidation of fully reduced glucose oxidase at pH 9.3 was dependent on ionic strength. PMID:27511
Stankovich, M T; Schopfer, L M; Massey, V
Electrode measurements of the oxidation-reduction potential in the Gotland Deep using medium-term moored profiling instrumentation
NASA Astrophysics Data System (ADS)
The variation of in situ redox potential (Eh) was studied in the stratified water column (30 - 185 m) of the central Baltic Sea, for a period of 56 days (November, 2010 - January, 2011) using the Gotland Deep Environmental Sampling Station (GODESS) in order to identify the processes that control Eh. During the deployment of the mooring 170 profiles of hydro-physical parameters were registered, including the oxidation-reduction potential, pH, dissolved oxygen, chlorophyll a fluorescence, turbidity, temperature and conductivity. In general, the measured Eh (with respect to standard hydrogen electrode, SHE) ranged from - 55 to 167 mV. A comparison of the measured Eh with that calculated for the particular redox couples was carried out by applying the Nernst-equation. The standard reduction potentials were corrected for temperature and pH. Furthermore, the concentrations of the most important redox components such as Fe, Mn, N, O, C and S used for comparison were estimated by using empirical functions or were based on measurements of discrete water samples, taken at the time of deployment and recovery of the mooring. The results reveal that the reduction of Fe(III) essentially controls the electrode potential of the redox sensor in most parts of the anoxic waters. Below the redoxcline the reduction of hematite and then ferric oxyhydroxid could be related to the redox potential and somewhat deeper Fe(III)/Fe(II) was found to be the dominant redox couple. Theoretically a mixed potential theory should have been applied because in natural waters a variety of redox pairs is present but Fe couples appear to dominate all the other redox equlibria. This could be explained by the relatively high exchange current of Fe and by the high concentrations (up to 1.5 ĄM) present at those depths in the study area. However, there are still gaps in our knowledge about the cycling of redox-sensitive elements and long-term moored profiling instrumentations may help to improve our understanding. Thus, we are pursuing the use of in situ analyzers for electro active compounds on moored systems in the future. In this case, analyzer data would be associated with chemical and physical parameters measured with high resolution in time and space, giving information on mixing processes and reaction kinetics. This approach is required to assess the relevance, for instance, of intrusions of oxygenated waters, vertical eddy-diffusion and fluctuations caused by internal waves on the cycle of redox-sensitive elements. This is particularly important as lateral transport appears to play a dominant role along isopycnal surfaces, especially in medium-sized stratified basins and yet have not been investigated extensively in the Baltic Sea with respect to the cycles of the most electro-active compounds.
Meyer, David; Prien, Ralf; Dellwig, Olaf; Schulz-Bull, Detlef
Roles of oxidation-reduction potential in electrolyzed oxidizing and chemically modified water for the inactivation of food-related pathogens.
This study investigates the properties of electrolyzed oxidizing (EO) water for the inactivation of pathogen and to evaluate the chemically modified solutions possessing properties similar to EO water in killing Escherichia coli O157:H7. A five-strain cocktail (10(10) CFU/ml) of E. coli O157:H7 was subjected to deionized water (control), EO water with 10 mg/liter residual chlorine (J.A.W-EO water), EO water with 56 mg/liter residual chlorine (ROX-EO water), and chemically modified solutions. Inactivation (8.88 log10 CFU/ml reduction) of E. coli O157:H7 occurred within 30 s after application of EO water and chemically modified solutions containing chlorine and 1% bromine. Iron was added to EO or chemically modified solutions to reduce oxidation-reduction potential (ORP) readings and neutralizing buffer was added to neutralize chlorine. J.A.W-EO water with 100 mg/liter iron, acetic acid solution, and chemically modified solutions containing neutralizing buffer or 100 mg/liter iron were ineffective in reducing the bacteria population. ROX-EO water with 100 mg/liter iron was the only solution still effective in inactivation of E. coli O157:H7 and having high ORP readings regardless of residual chlorine. These results suggest that it is possible to simulate EO water by chemically modifying deionized water and ORP of the solution may be the primary factor affecting microbial inactivation. PMID:10643764
Kim, C; Hung, Y C; Brackett, R E
Use of ORP (oxidation-reduction potential) to control oxygen dosing for online sulfide oxidation in anaerobic treatment of high sulfate wastewater.
In this study, oxidation-reduction potential (ORP) was used as a controlling parameter to regulate oxygen dosing to the recycled biogas for online sulfide oxidation in an upflow anaerobic filter (UAF) system. The UAF was operated with a constant influent COD of 18,000 mg/L, but with different influent sulfates of 1000, 3000 and 6000 mg/L. The reactor was initially operated under a natural ORP of -290 mV (without oxygen injection), and was then followed by oxygenation to raise its ORP by 25 mV above the natural level for each influent sulfate condition. At 6,000 mg/L sulfate without oxygen injection, the dissolved sulfide reached 733.8 mg S/L with a corresponding free sulfide of 250.3 mg S/L, thus showing a considerable inhibition to methanogens. Upon oxygenation to raise its ORP to -265 mV (i.e., a 25 mV increase), the dissolved sulfide was reduced by more than 98.5% with a concomitant 45.9% increase of the methane yield. Under lower influent sulfate levels of 1,000 and 3,000 mg/L, the levels of sulfides produced, even under the natural ORP, did not impose any noticeable toxicity to methanogens. Upon oxygenation to raise the ORP by +25 mV, the corresponding methane yields were actually reduced by 15.5% and 6.2%, respectively. However, such reductions were not due to the adverse impact of the elevated ORP; instead, they were due to a diversion of some organic carbon to support the facultative activities inside the reactor as a result of excessive oxygenation. In other words, to achieve satisfactory sulfide oxidation for the lower influent sulfate conditions, it was not necessary to raise the ORP by as much as +25 mV. The ORP increase actually needed depended on both the influent sulfate and also actual wastewater characteristics. This study had proved that the ORP controlled oxygenation was reliable for achieving consistent online sulfide control. PMID:12926687
Khanal, S K; Shang, C; Huang, J C
Direct electrochemical reduction of metal-oxides
A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.
Redey, Laszlo I. (Downers Grove, IL); Gourishankar, Karthick (Downers Grove, IL)
Oxidation--reduction midpoint potentials of the flavin, haem and Mo-pterin centres in spinach (Spinacia oleracea L.) nitrate reductase.
Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV (n = 2). The redox potential for reduction of the haem was determined by visible potentiometry to be -123 +/- 10 mV (n = 1), significantly lower than the previously published value of -60 mV [Fido, Hewitt, Notton, Jones & Nasrulhaq-Boyce (1979) FEBS Lett. 99, 180-182]. Potentials for the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) redox couples, determined by room-temperature e.p.r. potentiometry, were found to be +2 +/- 20 and -6 +/- 20 mV respectively. These values are very similar to the values previously determined for the FAD, haem and Mo-pterin centres in assimilatory nitrate reductase isolated from the unicellular green alga Chlorella vulgaris and indicate a close thermodynamic similarity between the two enzymes.
Kay, C J; Barber, M J; Notton, B A; Solomonson, L P
Oxidation--reduction midpoint potentials of the flavin, haem and Mo-pterin centres in spinach (Spinacia oleracea L.) nitrate reductase.
Oxidation-reduction midpoint potentials have been determined for the flavin, cytochrome b557 and Mo-pterin prosthetic groups of spinach (Spinacia oleracea L.) assimilatory nitrate reductase using visible, c.d. and room-temperature e.p.r. potentiometric titrations. At pH 7 and 25 degrees C, the midpoint potential for the FAD/FADH2 couple was determined by c.d. potentiometry to be -280 +/- 10 mV (n = 2). The redox potential for reduction of the haem was determined by visible potentiometry to be -123 +/- 10 mV (n = 1), significantly lower than the previously published value of -60 mV [Fido, Hewitt, Notton, Jones & Nasrulhaq-Boyce (1979) FEBS Lett. 99, 180-182]. Potentials for the Mo(VI)/Mo(V) and Mo(V)/Mo(IV) redox couples, determined by room-temperature e.p.r. potentiometry, were found to be +2 +/- 20 and -6 +/- 20 mV respectively. These values are very similar to the values previously determined for the FAD, haem and Mo-pterin centres in assimilatory nitrate reductase isolated from the unicellular green alga Chlorella vulgaris and indicate a close thermodynamic similarity between the two enzymes. PMID:2604699
Kay, C J; Barber, M J; Notton, B A; Solomonson, L P
Potential role of nitrite for abiotic Fe(II) oxidation and cell encrustation during nitrate reduction by denitrifying bacteria.
Microorganisms have been observed to oxidize Fe(II) at neutral pH under anoxic and microoxic conditions. While most of the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria become encrusted with Fe(III)-rich minerals, photoautotrophic and microaerophilic Fe(II) oxidizers avoid cell encrustation. The Fe(II) oxidation mechanisms and the reasons for encrustation remain largely unresolved. Here we used cultivation-based methods and electron microscopy to compare two previously described nitrate-reducing Fe(II) oxidizers ( Acidovorax sp. strain BoFeN1 and Pseudogulbenkiania sp. strain 2002) and two heterotrophic nitrate reducers (Paracoccus denitrificans ATCC 19367 and P. denitrificans Pd 1222). All four strains oxidized ?8 mM Fe(II) within 5 days in the presence of 5 mM acetate and accumulated nitrite (maximum concentrations of 0.8 to 1.0 mM) in the culture media. Iron(III) minerals, mainly goethite, formed and precipitated extracellularly in close proximity to the cell surface. Interestingly, mineral formation was also observed within the periplasm and cytoplasm; intracellular mineralization is expected to be physiologically disadvantageous, yet acetate consumption continued to be observed even at an advanced stage of Fe(II) oxidation. Extracellular polymeric substances (EPS) were detected by lectin staining with fluorescence microscopy, particularly in the presence of Fe(II), suggesting that EPS production is a response to Fe(II) toxicity or a strategy to decrease encrustation. Based on the data presented here, we propose a nitrite-driven, indirect mechanism of cell encrustation whereby nitrite forms during heterotrophic denitrification and abiotically oxidizes Fe(II). This work adds to the known assemblage of Fe(II)-oxidizing bacteria in nature and complicates our ability to delineate microbial Fe(II) oxidation in ancient microbes preserved as fossils in the geological record. PMID:24271182
Klueglein, Nicole; Zeitvogel, Fabian; Stierhof, York-Dieter; Floetenmeyer, Matthias; Konhauser, Kurt O; Kappler, Andreas; Obst, Martin
ChemTeacher Resource: Oxidation Reduction Reactions
NSDL National Science Digital Library
This computer resource goes over oxidation reduction reactions and how they are broken down into half reactions. It explains which half reaction is the oxidation reaction and which one is the reduction, then has some summary questions at the end.
Dr. Martin McClinton, Debbie McClinton, Dr. Miriam Douglass
Benzene oxidation coupled to sulfate reduction
Highly reduced sediments from San Diego Bay, Calif., that were incubated under strictly anaerobic conditions metabolized benzene within 55 days when they were exposed initially to I ??M benzene. The rate of benzene metabolism increased as benzene was added back to the benzene-adapted sediments. When a [14C]benzene tracer was included with the benzene added to benzene-adapted sediments, 92% of the added radioactivity was recovered as 14CO2. Molybdate, an inhibitor of sulfate reduction, inhibited benzene uptake and production of 14CO2 from [14C]benzene. Benzene metabolism stopped when the sediments became sulfate depleted, and benzene uptake resumed when sulfate was added again. The stoichiometry of benzene uptake and sulfate reduction was consistent with the hypothesis that sulfate was the principal electron acceptor for benzene oxidation. Isotope trapping experiments performed with [14C]benzene revealed that there was no production of such potential extracellular intermediates of benzene oxidation as phenol, benzoate, p-hydroxybenzoate, cyclohexane, catechol, and acetate. The results demonstrate that benzene can be oxidized in the absence of O2, with sulfate serving as the electron acceptor, and suggest that some sulfate reducers are capable of completely oxidizing benzene to carbon dioxide without the production of extracellular intermediates. Although anaerobic benzene oxidation coupled to chelated Fe(III) has been documented previously, the study reported here provides the first example of a natural sediment compound that can serve as an electron acceptor for anaerobic benzene oxidation.
Lovley, D. R.; Coates, J. D.; Woodward, J. C.; Phillips, E. J. P.
Thermodynamic constraints on microbial iron oxide reduction
NASA Astrophysics Data System (ADS)
Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit large surface areas which bind trace metals, nutrients and organic molecules. Under suboxic conditions, iron oxides can reductively dissolve via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. The aim of our study was to determine the thermodynamic energy yields of dissimilatory iron reduction for different Fe(III) substrates. We used the facultative anaerobic gram-positive bacterium Shewanella putrefaciens as model iron reducing bacterium, with ferrihydrite, hematite, goethite or Fe(III)-salicylate as electron acceptor, and lactate as electron donor. Experiments were conducted in an anaerobic pH-stat batch reactor, equipped with a polarographic electrode to monitor in situ the dissolved ferrous iron activity. The stoichiometry of total Fe(II) production and acid consumption during the experiments indicated that lactate was oxidized to acetate. From the Fe(II) activity and redox potential measurements, free energy yields were calculated for Fe(III) reduction coupled to lactate oxidation. The results showed that the redox potential of the overall reaction was poised by equilibrium between the Fe(III)-substrate and aqueous Fe(II). Hence, the energy yields decreased in the order ferrihydrite > Fe(III)-salicylate > hematite > goethite. Accumulation of Fe(II) in solution only caused small decreases in the energy yields over the course of the experiments. Cessation of iron reduction, which was observed in all experiments, was therefore not due to thermodynamic limitation, but more likely reflected the decline in cell level of activity.
Bonneville, S.; Behrends, T.; Haese, R.; van Cappellen, P.
Molecular Modeling of Environmentally Important Processes: Reduction Potentials
ERIC Educational Resources Information Center
The increasing use of computational quantum chemistry in the modeling of environmentally important processes is described. The employment of computational quantum mechanics for the prediction of oxidation-reduction potential for solutes in an aqueous medium is discussed.
Lewis, Anne; Bumpus, John A.; Truhlar, Donald G.; Cramer, Christopher J.
This study was undertaken as a part of developing treatment alternatives for waste materials, primarily waste rock and roaster tailings, from sites contaminated with mercury (Hg) mining wastes. Leaching profiles of waste rock over a range of different pH and oxidation-reduction (...
Influence of pH and oxidation-reduction potential (Eh) on the dissolution of mercury-containing mine wastes from the Sulfur Bank Mercury mine
ABSTRACT This study was undertaken as a part of developin g treatment alternatives for waste materials, primari ly waste rock and roaster tailings, from sites contaminated with mercury (Hg) mining wastes. Leaching profiles of waste rock over a range of different pH and oxidation -reduction (Eh) conditions were performed. Since iron (Fe) is present in large quantities in mining wastes,
Paul Randall
Relationship of arsenic concentration with ammonium-nitrogen concentration, oxidation reduction potential and pH of groundwater in arsenic-contaminated areas in Asia
NASA Astrophysics Data System (ADS)
This study examines how arsenic (As) concentration is related to ammonium-nitrogen (NH4-N) concentration, oxidation reduction potential (ORP) and pH in groundwater to determine if they have common characteristics in groundwater with high As concentrations in the As-contaminated areas of Bangladesh, Nepal, Cambodia and Vietnam. For the groundwater samples having the three highest As concentrations (top three groundwaters) selected as representatives at each location, As and NH4-N concentrations varied, but ORP and pH did not vary by locations. The ORP value of 30-110 mV, indicating the reducing condition, and the neutral to slightly alkaline pH (pH 7.0-7.6) were presumed to be the key conditions for high As concentrations in groundwater of the study areas. According to the ORP (Eh)-pH diagram, the dominant As species in the top three groundwaters from each location was hydrogen arsenate (HAsO42-). Out of the correlations between the four elements for the top three groundwaters in the areas, only the correlation between As and NH4-N concentrations was positive and significant. Thus, it was identified that NH4-N had an effect on increasing As concentration in groundwater.
Kurosawa, Kiyoshi; Egashira, Kazuhiko; Tani, Masakazu
Understanding Oxidation - Reduction in Organic Chemistry
Several years of teaching organic chemistry at the introductory level have made it obvious that understanding oxidation - reduction can be a difficult and sometimes traumatic experience for students. Mastery of the concepts and definitions of oxidation as the loss, and reduction as the gain of electrons is relatively simple (and comforting). However, the realization that the application of this
Jean-Pierre Anselme
Catalytic reduction of nitrogen oxides by ammonia
Of all the methods for treating gases to remove nitrogen oxides, the most widely used are methods based on catalytic reduction. The capital expense required for such methods is relatively small, and the equipment can be simpler and at the same time quite efficient. Among these methods, the most promising is the catalytic reduction of nitrogen oxides by ammonia, forming
A. F. Lunin; Yu. A. Adzhiev; R. I. Fedorova
Oxidation and Reduction Reactions in Organic Chemistry
ERIC Educational Resources Information Center
A variety of approaches to the concept of oxidation and reduction appear in organic textbooks. The method proposed here is different than most published approaches. The oxidation state is calculated by totaling the number of heterogeneous atoms, [pi]-bonds, and rings. A comparison of the oxidation states of reactant and product determine what typeģ
Shibley, Ivan A., Jr.; Amaral, Katie E.; Aurentz, David J.; McCaully, Ronald J.
Reversible electrical reduction and oxidation of graphene oxide.
We demonstrate that graphene oxide can be reversibly reduced and oxidized using electrical stimulus. Controlled reduction and oxidation in two-terminal devices containing multilayer graphene oxide films are shown to result in switching between partially reduced graphene oxide and graphene, a process which modifies the electronic and optical properties. High-resolution tunneling current and electrostatic force imaging reveal that graphene oxide islands are formed on multilayer graphene, turning graphene into a self-assembled heterostructure random nanomesh. Charge storage and resistive switching behavior is observed in two-terminal devices made of multilayer graphene oxide films, correlated with electrochromic effects. Tip-induced reduction and oxidation are also demonstrated. Results are discussed in terms of thermodynamics of oxidation and reduction reactions. PMID:21391707
Ekiz, Okan Oner; Urel, Mustafa; G³ner, Hasan; Mizrak, Alpay Koray; DŌna, Aykutlu
Carbothermal reduction of metal-oxide powders by synthetic pitch to carbide and nitride ceramics
The carbothermal reduction potential of mesophase synthetic pitch was investigated. Powders of cobalt oxide, iron oxide, zirconium\\u000a oxide, manganese oxide, silicon oxide, vanadium oxide, tantalum oxide, tungsten oxide, chromium oxide, and titanium oxide\\u000a were mixed with pitch and pyrolyzed at a variety of temperatures up to 1500Ā░C in nitrogen, 5% hydrogen balance argon, and\\u000a anhydrous ammonia. Pitch was found superior
B. M. Eick; J. P. Youngblood
Reduction of metal oxides through mechanochemical processing
The low temperature reduction of a metal oxide using mechanochemical processing techniques. The reduction reactions are induced mechanically by milling the reactants. In one embodiment of the invention, titanium oxide TiO.sub.2 is milled with CaH.sub.2 to produce TiH.sub.2. Low temperature heat treating, in the range of 400.degree. C. to 700.degree. C., can be used to remove the hydrogen in the titanium hydride.
Froes, Francis H. (Moscow, ID); Eranezhuth, Baburaj G. (Moscow, ID); Senkov, Oleg N. (Moscow, ID)
Stabilized tin-oxide-based oxidation/reduction catalysts
NASA Technical Reports Server (NTRS)
The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.
Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)
Reduction of Metal Oxide to Metal using Ionic Liquids
A novel pathway for the high efficiency production of metal from metal oxide means of electrolysis in ionic liquids at low temperature was investigated. The main emphasis was to eliminate the use of carbon and high temperature application in the reduction of metal oxides to metals. The emphasis of this research was to produce metals such as Zn, and Pb that are normally produced by the application of very high temperatures. The reduction of zinc oxide to zinc and lead oxide to lead were investigated. This study involved three steps in accomplishing the final goal of reduction of metal oxide to metal using ionic liquids: 1) Dissolution of metal oxide in an ionic liquid, 2) Determination of reduction potential using cyclic voltammetry (CV) and 3) Reduction of the dissolved metal oxide. Ionic liquids provide additional advantage by offering a wide potential range for the deposition. In each and every step of the process, more than one process variable has been examined. Experimental results for electrochemical extraction of Zn from ZnO and Pb from PbO using eutectic mixtures of Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3+Cl-) or (ChCl) in a molar ratio 2:1, varying voltage and temperatures were carried out. Fourier Transform Infra-Red (FTIR) spectroscopy studies of ionic liquids with and without metal oxide additions were conducted. FTIR and induction coupled plasma spectroscopy (ICPS) was used in the characterization of the metal oxide dissolved ionic liquid. Electrochemical experiments were conducted using EG&G potentiostat/galvanostat with three electrode cell systems. Cyclic voltammetry was used in the determination of reduction potentials for the deposition of metals. Chronoamperometric experiments were carried out in the potential range of -0.6V to -1.9V for lead and -1.4V to -1.9V for zinc. The deposits were characterized using XRD and SEM-EDS for phase, morphological and elemental analysis. The results showed that pure metal was deposited on the cathode. Successful extraction of metal from metal oxide dissolved in Urea/ChCl (2:1) was accomplished. The current efficiencies were relatively high in both the metal deposition processes with current efficiency greater than 86% for lead and 95% for zinc. This technology will advance the metal oxide reduction process by increasing the process efficiency and also eliminate the production of CO2 which makes this an environmentally benign technology for metal extraction.
Dr. Ramana Reddy
Biomimetic and microbial reduction of nitric oxide
The biomimetic reduction of nitric oxide (NO) to nitrous oxide (N2O) by dithiothreitol in the presence of cyanocobalamin and cobaltcentered porphyrins has been investigated. Reactions were\\u000a monitored directly using Fourier Transform Infrared (FTIR) Spectroscopy vapor-phase spectra. Reaction rates were twofold faster\\u000a for the corrin than for the cobalt-centered porphyrins. The stoichiometry showed the loss of two molecules of NO per
W. T. Potter; Uyen Le; Suzanne Ronda; Jeong-Guk Cho; Ramesh Shanmugasundram; Allison Chirkis; Kerry L. Sublette
Size dependent reduction-oxidation-reduction behaviour of cobalt oxide nanocrystals
NASA Astrophysics Data System (ADS)
Morphologically similar cobalt oxide nanoparticles (Co3O4) of four different sizes (3 nm, 6 nm, 11 nm and 29 nm) with narrow size distribution were prepared by subtle variation of synthesis conditions. These nanoparticles were used as model materials to understand the structural and morphological changes that occur to cobalt oxide during sequential reduction, oxidation and further re-reduction process as a function of the initial size of cobalt oxide. On reduction, spherical cobalt nanoparticles were obtained independent of the original size of cobalt oxide. In contrast, subsequent oxidation of the metal particles led to solid spheres, hollow spheres or core-shell structures depending on the size of the initial metal particle. Further re-reduction of the oxidized structures was also observed to be size dependent. The hollow oxide shells formed by the large particles (29 nm) fragmented into smaller particles on reduction, while the hollow shells of the medium sized particles (11 nm) did not re-disperse on further reduction. Similarly, no re-dispersion was observed in the case of the small particles (6 nm). This model study provides useful insights into the size dependent behavior of metal/metal oxide particles during oxidation/reduction. This has important implications in petrochemical industry where cobalt is used as a catalyst in the Fischer-Tropsch process.Morphologically similar cobalt oxide nanoparticles (Co3O4) of four different sizes (3 nm, 6 nm, 11 nm and 29 nm) with narrow size distribution were prepared by subtle variation of synthesis conditions. These nanoparticles were used as model materials to understand the structural and morphological changes that occur to cobalt oxide during sequential reduction, oxidation and further re-reduction process as a function of the initial size of cobalt oxide. On reduction, spherical cobalt nanoparticles were obtained independent of the original size of cobalt oxide. In contrast, subsequent oxidation of the metal particles led to solid spheres, hollow spheres or core-shell structures depending on the size of the initial metal particle. Further re-reduction of the oxidized structures was also observed to be size dependent. The hollow oxide shells formed by the large particles (29 nm) fragmented into smaller particles on reduction, while the hollow shells of the medium sized particles (11 nm) did not re-disperse on further reduction. Similarly, no re-dispersion was observed in the case of the small particles (6 nm). This model study provides useful insights into the size dependent behavior of metal/metal oxide particles during oxidation/reduction. This has important implications in petrochemical industry where cobalt is used as a catalyst in the Fischer-Tropsch process. Electronic supplementary information (ESI) available: (a) Powder X-ray diffractograms of nanoparticles (b) representative TEM image of cobalt oxide nanoparticles supported on MCM-41 after oxidation to remove the stabilizer (c) TEM image of a 29 nm and 6 nm cobalt oxide sample after reduction showing some sintering to form large particles and calculation to determine size of metallic cobalt sphere. See DOI: 10.1039/c3nr02877a
Sadasivan, Sajanikumari; Bellabarba, Ronan M.; Tooze, Robert P.
Reduction of nitric oxide by denitrifying bacteria
Two heterotrophic denitrifying bacteria, Paracoccus denitrificans and Pseudomonas denitrificans, have been shown to utilize nitric oxide (NO) as a terminal electron acceptor and succinate, yeast extract, and heat\\/alkali pretreated municipal sewage sludge as carbon and energy sources. Complete removal of NO (0.50%) from a feed gas sparged into the cultures was observed. It is suggested that reduction of NO may
R. Shanmugasundram; C. M. Lee; K. L. Sublette
Microbial reduction of manganese oxides - Interactions with iron and sulfur
NASA Technical Reports Server (NTRS)
Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.
Myers, Charles R.; Nealson, Kenneth H.
Coordinated reduction of genes of oxidative metabolism in humans with insulin resistance and diabetes: Potential role of PGC1 and NRF1
Type 2 diabetes mellitus (DM) is characterized by insulin resistance and pancreatic ? cell dysfunction. In high-risk subjects, the earliest detectable abnormality is insulin resistance in skeletal muscle. Impaired insulin-mediated signaling, gene expression, glycogen synthesis, and accumulation of intramyocellular triglycerides have all been linked with insulin resistance, but no specific defect responsible for insulin resistance and DM has been identified in humans. To identify genes potentially important in the pathogenesis of DM, we analyzed gene expression in skeletal muscle from healthy metabolically characterized nondiabetic (family history negative and positive for DM) and diabetic Mexican¢American subjects. We demonstrate that insulin resistance and DM associate with reduced expression of multiple nuclear respiratory factor-1 (NRF-1)-dependent genes encoding key enzymes in oxidative metabolism and mitochondrial function. Although NRF-1 expression is decreased only in diabetic subjects, expression of both PPAR? coactivator 1-? and-? (PGC1-?/PPARGC1 and PGC1-?/PERC), coactivators of NRF-1 and PPAR?-dependent transcription, is decreased in both diabetic subjects and family history-positive nondiabetic subjects. Decreased PGC1 expression may be responsible for decreased expression of NRF-dependent genes, leading to the metabolic disturbances characteristic of insulin resistance and DM.
Patti, Mary Elizabeth; Butte, Atul J.; Crunkhorn, Sarah; Cusi, Kenneth; Berria, Rachele; Kashyap, Sangeeta; Miyazaki, Yoshinori; Kohane, Isaac; Costello, Maura; Saccone, Robert; Landaker, Edwin J.; Goldfine, Allison B.; Mun, Edward; DeFronzo, Ralph; Finlayson, Jean; Kahn, C. Ronald; Mandarino, Lawrence J.
Estimating one-electron Reduction Potentials of Quinones
The one-electron reduction potential * E 7 of benzo-, naphtho-and anthracenequinones is related to their ability to undergo redox cycling and elicit cytotoxicity through oxidative stress. To evaluate a general approach to estimate the E 7 of benzo-, naphtho-and anthracenequinones, QSAR approaches based on gas phase and solvation based methods were employed.Stereoelectronic descriptors of ground state quinones, respective intermediates of
O. G. Mekenyan; S. P. Bradbury; V. B. Kamenska
Some Tungsten Oxidation-Reduction Chemistry: A Paint Pot Titration.
ERIC Educational Resources Information Center
Reports an oxidation-reduction experiment using tungsten, somewhat analogous to the classical student experiment involving oxidation-reduction of vanadium. Includes experimental procedures, results, and toxicity/cost of tungsten compounds. (Author/JN)
Pickering, Miles; Monts, David L.
Oxidation-reduction catalyst and its process of use
NASA Technical Reports Server (NTRS)
This invention relates generally to a ruthenium stabilized oxidation-reduction catalyst useful for oxidizing carbon monoxide, and volatile organic compounds, and reducing nitrogen oxide species in oxidizing environments, substantially without the formation of toxic and volatile ruthenium oxide species upon said oxidizing environment being at high temperatures.
Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor)
Lithium metal reduction of plutonium oxide to produce plutonium metal
This patent describes a method for production of plutonium metal from plutonium oxide by metallic lithium reduction, with regeneration of lithium reactant. It comprises: reacting the plutonium oxide with metallic lithium; oxides and unreacted lithium; subliming the product lithium oxide and unreacted lithium from unreacted plutonium oxide with high heat and low pressure; recapturing the product lithium oxides; reacting the
Analysis of potential helicopter vibration reduction concepts
NASA Technical Reports Server (NTRS)
Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.
Landgrebe, A. J.; Davis, M. W.
Processing of effluent salt from the direct oxide reduction process.
National Technical Information Service (NTIS)
The production of reactive metals by Direct Oxide Reduction (DOR) process using calcium in a molten calcium salt system generates significant amount of contaminated waste as calcium oxide saturated calcium chloride salt mix with calcium oxide content of u...
B. Mishra D. L. Olson W. A. Averill
Calculating Standard Reduction Potentials of [4Fe-4S] Proteins
The oxidation-reduction potentials of electron transfer proteins determine the driving forces for their electron transfer reactions. While the type of redox site determines the intrinsic energy required to add or remove an electron, the electrostatic interaction energy between the redox site and its surrounding environment can greatly shift the redox potentials. Here, a method for calculating the reduction potential versus the standard hydrogen electrode, E░, of a metalloprotein using a combination of density functional theory and continuum electrostatics is presented. This work focuses on the methodology for the continuum electrostatics calculations, including various factors that may affect the accuracy. The calculations are demonstrated using crystal structures of six homologous HiPIPs, which give E░ that are in excellent agreement with experimental results.
Perrin, Bradley Scott; Niu, Shuqiang; Ichiye, Toshiko
Lithium metal reduction of plutonium oxide to produce plutonium metal
A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by sublimation and converted to the chloride salt, and after electrolysis, is removed as lithium metal. Zinc may be used as a solvent metal to improve thermodynamics of the reduction reaction at lower temperatures. Lithium metal reduction enables plutonium oxide reduction without the production of huge quantities of CaO--CaCl.sub.2 residues normally produced in conventional direct oxide reduction processes.
Coops, Melvin S. (Livermore, CA)
Constructed wetlands designed and properly operated for treatment of swine wastewater may enhance oxidation -reduction processes and nutrient treatment performance. The objective of this investigation was to characterize soil wetland processes related to nitrogen (N) treatment (nitrification-denitrification) and phosphorus (P) removal using soil oxidation -reduction potential (ORP) data. We evaluated three surface-flow wetland systems constructed for treatment of swine wastewater
A. A. Sz÷gi; P. G. Hunt; E. J. Sadler; D. E. Evans
Microbial reduction of manganese oxides: Interactions with iron and sulfur
Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe{sup 3+} to Fe{sup 2+}, and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe{sup 2+} and sulfide act as rapid reductants of Mn. The addition of Fe{sup 3+} or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and extent of Mn reduction relative to that observed in the absence of Fe{sup 3+} or thiosulfate. Furthermore, when Fe{sup 3+} and Mn oxides are present conjointly, Fe{sup 2+} and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.
Myers, C.R.; Nealson, K.H. (Univ. of Wisconsin, Milwaukee (USA))
Gaseous reduction of iron oxides: Part III. Reduction-oxidation of porous and dense iron oxides and iron
The internal reduction of high-grade granular hematite ore in hydrogen and carbon monoxide, and also the internal oxidation\\u000a of porous iron granules in CO2-CO mixtures have been investigated. To assist the interpretation of the rate data for porous iron and iron oxides, rate measurements\\u000a have been made also with dense wustite, previously grown on iron by oxidation. The iron formed
E. T. Turkdogan; J. V. Vinters
Graphite Oxide: Structure, Reduction and Applications
NASA Astrophysics Data System (ADS)
This thesis proposes a modified structure model for graphite oxide (GO), an important precursor in graphene chemistry, develops a new strategy to convert GO back to graphene-like structure, and demonstrates its possible applications in both water purification and supercapacitor technologies. GO, a nontraditional compound first obtained from graphite oxidation over 150 years ago, is now becoming an important player in the production of graphene-based materials, which has high technological relevance. GO structure and reduction have been vigorously investigated, but its precise chemical structure still remains obscure, and the complete restoration of the sp2 carbon lattice has not yet been achieved. In our work, solid state 13C NMR (MAS) analysis offered a piece of evidence for five or six-membered ring lactol structure existing in GO that had never been assigned before, leading to a modified Lerf-Klinowski model for GO. A three-step reduction strategy, involving sodium borohydride (NaBH4), sulfuric acid, and high temperature thermal annealing, described in the thesis, successfully reduced GO back to chemically converted graphene (CCG) with the lowest heteroatom abundance among all those previously reported. In addition to the chemical significance of graphene/CCG production, GO and its derivatives were used as novel adsorbents in water purification. GO-coated sand showed higher retention than ordinary sand for both Rhodamine B and mercuric ion (Hg2+) contaminants in water. Further functionalization of GO with thiophenol resulted in better adsorption capacity toward Hg2+ than that of activated carbon. In addition, free-standing films of GO were treated and reduced with a CO 2 laser beam into different conductive reduced GO (RGO) patterns, and directly used as supercapacitor devices which showed good cyclic stability and energy storage capacities comparable to that of existing thin film ultracapacitors. GO turned out to be a solid electrolyte with anisotropic proton conductivity similar to Nafion, while the large amount of trapped water in GO played an important role.
Gao, Wei
Plutonium Oxidation and Subsequent Reduction by Mn (IV) Minerals
Plutonium sorbed to rock tuff was preferentially associated with manganese oxides. On tuff and synthetic pyrolusite (Mn{sup IV}O{sub 2}), Pu(IV) or Pu(V) was initially oxidized, but over time Pu(IV) became the predominant oxidation state of sorbed Pu. Reduction of Pu(V/VI), even on non-oxidizing surfaces, is proposed to result from a lower Gibbs free energy of the hydrolyzed Pu(IV) surface species versus that of the Pu(V) or Pu(VI) surface species. This work suggests that despite initial oxidation of sorbed Pu by oxidizing surfaces to more soluble forms, the less mobile form of Pu, Pu(IV), will dominate Pu solid phase speciation during long term geologic storage. The safe design of a radioactive waste or spent nuclear fuel geologic repository requires a risk assessment of radionuclides that may potentially be released into the surrounding environment. Geochemical knowledge of the radionuclide and the surrounding environment is required for predicting subsurface fate and transport. Although difficult even in simple systems, this task grows increasingly complicated for constituents, like Pu, that exhibit complex environmental chemistries. The environmental behavior of Pu can be influenced by complexation, precipitation, adsorption, colloid formation, and oxidation/reduction (redox) reactions (1-3). To predict the environmental mobility of Pu, the most important of these factors is Pu oxidation state. This is because Pu(IV) is generally 2 to 3 orders of magnitude less mobile than Pu(V) in most environments (4). Further complicating matters, Pu commonly exists simultaneously in several oxidation states (5, 6). Choppin (7) reported Pu may exist as Pu(IV), Pu(V), or Pu(VI) oxic natural groundwaters. It is generally accepted that plutonium associated with suspended particulate matter is predominantly Pu(IV) (8-10), whereas Pu in the aqueous phase is predominantly Pu(V) (2, 11-13). The influence of the character of Mn-containing minerals expected to be found in subsurface repository environments on Pu oxidation state distributions has been the subject of much recent research. Kenney-Kennicutt and Morse (14), Duff et al. (15), and Morgenstern and Choppin (16) observed oxidation of Pu facilitated by Mn(IV)-bearing minerals. Conversely, Shaughnessy et al. (17) used X-ray Absorption near-edge spectroscopy (XANES) to show reduction of Pu(VI) by hausmannite (Mn{sup II}Mn{sub 2}{sup III}O{sub 4}) and manganite ({gamma}-Mn{sup III}OOH) and Kersting et al., (18) observed reduction of Pu(VI) by pyrolusite (Mn{sup IV}O{sub 2}). In this paper, we attempt to reconcile the apparently conflicting datasets by showing that Mn-bearing minerals can indeed oxidize Pu, however, if the oxidized species remains on the solid phase, the oxidation step competes with the formation of Pu(IV) that becomes the predominant solid phase Pu species with time. The experimental approach we took was to conduct longer term (approximately two years later) oxidation state analyses on the Pu sorbed to Yucca Mountain tuff (initial analysis reported by Duff et al., (15)) and measure the time-dependant changes in the oxidation state distribution of Pu in the presence of the Mn mineral pyrolusite.
Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...
Mechanistic Study of the Selective Catalytic Reduction of Nitric Oxide with Methane over Yttrium Oxide
The catalytic activity of nanocrystalline Group IIIB metal oxides for the reduction of nitric oxide with methane was shown to be comparable to that of Co-ZSM-5. The mechanism of selective catalytic reduction of nitric oxide with methane in excess oxygen was examined over nanocrystalline yttrium oxide. A series of heterogeneous and homogeneous reaction steps was proposed to account for the
Mark D. Fokema; Jackie Y. Ying
Reduction of Amine N-Oxides by Diboron Reagents
Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis(pinacolato)- and in some cases bis(catecholato)diboron [(pinB)2 and (catB)2, respectively]. Reductions occur upon simply mixing the amine N-oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,NÆ-dioxide of (S)-(¢)-nicotine. Because it was observed that (pinB)2 was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)2, triethylborane reduced alkylamino-N-oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)2 has been probed by 1H and 11B NMR.
Kokatla, Hari Prasad; Thomson, Paul F.; Bae, Suyeal; Doddi, Venkata Ramana; Lakshman, Mahesh K.
Temperature-programmed reduction and CO oxidation studies over Ce¢Sn mixed oxides
The reduction behaviour of Ce¢Sn mixed oxides has been studied by a temperature-programmed hydrogen reduction technique and compared with that of pure SnO2 and CeO2. The mixed oxides were found to reduce at lower temperature as compared to that of individual oxides. Carbon monoxide oxidation studies showed that mixed oxides have better activity for CO oxidation reaction than the constituent
R. Sasikala; N. M. Gupta; S. K. Kulshreshtha
Incipient hydrous oxide species as inhibitors of reduction processes at noble metal electrode
Evidence is presented to illustrate the important role of hydrous oxide in noble metal electrocatalysis. It was demonstrated, for instance, that in the case of gold in acid the onset/termination potential, under potential sweep conditions, for hydrazine oxidation and persulfate or iodate reduction occurred at the end of the hydrous oxide reduction peak (recorded for a thick film growth grown by potential multicycling); there was also a maximum in the faradaic ac response for gold in acid in the same region. Both gold and platinum were investigated in acid and base electrolytes. In some cases a range of potential, rather than a discrete value, was found to be involved, different species react with (or are inhibited by) different types (or coverages) of these submonolayer species. In some, possibly electrocatalytically nondemanding, reduction reactions the hydrous oxide seemed to have little effect.
Burke, L.D.; O'Sullivan, J.F.; O'Dwyer, K.J.; Scannell, R.A.; Ahern, M.J.G.; McCarthy, M.M. (Dept. of Chemistry, Univ. College, Cork (IE))
Carbothermal Reduction of Manganese Oxide in Different Gas Atmospheres
Carbothermal reduction of manganese oxides was studied in hydrogen, helium, and argon at different temperatures and carbon-to-manganese\\u000a oxide ratios. Isothermal and temperature programmed carbothermal reduction experiments were conducted in a fixed bed reactor\\u000a in a vertical tube furnace, with on-line monitoring of gas composition by the CO-CO2 infrared sensor. The extent of reduction was calculated using the off-gas composition and
Ring Kononov; Oleg Ostrovski; Samir Ganguly
Electro-catalytic reduction of nitrogen oxides
Nitrogen oxides have been linked to a broad range of air pollution problems including acid rain and the atmospheric production of photochemical ozone. Over twenty million tons of nitrogen oxides are emitted into the atmosphere each year as a result of the high temperature combustion of fossil fuels. Efforts to control nitrogen oxides emissions have lagged because of the generally
Oxidation-Reduction Resistance of Advanced Copper Alloys
NASA Technical Reports Server (NTRS)
Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.
Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.
Lithium metal reduction of plutonium oxide to produce plutonium metal.
National Technical Information Service (NTIS)
A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha 5 plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by s...
M. S. Coops
Lithium metal reduction of plutonium oxide to produce plutonium metal
A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by sublimation and converted to the chloride salt, and after electrolysis, is removed as lithium metal. Zinc may be used
Coops; Melvin S
Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption
Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide.
Carl Ventrice; Nicholas Clark; Daniel Field; Heike Geisler; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff
Processing of effluent salt from the direct oxide reduction process
The production of reactive metals by Direct Oxide Reduction (DOR) process using calcium in a molten calcium salt system generates significant amount of contaminated waste as calcium oxide saturated calcium chloride salt mix with calcium oxide content of up to 15 wt. pct. Fused salt electrolysis of a simulated salt mix has been carried out to electrowin calcium, which can
B. Mishra; D. L. Olson; W. A. Averill
Highly active oxide photocathode for photoelectrochemical water reduction.
A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H(2) production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents of up to -7.6 mA cm(-2) at a potential of 0 V versus the reversible hydrogen electrode at mild pH. The electrodes remained active after 1 h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%. PMID:21552270
Paracchino, Adriana; Laporte, Vincent; Sivula, Kevin; Grõtzel, Michael; Thimsen, Elijah
Highly active oxide photocathode for photoelectrochemical water reduction
NASA Astrophysics Data System (ADS)
A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H2 production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents of up to -7.6?mA?cm-2 at a potential of 0?V versus the reversible hydrogen electrode at mild pH. The electrodes remained active after 1?h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%.
Paracchino, Adriana; Laporte, Vincent; Sivula, Kevin; Grõtzel, Michael; Thimsen, Elijah
This article deals with recent progress in the development of nonzeolitic catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with methane. Although metal-exchanged zeolitic catalysts exhibit high activities for this reaction, most of these metastable structures suffer from deactivation problems when exposed to wet exhaust streams at elevated temperatures. Nonzeolitic oxide catalysts have the potential for improved
Mark D. Fokema; Jackie Y. Ying
Oxidation and Reduction: Too Many Definitions?
ERIC Educational Resources Information Center
IUPAC gives several different definitions of oxidation: loss of electrons, increase in oxidation state, loss of hydrogen, or gain of oxygen. Most introductory or general chemistry textbooks use all of these definitions at one time or another, which can lead to some confusion in the minds of first-year chemistry students. Some paradoxicalģ
Silverstein, Todd P.
Seasonal Methane Oxidation Potential in Manure Crusts
Organic crusts on liquid manure storage tanks harbor ammonia- and nitrite-resistant methane oxidizers and may significantly reduce methane emissions. Methane oxidation potential (0.6 mol CH4 m?2 day?1) peaked during fall and winter, after 4 months of crust development. Consequences for methane mitigation potential of crusts are discussed.
Schramm, Andreas; Nielsen, Lars P.; Revsbech, Niels P.
Reduction of nitric oxide with ammonia on iron oxide-titanium oxide catalyst
The reduction of NO with NHŌ on iron oxide-titanium oxide was studied by using a flow reactor between 250 and 450┬░C. It was found that NO reacts with NHŌ at a 1:1 mole ratio in the presence of excess OŌ and the reaction is completely inhibited by the absence of OŌ. The formation of NŌO, if any, was negligible in
Akira Kato; Shimpei Matsuda; Fumito Nakajima; Makoto Imanari; Yoshihisa Watanabe
Strengthening Oxides by Reduction of Crystal Anisotropy.
National Technical Information Service (NTIS)
Literature information was used to demonstrate that the grain size dependence of strength increases with increasing crystal anisotropy in well-made pure oxide ceramics. Based upon this information a large grain size dependence of strength was predicted fo...
H. P. Kirchner R. M. Gruver R. A. Ewig
Benzene Oxidation Coupled to Sulfate Reduction
(14C)benzene tracer was included with the benzene added to benzene-adapted sediments, 92% of the added radioactivity was recovered as 14CO2. Molybdate, an inhibitor of sulfate reduction, inhibited benzene uptake and production of 14CO2from ( 14 C)benzene. Benzene metabolism stopped when the sediments became sulfate depleted,andbenzeneuptakeresumedwhensulfatewasaddedagain.Thestoichiometryofbenzeneuptakeand sulfate reduction was consistent with the hypothesis that sulfate was the principal electron acceptor for
Three-electrode metal oxide reduction cell
A method of electrochemically reducing a metal oxide to the metal in an electrochemical cell is disclosed along with the cell. Each of the anode and cathode operate at their respective maximum reaction rates. An electrolyte and an anode at which oxygen can be evolved, and a cathode including a metal oxide to be reduced are included as is a third electrode with independent power supplies connecting the anode and the third electrode and the cathode and the third electrode.
Dees, Dennis W. (Downers Groves, IL) [Downers Groves, IL; Ackerman, John P. (Downers Grove, IL) [Downers Grove, IL
Carbothermal Reduction of Manganese Oxide in Different Gas Atmospheres
NASA Astrophysics Data System (ADS)
Carbothermal reduction of manganese oxides was studied in hydrogen, helium, and argon at different temperatures and carbon-to-manganese oxide ratios. Isothermal and temperature programmed carbothermal reduction experiments were conducted in a fixed bed reactor in a vertical tube furnace, with on-line monitoring of gas composition by the CO-CO2 infrared sensor. The extent of reduction was calculated using the off-gas composition and LECO oxygen contents in the reduced samples. In all gas atmospheres, the reaction rate increased with temperature. The reduction rate of manganese oxide in hydrogen was higher than in helium, and in helium higher than in argon. This was attributed to the involvement of hydrogen in the reduction process and the difference in CO and CO2 diffusion coefficients in helium and argon.
Kononov, Ring; Ostrovski, Oleg; Ganguly, Samir
The Advanced Spent Fuel Conditioning Process (ACP) has been under development at Korea Atomic Energy Research Institute (KAERI) since 1997. The concept is to convert spent oxide fuel into metallic form and to remove high heat-load fission products such as Cs and Sr from the spent fuel. The heat power, volume, and radioactivity of spent fuel can decrease by a factor of a quarter via this process. For the realization of ACP, a concept of electrochemical reduction of spent oxide fuel in Li2O-LiCl molten salt was proposed and several cold tests using fresh uranium oxides have been carried out. In this new electrochemical reduction process, electrolysis of Li2O and reduction of uranium oxide are taking place simultaneously at the cathode part of electrolysis cell. The conversion of uranium oxide to uranium metal can reach more than 99% ensuring the feasibility of this process.
Hur, Jin-Mok; Seo, Chung-Seok; Kim, Ik-Soo; Hong, Sun-Seok; Kang, Dae-Seung; Park, Seong-Won
Enhanced reduction of nitrous oxide by Pseudomonas denitrificans with perfluorocarbons
Nitrous oxide reduction and nitrogen production by Pseudomonas denitrificans, as well as culture growth rates all increased 2-3 fold when cultured in the presence of perfluorocarbon emulsions (10% v\\/v) as compared to control cultures grown in the absence of perfluorocarbons. Initial nitrous oxide concentrations for consecutive experiments were 0.7 and 1.2 mM respectively.
Charles E. Turick; Deborah K. Bulmer
Bromide oxidation and bromine reduction in propylene carbonate
Bromide oxidation and bromine reduction in propylene carbonate (PC) +1 M LiClO4 was investigated voltammetrically using polycrystalline platinum rotating disc electrode. The corresponding voltammograms were compared to those of iodide oxidation and HCl decomposition. The oxidation 2Br??Br2+2e? was found to proceed through two steps, which are caused by the formation of a stable intermediate Br3? ion. The stability constant of
V. Vojinovic; S. Mentus; V. Komnenic
[Fundamental studies in oxidation reduction in relation to water photolysis
Objectives were to understand 3 elementary processes central to developing membrane-based integrated chemical systems for water photolysis: role of interfaces in charge separation/recombination reactions, pathways for transmembrane charge separation, and mechanisms of water oxidation catalyzed by transition metal coordination complexes. Research during this period is arranged under the headings transmembrane oxidation-reduction mechanisms, optically gated transmembrane redox, and mechanisms of water oxidation catalysis. Viologens are involved.
Hurst, J.K.
PDMS based coplanar microfluidic channels for the surface reduction of oxidized Galinstan.
Galinstan has the potential to replace mercury - one of the most popular liquid metals. However, the easy oxidation of Galinstan restricts wide applicability of the material. In this paper, we report an effective reduction method for the oxidized Galinstan using gas permeable PDMS (polydimethlysiloxane)-based microfluidic channel. The complete study is divided into two parts - reduction of Galinstan oxide and behavior of reduced Galinstan oxide in a microfluidic channel. The reduction of Galinstan oxide is discussed on the basis of static as well as dynamic angles. The contact angle analyses help to find the extent of reduction by wetting characteristics of the oxide, to optimize PDMS thickness and to select suitable hydrochloric acid (HCl) concentration. The highest advancing angle of 155░ and receding angle of 136░ is achieved with 200 ?m thick PDMS film and 37 wt% (weight percent) HCl solution. The behavior of reduced Galinstan oxide is analyzed in PDMS-based coplanar microfluidic channels fabricated using a simple micromolding technique. Galinstan in the microfluidic channel is surrounded by another coplanar channel filled with HCl solution. Due to the excellent permeability of PDMS, HCl permeates through the PDMS wall between the two channels (interchannel PDMS wall) and achieves a continuous chemical reaction with oxidized Galinstan. A Lab VIEW controlled syringe pump is used for observing the behavior of HCl treated Galinstan in the microfluidic channel. Further optimization of the microfluidic device has been conducted to minimize the reoxidation of reduced Galinstan oxide in the microfluidic channel. PMID:24193151
Li, Guangyong; Parmar, Mitesh; Kim, Daeyoung; Lee, Jeong-Bong J B; Lee, Dong-Weon
Reductive mobilization of oxide-bound metals
We have completed a large number of experiments which examine the release of MnO{sub 2}-bound Co, Ni, and Cu. Our work has focused upon the following areas: (1) competitive adsorption among the three toxic metals and Mn(II); (2) toxic metal release upon addition of low MW organic reductants and complexants; and (3) toxic metal release upon addition of natural organic matter-rich surface waters and IHSS organic matter reference material.
Stone, A.T.
A microbial fuel cell using manganese oxide oxygen reduction catalysts
Microbial fuel cells (MFCs) are a potential method for enhanced water and waste treatment, which offer the additional benefit\\u000a of energy generation. Manganese oxide was prepared by a simple chemical oxidation using potassium permanganate. Carbon-supported\\u000a manganese oxide nanoparticles were successfully characterised as cathode materials for MFCs. The manganese oxide particles\\u000a when used in a two-chamber MFC, using inoculum from an
I. Roche; K. Katuri; K. Scott
Modulation of Potassium Channel Function by Methionine Oxidation and Reduction
NASA Astrophysics Data System (ADS)
Oxidation of amino acid residues in proteins can be caused by a variety of oxidizing agents normally produced by cells. The oxidation of methionine in proteins to methionine sulfoxide is implicated in aging as well as in pathological conditions, and it is a reversible reaction mediated by a ubiquitous enzyme, peptide methionine sulfoxide reductase. The reversibility of methionine oxidation suggests that it could act as a cellular regulatory mechanism although no such in vivo activity has been demonstrated. We show here that oxidation of a methionine residue in a voltage-dependent potassium channel modulates its inactivation. When this methionine residue is oxidized to methionine sulfoxide, the inactivation is disrupted, and it is reversed by coexpression with peptide methionine sulfoxide reductase. The results suggest that oxidation and reduction of methionine could play a dynamic role in the cellular signal transduction process in a variety of systems.
Ciorba, Matthew A.; Heinemann, Stefan H.; Weissbach, Herbert; Brot, Nathan; Hoshi, Toshinori
Reductive mobilization of oxide-bound metals
This project is concerned with the mobilization of MnO{sub 2}- and FeOOH-bound toxic metals in subsurface environments arising from an influx of natural organic matter or organic-containing wastes. Our work to date emphasizes the importance of characterizing the reductant, complexant, and adsorptive characteristics of constituent organic chemicals. Organic chemicals may interact with pollutant metals directly, or may bring about changes in speciation and solubility indirectly by acting upon MnO{sub 2} and FeOOH host phases. The primary application of this work is the understanding of metal sorption and release processes within subsurface environments undergoing changes in redox status.
Stone, A.T.
Oxide reduction during triggered-lightning fulgurite formation
NASA Astrophysics Data System (ADS)
In this study triggered-lightning induced fulgurites were formed in 99.9% pure binary oxides of manganese (MnO) and nickel (NiO) in order to study oxide reduction mechanisms. The fulgurite formation process involved packing the oxide in PVC holders and using the standard rocket-and-wire technique to trigger a lightning strike through the oxide at the International Center for Lightning Research and Testing in Camp Blanding, Florida. These two oxides were chosen from the thermodynamic extrapolation of the oxide stability using the Ellingham Diagram. This diagram indicates that NiO is significantly less stable than MnO. Fulgurites from the pure oxides were analyzed in a scanning electron microscope (SEM); secondary electron images, backscattered images and energy dispersive spectroscopy (EDS) were used to determine the microstructure and composition of the fulgurites. SEM/EDS analysis of the NiO and MnO prior to fulgurite formation confirmed they were pure binary oxides with no metallic contamination. After fulgurite formation, it was found that the nickel oxide fulgurite contained metallic nickel particles; the manganese oxide fulgurite showed no metallic phase formation. Transmission electron microscopy (TEM) examination confirmed that the MnO was a pure oxide with no sign of metallic phase formation. However, TEM results of the NiO showed that approximately 50% of the NiO was reduced to metallic face-centered cubic Ni. The Ni and NiO were observed to be coherent with the [1 0 0]Ni//[1 0 0]NiO and [1 1 0]Ni//[1 1 0]NiO. These results are consistent with the aforementioned thermodynamic stability calculations and show that the presence of carbonaceous material or mixtures of oxides is not necessary for oxide reduction during fulgurite formation. These studies do not rule out the possibility that electrolysis plays a role in oxide reduction. However, these fulgurites were made simultaneously during the same lightning strike and therefore were subjected to the same electrical current, and thus it is proposed the thermodynamic stability of the oxide must play a role in oxide reduction.
Jones, B. E.; Jones, K. S.; Rambo, K. J.; Rakov, V. A.; Jerald, J.; Uman, M. A.
Nonisothermal reduction of oxides in carbon-saturated melts
NASA Astrophysics Data System (ADS)
The nonisothermal kinetics of carbon reduction of oxides in carbon-saturated melts has been studied. The numerical procedure involves the consecutive resolution and subtraction of individual peaks from a total evolution curve. The temperature-dependent background evolution and mixing effects in the gas system of the analyzer were also taken into account. The OxSeP original software allowing us to process FGA data has been realized for the modern TC-600 LECO gas analyzer. The problem of identification of oxides was found to be connected with the start temperature of carbothermal reduction of oxides (Ts). A considerable discrepancy between the equilibrium reduction temperatures of oxides calculated by thermodynamics and real values is observed. The identification OxID software, which includes a thermodynamic model of carbon reduction of oxide inclusions and dissociation of nitrides during the analysis, was developed. Results of numerous FGA studies of synthesized alloys and different steels are in a good agreement with experimental data obtained by X-ray microprobe analysis and quantitative metallography.
Grigorovich, K. V.
EPR studies of chromium(V) intermediates generated via reduction of chromium(VI) by DOPA and related catecholamines: potential role for oxidized amino acids in chromium-induced cancers.
The reductions of K2Cr2O7 by catecholamines, DOPA, DOPA-beta,beta-d2, N-acetyl-DOPA, alpha-methyl-DOPA, dopamine, adrenaline, noradrenaline, catechol, 1,2-dihydroxybenzoic acid (DHBA), and 4-tert-butylcatechol (TBC), produce a number of Cr(V) electron paramagnetic resonance (EPR) signals. These species are of interest in relation to the potential role of oxidized proteins and amino acids in Cr-induced cancers. With excess organic ligand, all of the substrates yield Cr species with signals at g(iso) approximately 1.972 (Aiso(53Cr) > 23.9 x 10(-4) cm(-1)). These are similar to signals reported previously but have been reassigned as octahedral Cr(V) species with mixed catechol-derived ligands, [CrV(semiquinone)2(catecholate)]+. Experiments with excess K2Cr2O7 show complex behavior with the catecholamines and TBC. Several weak Cr(V) signals are detected after mixing, and the spectra evolve over time to yield relatively stable substrate-dependent signals at g(iso) approximately 1.980. These signals have been attributed to [Cr(O)L2](L = diolato) species, in which the Cr is coordinated to two cyclized catecholamine ligands and an oxo ligand. Isotopic labeling studies with DOPA (ring or side chain deuteration or enrichment with 15N), and simulation of the signals, show that the superhyperfine couplings originate from the side chain protons, confirming that the catecholamine ligands are cyclized. At pH 3.5, a major short-lived EPR signal is observed for many of the substrates at g(iso) approximately 1.969, but the species responsible for this signal was not identified. Several other minor Cr signals are detected, which are attributed (by comparison with isoelectronic V(IV) species) to Cr(V) complexes coordinated by a single catecholamine ligand (and auxiliary ligands e.g. H2O), or to [Cr(O)L2]- (L = diolato) species with a sixth ligand (e.g. H2O). Addition of catalase or deoxygenation of the solutions did not affect the main EPR signals. When the substrates were in excess (pH > 4.5), primary and secondary (cyclized) semiquinones were also detected. Semiquinone stabilization by Zn(II) complexation yielded stronger EPR signals (g(iso) approximately 2.004). PMID:11232807
Pattison, D I; Lay, P A; Davies, M J
In-situ IR studies of graphene oxide reduction
Thermal reduction of graphene oxide (GO) synthesized by Hummer's method is studied by in-situ infrared absorption spectroscopy in a vacuum reactor. Initially, water and hydroxyl groups are removed (100^oC), with release of CO2. Upon reduction of epoxides and carbonyl groups, the appearance of sp2-bonded carbon (C=C bonds) is evident with detection of in-plane and out of plane vibrations. However, oxygen
Muge Acik; Laurence Goux; Yves Chabal
Sulfate reduction and anaerobic methane oxidation in Black Sea sediments
Beyond the shelf break at ca. 150m water depth, sulfate reduction is the only important process of organic matter oxidation in Black Sea sediments from the surface down to the sulfate¢methane transition at 2¢4m depth. Sulfate reduction rates were measured experimentally with 35SO42?, and the rates were compared with results of two diffusion-reaction models. The results showed that, even in
Bo Barker J°rgensen; Andreas Weber; Jakob Zopfi
Oxidation of aromatic contaminants coupled to microbial iron reduction
THE contamination of sub-surface water supplies with aromatic compounds is a significant environmental concern1,2. As these contaminated sub-surface environments are generally anaerobic, the microbial oxidation of aromatic compounds coupled to nitrate reduction, sulphate reduction and methane production has been studied intensively1-7. In addition, geochemical evidence suggests that Fe(III) can be an important electron acceptor for the oxidation of aromatic compounds in anaerobic groundwater. Until now, only abiological mechanisms for the oxidation of aromatic compounds with Fe(III) have been reported8-12. Here we show that in aquatic sediments, microbial activity is necessary for the oxidation of model aromatic compounds coupled to Fe(III) reduction. Furthermore, a pure culture of the Fe(III)-reducing bacterium GS-15 can obtain energy for growth by oxidizing benzoate, toluene, phenol or p-cresol with Fe(III) as the sole electron acceptor. These results extend the known physiological capabilities of Fe(III)-reducing organisms and provide the first example of an organism of any type which can oxidize an aromatic hydrocarbon anaerobically. ?? 1989 Nature Publishing Group.
Lovley, D. R.; Baedecker, M. J.; Lonergan, D. J.; Cozzarelli, I. M.; Phillips, E. J. P.; Siegel, D. I.
Hemin-functionalized reduced graphene oxide nanosheets reveal peroxynitrite reduction and isomerization activity.
Facile and efficient reduction of graphene oxide (GO) and novel applications of the reduced graphene oxide (RGO) based materials are of current interest. Herein, we report a novel and facile method for the reduction of GO by using a biocompatible reducing agent dithiothreitol (DTT). Stabilization of DTT by the formation of a six-membered ring with internal disulfide linkage upon oxidation is responsible for the reduction of GO. The reduced graphene oxide is characterized by several spectroscopic and microscopic techniques. Dispersion of RGO in DMF remained stable for several weeks suggesting that the RGO obtained by DTT-mediated reduction is hydrophobic in nature. This method can be considered for large scale production of good quality RGO. Treatment of RGO with hemin afforded a functional hemin-reduced graphene oxide (H-RGO) hybrid material that exhibited remarkable protective effects against the potentially harmful peroxynitrite (PN). A detailed inhibition study on PN-mediated oxidation and nitration reactions indicate that the interaction between hemin and RGO results in a synergistic effect, which leads to an efficient reduction of PN to nitrate. The RGO also catalyzes the isomerization of PN to nitrate as the RGO layers facilitate the rapid recombination of (Ę)NO(2) with Fe(IV)=O species. In the presence of reducing agents such as ascorbic acid, the Fe(IV)=O species can be reduced to Fe(III), thus helping to maintain the PN reductase cycle. PMID:23042238
Vernekar, Amit A; Mugesh, Govindasamy
Coverage of palladium by silicon oxide during reduction in H 2 and complete oxidation of methane
The interaction between silica and palladium following complete oxidation of methane or following reduction in H2 was investigated on a polycrystalline palladium foil and on supported Pd\\/SiO2 catalysts. During methane oxidation, oxidized silicon covered the palladium oxide surface as observed by TEM on Pd\\/SiO2 catalysts and by XPS on palladium foil. On the Pd foil, the source of silica was
Guanghui Zhu; Ken-ichiro Fujimoto; Dmitri Yu. Zemlyanov; Abhaya K. Datye; Fabio H. Ribeiro
Temperature-programmed reduction and oxidation of bimetallic Pd?Ni\\/Al 2 O 3 catalysts
Temperature-programmed reduction and oxidation of bimetallic catalysts Pd?Ni\\/Al2O3 seem to indicate phase segregation of palladium and nickel oxides and alloying of palladium and nickel in the process of reduction of oxidized catalysts.
T. Paryjczak; J. M. Farbotko; K. W. J¾?wiak
Drag reduction in turbulent pipe flow by applied electric potentials
A novel approach to drag reduction is presented on the basis of applied positive electric potentials to a pipe. This has been studied by measuring the pressure drop over a 13.1 m epoxy-coated pipe made of carbon steel, through which water was flowing under conditions of constant flow rate. Potentials were applied between the pipe and the counter electrode located
Magne Waskaas; Vytautas Daujotis; Kjell Wolden; Rimantas Raudonis; Deivis Plausinaitis
Oxidation-reduction reactions of copper-thiolate centres in Cu-thionein.
Cu-thionein from yeast was investigated by EPR spectroscopy to probe the oxidation state of copper, and the effects on it of oxidizing and reducing agents. At pH 0.2 the copper was released, but no EPR signal from Cu(II) was observed, unless air was present. Optical experiments did not detect any disulphide groups which might have been formed during anaerobic release of copper. The mercurial, p-hydroxymercuribenzoate caused the release of EPR-detectable copper only under aerobic conditions, and EDTA caused release of Cu(II) on heating. No reduction of the copper-thiolate units in Cu-thionein by ascorbate was detected. Potentiometric titrations with hexachloroiridate(IV) or hexacyanoferrate(III) produced several different Cu(II) EPR signals at various stages of oxidation. The former oxidizing agent required a lower oxidation-reduction potential (+350 mV) to oxidize the copper, than the latter (+410 mV) and neither titration was fully reversible. The EPR signal from Cu(II) oxidized by hexachloroiridate(IV) resembled that produced by p-hydroxy-mercuribenzoate in air, suggesting that the copper was released from its thiolate ligands. It is concluded that the EPR non-detectable copper in the native protein is Cu(I). Oxidation-reduction of the copper-thiolate clusters of Cu-thionein is proposed to be decisive for controlling storage and transport of cellular copper. PMID:226164
Rupp, H; Cammack, R; Hartmann, H J; Weser, U
Stigmatellin Induces Reduction of Iron-Sulfur Protein in the Oxidized Cytochrome bc1 Complex*
Stigmatellin, a QP site inhibitor, inhibits electron transfer from iron-sulfur protein (ISP) to cytochrome c1 in the bc1 complex. Stigmatellin raises the midpoint potential of ISP from 290 mV to 540 mV. The binding of stigmatellin to the fully oxidized complex, oxidized completely by catalytic amounts of cytochrome c oxidase and cytochrome c, results in ISP reduction. The extent of ISP reduction is proportional to the amount of inhibitor used and reaches a maximum when the ratio of inhibitor to enzyme complex reaches unity. A g = 2.005 EPR peak, characteristic of an organic free radical, is also observed when stigmatellin is added to the oxidized complex, and its signal intensity depends on the amount of stigmatellin. Addition of ferricyanide, a strong oxidant, to the oxidized complex also generates a g = 2.005 EPR peak that is oxidant concentration-dependent. Oxygen radicals are generated when stigmatellin is added to the oxidized complex in the absence of the exogenous substrate, ubiquinol. The amount of oxygen radical formed is proportional to the amount of stigmatellin added. Oxygen radicals are not generated when stigmatellin is added to a mutant bc1 complex lacking the Rieske iron-sulfur cluster. Based on these results, it is proposed that ISP becomes a strong oxidant upon stigmatellin binding, extracting electrons from an organic compound, likely an amino acid residue. This results in the reduction of ISP and generation of organic radicals.
Gurung, Buddha; Yu, Linda; Yu, Chang-An
Dissimilatory selenate reduction potentials in a diversity of sediment types
We measured potential rates of bacterial dissimilatory reduction of 75SeO42- to 75Se0 in a diversity of sediment types, with salinities ranging from freshwater (salinity = 1 g/liter) to hypersaline (salinity = 320 g/liter and with pH values ranging from 7.1 to 9.8. Significant biological selenate reduction occurred in all samples with salinities from 1 to 250 g/liter but not in samples with a salinity of 320 g/liter. Potential selenate reduction rates (25 nmol of SeO42- per ml of sediment added with isotope) ranged from 0.07 to 22 ??mol of SeO42- reduced liter-1 h-1. Activity followed Michaelis-Menten kinetics in relation to SeO42- concentration (K(m) of selenate = 7.9 to 720 ??M). There was no linear correlation between potential rates of SeO42- reduction and salinity, pH, concentrations of total Se, porosity, or organic carbon in the sediments. However, potential selenate reduction was correlated with apparent K(m) for selenate and with potential rates of denitrification (r = 0.92 and 0.81, respectively). NO3-, NO2-, MoO42-, and WO42- inhibited selenate reduction activity to different extents in sediments from both Hunter Drain and Massie Slough, Nev. Sulfate partially inhibited activity in sediment from freshwater (salinity = 1 g/liter) Massie Slough samples but not from the saline (salinity = 60 g/liter) Hunter Drain samples. We conclude that dissimilatory selenate reduction in sediments is widespread in nature. In addition, in situ selenate reduction is a first-order reaction, because the ambient concentrations of selenium oxyanions in the sediments were orders of magnitude less than their K(m)s.
Steinberg, N. A.; Oremland, R. S.
Dissimilatory Selenate Reduction Potentials in a Diversity of Sediment Types
We measured potential rates of bacterial dissimilatory reduction of 75SeO42? to 75Se0 in a diversity of sediment types, with salinities ranging from freshwater (salinity = 1 g/liter) to hypersaline (salinity = 320 g/liter and with pH values ranging from 7.1 to 9.8. Significant biological selenate reduction occurred in all samples with salinities from 1 to 250 g/liter but not in samples with a salinity of 320 g/liter. Potential selenate reduction rates (25 nmol of SeO42? per ml of sediment added with isotope) ranged from 0.07 to 22 ?mol of SeO42? reduced liter?1 h?1. Activity followed Michaelis-Menten kinetics in relation to SeO42? concentration (Km of selenate = 7.9 to 720 ?M). There was no linear correlation between potential rates of SeO42? reduction and salinity, pH, concentrations of total Se, porosity, or organic carbon in the sediments. However, potential selenate reduction was correlated with apparent Km for selenate and with potential rates of denitrification (r = 0.92 and 0.81, respectively). NO3?, NO2?, MoO42?, and WO42? inhibited selenate reduction activity to different extents in sediments from both Hunter Drain and Massie Slough, Nev. Sulfate partially inhibited activity in sediment from freshwater (salinity = 1 g/liter) Massie Slough samples but not from the saline (salinity = 60 g/liter) Hunter Drain samples. We conclude that dissimilatory selenate reduction in sediments is widespread in nature. In addition, in situ selenate reduction is a first-order reaction, because the ambient concentrations of selenium oxyanions in the sediments were orders of magnitude less than their Kms.
Steinberg, Nisan A.; Oremland, Ronald S.
Preparation of magnetic iron-oxide nanoparticles by successive reduction¢oxidation in reverse micelles: Effects of reducing agent and atmosphere
The chemical reduction of ferrous or ferric ions to metallic iron by a reducing agent such as sodium borohydride (NaBH4), hydrazine (N2H4), or sodium phosphonate (NaH2PO2) and its subsequent oxidation were investigated for the preparation of iron-oxide nanoparticles in reverse micelles. The crystal structure and crystallinity of the oxide nanoparticles were found to depend on the oxidation potential of the
Hironori Iida; Takuya Nakanishi; Harumi Takada; Tetsuya Osaka
Nox control for high nitric oxide concentration flows through combustion-driven reduction
An improved method for removing nitrogen oxides from concentrated waste gas streams, in which nitrogen oxides are ignited with a carbonaceous material in the presence of substoichiometric quantities of a primary oxidant, such as air. Additionally, reductants may be ignited along with the nitrogen oxides, carbonaceous material and primary oxidant to achieve greater reduction of nitrogen oxides. A scrubber and regeneration system may also be included to generate a concentrated stream of nitrogen oxides from flue gases for reduction using this method.
Yeh, James T. (Bethel Park, PA); Ekmann, James M. (Bethel Park, PA); Pennline, Henry W. (Bethel Park, PA); Drummond, Charles J. (Churchill, PA)
Methodology for the effective stabilization of tin-oxide-based oxidation/reduction catalysts
NASA Technical Reports Server (NTRS)
The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.
Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony N. (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)
Tyrosine can protect against oxidative stress through ferryl hemoglobin reduction.
The toxic mechanism of hemoglobin (Hb) under oxidative stress is linked to the formations of highly cytotoxic ferryl species and subsequently heme-to-protein cross-linked derivative of Hb (Hb-X). In this study, we have examined the effects of free tyrosine and its analogues (3-chlorotyrosine, phenylalanine) on the stability of ferryl hemoglobin and the formation of Hb-X. The results showed that free tyrosine (not phenylalanine, 10-500?M) was an efficient reducing agent of ferryl species and also effective at preventing the formation of cytotoxic Hb-X. Meanwhile, the dimeric tyrosine was formed as the oxidation product of tyrosine during Hb redox reaction. Compared with free tyrosine, 3-chlorotyrosine, an oxidation product of tyrosine and a proposed biomarker for hypochlorous acid (HOCl) in vivo, exhibited stronger antioxidant properties in Hb-induced oxidative stress, which was consistent with its more efficient ability in the reduction of ferryl species. These results showed that the presence of tyrosine and its derivative in vivo and vitro could ameliorate oxidative damage through ferryl heme reduction. The antioxidant ability, therefore, may provide new insights into the nutritional and physiological significance of free tyrosine with redox active heme proteins-related oxidative stress. PMID:24698734
Lu, Naihao; He, Yingjie; Chen, Chao; Tian, Rong; Xiao, Qiang; Peng, Yi-Yuan
Blockage by acetylene of nitrous oxide reduction in Pseudomonas perfectomarinus.
Suspensions of denitrifying cells of Pseudomonas perfectomarinus reduced nitrate and nitrate as expected to dinitrogen; but, in the presence of acetylene, nitrous oxide accumulated when nitrate or nitrate was reduced. When supplied at the outset in place of nitrate and nitrate, nitrous oxide was rapidly reduced to dinitrogen by cells incubated in anaerobic vessels in the absence of acetylene. In the presence of 0.01 atmospheres of acetylene, however, nitrous oxide was not reduced. Ethylene was not produced, nor did it influence the rate of nitrous oxide reduction when provided instead of acetylene. Cells exposed to 0.01 atmospheres of acetylene for as long as 400 min were able to reduce nitrous oxide after removal of acetylene at a rate comparable to that of cells not exposed to acetylene. Acetylene did not affect the production or functioning of assimilatory nitrate or nitrite reductase in axenic cultures of Enterobacter aerogenes or Trichoderma uride. While exposed to acetylene, bacteria in marine sediment slurries produced measurable quantities of nitrous oxide from glucose- or acetate-dependent reduction of added nitrate. Possible use of acetylene blockage for measurement of denitrification in unamended marine sediments is discussed.
Balderston, W L; Sherr, B; Payne, W J
The role of nitro-reduction and nitric oxide in the toxicity of chloramphenicol.
Recent work on the toxicology of chloramphenicol suggests that its propensity to cause damage to the blood forming organs may be related to its potential for nitro-reduction and the subsequent production of nitric oxide. In this study both aerobic and anaerobic nitro-reduction of chloramphenicol by human foetal and neonatal liver results in the production of the amine derivative. However intermediates of the reaction nitroso- or glutathionesulphinamido-chloramphenicol could not be detected by hplc. Perfusion of chloramphenicol through isolated lobules of human placentae caused a decrease in blood pressure at a time which coincided with a peak of nitric oxide production. However, although the pressure drop could be reversed by an inhibitor of nitric oxide synthetase, the nitric oxide profile remained the same. These observations suggest that involvement of the para-nitro group of chloramphenicol could cause both hemotoxicity and hypotension in susceptible individuals. PMID:10100024
Holt, D E; Bajoria, R
Control of metalloprotein reduction potential: compensation phenomena in the reduction thermodynamics of blue copper proteins.
The reduction thermodynamics (Delta H degrees '(rc) and Delta S degrees '(rc)) for native Paracoccus versutus amicyanin, for Alcaligenes faecalis S-6 pseudoazurin, and for the G45P, M64E, and K27C variants of Pseudomonas aeruginosa azurin were measured electrochemically. Comparison with the data available for other native and mutated blue copper proteins indicates that the features of metal coordination and the electrostatic potential due to the protein matrix and the solvent control the reduction enthalpy in a straightforward way. However, the effects on the reduction potential are rather unpredictable owing to the entropic contribution to E degrees ', which is mainly determined by solvent reorganization effects. Analysis of all the Delta H degrees '(rc) and Delta S degrees '(rc) values available for this protein class indicates that enthalpy-entropy compensation occurs in the reduction thermodynamics of wt cupredoxins from different sources, as well as for mutants of the same species. The findings indicate that the reduction enthalpies and entropies for these species are strongly affected by reduction-induced reorganization of solvent molecules within the solvation sphere of the protein. The absence of a perfect enthalpy-entropy compensation is due to the fact that while the differences between reduction entropies are dominated by solvent reorganization effects, those between reduction enthalpies are significantly controlled by intrinsic molecular factors related to the selective stabilization of the reduced form by coordination features of the copper site and electrostatic effects at the interface with the protein matrix. PMID:12885256
Battistuzzi, Gianantonio; Bellei, Marzia; Borsari, Marco; Canters, Gerard W; de Waal, Ellen; Jeuken, Lars J C; Ranieri, Antonio; Sola, Marco
Nanosized Iron Oxide Colloids Strongly Enhance Microbial Iron Reduction? å
Microbial iron reduction is considered to be a significant subsurface process. The rate-limiting bioavailability of the insoluble iron oxyhydroxides, however, is a topic for debate. Surface area and mineral structure are recognized as crucial parameters for microbial reduction rates of bulk, macroaggregate iron minerals. However, a significant fraction of iron oxide minerals in the subsurface is supposed to be present as nanosized colloids. We therefore studied the role of colloidal iron oxides in microbial iron reduction. In batch growth experiments with Geobacter sulfurreducens, colloids of ferrihydrite (hydrodynamic diameter, 336 nm), hematite (123 nm), goethite (157 nm), and akaganeite (64 nm) were added as electron acceptors. The colloidal iron oxides were reduced up to 2 orders of magnitude more rapidly (up to 1,255 pmol h?1 cell?1) than bulk macroaggregates of the same iron phases (6 to 70 pmol h?1 cell?1). The increased reactivity was not only due to the large surface areas of the colloidal aggregates but also was due to a higher reactivity per unit surface. We hypothesize that this can be attributed to the high bioavailability of the nanosized aggregates and their colloidal suspension. Furthermore, a strong enhancement of reduction rates of bulk ferrihydrite was observed when nanosized ferrihydrite aggregates were added.
Bosch, Julian; Heister, Katja; Hofmann, Thilo; Meckenstock, Rainer U.
Nanosized iron oxide colloids strongly enhance microbial iron reduction.
Microbial iron reduction is considered to be a significant subsurface process. The rate-limiting bioavailability of the insoluble iron oxyhydroxides, however, is a topic for debate. Surface area and mineral structure are recognized as crucial parameters for microbial reduction rates of bulk, macroaggregate iron minerals. However, a significant fraction of iron oxide minerals in the subsurface is supposed to be present as nanosized colloids. We therefore studied the role of colloidal iron oxides in microbial iron reduction. In batch growth experiments with Geobacter sulfurreducens, colloids of ferrihydrite (hydrodynamic diameter, 336 nm), hematite (123 nm), goethite (157 nm), and akaganeite (64 nm) were added as electron acceptors. The colloidal iron oxides were reduced up to 2 orders of magnitude more rapidly (up to 1,255 pmol h(-1) cell(-1)) than bulk macroaggregates of the same iron phases (6 to 70 pmol h(-1) cell(-1)). The increased reactivity was not only due to the large surface areas of the colloidal aggregates but also was due to a higher reactivity per unit surface. We hypothesize that this can be attributed to the high bioavailability of the nanosized aggregates and their colloidal suspension. Furthermore, a strong enhancement of reduction rates of bulk ferrihydrite was observed when nanosized ferrihydrite aggregates were added. PMID:19915036
Bosch, Julian; Heister, Katja; Hofmann, Thilo; Meckenstock, Rainer U
Biological reduction of graphene oxide using plant leaf extracts.
Two-dimensional graphene has attracted significant attention due to its unique mechanical, electrical, thermal, and optical properties. Most commonly employed methods to chemically reduce graphene oxide to graphene use hydrazine or its derivatives as the reducing agent. However, they are highly hazardous and explosive. Various phytochemicals obtained from different natural sources such as leaves and peels of a plant are used as reducing agents in the preparation of different gold, silver, copper, and platinum nanoparticles. In this study, seven plant leaf extracts (Cherry, Magnolia, Platanus, Persimmon, Pine, Maple, and Ginkgo) were compared for their abilities to reduce graphene oxide. The optimized reaction conditions for the reduction of graphene oxide were determined as follows. Type of plant: Cherry (Prunus serrulata), reaction time: 12 h, composition of the reaction mixture: 16.7% v/v of plant leaf extract in total suspension, and temperature: 95░C. The degree of reduction caused by Cherry leaf extract was analyzed by elemental analysis and X-ray photoelectron spectroscopy. The reduction of graphene oxide was also confirmed by ultraviolet-visible spectroscopy, Fourier transform-infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis. PMID:24375994
Lee, Geummi; Kim, Beom Soo
Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides
Experimental studies demonstrate that structural Fe(II) in magnetite and ilmenite heterogeneously reduce aqueous ferric, cupric, vanadate, and chromate ions at the oxide surfaces over a pH range of 1-7 at 25??C. For an aqueous transition metal m, such reactions are 3[Fe2+Fe3+2]O4(magnetite) + 2/nmz ??? 4[Fe3+2]O3(maghemite) + Fe2+ + 2/nmz-n and 3[Fe2+Ti]O3(ilmenite) + 2/nmz ??? Fe3+2Ti3O9(pseudorutile) + Fe2+ + 2/nmz-n, where z is the valance state and n is the charge transfer number. The half cell potential range for solid state oxidation [Fe(II)] ??? [Fe(III)] is -0.34 to -0.65 V, making structural Fe(II) a stronger reducing agent than aqueous Fe2+ (-0.77 V). Reduction rates for aqueous metal species are linear with time (up to 36 h), decrease with pH, and have rate constants between 0.1 and 3.3 ?? 10-10 mol m-2 s-1. Iron is released to solution both from the above reactions and from dissolution of the oxide surface. In the presence of chromate, Fe2+ is oxidized homogeneously in solution to Fe3+. X-ray photoelectron spectroscopy (XPS) denotes a Fe(III) oxide surface containing reduced Cr(III) and V(IV) species. Magnetite and ilmenite electrode potentials are insensitive to increases in divalent transition metals including Zn(II), Co(II), Mn(II), and Ni(II) and reduced V(IV) and Cr(III) but exhibit a log-linear concentration-potential response to Fe(III) and Cu(II). Complex positive electrode responses occur with increasing Cr(VI) and V(V) concentrations. Potential dynamic scans indicate that the high oxidation potential of dichromate is capable of suppressing the cathodic reductive dissolution of magnetite. Oxide electrode potentials are determined by the Fe(II)/Fe(III) composition of the oxide surface and respond to aqueous ion potentials which accelerate this oxidation process. Natural magnetite sands weathered under anoxic conditions are electrochemically reactive as demonstrated by rapid chromate reduction and the release of aqueous Fe(III) to experimental solution. In contrast, magnetite weathered under oxidizing vadose conditions show minimum reactivity toward chromate ions. The ability of Fe(II) oxides to reduce transition metals in soils and groundwaters will be strongly dependent on the redox environment.
White, A. F.; Peterson, M. L.
Anaerobic Oxidation of Arsenite Linked to Chlorate Reduction? å
Microorganisms play a significant role in the speciation and mobility of arsenic in the environment. In this study, the oxidation of arsenite [As(III)] to arsenate [As(V)] linked to chlorate (ClO3?) reduction was shown to be catalyzed by sludge samples, enrichment cultures (ECs), and pure cultures incubated under anaerobic conditions. No activity was observed in treatments lacking inoculum or with heat-killed sludge, or in controls lacking ClO3?. The As(III) oxidation was linked to the complete reduction of ClO3? to Cl?, and the molar ratio of As(V) formed to ClO3? consumed approached the theoretical value of 3:1 assuming the e? equivalents from As(III) were used to completely reduce ClO3?. In keeping with O2 as a putative intermediate of ClO3? reduction, the ECs could also oxidize As(III) to As(V) with O2 at low concentrations. Low levels of organic carbon were essential in heterotrophic ECs but not in autotrophic ECs. 16S rRNA gene clone libraries indicated that the ECs were dominated by clones of Rhodocyclaceae (including Dechloromonas, Azospira, and Azonexus phylotypes) and Stenotrophomonas under autotrophic conditions. Additional phylotypes (Alicycliphilus, Agrobacterium, and Pseudoxanthomonas) were identified in heterotrophic ECs. Two isolated autotrophic pure cultures, Dechloromonas sp. strain ECC1-pb1 and Azospira sp. strain ECC1-pb2, were able to grow by linking the oxidation of As(III) to As(V) with the reduction of ClO3?. The presence of the arsenite oxidase subunit A (aroA) gene was demonstrated with PCR in the ECs and pure cultures. This study demonstrates that ClO3? is an alternative electron acceptor to support the microbial oxidation of As(III).
Sun, Wenjie; Sierra-Alvarez, Reyes; Milner, Lily; Field, Jim A.
Anaerobic oxidation of arsenite linked to chlorate reduction.
Microorganisms play a significant role in the speciation and mobility of arsenic in the environment. In this study, the oxidation of arsenite [As(III)] to arsenate [As(V)] linked to chlorate (ClO??) reduction was shown to be catalyzed by sludge samples, enrichment cultures (ECs), and pure cultures incubated under anaerobic conditions. No activity was observed in treatments lacking inoculum or with heat-killed sludge, or in controls lacking ClO??. The As(III) oxidation was linked to the complete reduction of ClO?? to Cl?, and the molar ratio of As(V) formed to ClO?? consumed approached the theoretical value of 3:1 assuming the e? equivalents from As(III) were used to completely reduce ClO??. In keeping with O? as a putative intermediate of ClO?? reduction, the ECs could also oxidize As(III) to As(V) with O? at low concentrations. Low levels of organic carbon were essential in heterotrophic ECs but not in autotrophic ECs. 16S rRNA gene clone libraries indicated that the ECs were dominated by clones of Rhodocyclaceae (including Dechloromonas, Azospira, and Azonexus phylotypes) and Stenotrophomonas under autotrophic conditions. Additional phylotypes (Alicycliphilus, Agrobacterium, and Pseudoxanthomonas) were identified in heterotrophic ECs. Two isolated autotrophic pure cultures, Dechloromonas sp. strain ECC1-pb1 and Azospira sp. strain ECC1-pb2, were able to grow by linking the oxidation of As(III) to As(V) with the reduction of ClO??. The presence of the arsenite oxidase subunit A (aroA) gene was demonstrated with PCR in the ECs and pure cultures. This study demonstrates that ClO?? is an alternative electron acceptor to support the microbial oxidation of As(III). PMID:20729322
Sun, Wenjie; Sierra-Alvarez, Reyes; Milner, Lily; Field, Jim A
The role of volatiles in the reduction of iron oxides
NASA Astrophysics Data System (ADS)
With iron ore reduction processes using coal-ore pellets or mixtures, it is possible that volatiles from the coals can contribute to the overall reduction. By identifying the possible reducing species in the volatiles as H2/CO and simulating these constituents, the rates for H2 and CO were investigated in the temperature and reduction range of interest where hydrogen was the major reductant and studied in detail. In the initial stages of the present study, the fundamentals of hydrogen reduction of fine powder were found to be a complex mechanism of chemical kinetics and mass transfer. Complete uniform reduction for porous and dense iron ores were not observed contrary to existing work regarding this subject. Morphological observations of iron ores reduced at low and high temperatures showed a topochemical receding interface to be dominating with an intermediate region developing for higher temperature samples indicating the importance of pore mass transfer at the later stages of reduction. Although the activation energy of 50ś56 kJ/mole for these powder samples were comparable to the literature values for solely chemical kinetics controlled reactions, the reaction rates were not proportional to sample weight and also did not exhibit complete uniform internal reduction. The calculated mass transfer rates were comparable to the observed rate which suggested that bulk mass transfer is important to the mixed-control. The reaction rate at the mixed control regime was found to be first order with respect to hydrogen partial pressure. Results of reducing iron oxide powders in a mixture of He-40%H2 -5%CO and H2-1%H2S showed that H2S and CO which is involved with the volatiles does not affect the rate at the reduction range of interest indicating the role of volatiles is dominated by the hydrogen reduction. The single composite pellet experiments at 900 and 1000░C showed significant fixed carbon reduction to occur above 1000░C. Depending upon the type of carbon reductant in the composite pellet, secondary reactions with carbon and H2O was possible. Sintering of the pellets did not occur until a significant amount of reduction was obtained and thus for volatile reduction it is likely that the effects of sintering was negligible. To determine the possibility of volatile reduction, a layer of Fe 2O3 powders were spread over HV coals resulting in the reduction of the top layer by about 20% at 1000░C after 1000 seconds. The morphology of the reduced Fe2O3 layer indicated that the reduction is higher near the interface of Coal/Fe2O3. The volatile reduction of a single layer of composite pellet was found to be negligible. However, the reduction of Fe2O3 pellets at the top layer by the volatiles from the bottom layers of a three-layer pellet geometry was observed to be about 15%. From the morphological observations and the computed rates of bulk mass transfer, volatile reduction seems to be controlled by a mixed-controlled mechanism of bulk mass transfer and the limited-mixed control. Using the reduction information obtained from the single pellet experiments reduced in hydrogen, an empirical relationship was obtained to approximately predict the amount of volatile reduction up to 20%.
Sohn, Il
Direct oxide reduction demonstration, small-scale studies
This project was initiated to provide process design information to the Plutonium Recovery Project (PRP). Although direct oxide reduction (DOR) has been operated in a production mode both at the Rocky Flats Plant (now operated by EG&G, Inc.) and Los Alamos National Laboratory, many aspects of the process are ill-defined. Because the PRP plans include significant DOR capability, a well-defined process should minimize capital cost and maximize productivity. Reduced radiation exposure may also be realized. A detailed, statistically valid investigation of the direct oxide reduction process was carried out utilizing 100 grams or less of plutonium dioxide per experiment. Conditions were established for obtaining 95% + yields. Conclusions drawn from the results of the experimental work were utilized to make recommendations for future large-scale investigative and confirmative work as well large-scale production demonstration work. 4 refs., 5 figs., 14 tabs.
Long, J.L.; Santi, D.J.; Fisher, D.C.; Humiston, T.J.
Direct oxide reduction demonstration, small-scale studies
This project was initiated to provide process design information to the Plutonium Recovery Project (PRP). Although direct oxide reduction (DOR) has been operated in a production mode both at the Rocky Flats Plant (now operated by EG G, Inc.) and Los Alamos National Laboratory, many aspects of the process are ill-defined. Because the PRP plans include significant DOR capability, a well-defined process should minimize capital cost and maximize productivity. Reduced radiation exposure may also be realized. A detailed, statistically valid investigation of the direct oxide reduction process was carried out utilizing 100 grams or less of plutonium dioxide per experiment. Conditions were established for obtaining 95% + yields. Conclusions drawn from the results of the experimental work were utilized to make recommendations for future large-scale investigative and confirmative work as well large-scale production demonstration work. 4 refs., 5 figs., 14 tabs.
Long, J.L.; Santi, D.J.; Fisher, D.C.; Humiston, T.J.
Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.
Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 ?g L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step. PMID:24261992
Radjenovic, Jelena; Flexer, Victoria; Donose, Bogdan C; Sedlak, David L; Keller, Jurg
Landscape planning for agricultural nonpoint source pollution reduction III: Assessing phosphorus and sediment reduction potential
Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds (average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately 20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales, including the watershed scale. ?? 2008 Springer Science+Business Media, LLC.
Diebel, M. W.; Maxted, J. T.; Robertson, D. M.; Han, S.; Vander Zanden, M. J.
Temperature-programmed reduction of Ni-Mo oxides
Temperature-programmed reduction (TPR) has been employed to study Ni-Mo mixed oxides which were previously used as model hydrodesulphurization (HDS) catalysts, using compositions ranging from pure MoO3 to pure NiO. An assignment of TPR signals to the different bulk phases was attempted. Good agreement between TPR spectra and structural data obtained previously from X-ray and electron diffraction was observed. TPR traces
JoaquĒn L. Brito; Jorge Laine; Kerry C. Pratt
Reduction of Silicon Vidicon Dark Current by HCl Oxidation
The silicon vidicon dark current was markedly reduced by forming the target oxide layer in a mixture of dry O2 and a small amount of HCl. Dark current of less than 0.6 nA, which is about ten times smaller than has ever been reported, was realized in a standard 1'' silicon vidicon. It was found that this dark current reduction
Hiromitsu Shiraki
Reductive-gas sensor using iron oxide nanowires
We have proposed and developed a new gas sensor using the change in the permeability of iron oxide nanowires. ?-Fe2O3 nanowires are synthesized by the simple annealing of Fe bulks or films at 375░C in air. When the surface of ?-Fe2O3 nanowires is changed by a reductive gas into ?-Fe2O3 or Fe3O4, the permeability of the nanowires increases. Our sensor
Yuu Uriya; Keisuke Nagato; Tetsuya Hamaguchi; Masayuki Nakao
Reduction of iron-oxide-carbon composites: part III. Shrinkage of composite pellets during reduction
This article involves the evaluation of the volume change of iron-oxide-carbon composite pellets and its implications on reduction kinetics under conditions prevalent in a rotary hearth furnace (RHF) that were simulated in the laboratory. The pellets, in general, were found to shrink considerably during the reduction due to the loss of carbon and oxygen from the system, sintering of the iron-oxide, and formation of a molten slag phase at localized regions inside the pellets due to the presence of binder and coal/wood-charcoal ash at the reduction temperatures. One of the shortcomings of the RHF ironmaking process has been the inability to use multiple layers of composite pellets because of the impediment in heat transport to the lower layers of a multilayer bed. However, pellet shrinkage was found to have a strong effect on the reduction kinetics by virtue of enhancing the external heat transport to the lower layers. The volume change of the different kinds of composite pellets was studied as a function of reduction temperature and time. The estimation of the change in the amount of external heat transport with varying pellet sizes for a particular layer of a multilayer bed was obtained by conducting heat-transfer tests using inert low-carbon steel spheres. It was found that if the pellets of the top layer of the bed shrink by 30 pct, the external heat transfer to the second layer increases by nearly 6 times.
Halder, S.; Fruehan, R.J. [Praxair Inc., Tonawanda, NY (United States). Praxair Technological Center
Thermoelectric Powder Using an Oxide-Reduction Process
NASA Astrophysics Data System (ADS)
The present study focused on synthesis of Bi0.5Sb1.5Te3 thermoelectric powder using an oxide-reduction process. The phase structure and particle size of the synthesized powders were analyzed using x-ray diffractometry and scanning electron microscopy. The synthesized powder was sintered using the spark plasma sintering method. The thermoelectric properties of the sintered body were evaluated by measuring the Seebeck coefficient, electrical resistivity, and thermal conductivity. Bi0.5Sb1.5Te3 powder was synthesized using a combination of mechanical milling, calcination, and reduction processes, using a mixture of Bi2O3, Sb2O3, and TeO2 powders. The sintered body of the oxide-reduction-synthesized Bi0.5Sb1.5Te3 powder showed p-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depended on the reduction time. After being reduced for 2 h at 663 K, the sintered body of the Bi0.5Sb1.5Te3 powder showed a figure of merit of approximately 1.0 at room temperature.
Lee, Gilgeun; Ha, Gookhyun
Use of ion conductors in the pyrochemical reduction of oxides
An electrochemical process and electrochemical cell for reducing a metal oxide are provided. First the oxide is separated as oxygen gas using, for example, a ZrO.sub.2 oxygen ion conductor anode and the metal ions from the reduction salt are reduced and deposited on an ion conductor cathode, for example, sodium ion reduced on a .beta.-alumina sodium ion conductor cathode. The generation of and separation of oxygen gas avoids the problem with chemical back reaction of oxygen with active metals in the cell. The method also is characterized by a sequence of two steps where an inert cathode electrode is inserted into the electrochemical cell in the second step and the metallic component in the ion conductor is then used as the anode to cause electrochemical reduction of the metal ions formed in the first step from the metal oxide where oxygen gas formed at the anode. The use of ion conductors serves to isolate the active components from chemically reacting with certain chemicals in the cell. While applicable to a variety of metal oxides, the invention has special importance for reducing CaO to Ca.degree. used for reducing UO.sub.2 and PuO.sub.2 to U and Pu.
Miller, William E. (Naperville, IL); Tomczuk, Zygmunt (Lockport, IL)
Use of ion conductors in the pyrochemical reduction of oxides
An electrochemical process and electrochemical cell for reducing a metal oxide are provided. First the oxide is separated as oxygen gas using, for example, a ZrO[sub 2] oxygen ion conductor anode and the metal ions from the reduction salt are reduced and deposited on an ion conductor cathode, for example, sodium ion reduced on a [beta]-alumina sodium ion conductor cathode. The generation of and separation of oxygen gas avoids the problem with chemical back reaction of oxygen with active metals in the cell. The method also is characterized by a sequence of two steps where an inert cathode electrode is inserted into the electrochemical cell in the second step and the metallic component in the ion conductor is then used as the anode to cause electrochemical reduction of the metal ions formed in the first step from the metal oxide where oxygen gas formed at the anode. The use of ion conductors serves to isolate the active components from chemically reacting with certain chemicals in the cell. While applicable to a variety of metal oxides, the invention has special importance for reducing CaO to Ca[sup o] used for reducing UO[sub 2] and PuO[sub 2] to U and Pu. 2 figures.
Miller, W.E.; Tomczuk, Z.
Pathogenesis of Chronic Hyperglycemia: From Reductive Stress to Oxidative Stress
Chronic overnutrition creates chronic hyperglycemia that can gradually induce insulin resistance and insulin secretion impairment. These disorders, if not intervened, will eventually be followed by appearance of frank diabetes. The mechanisms of this chronic pathogenic process are complex but have been suggested to involve production of reactive oxygen species (ROS) and oxidative stress. In this review, I highlight evidence that reductive stress imposed by overflux of NADH through the mitochondrial electron transport chain is the source of oxidative stress, which is based on establishments that more NADH recycling by mitochondrial complex I leads to more electron leakage and thus more ROS production. The elevated levels of both NADH and ROS can inhibit and inactivate glyceraldehyde 3-phosphate dehydrogenase (GAPDH), respectively, resulting in blockage of the glycolytic pathway and accumulation of glycerol 3-phospate and its prior metabolites along the pathway. This accumulation then initiates all those alternative glucose metabolic pathways such as the polyol pathway and the advanced glycation pathways that otherwise are minor and insignificant under euglycemic conditions. Importantly, all these alternative pathways lead to ROS production, thus aggravating cellular oxidative stress. Therefore, reductive stress followed by oxidative stress comprises a major mechanism of hyperglycemia-induced metabolic syndrome.
Yan, Liang-Jun
Potential Toxic Effects of Nano-Oxides
NASA Astrophysics Data System (ADS)
The increasing use of nanomaterials in industrial and consumer products has aroused global concern regarding their potential impact on environment and human health. A number of studies on the effects of nanomaterials in in vitro and in vivo systems have been shown that some nanomaterials are potentially toxic. We address the understanding of the link of physicochemical characteristics of some nano-oxides including SiO2, TiO2, and ZnO to the observed toxic effects. Understanding the contribution of physicochemical characteristics of nanomaterials to toxic effects would allow safety to be built into the design of nanomaterials and their applications, to allow their safe integration into products.
Xu, Mingsheng; Chen, Hongzheng; Shi, Minmin; Wu, Gang; Fujita, Daisuke; Hanagata, Nobutaka
1. West facade of Plutonium Concentration Facility (Building 233S), ReductionOxidation ...
Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey
1. West facade of Plutonium Concentration Facility (Building 233-S), Reduction-Oxidation Building (REDOX-202-S) to the right. Looking east. - Reduction-Oxidation Complex, Plutonium Concentration Facility, 200 West Area, Richland, Benton County, WA
Catalysis of Reduction and Oxidation Reactions for Application in Gas Particle Filters
The present study is a first part of an investigation addressing the simultaneous occurrence of oxidation and reduction reactions in catalytic filters. It has the objectives (a) to assess the state of knowledge regarding suitable (types of) catalysts for reduction and oxidation, (b) to collect and analyze published information about reaction rates of both NOx reduction and VOC oxidation, and (c) to adjust a lab-scale screening method to the requirements of an activity test with various oxidation/reduction catalysts.
Udron, L.; Turek, T.
Effect of palladium and nickel on the temperature programmed reduction of metal oxides and metal oxide layers
A new binary oxide support was suggested as being useful in many commercial reactions. Our study was focused on the reduction\\u000a effect of metal oxide layer on alumina during reaction. Hence temperature programmed reduction of both bulk metal oxide and\\u000a metal oxide layer on alumina was studied first and the effect of palladium and nickel on the reduction of the
Jong Pal Kim
Processing of effluent salt from the direct oxide reduction process
The production of reactive metals by Direct Oxide Reduction (DOR) process using calcium in a molten calcium salt system generates significant amount of contaminated waste as calcium oxide saturated calcium chloride salt mix with calcium oxide content of up to 15 wt. pct. Fused salt electrolysis of a simulated salt mix has been carried out to electrowin calcium, which can be recycled to the DOR reactor along with the calcium chloride salt or may be used in-situ in a combined DOR and electrowinning process. Many reactive metal oxides could thus be reduced in a one-step process without generating a significant amount of waste. The process has been optimized in terms of the calcium solubility, cell temperature, current density and the cell design to maximize the current efficiency. Based on the information available regarding the solubility of calcium in calcium chloride salt in the presence of calcium oxide, and the back reactions occurring in-situ between the electrowon calcium and other components present in the cell, e.g. carbon, oxygen, carbon dioxide and calcium oxide, it is difficult to recover elemental calcium within the system. However, a liquid cathode or a rising cathode has been used in the past to recover calcium. The solubility has also been found to depend on the use of graphite as the anode material as evidenced by the presence of calcium carbonate in the final salt. The rate of recovery for metallic calcium has to be enhanced to levels that overcome the back reactions in a system where quick removal of anodic gases is achieved. Calcium has been detected by the hydrogen evolution technique and the amount of calcia has been determined by titration. A porous ceramic sheath has been used in the cell to prevent the chemical reaction of electrowon calcium to produce oxide or carbonate and to prevent the contamination of salt by the anodic carbon.
Mishra, B.; Olson, D.L. [Colorado School of Mines, Golden, CO (United States). Kroll Inst. for Extractive Metallurgy; Averill, W.A. [EG and G Rocky Flats, Inc., Golden, CO (United States)
Processing of effluent salt from the direct oxide reduction process
The production of reactive metals by Direct Oxide Reduction (DOR) process using calcium in a molten calcium salt system generates significant amount of contaminated waste as calcium oxide saturated calcium chloride salt mix with calcium oxide content of up to 15 wt. pct. Fused salt electrolysis of a simulated salt mix has been carried out to electrowin calcium, which can be recycled to the DOR reactor along with the calcium chloride salt or may be used in-situ in a combined DOR and electrowinning process. Many reactive metal oxides could thus be reduced in a one-step process without generating a significant amount of waste. The process has been optimized in terms of the calcium solubility, cell temperature, current density and the cell design to maximize the current efficiency. Based on the information available regarding the solubility of calcium in calcium chloride salt in the presence of calcium oxide, and the back reactions occurring in-situ between the electrowon calcium and other components present in the cell, e.g. carbon, oxygen, carbon dioxide and calcium oxide, it is difficult to recover elemental calcium within the system. However, a liquid cathode or a rising cathode has been used in the past to recover calcium. The solubility has also been found to depend on the use of graphite as the anode material as evidenced by the presence of calcium carbonate in the final salt. The rate of recovery for metallic calcium has to be enhanced to levels that overcome the back reactions in a system where quick removal of anodic gases is achieved. Calcium has been detected by the hydrogen evolution technique and the amount of calcia has been determined by titration. A porous ceramic sheath has been used in the cell to prevent the chemical reaction of electrowon calcium to produce oxide or carbonate and to prevent the contamination of salt by the anodic carbon.
Mishra, B.; Olson, D.L. (Colorado School of Mines, Golden, CO (United States). Kroll Inst. for Extractive Metallurgy); Averill, W.A. (EG and G Rocky Flats, Inc., Golden, CO (United States))
Pre-converted nitric oxide gas in catalytic reduction system
A two-stage catalyst comprises an oxidative first stage and a reductive second stage. The first stage is intended to convert NO to NO{sub 2} in the presence of O{sub 2}. The second stage serves to convert NO{sub 2} to environmentally benign gases that include N{sub 2}, CO{sub 2}, and H{sub 2}O. By preconverting NO to NO{sub 2} in the first stage, the efficiency of the second stage for NO{sub x} reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber. An oxidizing first catalyst converts NO to NO{sub 2} in the presence of O{sub 2} and includes platinum/alumina, e.g., Pt/Al{sub 2}O{sub 3} catalyst. A flow of hydrocarbons (C{sub x}H{sub y}) is input from a pipe into a second chamber. For example, propene can be used as a source of hydrocarbons. The NO{sub 2} from the first catalyst mixes with the hydrocarbons in the second chamber. The mixture proceeds to a second reduction catalyst that converts NO{sub 2} to N{sub 2}, CO{sub 2}, and H{sub 2}O, and includes a {gamma}-Al{sub 2}O{sub 3}. The hydrocarbons and NO{sub x} are simultaneously reduced while passing through the second catalyst. 9 figs.
Hsiao, M.C.; Merritt, B.T.; Penetrante, B.M.; Vogtlin, G.E.
Pre-converted nitric oxide gas in catalytic reduction system
A two-stage catalyst comprises an oxidative first stage and a reductive second stage. The first stage is intended to convert NO to NO.sub.2 in the presence of O.sub.2. The second stage serves to convert NO.sub.2 to environmentally benign gases that include N2, CO2, and H.sub.2 O. By preconverting NO to NO.sub.2 in the first stage, the efficiency of the second stage for NO.sub.x reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber. An oxidizing first catalyst converts NO to NO.sub.2 in the presence of O.sub.2 and includes platinum/alumina, e.g., Pt/Al.sub.2 O.sub.3 catalyst. A flow of hydrocarbons (C.sub.x H.sub.y) is input from a pipe into a second chamber. For example, propene can be used as a source of hydrocarbons. The NO.sub.2 from the first catalyst mixes with the hydrocarbons in the second chamber. The mixture proceeds to a second reduction catalyst that converts NO.sub.2 to N2, CO2, and H.sub.2 O, and includes a gamma-alumina .gamma.-Al.sub.2 O.sub.3. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the second catalyst.
Hsiao, Mark C. (Livermore, CA); Merritt, Bernard T. (Livermore, CA); Penetrante, Bernardino M. (San Ramon, CA); Vogtlin, George E. (Fremont, CA)
Oxidation Potentials in Iron and Steel Making
NASA Astrophysics Data System (ADS)
The state of oxidation of a pyrometallurgical process given by the partial pressure of oxygen and the temperature (the oxidation potential) is one of the important properties monitored and controlled in the smelting and refining of iron and the nonferrous metals. Solid electrolyte sensors based on ZrO2 and a reference electrode such as Cr/Cr2O3 to measure the oxygen pressure found early application in the steel industry, followed soon after in copper, nickel, lead, and zinc smelting. Similar devices are installed in automobile postcombustion/exhaust trains as part of emission control systems. The current discussion reviews this technology as applied in the primary steps of iron and steel making and refining.
Matousek, J. W.
Quantifying the potential for dose reduction with visual grading regression.
Objectives To propose a method to study the effect of exposure settings on image quality and to estimate the potential for dose reduction when introducing dose-reducing measures. Methods Using the framework of visual grading regression (VGR), a log(mAs) term is included in the ordinal logistic regression equation, so that the effect of reducing the dose can be quantitatively related to the effect of adding post-processing. In the ordinal logistic regression, patient and observer identity are treated as random effects using generalised linear latent and mixed models. The potential dose reduction is then estimated from the regression coefficients. The method was applied in a single-image study of coronary CT angiography (CTA) to evaluate two-dimensional (2D) adaptive filters, and in an image-pair study of abdominal CT to evaluate 2D and three-dimensional (3D) adaptive filters. Results For five image quality criteria in coronary CTA, dose reductions of 16-26% were predicted when adding 2D filtering. Using five image quality criteria for abdominal CT, it was estimated that 2D filtering permits doses were reduced by 32-41%, and 3D filtering by 42-51%. Conclusions VGR including a log(mAs) term can be used for predictions of potential dose reduction that may be useful for guiding researchers in designing subsequent studies evaluating diagnostic value. With appropriate statistical analysis, it is possible to obtain direct numerical estimates of the dose-reducing potential of novel acquisition, reconstruction or post-processing techniques. PMID:23239690
Smedby, O; Fredrikson, M; De Geer, J; Borgen, L; Sandborg, M
Hemicarceplexes modify the solubility and reduction potentials of C60.
A highly stable C60-incarcerated hemicarceplex, which retains its molecular integrity after heating at 523 K in air for at least 3 h, significantly increases the solubility of C60 in nonpolar solvents and increases the reduction potentials of the entrapped fullerene. Modification with [(?(5)-C5Me5)Ru(II)](+) dramatically increases the solubility of this hemicarceplex in polar, protic solvents (e.g., MeOH). PMID:24665822
Wong, Tzu-Huan; Chang, Jia-Cheng; Lai, Chien-Chen; Liu, Yi-Hung; Peng, Shie-Ming; Chiu, Sheng-Hsien
Floating Potential Probe Langmuir Probe Data Reduction Results
NASA Technical Reports Server (NTRS)
During its first five months of operations, the Langmuir Probe on the Floating Potential Probe (FPP) obtained data on ionospheric electron densities and temperatures in the ISS orbit. In this paper, the algorithms for data reduction are presented, and comparisons are made of FPP data with ground-based ionosonde and Incoherent Scattering Radar (ISR) results. Implications for ISS operations are detailed, and the need for a permanent FPP on ISS is examined.
Morton, Thomas L.; Minow, Joseph I.
Potential role of bicarbonate during pyrite oxidation
The need to prevent the development of acid mine drainage (AMD) by oxidation of pyrite has triggered numerous investigations into the mechanisms of its oxidation. According to Frontier molecular orbital (FMO) theory, the surface-exposed sulfur atom of pyrite possesses an unshared electron pair which produces a slightly negatively charged pyrite surface that can attract cations such as Fe{sup 2+}. Because of surface electroneutrality and pH considerations, however, the pyrite surface Fe{sup 2+} coordinates OH. The authors proposed that this surface Fe{sup 2+} OH when in the presence of CO{sub 2} is converted to {minus}FeCO{sub 3} or {minus}FeHCO{sub 3}, depending on pH. In this study, using Fourier transform infrared spectroscopy (FT-IR) they demonstrated that such complexes form on the surface of pyrite and continue to persist even after a significant fraction of the surface Fe{sup 2+} was oxidized to Fe{sup 3+}. FT-IR spectra also showed the presence of two carbonyl absorption bands (1,682 and 1,653 cm{sup {minus}1}) on the surface of pyrite upon exposure to CO{sub 2} which suggested that pyrite surface carbon complexes existed in two different surface chemical environments, pointing out two potential mechanisms of pyrite surface-CO{sub 2} interactions. One potential mechanism involved formation of a pyrite surface-Fe(II)HCO{sub 3} complex, whereas a second potential mechanism involved formation of a pyrite surface-carboxylic acid group complex [{minus}Fe(II)SSCOOFe-(II)].
Evangelou, V.P.; Holt, A. [Univ. of Kentucky, Lexington, KY (United States). Dept. of Agronomy] [Univ. of Kentucky, Lexington, KY (United States). Dept. of Agronomy; Seta, A.K. [Univ. Bengkulu (Indonesia). Fakultas Pertanian] [Univ. Bengkulu (Indonesia). Fakultas Pertanian
Impact of Iron Oxide Structure on Fe(II)-Catalyzed Reductive Biomineralization
NASA Astrophysics Data System (ADS)
Due to the reactivity of ferrous Fe, the fate of Fe(II) following dissimilatory iron reduction will have a profound bearing on biogeochemical cycles. Ferric (hydr)oxides vary from well-ordered phases in mature environments to short-range order minerals such as ferrihydrite in those subject to varying redox conditions. Structural order may have appreciable impacts on the extent and rate of Fe(III) reduction and subsequent Fe(II) generation. Here we compare the reducing capacity, biomineralization, and microbial colonization of goethite and hematite to 2-line ferrihydrite under advective flow. Introduction of organic carbon results in the onset of reduction of all three Fe phases. Although overall surface area normalized reduction rates are equivalent, the extent of Fe(III) reduction and fate of Fe(II) differs among the three systems. The amount of Fe(III) reduced within the ferrihydrite, goethite, and hematite columns is 25, 5, and 1%, respectively. While 83% of Fe(II) produced in the ferrihydrite system is retained within the solid-phase, merely 17% is retained by goethite and hematite. The fate of Fe(II) within all three systems involves sequestration of Fe(II) within magnetite yet the degree of conversion varies as a function of Fe(II) production. Goethite and hematite illustrate a similar control on Fe(II) dynamics, where Fe(II) primarily remains in the aqueous phase and is eluted from the system. Despite differences in initial reduction and sequestration, subsequent Fe(II) generation and accumulation within the three Fe oxides reaches an equivalent steady-state (300 h), where similar aqueous Fe(II) concentrations, cell colonization, and Fe(III) reduction rates are supported. The decline in microbial reduction is, most likely, due to preferential consumption of higher energy surface sites via reductive dissolution and magnetite nucleation, regardless of oxide structural order and surface area. Due to the transient nature of reactive sites on ferrihydrite, prolonged microbial reduction and colonization of ferrihydrite may not differ substantially from that of goethite and hematite. Given the greater abundance of crystalline iron oxides in the environment, reduction of phases such as goethite and hematite may impart an equivalent or potentially greater impact on sustained Fe(II) generation and sequestration.
Hansel, C. M.; Benner, S. G.; Fendorf, S.
The effect of alkali salt catalyst on the carbothermic reduction of nickel oxide
The purpose of this communication is to report the experimental measurements on the rate of carbothermic reduction of nickel\\u000a oxide with and without catalyst added. While kinetic studies on the molten salt enhanced carbothermic reduction of iron oxides[1,2] and zinc oxide[3] have been reported, no report has been found on the kinetics of carbothermic reduction of nickel oxide with catalyst
C. I. Lin
Nitrate Reduction Functional Genes and Nitrate Reduction Potentials Persist in Deeper Estuarine Sediments. Why?
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This raises interesting questions as to what the alternative metabolic roles for the various nitrate reductases could be, analogous to the alternative metabolic roles found for nitrite reductases.
Papaspyrou, Sokratis; Smith, Cindy J.; Dong, Liang F.; Whitby, Corinne; Dumbrell, Alex J.; Nedwell, David B.
Nitrate reduction functional genes and nitrate reduction potentials persist in deeper estuarine sediments. Why?
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This raises interesting questions as to what the alternative metabolic roles for the various nitrate reductases could be, analogous to the alternative metabolic roles found for nitrite reductases. PMID:24728381
Papaspyrou, Sokratis; Smith, Cindy J; Dong, Liang F; Whitby, Corinne; Dumbrell, Alex J; Nedwell, David B
Promotion of Iron Oxide Reduction and Extracellular Electron Transfer in Shewanella oneidensis by DMSO
The dissimilatory metal reducing bacterium Shewanella oneidensis MR-1, known for its capacity of reducing iron and manganese oxides, has great environmental impacts. The iron oxides reducing process is affected by the coexistence of alternative electron acceptors in the environment, while investigation into it is limited so far. In this work, the impact of dimethyl sulphoxide (DMSO), a ubiquitous chemical in marine environment, on the reduction of hydrous ferric oxide (HFO) by S. oneidensis MR-1 was investigated. Results show that DMSO promoted HFO reduction by both wild type and ?dmsE, but had no effect on the HFO reduction by ?dmsB, indicating that such a promotion was dependent on the DMSO respiration. With the DMSO dosing, the levels of extracellular flavins and omcA expression were significantly increased in WT and further increased in ?dmsE. Bioelectrochemical analysis show that DMSO also promoted the extracellular electron transfer of WT and ?dmsE. These results demonstrate that DMSO could stimulate the HFO reduction through metabolic and genetic regulation in S. oneidensis MR-1, rather than compete for electrons with HFO. This may provide a potential respiratory pathway to enhance the microbial electron flows for environmental and engineering applications.
Cheng, Yuan-Yuan; Li, Bing-Bing; Li, Dao-Bo; Chen, Jie-Jie; Li, Wen-Wei; Tong, Zhong-Hua; Wu, Chao; Yu, Han-Qing
Promotion of iron oxide reduction and extracellular electron transfer in Shewanella oneidensis by DMSO.
The dissimilatory metal reducing bacterium Shewanella oneidensis MR-1, known for its capacity of reducing iron and manganese oxides, has great environmental impacts. The iron oxides reducing process is affected by the coexistence of alternative electron acceptors in the environment, while investigation into it is limited so far. In this work, the impact of dimethyl sulphoxide (DMSO), a ubiquitous chemical in marine environment, on the reduction of hydrous ferric oxide (HFO) by S. oneidensis MR-1 was investigated. Results show that DMSO promoted HFO reduction by both wild type and ?dmsE, but had no effect on the HFO reduction by ?dmsB, indicating that such a promotion was dependent on the DMSO respiration. With the DMSO dosing, the levels of extracellular flavins and omcA expression were significantly increased in WT and further increased in ?dmsE. Bioelectrochemical analysis show that DMSO also promoted the extracellular electron transfer of WT and ?dmsE. These results demonstrate that DMSO could stimulate the HFO reduction through metabolic and genetic regulation in S. oneidensis MR-1, rather than compete for electrons with HFO. This may provide a potential respiratory pathway to enhance the microbial electron flows for environmental and engineering applications. PMID:24244312
Cheng, Yuan-Yuan; Li, Bing-Bing; Li, Dao-Bo; Chen, Jie-Jie; Li, Wen-Wei; Tong, Zhong-Hua; Wu, Chao; Yu, Han-Qing
Redox-inactive metals modulate the reduction potential in heterometallic manganese-oxido clusters
NASA Astrophysics Data System (ADS)
Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but, at present, their roles in catalysis are not well understood. Here, we report a series of high-oxidation-state tetranuclear-dioxido clusters comprising three manganese centres and a redox-inactive metal (M). Crystallographic studies show an unprecedented Mn3M(Ą4-O)(Ą2-O) core that remains intact on changing M or the manganese oxidation state. Electrochemical studies reveal that the reduction potentials span a window of 700 mV and are dependent on the Lewis acidity of the second metal. With the pKa of the redox-inactive metal-aqua complex as a measure of Lewis acidity, these compounds demonstrate a linear dependence between reduction potential and acidity with a slope of ś100 mV per pKa unit. The Sr2+ and Ca2+ compounds show similar potentials, an observation that correlates with the behaviour of the oxygen-evolving complex of photosystem II, which is active only if one of these two metals is present.
Tsui, Emily Y.; Tran, Rosalie; Yano, Junko; Agapie, Theodor
Redox-Inactive Metals Modulate the Reduction Potential in Heterometallic Manganese-Oxido Clusters
Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but their roles in catalysis are currently not well understood. A series of high oxidation state tetranuclear-dioxido clusters comprised of three manganese centers and a redox-inactive metal (M) of various charge is reported. Crystallographic studies show an unprecedented Mn3M(?4-O)(?2-O) core that remains intact upon changing M or the manganese oxidation state. Electrochemical studies reveal that the reduction potentials span a window of 700 mV, dependent upon the Lewis acidity of the second metal. With the pKa of the redox-inactive metal-aqua complex as a measure of Lewis acidity, these compounds display a linear dependence between reduction potential and acidity with a slope of ca. 100 mV per pKa unit. The Sr2+ and Ca2+ compounds show similar potentials, an observation that correlates with the behavior of the OEC, which is active only in the presence of one of these two metals.
Tsui, Emily Y.; Tran, Rosalie; Yano, Junko; Agapie, Theodor
Hydrogen Reduction of Zinc and Iron Oxides Containing Mixtures
NASA Astrophysics Data System (ADS)
Zinc is a metal of significant technological importance and its production from secondary sources has motivated the development of alternative processes, such as the chemical treatment of electrical arc furnace (EAF) dust. Currently, the extraction of zinc from the mentioned residue using a carbon-containing reducing agent is in the process of being established commercially and technically. In the current study, the possibility of reducing zinc from an EAF dust sample through a H2 constant flux in a horizontal oven is studied. The reduction of a synthetic oxide mixture of analogous composition is also investigated. The results indicated that the reduction process is thermodynamically viable for temperatures higher than 1123 K (850 ░C), and all zinc metal produced is transferred to the gas stream, enabling its complete separation from iron. The same reaction in the presence of zinc crystals was considered for synthesizing FeZn alloys. However, for the experimental conditions employed, although ZnO reduction was indeed thermodynamically hindered because of the presence of zinc crystals (the metal's partial pressure was enhanced), the zinc metal's escape within the gaseous phase could not be effectively avoided.
de Siqueira, Rogķrio Navarro C.; de Albuquerque Brocchi, Eduardo; de Oliveira, Pamela Fernandes; Motta, Marcelo Senna
Nitrous oxide emission reduction in temperate biochar-amended soils
NASA Astrophysics Data System (ADS)
Biochar, a pyrolysis product of organic residues, is an amendment for agricultural soils to improve soil fertility, sequester CO2 and reduce greenhouse gas (GHG) emissions. In highly weathered tropical soils laboratory incubations of soil-biochar mixtures revealed substantial reductions for nitrous oxide (N2O) and carbon dioxide (CO2). In contrast, evidence is scarce for temperate soils. In a three-factorial laboratory incubation experiment two different temperate agricultural soils were amended with green waste and coffee grounds biochar. N2O and CO2 emissions were measured at the beginning and end of a three month incubation. The experiments were conducted under three different conditions (no additional nutrients, glucose addition, and nitrate and glucose addition) representing different field conditions. We found mean N2O emission reductions of 60 % compared to soils without addition of biochar. The reduction depended on biochar type and soil type as well as on the age of the samples. CO2 emissions were slightly reduced, too. NO3- but not NH4+ concentrations were significantly reduced shortly after biochar incorporation. Despite the highly significant suppression of N2O emissions biochar effects should not be transferred one-to-one to field conditions but need to be tested accordingly.
Felber, R.; H³ppi, R.; Leifeld, J.; Neftel, A.
Stable platinum nanoclusters on genomic DNA-graphene oxide with a high oxygen reduction reaction activity.
Nanosize platinum clusters with small diameters of 2-4?nm are known to be excellent catalysts for the oxygen reduction reaction. The inherent catalytic activity of smaller platinum clusters has not yet been reported due to a lack of preparation methods to control their size (<2?nm). Here we report the synthesis of platinum clusters (diameter ?1.4?nm) deposited on genomic double-stranded DNA-graphene oxide composites, and their high-performance electrocatalysis of the oxygen reduction reaction. The electrochemical behaviour, characterized by oxygen reduction reaction onset potential, half-wave potential, specific activity, mass activity, accelerated durability test (10,000 cycles) and cyclic voltammetry stability (10,000 cycles) is attributed to the strong interaction between the nanosize platinum clusters and the DNA-graphene oxide composite, which induces modulation in the electronic structure of the platinum clusters. Furthermore, we show that the platinum cluster/DNA-graphene oxide composite possesses notable environmental durability and stability, vital for high-performance fuel cells and batteries. PMID:23900456
Tiwari, Jitendra N; Nath, Krishna; Kumar, Susheel; Tiwari, Rajanish N; Kemp, K Christian; Le, Nhien H; Youn, Duck Hyun; Lee, Jae Sung; Kim, Kwang S
Stable platinum nanoclusters on genomic DNA-graphene oxide with a high oxygen reduction reaction activity
Nanosize platinum clusters with small diameters of 2¢4?nm are known to be excellent catalysts for the oxygen reduction reaction. The inherent catalytic activity of smaller platinum clusters has not yet been reported due to a lack of preparation methods to control their size (<2?nm). Here we report the synthesis of platinum clusters (diameter ?1.4?nm) deposited on genomic double-stranded DNA¢graphene oxide composites, and their high-performance electrocatalysis of the oxygen reduction reaction. The electrochemical behaviour, characterized by oxygen reduction reaction onset potential, half-wave potential, specific activity, mass activity, accelerated durability test (10,000 cycles) and cyclic voltammetry stability (10,000 cycles) is attributed to the strong interaction between the nanosize platinum clusters and the DNA¢graphene oxide composite, which induces modulation in the electronic structure of the platinum clusters. Furthermore, we show that the platinum cluster/DNA¢graphene oxide composite possesses notable environmental durability and stability, vital for high-performance fuel cells and batteries.
Tiwari, Jitendra N.; Nath, Krishna; Kumar, Susheel; Tiwari, Rajanish N.; Kemp, K. Christian; Le, Nhien H.; Youn, Duck Hyun; Lee, Jae Sung; Kim, Kwang S.
Oxidation of Inconel alloy MA754 at low oxidation potential
It has been known for some time that the addition of small oxide particles to an 80 Ni-20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance was studied. Initial experiments were performed using inconel alloy MA754, which is nominally: 78 Ni,
D. N. Braski; P. D. Goodell; J. V. Cathcart; R. H. Kane
Drag reduction in turbulent pipe flow by applied electric potentials
NASA Astrophysics Data System (ADS)
A novel approach to drag reduction is presented on the basis of applied positive electric potentials to a pipe. This has been studied by measuring the pressure drop over a 13.1 m epoxy-coated pipe made of carbon steel, through which water was flowing under conditions of constant flow rate. Potentials were applied between the pipe and the counter electrode located at the pipe inlet. The results show a decrease in the pressure drop (up to 2%) when positive electric DC-potentials in the range 0.6 -- 1.6V were applied to the pipe. However, no significant changes was obtained for applied potentials in the ranges of 0 to 0.6 V, 1.6 to 2.0 V or 0 to -2.0 V. Waterflow through an epoxy coated turbine pipe (length 1562 m, diameter 1 m, total fall 380 m) in a hydroelectric power plant has also been studied. A 1.1 V potential was applied between the pipe and the manlock (made of stainless steel and electrically insulated from the pipe). Results show that the head loss decreased from 45.9 m to 39.8 m at maximum flow rate, which corresponds to a 1.8% increase in the electricity production. Although small, the effect represents the possibility of significant cost savings. The mechanism by which the drag is reduced is not currently understood.
Waskaas, Magne; Daujotis, Vytautas; Wolden, Kjell; Raudonis, Rimantas; Plausinaitis, Deivis
Adaptive stimulus artifact reduction in noncortical somatosensory evoked potential studies.
Somatosensory evoked potentials (SEP's) are an important class of bioelectric signals which contain clinically valuable information. The surface measurements of these potentials are often contaminated by a stimulus evoked artifact. The stimulus artifact (SA), depending upon the stimulator and measurement system characteristics, may obscure some of the information carried by the SEP's. Conventional methods for SA reduction employ hardware-based circuits which attempt to eliminate the SA by blanking the input during SA period. However, there is a danger of losing some of the important SEP information, especially if the stimulating and recording electrodes are close together. In this paper, we apply both linear and nonlinear adaptive filtering techniques to the problem of SA reduction. Nonlinear adaptive filters (NAF's) based on truncated second-order Volterra series expansion are discussed and their applicability to SA cancellation is explored through processing both simulated and in vivo SEP data. The performances of the NAF and the finite impulse response (FIR) linear adaptive filter (LAF) are compared by processing experimental SEP data collected from different recording sites. Due to the inherent nonlinearities in the generation of the SA, the NAF is shown to achieve significantly better SA cancellation compared to the LAF. PMID:9473840
Parsa, V; Parker, P A; Scott, R N
Reduction of Oxidative Melt Loss of Aluminum and Its Alloys
This project led to an improved understanding of the mechanisms of dross formation. The microstructural evolution in industrial dross samples was determined. Results suggested that dross that forms in layers with structure and composition determined by the local magnesium concentration alone. This finding is supported by fundamental studies of molten metal surfaces. X-ray photoelectron spectroscopy data revealed that only magnesium segregates to the molten aluminum alloy surface and reacts to form a growing oxide layer. X-ray diffraction techniques that were using to investigate an oxidizing molten aluminum alloy surface confirmed for the first time that magnesium oxide is the initial crystalline phase that forms during metal oxidation. The analytical techniques developed in this project are now available to investigate other molten metal surfaces. Based on the improved understanding of dross initiation, formation and growth, technology was developed to minimize melt loss. The concept is based on covering the molten metal surface with a reusable physical barrier. Tests in a laboratory-scale reverberatory furnace confirmed the results of bench-scale tests. The main highlights of the work done include: A clear understanding of the kinetics of dross formation and the effect of different alloying elements on dross formation was obtained. It was determined that the dross evolves in similar ways regardless of the aluminum alloy being melted and the results showed that amorphous aluminum nitride forms first, followed by amorphous magnesium oxide and crystalline magnesium oxide in all alloys that contain magnesium. Evaluation of the molten aluminum alloy surface during melting and holding indicated that magnesium oxide is the first crystalline phase to form during oxidation of a clean aluminum alloy surface. Based on dross evaluation and melt tests it became clear that the major contributing factor to aluminum alloy dross was in the alloys with Mg content. Mg was identified as the primary factor that accelerates dross formation specifically in the transition from two phases to three phase growth. Limiting magnesium oxidation on the surface of molten aluminum therefore becomes the key to minimizing melt loss, and technology was developed to prevent magnesium oxidation on the aluminum surface. This resulted in a lot of the work being focused on the control of Mg oxidation. Two potential molten metal covering agents that could inhibit dross formation during melting and holding consisting of boric acid and boron nitride were identified. The latter was discounted by industry as it resulted in Boron pick up by the melt beyond that allowed by specifications during plant trials. The understanding of the kinetics of dross formation by the industry partners helped them understand how temperature, alloy chemistry and furnace atmosphere (burner controls--e.g. excess air) effected dross formation. This enables them to introduce in their plant process changes that reduced unnecessary holding at high temperatures, control burner configurations, reduce door openings to avoid ingress of air and optimize charge mixes to ensure rapid melting and avoid excess oxidation.
Dr. Subodh K. Das; Shridas Ningileri
Chemically modified graphene sheets produced by the solvothermal reduction of colloidal dispersions of graphite oxide
Chemically modified graphene sheets are obtained through solvothermal reduction of colloidal dispersions of graphite oxide in various solvents. Reduction occurs at relatively low temperatures (120¢200░C). Reaction temperature, the self-generated pressure in the sealed reaction vessel and the reducing power of the solvent influences the extent of reduction of graphite oxide sheets to modified graphene sheets.
C. Nethravathi; Michael Rajamathi
Temperature-programmed reduction study of chromium oxide supported on zirconia and lanthana¢zirconia
Temperature-programmed reduction (TPR) has been applied to study the reduction behavior of chromium oxide supported on pure zirconia and on lanthana-containing zirconia. The results revealed influences of support nature and chromium loading on the state of the supported chromium oxide. With catalysts containing lanthana and only low amounts of chromium, the decrease of the chromium oxidation state during TPR corresponded
D. L Hoang; H Lieske
Chemical reduction of individual graphene oxide sheets as revealed by electrostatic force microscopy.
We report continuous monitoring of heterogeneously distributed oxygenated functionalities on the entire surface of the individual graphene oxide flake during the chemical reduction process. The charge densities over the surface with mixed oxidized and graphitic domains were observed for the same flake after a step-by-step chemical reduction process using electrostatic force microscopy. Quantitative analysis revealed heavily oxidized nanoscale domains (50-100 nm across) on the graphene oxide surface and a complex reduction mechanism involving leaching of sharp oxidized asperities from the surface followed by gradual thinning and formation of uniformly mixed oxidized and graphitic domains across the entire flake. PMID:24749548
Kulkarni, Dhaval D; Kim, Songkil; Chyasnavichyus, Marius; Hu, Kesong; Fedorov, Andrei G; Tsukruk, Vladimir V
Catalyst and method for reduction of nitrogen oxides
A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).
Ott, Kevin C. (Los Alamos, NM)
Catalyst and method for reduction of nitrogen oxides
A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).
Ott, Kevin C. (Los Alamos, NM)
The Oxidation (Not Reduction) of Ordinary Chondrites During Metamorphism
NASA Astrophysics Data System (ADS)
Subtle but systematic changes in the compositions and relative abundances of olivine, pyroxene, and metal with increasing petrologic type in equilibrated (types 4-6) H, L, and LL chondrites suggest that metallic Fe in these meteorites was oxidized during metamorphism. Observed changes include increases in the mean Fe contents of olivine and pyroxene and in the mean Ni and Co contents of bulk metal, as well as increases in the olivine:low-Ca pyroxene ratio with decreasing metal abundance. This evidence for oxidation is at variance with the commonly accepted idea that chondritic Fe was reduced by graphite during metamorphism (Ringwood, 1965; Williams, 1971; Brett and Sato, 1984; Rubin et al., 1988). We suggest that graphite activity was lowered by its dissolution in taenite at metamorphic temperatures, so that redox state was determined largely by equilibrium between ferromagnesian silicates and metal. Oxygen fugacities calculated from chondrite mineral equilibria are 2-3 log units below intrinsic fO(sub)2 measurements (Brett and Sato, 1984). The mineralogies of type 3 chondrites do not conform to the oxidation sequence seen in types 4-6 chondrites, and there is some evidence to suggest that Fe in unequilibrated chondrites was actually reduced during mild heating. Apparently, redox conditions in the surficial layers of parent bodies were reducing, but were oxidizing in the hotter interiors. Much of the current confusion over oxidation versus reduction is attributable to comparing unequilibrated and equilibrated chondrites. Progressive oxidation of Fe during metamorphism implies reaction with an oxidizing agent no longer present in the meteorites. We suggest that this oxidant was an aqueous vapor, derived from heating small amounts of ices originally accreted into the parent asteroids. The condensation of this vapor in cooler, outer layers of asteroids could account for aqueous alteration phases documented in some type 3 chondrites (Alexander et al., 1989). Assuming that the vapor was pure H2O, the water:rock weight ratio required to account for the observed Fe oxidation was very modest, less than 3o/oo. However, the presence of even minor amounts of a fluid attending metamorphism has important implications for the interpretation of chemical and isotopic patterns in ordinary chondrites. For example, this vapor may have acted as a carrier gas to facilitate redistribution of volatile trace elements during metamorphism (Sugiura et al., 1984). Open-system metamorphism may also explain oxygen isotopic patterns seen in the data of Clayton et al. (1991). This pattern could have resulted from varying exchange with an isotopically light vapor at different temperatures, or with a vapor whose isotopic composition evolved as it permeated through the parent bodies. References: Alexander C.M. et al. (1989) Geochim. Cosmochim. Acta 53, 3045-3057. Brett R. and Sato M. (1984) Geochim. Cosmochim. Acta 48, 111-120. Clayton R.N. et al. (1991) Geochim. Cosmochim. Acta 55, 2317-2337. Ringwood A.E. (1965) Nature 207, 701-704. Rubin A.E. et al. (1988) In Meteorites and the Early Solar System (eds. J.F. Kerridge and M.S. Matthews), pp. 488-511. Univ. Arizona Press, Tucson, AZ. Sugiura N. et al. (1984) J. Geophys. Res. 89, B641-644. Williams R.J. (1971) Geochim. Cosmochim. Acta 35, 407-411.
McSween, H. Y., Jr.; Labotka, T. C.
Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders
NASA Technical Reports Server (NTRS)
Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.
Herbell, T. P.
Perovskite-type oxides as catalysts for selective reduction of nitric oxide by ethylene
NASA Astrophysics Data System (ADS)
The selective catalytic reduction of NO with C 2H 4 (C 2H 4-SCR) was investigated over perovskites containing Co, Mn, Fe, Cr, Al, Sn and Ti as host B-site cations. The C 2H 4-SCR activity was observed over Al-, Sn- and Ti-based oxides which were free from redox-active metal cations such as Co and Cu and innately poor in oxidation activity. Over perovskites containing redox-active metal cations, the undesirable consumption of C 2H 4 by O 2 proceeded preferentially.
Harada, T.; Teraoka, Y.; Kagawa, S.
Photocatalytic reduction of benzonitrile to benzylamine in aqueous suspensions of palladium-loaded titanium(IV) oxide.
Benzonitrile (PhCN) was successfully reduced to benzyl amine in acidic aqueous suspensions of a palladium (Pd)-loaded titanium(IV) oxide (TiO2) photocatalyst in the presence of oxalic acid as a hole scavenger, although the reduction potential of PhCN is believed to be much higher than the potential of the conduction band (CB) of TiO2, indicating that a Pd co-catalyst strongly contributes to PhCN reduction and that the applicability of photocatalytic reduction is not limited by the CB position of semiconductor photocatalysts. PMID:24129580
Imamura, Kazuya; Yoshikawa, Takayuki; Nakanishi, Kousuke; Hashimoto, Keiji; Kominami, Hiroshi
Oxidation of Inconel alloy MA754 at low oxidation potential
It has been known for some time that the addition of small oxide particles to an 80 Ni-20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance is being studied. Small disks (3 mm diam x 0.38 mm thick) were cut from
D. N. Braski; P. D. Goodell; J. V. Cathcart; R. H. Kane
Oxidation of Inconel Alloy MA754 at Low Oxidation Potential.
National Technical Information Service (NTIS)
It has been known for some time that the addition of small oxide particles to an 80 Ni-20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid en...
D. N. Braski P. D. Goodell J. V. Cathcart R. H. Kane
The effects of freeze¢thaw and sonication on mitochondrial oxygen consumption, electron transport chain-linked metmyoglobin reduction, lipid oxidation, and oxymyoglobin oxidation
Mitochondria potentially influence Mb redox stability in meat by (1) decreasing partial oxygen pressure via oxygen consumption, (2) mitochondrial electron transport chain (ETC)-linked reduction of MetMb, and\\/or (3) oxidation of mitochondrial membrane lipid. The objective of this study was to investigate the effect of freeze¢thaw and sonication treatments on mitochondrial oxygen consumption, ETC-dependent MetMb reducing activity, lipid oxidation, and Mb
Jiali Tang; Cameron Faustman; Richard A. Mancini; Mark Seyfert; Melvin C. Hunt
Oxidation-reduction studies of the Mo-(2Fe-2S) protein from Desulfovibrio gigas.
Potentiometric titration followed by e.p.r. measurements were used to determine the midpoint reduction potentials of the redox centres of a molybdenum-containing iron-sulphur protein previously isolated from Desulfovibrio gigas, a sulphate-reducing bacterium (Moura, Xavier, Bruschi, Le Gall, Hall & Cammack (1976) Biochem. Biophys. Res. Commun. 728 782-789; Moura, Xavier, Bruschi, Le Gall & Cabral (1977) J. Less Common Metals 54, 555-562). The iron-sulphur centres could readily be distinguished into three types by means of g values, temperature effect, oxidation-reduction potential values and reduction rates. The type-I Fe-S centres are observed at 77 K. They show mid-point potential values of -260mV (Fe-S type IA) and -440 mV (Fe-S type IB). Centres of types IA and IB appear to have similar spectra at 77 K and 24 K. The Fe-S type-II centres are only observed below 65 K and have a midpoint potential of -28mV. Long equilibration times (30 min) with dye mediators under reducing conditions were necessary to observe the very slow equilibrating molybdenum signals. The potential values associated with this signal were estimated to be approx. -415 mV for Mo(VI)/Mo(V) and-530mV for Mo(V)/Mo(IV).
Moura, J J; Xavier, A V; Cammack, R; Hall, D O; Bruschi, M; Le Gall, J
Reduction potentials of heterometallic manganese-oxido cubane complexes modulated by redox-inactive metals.
Understanding the effect of redox-inactive metals on the properties of biological and heterogeneous water oxidation catalysts is important both fundamentally and for improvement of future catalyst designs. In this work, heterometallic manganese-oxido cubane clusters [MMn3O4] (M = Sr(2+), Zn(2+), Sc(3+), Y(3+)) structurally relevant to the oxygen-evolving complex (OEC) of photosystem II were prepared and characterized. The reduction potentials of these clusters and other related mixed metal manganese-tetraoxido complexes are correlated with the Lewis acidity of the apical redox-inactive metal in a manner similar to a related series of heterometallic manganese-dioxido clusters. The redox potentials of the [SrMn3O4] and [CaMn3O4] clusters are close, which is consistent with the observation that the OEC is functional only with one of these two metals. Considering our previous studies of [MMn3O2] moieties, the present results with more structurally accurate models of the OEC ([MMn3O4]) suggest a general relationship between the reduction potentials of heterometallic oxido clusters and the Lewis acidities of incorporated cations that applies to diverse structural motifs. These findings support proposals that one function of calcium in the OEC is to modulate the reduction potential of the cluster to allow electron transfer. PMID:23744039
Tsui, Emily Y; Agapie, Theodor
Niobium Oxide-Supported Platinum Ultra-Low Amount Electrocatalysts for Oxygen Reduction
We demonstrate a new approach to synthesizing high-activity electrocatalysts for the O2 reduction reaction with ultra low Pt content. The synthesis involves placing a small amount of Pt, the equivalent of a monolayer, on carbon-supported niobium oxide nanoparticles (NbO2 or Nb2O5). Rotating disk electrode measurements show that the Pt/NbO2/C electrocatalyst has three times higher Pt mass activity for the O2 reduction reaction than a commercial Pt/C electrocatalyst. The observed high activity of the Pt deposit is attributed to the reduced OH adsorption caused by lateral repulsion between PtOH and oxide surface species. The new electrocatalyst also exhibits improved stability against Pt dissolution under a potential cycling regime (30000 cycles from 0.6 V to 1.1 V). These findings demonstrate that niobium-oxide (NbO2) nanoparticles can be adequate supports for Pt and facilitate further reducing the noble metal content in electrocatalysts for the oxygen reduction reaction.
Sasaki,K.; Zhang, L.; Adzic, R.
Oxidation of Inconel alloy MA754 at low oxidation potential
It has been known for some time that the addition of small oxide particles to an 80 Ni-20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance is being studied. Small disks (3 mm diam x 0.38 mm thick) were cut from Inconel MA754 plate stock and prepared with two different surface conditions. Disks having both surface treatments were oxidized in a radiantly heated furnace for 30 s at 1000/sup 0/C. Three different environments were investigated: hydrogen with nomninal dew points of 0/sup 0/C, -25/sup 0/C, and -55/sup 0/C. The oxide particles and films were examined in TEM by using extraction replicas (carbon) and by back-polishing to the oxide/metal interface. The particles were analyzed by EDS and SAD.
Braski, D.N.; Goodell, P.D.; Cathcart, J.V.; Kane, R.H.
Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria
NASA Technical Reports Server (NTRS)
The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.
Wang, J.; Brune, D. C.; Blankenship, R. E.
A micro-nano porous oxide hybrid for efficient oxygen reduction in reduced-temperature solid oxide fuel cells
Tremendous efforts to develop high-efficiency reduced-temperature (? 600░C) solid oxide fuel cells are motivated by their potentials for reduced materials cost, less engineering challenge, and better performance durability. A key obstacle to such fuel cells arises from sluggish oxygen reduction reaction kinetics on the cathodes. Here we reported that an oxide hybrid, featuring a nanoporous Sm0.5Sr0.5CoO3?? (SSC) catalyst coating bonded onto the internal surface of a high-porosity La0.9Sr0.1Ga0.8Mg0.2O3?? (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 ? cm2 at 650░C and 0.043 ? cm2 at 600░C. We further demonstrated that such a micro-nano porous hybrid, adopted as the cathode in a thin LSGM electrolyte fuel cell, produced impressive power densities of 2.02?W cm?2 at 650░C and 1.46?W cm?2 at 600░C when operated on humidified hydrogen fuel and air oxidant.
Da Han; Liu, Xuejiao; Zeng, Fanrong; Qian, Jiqin; Wu, Tianzhi; Zhan, Zhongliang
The electrochemical behavior of tin-doped indium oxide during reduction in 0.3 M hydrochloric acid
The electrochemical behavior of tin-doped indium oxide (ITO) on SiO2 in 0.3 M HCl was studied using voltammetric scanning method. The result showed that an obvious reduction current peak occurred during the first cathodic potential scanning. The reduction reaction became less active after annealing ITO at 500░C for 1 h. The result was attributed to the replenishment of oxygen-deficient site,
C. A. Huang; K. C. Li; G. C. Tu; W. S. Wang
Reduction of Tantalum Pentoxide Using Graphite and Tin-Oxide-Based Anodes via the FFC-Cambridge Process
An investigation into the electrochemical reduction of tantalum pentoxide (Ta2O5) to tantalum metal in molten calcium chloride was performed. The oxide was made the cathode, and either graphite or tin oxide\\u000a rods were selected as the anodes. The experiments were terminated after 8Āhours of potentiostatic electrolysis using a two-electrode\\u000a setup, with the current and anodic potential recorded. The cathode products
Roger Barnett; Kamal Tripuraneni Kilby; Derek J. Fray
Computational electrochemistry: prediction of liquid-phase reduction potentials.
This article reviews recent developments and applications in the area of computational electrochemistry. Our focus is on predicting the reduction potentials of electron transfer and other electrochemical reactions and half-reactions in both aqueous and nonaqueous solutions. Topics covered include various computational protocols that combine quantum mechanical electronic structure methods (such as density functional theory) with implicit-solvent models, explicit-solvent protocols that employ Monte Carlo or molecular dynamics simulations (for example, Car-Parrinello molecular dynamics using the grand canonical ensemble formalism), and the Marcus theory of electronic charge transfer. We also review computational approaches based on empirical relationships between molecular and electronic structure and electron transfer reactivity. The scope of the implicit-solvent protocols is emphasized, and the present status of the theory and future directions are outlined. PMID:24958074
Marenich, Aleksandr V; Ho, Junming; Coote, Michelle L; Cramer, Christopher J; Truhlar, Donald G
Temperature programmed reduction and oxidation of Ir\\/Al 2 O 3 catalysts
3 % Ir\\/Al2O3 catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher Tox) reducibility of the catalysts at low temperatures decreases.
T. Paryjczak; P. Zieli?ski; W. K. J¾?wiak
Oxidation and reduction in irradiated binary crystals of resorcinol and progesterone
The binary single crystals of resorcinol and progesterone were x-irradiated at 4.2 K. The semiquinone of resorcinol was generated by radiation induced oxidation. The oxidation and reduction products were identified from ESR and ENDOR measurements. (AIP)
Box, H.C.; Budzinski, E.E.
Oxygen reduction by lithium on model carbon and oxidized carbon structures
Li-air batteries have attracted substantial interest for their high theoretical specific energies, but the oxygen reduction reaction by Li (Li-ORR) that occurs at the carbon cathode remains poorly understood. Periodic density functional theory calculations have been performed to examine the Li-ORR on several model carbon structures, including the graphite(0001) basal plane, the (8,0) single-wall nanotube, the armchair-type edge, and a di-vacancy in the basal plane. The inertness of the basal plane limits the reversible potential of O{sub 2} reduction to 1.1 V, and slightly higher to 1.2 V on the curved nanotube. The armchair edge and di-vacancy are highly reactive and significantly oxidized at ambient conditions to various CO{sub x} groups, which are reduced by Li via redox mechanisms at 1.2-1.4 V. These CO{sub x} groups can also catalyze O{sub 2} reduction at up to 2.3 V (an overpotential of 0.4 V vs. the calculated equilibrium potential for bulk Li{sub 2}O{sub 2} formation) by chelating and stabilizing the LiO{sub 2} intermediate. The Li-ORR on graphitic carbon, if via concerted Li{sup +}/e{sup -} transfer and involving carbon, lithium, and oxygen only, is therefore expected to initiate with the smallest overpotential at under-coordinated carbon centers that are oxidized at ambient conditions.
Xu, Ye [ORNL; Shelton Jr, William Allison [ORNL
Molecular Underpinnings of Fe(III) Oxide Reduction by Shewanella Oneidensis MR-1.
In the absence of O(2) and other electron acceptors, the Gram-negative bacterium Shewanella oneidensis MR-1 can use ferric [Fe(III)] (oxy)(hydr)oxide minerals as the terminal electron acceptors for anaerobic respiration. At circumneutral pH and in the absence of strong complexing ligands, Fe(III) oxides are relatively insoluble and thus are external to the bacterial cells. S. oneidensis MR-1 and related strains of metal-reducing Shewanella have evolved machinery (i.e., metal-reducing or Mtr pathway) for transferring electrons from the inner-membrane, through the periplasm and across the outer-membrane to the surface of extracellular Fe(III) oxides. The protein components identified to date for the Mtr pathway include CymA, MtrA, MtrB, MtrC, and OmcA. CymA is an inner-membrane tetraheme c-type cytochrome (c-Cyt) that belongs to the NapC/NrfH family of quinol dehydrogenases. It is proposed that CymA oxidizes the quinol in the inner-membrane and transfers the released electrons to MtrA either directly or indirectly through other periplasmic proteins. A decaheme c-Cyt, MtrA is thought to be embedded in the trans outer-membrane and porin-like protein MtrB. Together, MtrAB deliver the electrons through the outer-membrane to the MtrC and OmcA on the outmost bacterial surface. MtrC and OmcA are the outer-membrane decaheme c-Cyts that are translocated across the outer-membrane by the bacterial type II secretion system. Functioning as terminal reductases, MtrC and OmcA can bind the surface of Fe(III) oxides and transfer electrons directly to these minerals via their solvent-exposed hemes. To increase their reaction rates, MtrC and OmcA can use the flavins secreted by S. oneidensis MR-1 cells as diffusible co-factors for reduction of Fe(III) oxides. Because of their extracellular location and broad redox potentials, MtrC and OmcA can also serve as the terminal reductases for soluble forms of Fe(III). In addition to Fe(III) oxides, Mtr pathway is also involved in reduction of manganese oxides and other metals. Although our understanding of the Mtr pathway is still far from complete, it is the best characterized microbial pathway used for extracellular electron exchange. Characterizations of the Mtr pathway have made significant contributions to the molecular understanding of microbial reduction of Fe(III) oxides. PMID:22363328
Shi, Liang; Rosso, Kevin M; Clarke, Tomas A; Richardson, David J; Zachara, John M; Fredrickson, James K
Reduction of aromatic nitrocompounds with hydrazine hydrate in the presence of an iron oxide hydroxide catalyst
The catalytic activities of several iron oxides and oxide hydroxides have been tested in the reduction of substituted nitroarenes using hydrazine hydrate as reducing agent. An iron oxide catalyst, prepared by rapid precipitation of iron hydroxides from solutions of iron(III)chloride, showed the highest activity mainly due to its large BET surface area compared to other iron oxides. M÷ssbauer spectroscopy and
M Benz; A. M van der Kraan; R Prins
Reductive heme-dependent activation of the n-oxide prodrug AQ4N by nitric oxide synthase.
Anaerobic reduction of anticancer prodrugs is a promising route to achieve targeting and selectivity in anticancer drug design. Most reductive prodrug activations involve simple electron transfer from a flavoprotein and are not amenable to specific targeting. Here, we report that the N-oxide AQ4N is reduced by a nitric oxide synthase. This reduction involves interaction with the heme iron atom in the active site and is thus subject to specific protein constraints. PMID:18681417
Nishida, Clinton R; Ortiz de Montellano, Paul R
Iron isotope fractionation during microbial dissimilatory iron oxide reduction in simulated Archaean seawater.
The largest Fe isotope excursion yet measured in marine sedimentary rocks occurs in shales, carbonates, and banded iron formations of Neoarchaean and Paleoproterozoic age. The results of field and laboratory studies suggest a potential role for microbial dissimilatory iron reduction (DIR) in producing this excursion. However, most experimental studies of Fe isotope fractionation during DIR have been conducted in simple geochemical systems, using pure Fe(III) oxide substrates that are not direct analogues to phases likely to have been present in Precambrian marine environments. In this study, Fe isotope fractionation was investigated during microbial reduction of an amorphous Fe(III) oxide-silica coprecipitate in anoxic, high-silica, low-sulphate artificial Archaean seawater at 30 ░C to determine if such conditions alter the extent of reduction or isotopic fractionations relative to those observed in simple systems. The Fe(III)-Si coprecipitate was highly reducible (c. 80% reduction) in the presence of excess acetate. The coprecipitate did not undergo phase conversion (e.g. to green rust, magnetite or siderite) during reduction. Iron isotope fractionations suggest that rapid and near-complete isotope exchange took place among all Fe(II) and Fe(III) components, in contrast to previous work on goethite and hematite, where exchange was limited to the outer few atom layers of the substrate. Large quantities of low-?(56)Fe Fe(II) (aqueous and solid phase) were produced during reduction of the Fe(III)-Si coprecipitate. These findings shed new light on DIR as a mechanism for producing Fe isotope variations observed in Neoarchaean and Paleoproterozoic marine sedimentary rocks. PMID:21504536
Percak-Dennett, E M; Beard, B L; Xu, H; Konishi, H; Johnson, C M; Roden, E E
Electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices
NASA Astrophysics Data System (ADS)
The focus of this dissertation is the electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices. The electrochemical reduction of metal oxides to metals has been studied for decades as an alternative to pyrometallurgical processes for the metallurgy industry. However, the previous work was conducted on bulk polycrystalline metal oxides. Paper I in this dissertation shows that epitaxial face-centered cubic magnetite (Fe3O4 ) thin films can be electrochemically reduced to epitaxial body-centered cubic iron (Fe) thin films in aqueous solution on single-crystalline Au substrates at room temperature. This technique opens new possibilities to produce special epitaxial metal/metal oxide heterojunctions and a wide range of epitaxial metallic alloy films from the corresponding mixed metal oxides. Electrodeposition, like biomineralization, is a soft solution processing method which can produce functional materials with special properties onto conducting or semiconducting solid surfaces. Paper II in this dissertation presents the electrodeposition of cobalt-substituted magnetite (CoxFe3-xO4, 0 of cobalt-substituted magnetite (CoxFe3-xO4, 0
He, Zhen
Temperature dependence of the formal reduction potential of putidaredoxin.
Putidaredoxin (Pdx), a [2Fe-2S] redox protein of size M(r) 11,600, transfers two electrons in two separate steps from the flavin containing putidaredoxin reductase to the heme protein, cytochrome CYP101 in the P450cam catalytic cycle. It has recently come to light, through NMR measurements, that there can be appreciable differences in the Pdx conformational dynamics between its reduced and oxidized states. The redox reaction entropy, deltaS(0')rc = (S(0')Pdx(r)-S(0')Pdx(0)), as determined from measurements of the variation in formal potential with temperature, E0'(T), provides a measure of the strength of this influence on Pdx function. We designed a spectroelectrochemical cell using optically transparent tin oxide electrodes, without fixed or diffusible mediators, to measure E0'(T) over the temperature range 0-40 degrees C. The results indicate that the redox reaction entropy for Pdx is biphasic, decreasing from -213 +/- 27 J mol(-1) K(-1) over 0-27 degrees C, to -582 +/- 150 J mol(-1) K (-1) over 27-40 degrees C. These redox reaction entropy changes are significantly more negative than the changes reported for most cytochromes, although our measurement over the temperature interval 0-27 degrees C is in the range reported for other iron-sulfur proteins. This suggests that Pdx (and other ferredoxins) is a less rigid system than monohemes, and that redox-linked changes in conformation, and/or conformational dynamics, impart to these proteins the ability to interact with a number of redox partners. PMID:10924895
Reipa, V; Holden, M J; Mayhew, M P; Vilker, V L
A method to measure nitrous oxide reduction in soil
NASA Astrophysics Data System (ADS)
The greenhouse gas nitrous oxide (N2O) is produced in the soil by naturally occurring microbial processes. A major portion of the gross N2O production is however further reduced to benign nitrogen gas (N2) in the final step of (nitrifier) denitrification before it escapes to the atmosphere. Topsoil fluxes of N2O therefore are the resultant of a variety of production and consumption processes through the soil profile. However, quantitative insight into the relation between, net N2O fluxes on the one hand and the underlying production and consumption processes on the other, is still limited. In this study we developed a novel methodology to directly measure reduction of N2O within the soil profile. Columns (20 cm length, 18.5 cm diameter) were repacked with sandy soil. Extra quartz sand treatments were included in order to separate biological from physical effects. At the bottom of the columns, a silicon tube coil was installed. This silicon tube, which is permeable to N2O, was connected with an outside N2O reservoir. Together, the silicon tube with the reservoir (300ml) simulated a subsoil in which a high concentration of N2O could be imposed. After a pre-incubation phase of 7 days, 5 ml of 10 % N2O was injected every 12 hours in the reservoir. Separate control treatments were established that received a similar amount of N2 gas. Subsequently, N2O emission from the top of the column were monitored during 21 days and the reduction of N2O while diffusing through the soil could be determined. At the end of the experiment, a full N2O budget could be established. We applied this approach in an experiment with soils at three different moisture content - 40, 65 and 90% water-filled pore space (WFPS). Preliminary results indicated that, in the control treatments, higher moisture content resulted in higher N2O emission (0.031, 0.034 and 0.182 mg N2O-N.m-2.d-1 at 40, 65 and 90% WFPS, respectively). However, with sub-soil addition of N2O the opposite trend occurred and N2O emissions decreased with soil moisture (1.895, 0.454 and 0.202 mg N2O-N.m-2.d-1 at 40, 65 and 90% WFPS, respectively). The N2O budget analyses established that this was not due to slower diffusion but to actual consumption of N2O in the profile. Our results show that N2O dynamics in the profile should be taken into account when linking soil characteristics to N2O emissions based on the N2O concentrations in the subsoil. A wet soil can either lead to higher or lower emissions as compared to a drier soil, depending on the situation in the subsoil. Further studies will focus on (i) the effects of available C and N on N2O reduction; (ii) quantifying N2O reduction in an undisturbed profile, and (iii) isotope tracing for a more detailed analyses of N2O reduction dynamics.
Klefoth, R.; Oenema, O.; van Groenigen, J.
Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacterium.
Water treatment technologies are needed that can remove perchlorate from drinking water without introducing organic chemicals that stimulate bacterial growth in water distribution systems. Hydrogen is an ideal energy source for bacterial degradation of perchlorate as it leaves no organic residue and is sparingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium (Dechloromonas sp. strain HZ) that grows with carbon dioxide as sole carbon source. Strain HZ is a Gram-negative, rod-shaped facultative anaerobe that was isolated from a gas-phase anaerobic packed-bed biofilm reactor treating perchlorate-contaminated groundwater. The ability of strain HZ to grow autotrophically with carbon dioxide as the sole carbon source was confirmed by demonstrating that biomass carbon (100.9%) was derived from CO2. Chemolithotrophic growth with hydrogen was coupled with complete reduction of perchlorate (10 mM) to chloride with a maximum doubling time of 8.9 h. Strain HZ also grew using acetate as the electron donor and chlorate, nitrate, or oxygen (but not sulphate) as an electron acceptor. Phylogenetic analysis of the 16S rRNA sequence placed strain HZ in the genus Dechloromonas within the beta subgroup of the Proteobacteria. The study of this and other novel perchlorate-reducing bacteria may lead to new, safe technologies for removing perchlorate and other chemical pollutants from drinking water. PMID:12366751
Zhang, Husen; Bruns, Mary Ann; Logan, Bruce E
Oxidation of Inconel alloy MA754 at low oxidation potential
It has been known for some time that the addition of small oxide particles to an 80 Ni-20 Cr alloy not only increases its elevated-temperature strength, but also markedly improves its resistance to oxidation. The mechanism by which the oxide dispersoid enhances the oxidation resistance was studied. Initial experiments were performed using inconel alloy MA754, which is nominally: 78 Ni, 20 Cr, 0.05 C, 0.3 Al, 0.5 Ti, 1.0 Fe, and 0.6 Y/sub 2/O/sub 3/ (wt %). Small disks (3 mm diam x 0.38 mm thick) were cut from MA754 plate stock and prepared with two different surface conditions. The first was prepared by mechanically polishing one side of a disk through 0.5 ..mu..m diamond on a syntron polisher while the second used an additional sulfuric acid-methanol electropolishing treatment to remove the cold-worked surface layer. Disks having both surface treatments were oxidized in a radiantly heated furnace for 30 s at 1000/sup 0/C. Three different environments were investigated: hydrogen with nominal dew points of 0/sup 0/C, -25/sup 0/C, and -55/sup 0/C. The oxide particles and films were examined in TEM by using extraction replicas (carbon) and by backpolishing to the oxide/metal interface. The particles were analyzed by EDS and SAD. Preliminary results are given.
Braski, D.N.; Goodell, P.D.; Cathcart, J.V.; Kane, R.H.
Identifying prospective antifouling coatings for venturis: Zeta potential measurements of oxides at elevated temperatures
This report describes the results of research to determine the zeta potential of oxides responsible for fouling of heat transfer, venturi, and other flow measurement device surfaces. Fouling deposits formed on these surfaces reduce mass flow rates of water, causing power reductions of as much as 3 to 4%. There is considerable evidence that deposit formation can be prevented by
P. Jayaweera; S. Hettiarachchi; B. G. Pound
Simulation of catalytic oxidation and selective catalytic NOx reduction in lean-exhaust hybrid vehicles
We utilize physically-based models for diesel exhaust catalytic oxidation and urea-based selective catalytic NOx reduction to study their impact on drive cycle performance of hypothetical light-duty diesel powered hybrid vehicles. The models have been implemented as highly flexible SIMULINK block modules that can be used to study multiple engine-aftertreatment system configurations. The parameters of the NOx reduction model have been adjusted to reflect the characteristics of Cu-zeolite catalysts, which are of widespread current interest. We demonstrate application of these models using the Powertrain System Analysis Toolkit (PSAT) software for vehicle simulations, along with a previously published methodology that accounts for emissions and temperature transients in the engine exhaust. Our results illustrate the potential impact of DOC and SCR interactions for lean hybrid electric and plug-in hybrid electric vehicles.
Gao, Zhiming [ORNL; Daw, C Stuart [ORNL; Chakravarthy, Veerathu K [ORNL
Electrochemical investigation of polyhalide ion oxidation-reduction on carbon nanotube electrodes for redox flow batteries
Polyhalide ions (Br-/BrCl2-) are an important redox couple for redox flow batteries. The oxidation-reduction behavior of polyhalide ions on a carbon nanotube (CNT) electrode has been investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The onset oxidation potential of Br-/BrCl2- is negatively shifted by >100 mV, and the redox current peaks are greatly enhanced on a CNT electrode compared with that on the most widely-used graphite electrode. The reaction resistance of the redox couple (Br-/BrCl2-) is decreased on a CNT electrode. The redox reversibility is increased on a CNT electrode even though it still needs further improvement. CNT is a promising electrode material for redox flow batteries.
Shao, Yuyan; Engelhard, Mark H.; Lin, Yuehe
Sulfidation and reduction of zinc titanate and zinc oxide sorbents for injection in gasifier exit ducts
The sulfidation reaction kinetics of fine particles of zinc titanate and zinc oxide with H{sub 2}S were studied in order to test the potential of the sorbent injection hot-gas desulfurization process. Fine sorbent particles with diameter between 0.3 and 60 {mu}m were sulfided with H{sub 2}S and/or reduced with H{sub 2} in a laminar flow reactor over the temperature range of 500-900{degrees}C. Sulfidation/reduction conversion was compared for different particle sizes and sorbents with various porosities and atomic ratios of Zn and Ti. In reduction of ZnO with H{sub 2} and without H{sub 2}S, significant amount of Zn was formed and vaporized, while the presence of H{sub 2}S suppressed elemental Zn formation. This suggests that H{sub 2}S may suppress the surface reduction of ZnO and/or gaseous Zn may react with H{sub 2}S homogeneously and form fine particles of ZnS. Formation and vaporization of elemental Zn from zinc titanate sorbents was slower than from zinc oxide with and without H{sub 2}S.
Ishikawa, K. [Tufts Univ., Medford, MA (United States). Dept. of Chemical Engineering]|[Kawasaki Heavy Industries Ltd., Akashi, Hyogo (Japan). Technical Inst.; Krueger, C.; Flytzani-Stephanopoulos, M. [Tufts Univ., Medford, MA (United States). Dept. of Chemical Engineering; Jl, W.; Higgins, R.J.; Bishop, B.A.; Goldsmith, R.L. [CeraMem Corp., Waltham, MA (United States)
Reversible phenol oxidation-reduction in the structurally well-defined 2-mercaptophenol-?3C proteinå,ć
2-mercaptophenol-?3C serves as a biomimetic model for enzymes that use tyrosine residues in redox catalysis and multistep electron transfer. This model protein was tailored for electrochemical studies of phenol oxidation-reduction with specific emphasis on the redox-driven protonic reactions occurring at the phenol oxygen. This protein contains a covalently modified 2-mercaptophenol-cysteine residue. The radical site and the phenol compound were specifically chosen to bury the phenol OH group inside the protein. A solution nuclear magnetic resonance structural analysis: (i) demonstrates that the synthetic 2-mercaptophenol-?3C model protein behaves structurally as a natural protein, (ii) confirms the design of the radical site, (iii) reveals that the ligated phenol forms an inter helical hydrogen bond to glutamate-13 (phenol oxygen/carboxyl oxygen distance 3.2 ▒ 0.5 ┼), and (iv) suggests a proton-transfer pathway from the buried phenol OH (average solvent accessible surface area of 3 ▒ 5%) via glutamate-13 (average solvent accessible surface area of the carboxyl oxygens 37 ▒ 18%) to the bulk solvent. A square-wave voltammetry analysis of 2-mercaptophenol-?3C further demonstrates: (v) that the phenol oxidation-reduction cycle is reversible, (vi) that formal reduction potentials can be obtained, and (vii) that the phenol-OĢ state is long lived with an estimated lifetime of ? 180 milliseconds. These properties make 2-mercaptophenol-?3C a unique system to characterize phenol-based proton-coupled electron transfer in a low dielectric and structured protein environment.
Tommos, Cecilia; Valentine, Kathleen G.; Martinez-Rivera, Melissa C.; Liang, Li; Moorman, Veronica R.
Microbial reduction of graphene oxide by Escherichia coli: a green chemistry approach.
Graphene and graphene related materials are an important area of research in recent years due to their unique properties. The extensive industrial application of graphene and related compounds has led researchers to devise novel and simple methods for the synthesis of high quality graphene. In this paper, we developed an environment friendly, cost effective, simple method and green approaches for the reduction of graphene oxide (GO) using Escherichia coli biomass. In biological method, we can avoid use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The biomass of E. coli reduces exfoliated GO to graphene at 37░C in an aqueous medium. The E. coli reduced graphene oxide (ERGO) was characterized with UV-visible absorption spectroscopy, particle analyzer, high resolution X-ray diffractometer, scanning electron microscopy and Raman spectroscopy. Besides the reduction potential, the biomass could also play an important role as stabilizing agent, in which synthesized graphene exhibited good stability in water. This method can open up the new avenue for preparing graphene in cost effective and large scale production. Our findings suggest that GO can be reduced by simple eco-friendly method by using E. coli biomass to produce water dispersible graphene. PMID:23107955
Gurunathan, Sangiliyandi; Han, Jae Woong; Eppakayala, Vasuki; Kim, Jin-Hoi
Extraction of copper from an oxidized (lateritic) ore using bacterially catalysed reductive dissolution.
An oxidized lateritic ore which contained 0.8Ā% (by weight) copper was bioleached in pH- and temperature-controlled stirred reactors under acidic reducing conditions using pure and mixed cultures of the acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Sulfur was provided as the electron donor for the bacteria, and ferric iron present in goethite (the major ferric iron mineral present in the ore) acted as electron acceptor. Significantly more copper was leached by bacterially catalysed reductive dissolution of the laterite than in aerobic cultures or in sterile anoxic reactors, with up to 78Ā% of the copper present in the ore being extracted. This included copper that was leached from acid-labile minerals (chiefly copper silicates) and that which was associated with ferric iron minerals in the lateritic ore. In the anaerobic bioreactors, soluble iron in the leach liquors was present as iron (II) and copper as copper (I), but both metals were rapidly oxidized (to iron (III) and copper (II)) when the reactors were aerated. The number of bacteria added to the reactors had a critical role in dictating the rate and yield of copper solubilised from the ore. This work has provided further evidence that reductive bioprocessing, a recently described approach for extracting base metals from oxidized deposits, has the potential to greatly extend the range of metal ores that can be biomined. PMID:24687752
Nancucheo, Ivan; Grail, Barry M; Hilario, Felipe; du Plessis, Chris; Johnson, D Barrie
Direct electron transfer from pseudoazurin to nitrous oxide reductase in catalytic N2O reduction.
Pseudoazurin (PAz), a well-characterized blue copper electron-transfer protein, is shown herein to be capable of mediating electron transfer to the nitrous oxide reductase (N(2)OR) from Achromobacter cycloclastes (Ac). Spectroscopic measurements demonstrate that reduced PAz is efficiently re-oxidized by a catalytic amount of N(2)OR in the presence of N(2)O. Fits of the kinetics resulted in K(M) (N(2)O) and k(cat) values of 19.1▒3.8 ?M and 89.3▒4.2s(-1) respectively. The K(M) (PAz) was 28.8▒6.6 ?M. The electrochemistry of Ac pseudoazurin (AcPAz) in the presence of Ac nitrous oxide reductase (AcN(2)OR) and N(2)O displayed an enhanced cathodic sigmoidal current-potential curve, in excellent agreement with the re-oxidation of reduced AcPAz during the catalytic reduction of N(2)O by AcN(2)OR. Modeling the structure of the AcPAz-AcN(2)OR electron transfer complex indicates that AcPAz binds near Cu(A) in AcN(2)OR, with parameters consistent with the formation of a transient, weakly-bound complex. Multiple, potentially efficient electron-transfer pathways between the blue-copper center in AcPAz and Cu(A) were also identified. Collectively, the data establish that PAz is capable of donating electrons to N(2)OR in N(2)O reduction and is a strong candidate for the physiological electron donor to N(2)OR in Ac. PMID:22910335
Fujita, Koyu; Hirasawa-Fujita, Mika; Brown, Doreen E; Obara, Yuji; Ijima, Fumihiro; Kohzuma, Takamitsu; Dooley, David M
Increased redox-sensitive green fluorescent protein reduction potential in the endoplasmic reticulum following glutathione-mediated dimerization.
As the endoplasmic reticulum (ER) is the compartment where disulfide bridges in secreted and cell surface proteins are formed, the disturbance of its redox state has profound consequences, yet regulation of ER redox potential remains poorly understood. To monitor the ER redox state in live cells, several fluorescence-based sensors have been developed. However, these sensors have yielded results that are inconsistent with each other and with earlier non-fluorescence-based studies. One particular green fluorescent protein (GFP)-based redox sensor, roGFP1-iL, could detect oxidizing changes in the ER despite having a reduction potential significantly lower than that previously reported for the ER. We have confirmed these observations and determined the mechanisms by which roGFP1-iL detects oxidizing changes. First, glutathione mediates the formation of disulfide-bonded roGFP1-iL dimers with an intermediate excitation fluorescence spectrum resembling a mixture of oxidized and reduced monomers. Second, glutathione facilitates dimerization of roGFP1-iL, which shifted the equilibrium from oxidized monomers to dimers, thereby increasing the molecule's reduction potential compared with that of a dithiol redox buffer. We conclude that the glutathione redox couple in the ER significantly increased the reduction potential of roGFP1-iL in vivo by facilitating its dimerization while preserving its ratiometric nature, which makes it suitable for monitoring oxidizing and reducing changes in the ER with a high degree of reliability in real time. The ability of roGFP1-iL to detect both oxidizing and reducing changes in ER and its dynamic response in glutathione redox buffer between approximately -190 and -130 mV in vitro suggests a range of ER redox potentials consistent with those determined by earlier approaches that did not involve fluorescent sensors. PMID:23594148
Sarkar, Deboleena Dipak; Edwards, Sarah K; Mauser, Justin A; Suarez, Allen M; Serowoky, Maxwell A; Hudok, Natalie L; Hudok, Phylicia L; Nu±ez, Martha; Weber, Craig S; Lynch, Ronald M; Miyashita, Osamu; Tsao, Tsu-Shuen
Analysis of long-term bacterial vs. chemical Fe(III) oxide reduction kinetics
NASA Astrophysics Data System (ADS)
Data from studies of dissimilatory bacterial (10 8 cells mL -1 of Shewanella putrefaciens strain CN32, pH 6.8) and ascorbate (10 mM, pH 3.0) reduction of two synthetic Fe(III) oxide coated sands and three natural Fe(III) oxide-bearing subsurface materials (all at ca. 10 mmol Fe(III) L -1) were analyzed in relation to a generalized rate law for mineral dissolution (J t/m 0 = k'(m/m 0) ?, where J t is the rate of dissolution and/or reduction at time t, m 0 is the initial mass of oxide, and m/m 0 is the unreduced or undissolved mineral fraction) in order to evaluate changes in the apparent reactivity of Fe(III) oxides during long-term biological vs. chemical reduction. The natural Fe(III) oxide assemblages demonstrated larger changes in reactivity (higher ? values in the generalized rate law) compared to the synthetic oxides during long-term abiotic reductive dissolution. No such relationship was evident in the bacterial reduction experiments, in which temporal changes in the apparent reactivity of the natural and synthetic oxides were far greater (5-10 fold higher ? values) than in the abiotic reduction experiments. Kinetic and thermodynamic considerations indicated that neither the abundance of electron donor (lactate) nor the accumulation of aqueous end-products of oxide reduction (Fe(II), acetate, dissolved inorganic carbon) are likely to have posed significant limitations on the long-term kinetics of oxide reduction. Rather, accumulation of biogenic Fe(II) on residual oxide surfaces appeared to play a dominant role in governing the long-term kinetics of bacterial crystalline Fe(III) oxide reduction. The experimental findings together with numerical simulations support a conceptual model of bacterial Fe(III) oxide reduction kinetics that differs fundamentally from established models of abiotic Fe(III) oxide reductive dissolution, and indicate that information on Fe(III) oxide reactivity gained through abiotic reductive dissolution techniques cannot be used to predict long-term patterns of reactivity toward enzymatic reduction at circumneutral pH.
Roden, Eric E.
High-temperature reduction of nitrogen oxides in oxy-fuel combustion
The possibility of high-temperature reduction of nitrogen oxides (NOx) in oxy-fuel combustion is investigated. A detailed gas-phase model identifies the effect of temperature, stoichiometric ratio, residence time and composition of the oxidizer on NOx reduction. It is concluded that an efficient high-temperature reduction of NOx is achieved with high-purity oxygen, negligible amount of air ingress, presence of a sub-stoichiometric combustion
Fredrik Normann; Klas Andersson; Bo Leckner; Filip Johnsson
Au\\/iron oxide catalysts: temperature programmed reduction and X-ray diffraction characterization
Gold on iron oxides catalysts have been characterized by temperature programmed reduction (TPR) and X-ray diffraction spectroscopy (XRD). The influence of preparation method, gold loading and pretreatment conditions on the reducibility of iron oxides have been investigated. On the impregnated Au\\/iron oxide catalysts as well as on the support alone the partial reduction of Fe(III) oxy(hydroxides) to Fe3O4 starts in
G Neri; A. M Visco; S Galvagno; A Donato; M Panzalorto
Process for removing nitrogen oxides using ammonia as a reductant and sulfated metallic catalysts
Nitrogen oxides are removed from flue gas evolving from stationary sources and containing the nitrogen oxides through reduction of nitrogen oxides to nitrogen by passing the flue gas over a catalyst of metal compounds containing oxysulfur compounds in the presence of an ammonia gas.
T. Mori; M. Takeuchi; O. Hitomi; S. Uno; J. Imahashi; F. Nakajima
Determination of carbonyl groups in oxidatively modified proteins by reduction with tritiated sodium borohydride
Oxidatively modified proteins have been implicated in a variety of physiologic and pathologic processes. Oxidative modification typically causes inactivation of enzymes and also the introduction of carbonyl groups into amino acid side chains of the protein. We describe a method to quantify oxidatively modified proteins through reduction of these carbonyl groups with tritiated borohydride. The technique was applied to purified,
A. G. Lenz; U. Costabel; S. Shaltiel; R. L. Levine
Reductive dissolution of manganese(III/IV) oxides by substituted phenols
Kinetics of the reaction of manganese(III/IV) oxides with 11 substituted phenols were examined in order to assess the importance of manganese oxides in the abiotic degradation of phenolic pollutants. At pH 4.4, 10/sup -4/ M solutions of substituted phenols reduced and dissolved synthetic manganese oxide particles in the following order: p-methylphenol > p-ethylphenol > m-methylphenol > p-chlorophenol > phenol > m-chlorophenol > p-hydroxybenzoate > o-hydroxybenzoate > 4'-hydroxyacetophenone > p-nitrophenol. Rates of reductive dissolution generally decrease as the Hammett constants of ring substituents become more positive, reflecting trends in the basicity, nucleophilicity, and half-wave potential of substituted phenols. Evidence indicates that the fraction of oxide surface sites occupied by substituted phenols is quite low. The apparent reaction order with respect to (H/sup +/) is not a constant but varies between 0.45 and 1.30 as the pH range, phenol concentration, and phenol structure are varied. A mechanism for the surface chemical reaction has been postulated to account for these effects.
Stone, A.T.
Silicon Surface Potential Modified by Titanium Oxide.
National Technical Information Service (NTIS)
Chemically vapor deposited (CVD) titanium oxide offers some utility in insulated-gate devices. Films 2000A thick show breakdown voltages as large as 10 volts. The capacitance-voltage curves have very low values of off-set from zero bias because of the hig...
D. R. Harbison H. L. Taylor
Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction
The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements.
Method For Selective Catalytic Reduction Of Nitrogen Oxides
A method for catalytically reducing nitrogen oxide compounds (NO.sub.x, defined as nitric oxide, NO, +nitrogen dioxide, NO.sub.2) in a gas by a material comprising a base metal consisting essentially of CuO and Mn, and oxides of Mn, on an activated metal hydrous metal oxide support, such as HMO:Si. A promoter, such as tungsten oxide or molybdenum oxide, can be added and has been shown to increase conversion efficiency. This method provides good conversion of NO.sub.x to N.sub.2, good selectivity, good durability, resistance to SO.sub.2 aging and low toxicity compared with methods utilizing vanadia-based catalysts.
Mowery-Evans, Deborah L. (Broomfield, CO); Gardner, Timothy J. (Albuquerque, NM); McLaughlin, Linda I. (Albuquerque, NM)
The role of volatiles in the reduction of iron oxides
With iron ore reduction processes using coal-ore pellets or mixtures, it is possible that volatiles from the coals can contribute to the overall reduction. By identifying the possible reducing species in the volatiles as H2\\/CO and simulating these constituents, the rates for H2 and CO were investigated in the temperature and reduction range of interest where hydrogen was the major
Il Sohn
One of the clean product research projects being funded by the EPA's Pollution Prevention Research Branch in Cincinnati, Ohio, involves evaluating the possibility of dramatic reductions in hazardous waste and toxic chemical exposure associated with commercial products. y identify...
Reduction of Soluble Iron and Reductive Dissolution of Ferric Iron-Containing Minerals by Moderately Thermophilic Iron-Oxidizing Bacteria
Five moderately thermophilic iron-oxidizing bacteria, including representative strains of the three classified species (Sulfobacillus thermosulfidooxidans, Sulfobacillus acidophilus, and Acidimicrobium ferrooxidans), were shown to be capable of reducing ferric iron to ferrous iron when they were grown under oxygen limitation conditions. Iron reduction was most readily observed when the isolates were grown as mixotrophs or hetero- trophs with glycerol as an
Effect of preadsorbed sulfur on the electrochemical reduction of nitric oxide
The effect of adsorbed sulfur on platinum black/Teflon gas diffusion electrodes has been studied. The controlled deposition and characterization of intermediate coverages of sulfur (fractional sulfur coverages, {Theta}, between 0 and 1.0, based on the total number of Pt surface sites) was first studied, followed by an investigation of the effects of this preadsorbed sulfur on the electrogenerative (i.e. galvanic) reduction of pure and dilute (3%) NO feeds. These effects are discussed in terms of possible applications for electrogenerative NO reduction, especially hydroxylamine production and flue gas scrubbing applications. Sulfur was deposited through electrochemical reduction of sulfur dioxide which had bene previously adsorbed from SO{sub 2}-containing aqueous sulfuric acid solutions. The sulfur layers deposited in this manner were electrochemically characterized using linear sweep and cyclic voltammetry. Sulfur/hydrogen coadsorption coverage plots constructed from coulometric measurements were studied and yielded evidence that a sulfur bilayer is formed on the electrode. In the presence of adsorbed sulfur (0.2 < {Theta} < 1.0) the current generated by the nitric oxide-hydrogen electrogenerative cell was diminished. This effect was more pronounced with pure NO feeds. The decreased cell current involved not only diminished NO conversion, but also a change in product distribution brought about by adsorbed sulfur. At low sulfur coverages and low cell potentials ammonia is the predominant product, but at higher sulfur coverages selectivity shifts to favor hydroxylamine production. Nitrous oxide is formed only at high cell potentials at all sulfur coverages, and nitrogen formation is allowed at lower sulfur coverages but inhibited at higher coverages.
Foral, M.J.
Monitoring of the Oxidation-Reduction State of Brain Structures in Freely Moving Rats during Sleep¢Waking Cycles by Potentiometric Recording
Freely mobile mongrel male rats weighing 300¢350 g were used for studies of changes in the oxidative-reductive (redox) state of brain tissue during cycles of waking, slow-wave sleep, and paradoxical sleep, by recording the potential of the oxidative-reductive state of brain tissue with platinum electrodes implanted into the cerebral cortex ad hippocampus. Electromyograms were also recorded from the cervical muscles,
T. B. Shvets-Tķnķta-Gurii; G. I. Troshin; M. R. Novikova; N. M. Khonicheva; O. A. Shostak; I. V. Borovskaya
Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol
Graphene oxide platelets synthesized by using a chemical exfoliation method were dispersed in a suspension of ZnO nanoparticles to fabricate ZnO\\/graphene oxide composite. Formation of graphene oxide platelets (with average thickness of ?0.8nm) hybridized by ZnO nanoparticles (with average diameter of ?20nm) was investigated. The 2D band in Raman spectrum confirmed formation of single-layer graphene oxides. The gradual photocatalytic reduction
O. Akhavan
Potential of gold nanoparticles for oxidation in fine chemical synthesis.
In recent years supported gold nanoparticles have emerged as efficient catalysts with considerable synthetic potential for liquid-phase oxidation reactions based on molecular oxygen as oxidant. Here we critically review the most attractive applications related to the selective oxidation of functional groups containing O, N, or Si heteroatoms. The reactions include the oxidation of alcohols, aldehydes, and organosilanes; the diverse transformations of amines; benzylic oxidations; and some one-pot multistep reactions starting with alcohol or amine oxidation. In complex liquid-phase transformations relying on bifunctional catalysis, appropriate choice of the support is frequently more important than the size of the gold particles. In some oxidation reactions gold nanoparticles outperform the traditional platinum-group metal catalysts, but the latest results indicate the superiority of bimetallic particles containing gold and platinum, palladium, or rhodium. The environmentally benign nature of the transformations is discussed. PMID:22691089
Mallat, Tamas; Baiker, Alfons
Particulate Matter Oxidative Potential from Waste Transfer Station Activity
Background Adverse cardiorespiratory health is associated with exposure to ambient particulate matter (PM). The highest PM concentrations in London occur in proximity to waste transfer stations (WTS), sites that experience high numbers of dust-laden, heavy-duty diesel vehicles transporting industrial and household waste. Objective Our goal was to quantify the contribution of WTS emissions to ambient PM mass concentrations and oxidative potential. Methods PM with a diameter < 10 ?m (PM10) samples were collected daily close to a WTS. PM10 mass concentrations measurements were source apportioned to estimate local versus background sources. PM oxidative potential was assessed using the extent of antioxidant depletion from a respiratory tract lining fluid model. Total trace metal and bioavailable iron concentrations were measured to determine their contribution to PM oxidative potential. Results Elevated diurnal PM10 mass concentrations were observed on all days with WTS activity (Monday¢Saturday). Variable PM oxidative potential, bioavailable iron, and total metal concentrations were observed on these days. The contribution of WTS emissions to PM at the sampling site, as predicted by microscale wind direction measurements, was correlated with ascorbate (r = 0.80; p = 0.030) and glutathione depletion (r = 0.76; p = 0.046). Increased PM oxidative potential was associated with aluminum, lead, and iron content. Conclusions PM arising from WTS activity has elevated trace metal concentrations and, as a consequence, increased oxidative potential. PM released by WTS activity should be considered a potential health risk to the nearby residential community.
Godri, Krystal J.; Duggan, Sean T.; Fuller, Gary W.; Baker, Tim; Green, David; Kelly, Frank J.; Mudway, Ian S.
New insights into the structure and reduction of graphite oxide
Graphite oxide is one of the main precursors of graphene-based materials, which are highly promising for various technological applications because of their unusual electronic properties. Although epoxy and hydroxyl groups are widely accepted as its main functionalities, the complete structure of graphite oxide has remained elusive. By interpreting spectroscopic data in the context of the major functional groups believed to
Wei Gao; Lawrence B. Alemany; Lijie Ci; Pulickel M. Ajayan
In-situ chemical oxidation (ISCO) is a rapidly developing technology used at hazardous waste sites where oxidants and complimentary reagents are injected into the subsurface to transform organic contaminants into less toxic byproducts. This technology is being used at new sites ...
Oxidized zirconium: a potentially longer lasting hip implant
Because younger, more active patients are receiving total hip replacements, it is necessary to develop materials, which would increase the life span of the implants and challenge their wear potential under adverse conditions. Oxidized zirconium (OxZr) is a metal with the surface transformed to ceramic by oxidation that offers low fracture risk and excellent abrasion resistance. This study compared wear
V. Good; K. Widding; G. Hunter; D. Heuer
High-quality reduced graphene oxide by a dual-function chemical reduction and healing process.
A new chemical dual-functional reducing agent, thiophene, was used to produce high-quality reduced graphene oxide (rGO) as a result of a chemical reduction of graphene oxide (GO) and the healing of rGO. Thiophene reduced GO by donation of electrons with acceptance of oxygen while it was converted into an intermediate oxidised polymerised thiophene that was eventually transformed into polyhydrocarbon by loss of sulphur atoms. Surprisingly, the polyhydrocarbon template helped to produce good-quality rGOC (chemically reduced) and high-quality rGOCT after thermal treatment. The resulting rGOCT nanosheets did not contain any nitrogen or sulphur impurities, were highly deoxygenated and showed a healing effect. Thus the electrical properties of the as-prepared rGOCT were superior to those of conventional hydrazine-produced rGO that require harsh reaction conditions. Our novel dual reduction and healing method with thiophene could potentially save energy and facilitate the commercial mass production of high-quality graphene. PMID:23722643
Some, Surajit; Kim, Youngmin; Yoon, Yeoheung; Yoo, HeeJoun; Lee, Saemi; Park, Younghun; Lee, Hyoyoung
A novel bimediator amperometric sensor for electrocatalytic oxidation of gallic acid and reduction of hydrogen peroxide.
A novel bimediator amperometric sensor is fabricated for the first time by surface modification of graphite electrode with thionine (TH) and nickel hexacyanoferrate (NiHCF). The electrochemical behavior of the TH/NiHCF bimediator modified electrode was characterized by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The TH/NiHCF bimediator modified electrode exhibited a pair of distinct redox peaks for NiHCF and TH with formal potentials of 0.33V and -0.27V vs. SCE at a scan rate of 50mV s(-1) in 0.1M NaNO3 and 0.1M NH4NO3 respectively. The electrocatalytic activity of the bimediator modified electrode towards oxidation of gallic acid with NiHCF and reduction of hydrogen peroxide with TH was evaluated and it was observed that the modified electrode showed an electrocatalytic activity towards the oxidation of gallic acid in the concentration range of 4.99ū10(-6)-1.20ū10(-3)M with a detection limit of 1.66ū10(-6)M (S/N=3) and reduction of H2O2 in the concentration range of 1.67ū10(-6)-1.11ū10(-3)M with a detection limit of 5.57ū10(-7)M (S/N=3). The bimediator modified electrode was found to exhibit good stability and reproducibility. PMID:24845813
Sangeetha, N S; Narayanan, S Sriman
Purification and characterization of a nitrous oxide reductase from Thiosphaera pantotropha. Implications for the mechanism of aerobic nitrous oxide reduction.
The aerobic denitrifer Thiosphaera pantotropha is able to reduce simultaneously nitrous oxide and oxygen even after anaerobic growth [Bell, L. C. & Ferguson, S. J. (1991) Biochem J. 273, 423-427]. A nitrous oxide reductase was purified from anaerobically grown T. pantotropha cells. It is argued, on the basis of inhibitor sensitivities and from immunological evidence, that the same nitrous oxide reductase is involved in nitrous oxide reduction in aerobically grown cells. The purified nitrous oxide reductase was shown to have molecular properties very similar to nitrous oxide reductases previously isolated from anaerobically denitrifying bacteria. The visible absorption spectra of the T. pantotropha enzyme resemble those of the oxygen-affected form of nitrous oxide reductases from other organisms. It is thus concluded that the T. pantotropha nitrous oxide reductase is not peculiarly resistant to the structural changes caused by oxygen. The activity of the purified T. pantotropha nitrous oxide reductase was reconstituted in vitro using horse heart cytochrome c, T. pantotropha cytochrome c551 and T. pantotropha pseudoazurin as electron donors. It is suggested on this basis that either of the T. pantotropha electron-carrier proteins are possible physiological electron donors to T. pantotropha nitrous oxide reductase. Oxygen was shown not to inhibit the in-vitro reduction of nitrous oxide with horse heart ferrocytochrome c as electron donor to the reductase. PMID:8383047
Berks, B C; Baratta, D; Richardson, J; Ferguson, S J
Potential Production of Photochemical Oxidants from Coal Gasification Facilities.
National Technical Information Service (NTIS)
Coal gasification facilities are potential sources of both reactive hydrocarbons and nitrogen oxides. It is thus conceivable that photochemical reactions may produce ozone in the plumes of these facilities. This possibility was examined by a three-step pr...
M. D. Williams
Unified interatomic potential and energy barrier distributions for amorphous oxides
NASA Astrophysics Data System (ADS)
Amorphous tantala, titania, and hafnia are important oxides for biomedical implants, optics, and gate insulators. Understanding the effects of oxide doping is crucial to optimize performance in these applications. However, no molecular dynamics potentials have been created to date that combine these and other oxides that would allow computational analyses of doping-dependent structural and mechanical properties. We report a novel set of computationally efficient, two-body potentials modeling van der Waals and covalent interactions that reproduce the structural and elastic properties of both pure and doped amorphous oxides. In addition, we demonstrate that the potential accurately produces energy barrier distributions for pure and doped samples. The distributions can be directly compared to experiment and used to calculate physical quantities such as internal friction to understand how doping affects material properties. Future analyses using these potentials will be of great value to determine optimal doping concentrations and material combinations for myriad material science applications.
Trinastic, J. P.; Hamdan, R.; Wu, Y.; Zhang, L.; Cheng, Hai-Ping
Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor
NASA Technical Reports Server (NTRS)
Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.
Myers, Charles R.; Nealson, Kenneth H.
Quantitative Structure-Reduction Potential Relationship Study ofĀSome Quinones in Five Solvents
The reduction half-wave potentials of nine quinones in five solvents are predicted by a statistically validated quantitative\\u000a structure¢reduction potential relationship modeling approach. The multiple linear regressions obtained were constructed based\\u000a on a variety of electronic molecular descriptors calculated by the MOPAC software along with some solvent characteristics\\u000a as independent variables. Reduction half-wave potentials of quinones were considered as dependent variables.
Mohammad Reza Hadjmohammadi; Kamyar Kamel; Pourya Biparva
Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals
Iron-reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so play an important role in the geochemical cycling of iron. This study was undertaken to investigate mineral transformations associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals. A fluid sample from the 2450 m depth of the Chinese Continental Scientific Drilling project was collected, and Fe3+-reducing and Fe2+-oxidizing microorganisms were enriched. The enrichment cultures displayed reduction of Fe3+ in nontronite and ferric citrate, and oxidation of Fe2+ in vivianite, siderite, and monosulfide (FeS). Additional experiments verified that the iron reduction and oxidation was biological. Oxidation of FeS resulted in the formation of goethite, lepidocrocite, and ferrihydrite as products. Although our molecular microbiological analyses detected Thermoan-aerobacter ethanolicus as a predominant organism in the enrichment culture, Fe3+ reduction and Fe2+ oxidation may be accomplished by a consortia of organisms. Our results have important environmental and ecological implications for iron redox cycling in solid minerals in natural environments, where iron mineral transformations may be related to the mobility and solubility of inorganic and organic contaminants.
Zhang, G.; Dong, H.; Jiang, H.; Kukkadapu, R. K.; Kim, J.; Eberl, D.; Xu, Z.
Oxygen Reduction Kinetics Enhancement on a 2 Heterostructured Oxide Surface for Solid Oxide Fuel Cells
Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of {approx}85 nm thick La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC{sub 113}) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced ({approx} 3-4 orders of magnitude above bulk LSC{sub 113}) by surface decorations of (La{sub 0.5}Sr{sub 0.5}){sub 2}CoO{sub 4{+-}{delta}} (LSC{sub 214}) with coverage in the range from {approx}0.1 to {approx}15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC{sub 113}/LSC{sub 214} regions, which were shown to be atomically sharp.
Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Mutoro, Eva [ORNL; Ahn, Sung Jin [Massachusetts Institute of Technology (MIT); Jose la O', Gerardo [Massachusetts Institute of Technology (MIT); Leonard, Donovan N [ORNL; Borisevich, Albina Y [ORNL; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)
Technetium reduction in sediments of a shallow aquifer exhibiting dissimilatory iron reduction potential
Pertechnetate ion [Tc(VII)O4?] reduction rate was determined in core samples from a shallow sandy aquifer located on the US Atlantic Coastal Plain. The aquifer is generally low in dissolved O2 (<1 mgL?1) and composed of weakly indurated late Pleistocene sediments differing markedly in physicochemical properties. Thermodynamic calculations, X-ray absorption spectroscopy and statistical analyses were used to establish the dominant reduction
Raymond E. Wildung; Shu-Mei W. Li; Christopher J. Murray; Kenneth M. Krupka; YuLong Xie; Nancy J. Hess; Eric E. Roden
Potential for Mercury Reduction by Microbes in the High Arctic
The contamination of polar regions due to the global distribution of anthropogenic pollutants is of great concern because it leads to the bioaccumulation of toxic substances, methylmercury among them, in Arctic food chains. Here we present the first evidence that microbes in the high Arctic possess and express diverse merA genes, which specify the reduction of ionic mercury (Hg(II)) to
Alexandre J. Poulain; Sinead M. N§ ┤ Chadhain; Parisa A. Ariya; Marc Amyot; Edenise Garcia; Peter G. C. Campbell; Gerben J. Zylstra; Tamar Barkay
Ethylene Oxide - Styrene Block Copolymer Surfaces for Turbulent Drag Reduction.
National Technical Information Service (NTIS)
A drag reduction test facility was constructed to evaluate the effects of hydrophilic coatings on the turbulent friction factor for nylon tubes. A cobalt 60 gamma irradiation cell was reactivated. Procedures were developed to use this source to graft copo...
C. C. Gryte
The study was undertaken to identify principal oxidizing and reducing chemical species in groundwater with the goal of determining the utility of platinum electrode (Eh) measurements to characterize subsurface redox conditions. Serial measurements of Eh and groundwater analyses w...
The study was undertaken to identify principal oxidizing and reducing chemical species in groundwater with the goal of determining the utility of platinum electrode (Eh) measurements to characterize subsurface redox conditions. erial measurements of Eh and groundwater analyses we...
Fluidized reduction of oxides on fine metal powders without sintering
NASA Technical Reports Server (NTRS)
In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts.
Hayashi, T.
Developing Investigation Skills in an Introductory Multistep Synthesis Using Fluorene Oxidation and Reduction
ERIC Educational Resources Information Center
A two-step oxidation-reduction sequence that incorporates several important aspects of synthesis into introductory organic chemistry laboratories is described. This experiment is an excellent vehicle for introducing elements of discovery and intermediate yield improvement strategies.
Stocksdale, Mark G; Pointer, Roy D; Benson, Barret W.; Fletcher, Steven E. S.; Henry, Ian; Ogren, Paul J.; Berg, Michael A. G.
Redox conditions are among the most important parameters for controlling contaminant transport and fate in ground-water systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting solubility, rea...
Sequential Oxidative and Reductive Bleaching in a Multicomponent Single Liquor System.
National Technical Information Service (NTIS)
The present invention relates to processes for oxidative (using hydrogen peroxide) and reductive bleaching of fibers, and fibers bleached by the aforementioned processes. Both of the bleaching processes of the present invention may be utilized to great ad...
W. N. Marmer
Photochemical and Thermal Reduction of Cerium (IV) Carboxylates. Formation and Oxidation of Alkyl Radicals.
National Technical Information Service (NTIS)
The photochemical and thermal reduction of Ce(IV) carboxylates to Ce(III) proceed by decarboxylation and liberation of alkyl radicals. Alkanes are subsequently formed by hydrogen transfer, and alkenes, together with esters, result from oxidation of alkyl ...
R. A. Sheldon J. K. Kochi
Process for nitrogen oxides reduction to lowest achievable level
A process is described for reducing nitrogen oxides in the effluent from the combustion of a carbonaceous fuel which is at a temperature of at least about 1,900 C using a nitrogenous treatment agent comprising urea, ammonia, cyanuric acid, ammonium carbonate, mixtures of ammonia and ammonium bicarbonate, one or more of the hydrolysis products of urea or mixtures or complexes thereof, compounds which produce ammonia as a byproduct, ammonium formate, ammonium oxalate, hexamethylenetetramine, ammonium salts of organic acids, 5- or 6-membered heterocyclic hydrocarbons having at least one cyclic nitrogen, hydroxy amino hydrocarbons, amino acids, proteins, monoethanolamine, or mixtures thereof, the process comprising: (a) determining the lowest achievable nitrogen oxides concentration for said treatment agent at the conditions existing in the effluent at the point of introduction; (b) determining the baseline nitrogen oxides concentration at the point of introduction; (c) determining the amount by which the baseline nitrogen oxides concentration exceeds the lowest achievable nitrogen oxides concentration; and (d) introducing said treatment agent into the effluent under conditions effective to reduce the effluent nitrogen oxides concentration when said determined amount is a positive number.
Hofmann, J.E.; Sun, W.H.
Crystallographic studies of V44 mutants of Clostridium pasteurianum rubredoxin: Effects of side-chain size on reduction potential
Understanding the structural origins of differences in reduction potentials is crucial to understanding how various electron transfer proteins modulate their reduction potentials and how they evolve for diverse functional roles. Here, the high-resolution structures of several Clostridium pasteurianum rubredoxin (Cp Rd) variants with changes in the vicinity of the redox site are reported in order to increase this understanding. Our crystal structures of [V44L] (at 1.8 {angstrom} resolution), [V44A] (1.6 {angstrom}), [V44G] (2.0 {angstrom}) and [V44A, G45P] (1.5 {angstrom}) Rd (all in their oxidized states) show that there is a gradual decrease in the distance between Fe and the amide nitrogen of residue 44 upon reduction in the size of the side chain of residue 44; the decrease occurs from leucine to valine, alanine or glycine and is accompanied by a gradual increase in their reduction potentials. Mutation of Cp Rd at position 44 also changes the hydrogen-bond distance between the amide nitrogen of residue 44 and the sulfur of cysteine 42 in a size-dependent manner. Our results suggest that residue 44 is an important determinant of Rd reduction potential in a manner dictated by side-chain size. Along with the electric dipole moment of the 43-44 peptide bond and the 44-42 NHS type hydrogen bond, a modulation mechanism for solvent accessibility through residue 41 might regulate the redox reaction of the Rds. Proteins 2004.
Park, Il Yeong; Eidsness, Marly K.; Lin, I-Jin; Gebel, Erika B.; Youn, Buhyun; Harley, Jill L.; Machonkin, Timothy E.; Frederick, Ronnie O.; Markley, John L.; Smith, Eugene T.; Ichiye, Toshiko; Kang, ChulHee (Wilkes); (Georgetown); (UW); (WSUP); (Georgia)
The kinetic study of temperature-programmed reduction of nickel oxide in hydrogen atmosphere
The powder samples of nickel oxide were synthesized by sol¢gel procedure. The non-isothermal reduction of nickel oxide using hydrogen was investigated by temperature-programmed reduction (TPR) at four different heating rates (2.5, 5, 10 and 20?Cmin-1). Reaction kinetics parameters (Ea, lnA) were determined using a few methods: Stationary point (SP), Kissinger, Friedman, Flynn¢Wall¢Ozawa and Kissinger¢Akahira¢Sunose methods. The Mßlek's kinetic procedure was
B. Jankovi?; B. Adna?evi?; S. Mentus
Extracting indium and preparing ferric oxide for soft magnetic ferrite materials from zinc calcine reduction lixivium
A hydrometallurgical process for indium extraction and ferric oxide powder preparation for soft magnetic ferrite material\\u000a was developed. Using reduction lixivium from high-acid reductive leaching of zinc oxide calcine as raw solution, copper and\\u000a indium were firstly recovered by iron powder cementation and neutralization. The recovery ratios of Cu and In are 99% and\\u000a 95%, respectively. Some harmful impurities that
Jing He; Mo-tang Tang; Cun Zhou; Sheng-nan Wu; Yong-ming Chen; Tao Wang; Ling Huang
Ceruloplasmin copper induces oxidant damage by a redox process utilizing cell-derived superoxide as reductant
NASA Technical Reports Server (NTRS)
Oxidative damage by transition metals bound to proteins may be an important pathogenic mechanism. Ceruloplasmin (Cp) is a Cu-containing plasma protein thought to be involved in oxidative modification of lipoproteins. We have previously shown that Cp increased cell-mediated low-density lipoprotein (LDL) oxidation by a process requiring cell-derived superoxide, but the underlying chemical mechanism(s) is (are) unknown. We now show that superoxide reduction of Cp Cu is a critical reaction in cellular LDL oxidation. By bathocuproine disulfonate (BCS) binding and by superoxide utilization, we showed that exogenous superoxide reduces a single Cp Cu atom, the same Cu required for LDL oxidation. The Cu atom remained bound to Cp during the redox cycle. Three avenues of evidence showed that vascular cells reduce Cp Cu by a superoxide-dependent process. The 2-fold higher rate of Cp Cu reduction by smooth muscle cells (SMC) compared to endothelial cells (EC) was consistent with their relative rates of superoxide release. Furthermore, Cp Cu reduction by cells was blocked by Cu,Zn superoxide dismutase (SOD1). Finally, the level of superoxide produced by EC and SMC was sufficient to cause the amount of Cu reduction observed. An important role of Cp Cu reduction in LDL oxidation was suggested by results showing that SOD1 inhibited Cp Cu reduction and LDL oxidation by SMC with equal potency, while tumor necrosis factor-alpha stimulated both processes. In summary, these results show that superoxide is a critical cellular reductant of divalent transition metals involved in oxidation, and that protein-bound Cu is a substrate for this reaction. The role of these mechanisms in oxidative processes in vivo has yet to be defined.
Mukhopadhyay, C. K.; Fox, P. L.
Sulfur-reduction potential of the coals of Ohio
This report presents the results of a washability study of 148 raw coal channel samples with an emphasis on sulfur reduction. These raw coals contained on the average 13.1 percent ash, 2.47 percent pyritic sulfur, 3.86 percent total sulfur, 12,585 Btu\\/lb, and 6.2 pounds of SOŌ emissions per million Btu, on a moisture-free basis. The complete washability data and ultimate-proximate
J. T. Wizzard; J. A. Cavallaro; A. W. Deurbrouck
Synthesis of free standing conducting graphene paper by thermal reduction of graphene oxide paper
NASA Astrophysics Data System (ADS)
Graphene is one atom thick two dimensional material with unusual mechanical, electrical, thermal and optical properties. Graphene, on larger scale is produced through reduction of graphene oxide which in turn is synthesized by chemical oxidation of graphite. Generally large area graphene oxide paper can be easily fabricated by solution filtration process, spin casting method and Langmuir-Blodgett assembly. In present study graphene oxide was synthesized by modified Hummers method. Free standing graphene oxide paper (GOP) was developed by simple drying of graphene oxide suspended in water followed by reduction by thermal treatment to synthesize free standing conducting graphene paper (Thermally Reduced Graphene Paper, TRGP). Thermal reduction was carried out for 30, 60, 90 and 120min and samples referred as TRGP_30, TRGP_60, TRGP_90 and TRGP_120 respectively. XRD results show decrease in inter layer spacing (d002) from 0.87 nm to ~0.35 nm after reduction of GO paper. This shows gradual removal of oxygen functionalities and adsorbed water during reduction. Meanwhile the size of sp2 domains of graphene also decrease as studied by Raman spectroscopy. SEM results also show change in morphology of thermally reduced graphene paper. The electrical conductivity of reduced graphene paper increases from 2.8 ū 10-2 S/m for as such graphene oxide paper to 1.3 ū 102 S/m for graphene paper.
Manocha, L. M.; Gajera, H. L.; Manocha, S.
Nitric oxide reductions in a multi-zone reheat furnace
A reduced excess air combustion control technique was developed for an existing 3-zone reheat furnace that would reduce NO[sub x] emissions to conform with regulatory air quality requirements. The results indicate that reduced excess air combustion controls can be utilized for obtaining NO[sub x] reductions in a multi-zone steel reheat furnace. This study provides support for considering this control strategy as a possible first step toward reheat furnace NO[sub x] control. For new furnace installations, low NO[sub x] burners combined with other technologies provide the greatest benefit. However, for existing furnaces, a control system retrofit may be the most cost-effective short range option. Regarding actual NO[sub x] reduction costs after installation and testing were complete, this control methodology cost approximately $8,500/ton NO[sub x] reduction.
Harder, R.F. (George Fox Coll., Newberg, OR (United States))
Determination of carbon by the oxidation reduction reaction with chromium
NASA Technical Reports Server (NTRS)
Free carbon was determined in silicon and boron carbides in ash, oxides, and other materials by oxidation to carbon dioxide with a mixture of K2Cr2O7 + H2SO4. The determination was made from the amount of CR(6) consumed, by adding excess Mohr's salt and titrating with a standard solution of KMnO4. The amount of Cr(6) self reduced was determined in a blank test. Optimum oxidation and conditions were achieved when the volumes of 5% k2Cr2Oz and H2SO4 were equal. The mixture was boiled for 1-2 hours using a reflex condenser. The volume should not be reduced, in order to avoid an increase in the sulfuric acid concentration. The relative error was 4-7% for 0.005-0.04 g C and less than or equal to 3.5% for 0.1 g C.
Mashkovich, L.; Kuteynikov, A. F.
Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles
The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidation and reduction reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 kelvin. A Wulff analysis of high-resolution in situ
P. Nolte; A. Stierle; N. Y. Jin-Phillipp; N. Kasper; T. U. Schulli; H. Dosch
Oxidation-reduction reactions, catalyzed by iron and manganese oxides, influence the subsurface mobility of a variety of toxic metals. In the work reported here, we develop a new model for the transport of the redox-sensitive CoEDTA complex, and we test the model against publishe...
Voltammetry of a flavocytochrome c(3): the lowest potential heme modulates fumarate reduction rates.
Iron-induced flavocytochrome c(3), Ifc(3), from Shewanella frigidimarina NCIMB400, derivatized with a 2-pyridyl disulfide label, self-assembles on gold electrodes as a functional array whose fumarate reductase activity as viewed by direct electrochemistry is indistinguishable from that of Ifc(3) adsorbed on gold or graphite electrodes. The enhanced stability of the labeled protein's array permits analysis at a rotating electrode and limiting catalytic currents fit well to a Michaelis-Menten description of enzyme kinetics with K(M) = 56 +/- 20 microM, pH 7.5, comparable to that obtained in solution assays. At fumarate concentrations above 145 microM cyclic voltammetry shows the catalytic response to contain two features. The position and width of the lower potential component centered on -290 mV and corresponding to a one-electron wave implicates the oxidation state of the lowest potential heme of Ifc(3) as a defining feature in the mechanism of fumarate reduction at high turnover rates. We propose the operation of dual pathways for electron transfer to the active site of Ifc(3) with the lowest potential heme acting as an electron relay on one of these pathways.
Butt, J N; Thornton, J; Richardson, D J; Dobbin, P S
Reductive Pentose Phosphate Cycle and Oxidative Carbohydrate Metabolic Activities in Pea Chloroplast Stroma Extracts 1
Oxidative and reductive carbohydrate metabolism was studied in reaction mixtures based on chlorophyll-free stromal extracts from chloroplasts of Pisum sativum. A new assay system for the reductive pentose phosphate cycle was characterized. When provided with ATP, an enzymic ATP-regenerating system and reduced pyridine nucleotide, substantial rates of CO2 fixation and pyridine nucleotide oxidation were observed following the addition of millimolar concentrations of reductive pentose phosphate cycle intermediates. The reduced pyridine nucleotide requirement could be met either by NADPH, or by NADH plus the added enzymes NAD+-glyceraldehyde phosphate dehydrogenase and phosphoglycerate kinase. When the assay system was primed with small amounts of reductive pentose phosphate cycle intermediates, lower rates of pyridine nucleotide oxidation were observed, but turnover of the complete cycle was demonstrated. Autocatalytic effects were not evident. The optimum pH and Mg concentrations for cycle turnover were similar to those believed to exist in the stroma of intact chloroplasts in the light. Oxidative carbohydrate metabolism was studied by supplying oxidized pyridine nucleotide and measuring its rate of reduction in the presence of sugar phosphates. Glycolytic activity, estimated as the rate of fructose-6-phosphate entry to the phosphofructokinase reaction was 2.7 micromoles per milligram chlorophyll per hour when fructose-6-phosphate was provided as substrate. Evidence based on glucose-6-phosphate and ribose-5-phosphate-dependent NADP+ reduction showed that the oxidative pentose phosphate cycle was also active. Apparent oxidative pentose phosphate cycle turnover in the presence of ribose-5-phosphate, estimated as the rate of glucose-6-phosphate entry to the glucose-6-phosphate dehydrogenase reaction, was 1.7 micromoles per milligram chlorophyll per hour. It was concluded that under the defined conditions, reductive pentose phosphate cycle activity could be measured without interference from oxidative carbohydrate metabolism in this experimental system.
Furbank, Robert T.; Lilley, Ross McC.
Observations of Oxygen Ion Behavior in the Lithium-Based Electrolytic Reduction of Uranium Oxide
Parametric studies were performed on a lithium-based electrolytic reduction process at bench-scale to investigate the behavior of oxygen ions in the reduction of uranium oxide for various electrochemical cell configurations. Specifically, a series of eight electrolytic reduction runs was performed in a common salt bath of LiCl 1 wt% Li2O. The variable parameters included fuel basket containment material (i.e., stainless
Steven D. Herrmann; Shelly X. Li; Brenda E. Serrano-Rodriguez
A Combined Chemical Reduction and Biological Oxidation Process for the Treatment of Textile Wastewater
We report on the effectiveness of a combined reduction-biological treatment system for the decolourization of non-biodegradable textile dyeing wastewater. In this treatment system a bisulfite-catalyzed sodium borohydride reduction followed by activated sludge technique was used in order to remove the colours at ambient temperature and pressure. This experimental investigation consist- ed of two major parts: reduction treatment and biological oxidation.
Sodium citrate: A universal reducing agent for reduction \\/ decoration of graphene oxide with au nanoparticles
A facile method is proposed for the synthesis of reduced graphene oxide nanosheets (RGONS) and Au nanoparticle-reduced graphene\\u000a oxide nanosheet (Au-RGONS) hybrid materials, using graphene oxide (GO) as precursor and sodium citrate as reductant and stabilizer.\\u000a The resulting RGONS and Au-RGONS hybrid materials were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy,\\u000a Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy,
Zhe Zhang; Huihui Chen; Chunyan Xing; Mingyi Guo; Fugang Xu; Xiaodan Wang; Hermann J. Gruber; Bailin Zhang; Jilin Tang
Measurement of the Md3+/Md2+ reduction potential studied with flow electrolytic chromatography.
The reduction behavior of mendelevium (Md) was studied using a flow electrolytic chromatography apparatus. By application of the appropriate potentials on the chromatography column, the more stable Md(3+) is reduced to Md(2+). The reduction potential of the Md(3+) + e(-) ? Md(2+) couple was determined to be -0.16 ▒ 0.05 V versus a normal hydrogen electrode. PMID:24116851
Toyoshima, Atsushi; Li, Zijie; Asai, Masato; Sato, Nozomi; Sato, Tetsuya K; Kikuchi, Takahiro; Kaneya, Yusuke; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; Schõdel, Matthias; Ooe, Kazuhiro; Kasamatsu, Yoshitaka; Shinohara, Atsushi; Haba, Hiromitsu; Even, Julia
Oxidative stress in uremia: nature, mechanisms, and potential consequences.
Oxidative stress has emerged as a constant feature of chronic renal failure (CRF). The presence of oxidative stress in CRF is evidenced by an overabundance of lipid, carbohydrate, and protein oxidation products in the plasma and tissues of uremic patients and animals. We recently have shown that oxidative stress in CRF animals is associated with and, in part, owing to up-regulation of superoxide-producing enzyme, nicotinamide-adenine dinucleotide phosphate (NAD(P)H) oxidase, and down-regulation of superoxide dismutase (SOD). The functional significance of these findings was confirmed by favorable response to administration of the cell-permeable SOD-mimetic agent, tempol, in CRF rats. Oxidative stress in CRF plays an important role in the pathogenesis of the associated hypertension (oxidation of NO and arachidonic acid and vascular remodeling), cardiovascular disease (oxidation of lipoproteins, atherogenesis), neurologic disorders (nitration of brain proteins, oxidation of myelin), anemia (reduction of erythrocyte lifespan), inflammation (nuclear factor kappa B activation), fibrosis, apoptosis, and accelerated aging. The CRF-induced oxidative stress is aggravated by diabetes, uncontrolled hypertension, and autoimmune diseases, which independently increase production of reactive oxygen intermediates, and frequently are associated with CRF. In addition, dialysis treatment (blood interaction with dialyzer membrane and dialysate impurities), acute and chronic infections (blood access infection, hepatitis, and so forth), and excessive parenteral iron administration intensify CRF-associated oxidative stress and its adverse consequences in patients with end-stage renal disease. The problem is compounded by limited intake of fresh fruits and vegetables (K(+) restriction), which contain numerous natural phytochemicals and antioxidant vitamins. PMID:15490413
Vaziri, Nosratola D
Oxidation-Reduction Resistance of Advanced Copper Alloys.
National Technical Information Service (NTIS)
Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS...
L. Greenbauer-Seng L. Thomas-Ogbuji D. L. Humphrey J. A. Setlock
Assessment of potential carbon dioxide reductions due to biomass-coal cofiring in the United States.
Cofiring biomass with coal in existing power plants offers a relatively inexpensive and efficient option for increasing near-term biomass energy utilization. Potential benefits include reduced emissions of carbon dioxide, sulfur, and nitrogen oxides and development of biomass energy markets. To understand the economics of this strategy, we develop a model to calculate electricity and pollutant mitigation costs with explicit characterization of uncertainty in fuel and technology costs and variability in fuel properties. The model is first used to evaluate the plant-level economics of cofiring as a function of biomass cost. It is then integrated with state-specific coal consumption and biomass supply estimates to develop national supply curves for cofire electricity and carbon mitigation. A delivered cost of biomass below 15 dollars per ton is required for cofire to be competitive with existing coal-based generation. Except at low biomass prices (less than 15 dollars per ton), cofiring is unlikely to be competitive for NOx or SOx control, but it can provide comparatively inexpensive control of CO2 emissions: we estimate that emissions reductions of 100 Mt-CO2/year (a 5% reduction in electric-sector emissions) can be achieved at 25 +/- 20 dollars/tC. The 2-3 year time horizon for deployment--compared with 10-20 years for other CO2 mitigation options--makes cofiring particularly attractive. PMID:14655692
Robinson, A L; Rhodes, J S; Keith, D W
Potential for abiotic reduction of pesticides in Prairie pothole porewaters.
Prairie pothole lakes (PPLs) are critical hydrological and ecological components of central North America and represent one of the largest inland wetland systems on Earth. These lakes are located within an agricultural region, and many of them are subject to nonpoint-source pesticide pollution. Limited attention, however, has been paid to understanding the impact of PPL water chemistry on the fate and persistence of pesticides. In this study, the abiotic reductive transformation of seven dinitroaniline pesticides was investigated in PPL sediment porewaters containing naturally abundant levels of reduced sulfur species (i.e., bisulfide (HS(-)) and polysulfides (S(n)(2-))) and dissolved organic matter (DOM). Target dinitroanilines underwent rapid degradation in PPL porewaters and were transformed into corresponding amine products. While the largest fraction of the transformation could be attributed to reduced sulfur species, experimental evidence suggested that other reactive entities in PPL porewaters, such as DOM and mineral phases, might also affect the reaction rates of dinitroanilines. Results from this study highlight the importance of reductive transformation as an abiotic natural attenuation pathway for pesticides entering the PPL sedimentary environment. PMID:22313175
Zeng, Teng; Chin, Yu-Ping; Arnold, William A
In Vitro Enzymatic Reduction Kinetics of Mineral Oxides by Membrane Fractions from Shewanella oneidensis MR-1
This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite reduction. The Michaelis-Menten K{sub m} values of 71 {+-} 22 m{sup 2}/L for hematite and 50 {+-} 16 m{sup 2}/L for goethite were calculated as a function of surface area of the two insoluble minerals. V{sub max} was determined to be 123 {+-} 14 and 156 {+-} 13 nmol Fe(II)/min/mg of TM protein for hematite and goethite, respectively. These values are consistent with in vivo rates of reduction reported in the literature. These observations are consistent with our conclusion that the enzymatic reduction of mineral oxides is an effective probe that will allow elucidation of molecular chemistry of the membrane-mineral interface where electron transfer occurs.
Ruebush,S.; Icopini, G.; Brantley, S.; Tien, M.
In vitro enzymatic reduction kinetics of mineral oxides by membrane fractions from Shewanella oneidensis MR-1
NASA Astrophysics Data System (ADS)
This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite reduction. The Michaelis-Menten Km values of 71 ▒ 22 m 2/L for hematite and 50 ▒ 16 m 2/L for goethite were calculated as a function of surface area of the two insoluble minerals. Vmax was determined to be 123 ▒ 14 and 156 ▒ 13 nmol Fe(II)/min/mg of TM protein for hematite and goethite, respectively. These values are consistent with in vivo rates of reduction reported in the literature. These observations are consistent with our conclusion that the enzymatic reduction of mineral oxides is an effective probe that will allow elucidation of molecular chemistry of the membrane-mineral interface where electron transfer occurs.
Ruebush, Shane S.; Icopini, Gary A.; Brantley, Susan L.; Tien, Ming
Fast fragmentation of metal oxide nanoparticles via reduction in oxyhydrogen flame
Fast fragmentation of 20 nm iron oxide and 60 nm tin oxide nanoparticles into a few nanometer nanoparticles in a diffusion oxyhydrogen flame is reported. The phenomenon is explained by the in situ reduction of generated 20-60 nm nanoparticles. The fragmentation occurs due to reduction induced instability in the oxygen-deficient surface. Simulated experiments with electron irradiation and characterization with x-ray absorption spectroscopy substantiated this mechanism. This finding may open a route to continuously generate a few nanometer scale nanoparticles of various oxides in a flame synthesis.
Pikhitsa, Peter V.; Choi, Mansoo; Yang, Sangsun; Kim, Jae-Young; Jang, Hoyoung; Park, Jae-Hoon [National CRI Center for Nano Particle Control, Institute of Advanced Machinery and Design, Seoul National University, Seoul 151-742 (Korea, Republic of) and School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742 (Korea); Powder Materials Research Center, Korea Institute of Machinery and Materials, Changwon 641-831 (Korea, Republic of); Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of) and Department of Physics and Electron Spin Science Center, Pohang University of Science and Technology, Pohang 790-784 (Korea)
Reduction behavior of iron oxides in hydrogen and carbon monoxide atmospheres
The reduction of various iron oxides in hydrogen and carbon monoxide atmospheres has been investigated by temperature programmed reduction (TPRH2 and TPRCO), thermo-gravimetric and differential temperature analysis (TG-DTA-MS), and conventional and ōin situö XRD methods. Five different compounds of iron oxides were characterized: hematite ?-Fe2O3, goethite ?-FeOOH, ferrihydrite Fe5HO8Ę4H2O, magnetite Fe3O4 and w³stite FeO. In the case of iron oxide-hydroxides,
W. K. Jozwiak; E. Kaczmarek; T. P. Maniecki; W. Ignaczak; W. Maniukiewicz
Electric coupling between distant nitrate reduction and sulfide oxidation in marine sediment.
Filamentous bacteria of the Desulfobulbaceae family can conduct electrons over centimeter-long distances thereby coupling oxygen reduction at the surface of marine sediment to sulfide oxidation in deeper anoxic layers. The ability of these cable bacteria to use alternative electron acceptors is currently unknown. Here we show that these organisms can use also nitrate or nitrite as an electron acceptor thereby coupling the reduction of nitrate to distant oxidation of sulfide. Sulfidic marine sediment was incubated with overlying nitrate-amended anoxic seawater. Within 2 months, electric coupling of spatially segregated nitrate reduction and sulfide oxidation was evident from: (1) the formation of a 4-6-mm-deep zone separating sulfide oxidation from the associated nitrate reduction, and (2) the presence of pH signatures consistent with proton consumption by cathodic nitrate reduction, and proton production by anodic sulfide oxidation. Filamentous Desulfobulbaceae with the longitudinal structures characteristic of cable bacteria were detected in anoxic, nitrate-amended incubations but not in anoxic, nitrate-free controls. Nitrate reduction by cable bacteria using long-distance electron transport to get privileged access to distant electron donors is a hitherto unknown mechanism in nitrogen and sulfur transformations, and the quantitative importance for elements cycling remains to be addressed. PMID:24577351
Marzocchi, Ugo; Trojan, Daniela; Larsen, Steffen; Louise Meyer, Rikke; Peter Revsbech, Niels; Schramm, Andreas; Peter Nielsen, Lars; Risgaard-Petersen, Nils
Thermogravimetric study of the reduction of oxides of nickel and chromium
NASA Technical Reports Server (NTRS)
The controlled hydrogen, carbon, and hydrogen-carbon reductions of the oxides of nickel and chromium were evaluated by thermogravimetric means. The materials studied were nickel (nickelous) oxide (NiO) and chromic sesquioxide (Cr2O3), mixed NiO-Cr2O3, and oxidized nickel - 20-percent chromium (Ni-20Cr). NiO was effectively reduced by all three atmospheres, Cr2O3 only by hydrogen-carbon, NiO-Cr2O3 by hydrogen and hydrogen-carbon, and oxidized Ni-20Cr by hydrogen and hydrogen-carbon and to a considerable extent by carbon alone. The results suggest that the presence of nickel promotes the reduction of Cr2O3. However, no definite explanation could be reached for the effectiveness of the hydrogen-carbon reduction of Cr2O3.
Herbell, T. P.
The Fundamental Role of Nano-Scale Oxide Films in the Oxidation of Hydrogen and the Reduction of Oxygen on Noble Metal Electrocatalysts
The derivation of successful fuel cell technologies requires the development of more effective, cheaper, and poison-resistant electrocatalysts for both the anode (H{sub 2} oxidation in the presence of small amounts of CO from the reforming of carbonaceous fuels) and the cathode (reduction of oxygen in the presence of carried-over fuel). The proposed work is tightly focused on one specific aspect of electrocatalysis; the fundamental role(s) played by nanoscale (1-2 nm thick) oxide (''passive'') films that form on the electrocatalyst surfaces above substrate-dependent, critical potentials, on charge transfer reactions, particularly at elevated temperatures (25 C < T < 200 C). Once the role(s) of these films is (are) adequately understood, we will then use this information to specify, at the molecular level, optimal properties of the passive layer for the efficient electrocatalysis of the oxygen reduction reaction.
Digby Macdonald
Catalytic reduction of nitric oxide with carbon monoxide on copper-cobalt oxides supported on nano-titanium dioxide
A series of copper-cobalt oxides supported on nano-titanium dioxide were prepared for the reduction of nitric oxide with carbon monoxide and characterized using techniques such as XRD, BET and TPR. Catalyst CuCoOx\\/TiO2 with Cu\\/Co molar ratio of 1\\/2, Cu-Co total loading of 30% at the calcination temperature of 350░C formed CuCo2O4 spinel and had the highest activity. NO conversion reached
Xia CHEN; Junfeng ZHANG; Yan HUANG; Zhiquan TONG; Ming HUANG
Potential for Sonic Boom Reduction of the Boeing HSCT
NASA Technical Reports Server (NTRS)
The HSR sonic boom technology program includes a goal of reducing the objectionable aspects of sonic boom. Earlier HSCT sonic boom studies considered achieving significant sonic boom reduction by the use of arrow-wing planforms and detailed shaping of the airplane to produce shaped waveforms (non N-waves) at the ground. While these design efforts were largely successful, the added risk and cost of the airplanes were judged to be unacceptable. The objective of the current work is to explore smaller configuration refinements that could lead to reduced sonic boom impact, within design and operational constraints. A somewhat modest target of 10% reduction in sonic boom maximum overpressure was selected to minimize the effect on the configuration performance. This work was a joint NASA/Industry effort, utilizing the respective strengths of team members at Boeing, NASA Langley, and NASA Ames. The approach used was to first explore a wide range of modifications and airplane characteristics for their effects on sonic boom and drag, using classical Modified Linear Theory (MLT) methods. CFD methods were then used to verify promising, modifications and to analyze modifications for which the MLT methods were not appropriate. The tea m produced a list of configuration changes with their effects on sonic boom and, in some cases, an estimate of the drag penalty. The most promising modifications were applied to produce a boom-softened derivative of the baseline Boeing High Speed Civil Transport (HSCT) configuration. This boom-softened configuration was analyzed in detail for the reduce sonic boom impact and also for the effect of the configuration modifications on drag, weight, and overall performance relative to the baseline.
Haglund, George T.
Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction
Iron (Fe) has long been a recognized physiological requirement for life, yet for many microorganisms that persist in water, soils and sediments, its role extends well beyond that of a nutritional necessity. Fe(II) can function as an electron source for iron-oxidizing microorganisms under both oxic and anoxic conditions and Fe(III) can function as a terminal electron acceptor under anoxic conditions
Karrie A. Weber; Laurie A. Achenbach; John D. Coates
Raman study of oxidation-reduction dispersion of silver
We have examined the process of redox dispersion of silver, using a solution simultaneously containing an oxidizing agent\\u000a (potassium ferricyanide) and a reducing agent (sodium borohydride). We have studied the changes over time in the Raman spectra\\u000a of the indicated solution when no silver particles are present and when such particles are added to the solution. We have\\u000a established that
A. E. Kolyago; O. V. Sergeeva; S. K. Rakhmanov
Simultaneous Nitrogen-Doping and Reduction of Graphene Oxide
We develop a simple chemical method to obtain bulk quantities of N-doped, reduced graphene oxide (GO) sheets through thermal annealing of GO in ammonia. X-ray photoelectron spectroscopy (XPS) study of GO sheets annealed at various reaction temperatures reveals that N-doping occurs at a temperature as low as 300C, while the highest doping level of ~5% N is achieved at 500C.
Xiaolin Li; Hailiang Wang; Joshua T. Robinson; Hernan Sanchez; Georgi Diankov; Hongjie Dai
Nitrogen oxide reduction strategies for compression ignition engines
NASA Astrophysics Data System (ADS)
The scope of this investigation is to explore strategies to reduce NOx emissions from compression ignition engines. Two methods are presented in this collection of studies: (1) NOx reduction accomplished through a change in fuel formulation, specifically through a change in the saturated fuel carbon chains of biodiesel; and (2) NOx reduction accomplished through a mixed mode combustion process utilizing a fumigated fuel and a pilot injection of diesel fuel. In the first study, a light duty diesel engine was used to investigate the change in saturation of a biodiesel fuel and its impact on NOx emissions. Previous studies have shown that a reduction in the iodine value of a biodiesel fuel produces a reduction in NOx emissions. The iodine value of the fuel is reduced through the saturation of the C18 molecules via hydrogenation of biodiesel fuel. Experiments were performed at several speeds and loads without exhaust gas recirculation (EGR), and a NOx reduction with the hydrogenated diesel fuel was observed. For all the modes studied, the NOx emission was higher for the biodiesel and lower for the hydrogenated biodiesel in comparison to the ultra low sulfur diesel (ULSD) fuel. Results from the calculation of the adiabatic flame temperature shows that the results could be explained by the difference in adiabatic flame temperature of the fuel, thus influencing the prompt NOx contribution in addition to the thermal contribution. Since the adiabatic flame temperatures are similar for the hydrogenated biodiesel and the ULSD, yet the NOx reduction with the hydrogenated biodiesel is much lower than the ULSD levels, another explanation for the reduction is suggested: the additional prompt NOx contribution from the change in fuel chemistry. The second study investigated the NOx reductions which could be achieved with a mixed mode combustion process utilizing a fumigated fuel and a pilot injection of diesel fuel. In this research, the fumigated fuel was dimethyl ether (DME) and DME/Methane blends, while the pilot injection fuel was ULSD. Several sets of experiments were performed to study the ignition of the fumigated fuel, and its impact on the NOx emissions. In the first set of experiments, the DME concentration was spanned over a range of 15 to 44% energy equivalent of the total fuel requirement. An approximately 20% reduction in NOx emissions was observed up to 35% DME energy equivalent. As the energy equivalent increased above 35%, the NOx emissions began to increase with the increase in the peak of the high temperature heat release (HTHR). While the NOx emissions decreased, there was also a significant shift in the NO to NO2 conversion for all DME fumigation test conditions in comparison to the baseline diesel cases. For 25% DME energy equivalent, the injection timing of the pilot diesel was retarded and a reduction in the NOx emissions was observed. The low temperature heat release (LTHR) and the HTHR remained constant in magnitude and timing while the injection timing of the pilot diesel was retarded. The peak pressure for the premixed and diffusion portions merged, with increasing premixed DME combustion. With retarded injection timing, NOx reduction occurred as a result of the decrease in the bulk cylinder temperature and in the combustion duration before cylinder quenching from the exhaust stroke. In the second set of experiments, the intake air temperature was increased to study the impact on NOx and the mixed mode combustion process. While the amount of DME residual in the exhaust decreased along with the total hydrocarbon and CO emissions, the NOx emissions increased with increasing bulk cylinder temperature. For the speed and load used in this experiment, there was enough fuel and compression to combust most of the fuel, yet not enough to complete the combustion of the unburned hydrocarbons and CO. While air heating shifted the stoichiometry of the fuel and air mixture by reducing the density of air, the heating led to increased NOx with reduction in the NO to NO2 conversion. This may indicate that the system was above
Chapman, Elana M.
Hydrogen and formate oxidation coupled to dissimilatory reduction of iron or manganese by Alteromonas putrefaciens
The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.
Lovley, D. R.; Phillips, E. J. P.; Lonergan, D. J.
In situ X-ray absorption spectroscopy investigation of a bifunctional manganese oxide catalyst with high activity for electrochemical water oxidation and oxygen reduction.
In situ X-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs RHE produces a disordered Mn3(II,III,III)O4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed Mn(III,IV) oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3(II,III,III)O4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the Mn(III,IV) oxide, rather than Mn3(II,III,III)O4, is the phase pertinent to the observed OER activity. PMID:23758050
Gorlin, Yelena; Lassalle-Kaiser, Benedikt; Benck, Jesse D; Gul, Sheraz; Webb, Samuel M; Yachandra, Vittal K; Yano, Junko; Jaramillo, Thomas F
In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction
In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity.
Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.
Lasofoxifene Is Potential New Option for Breast Cancer Risk Reduction
An investigational agent in the same family of drugs as tamoxifen and raloxifene may be as or more effective in reducing breast cancer risk in some women. The drug, lasofoxifene, also appears to have important benefits for both bone and heart health and, with one exception, appears to lack the rare but potentially serious side effects associated with tamoxifen and raloxifene, according to results published November 4, 2010, in the Journal of the National Cancer Institute.
Molecular Underpinnings of Fe(III) Oxide Reduction by Shewanella oneidensis MR-1
In the absence of O2 and other electron acceptors, the Gram-negative bacterium Shewanella oneidensis MR-1 can use ferric [Fe(III)] (oxy)(hydr)oxide minerals as the terminal electron acceptors for anaerobic respiration. At circumneutral pH and in the absence of strong complexing ligands, Fe(III) oxides are relatively insoluble and thus are external to the bacterial cells. S. oneidensis MR-1 and related strains of metal-reducing Shewanella have evolved the machinery (i.e., metal-reducing or Mtr pathway) for transferring electrons from the inner-membrane, through the periplasm and across the outer-membrane to the surface of extracellular Fe(III) oxides. The protein components identified to date for the Mtr pathway include CymA, MtrA, MtrB, MtrC and OmcA. CymA is an inner-membrane tetraheme c-type cytochrome (c-Cyt) that belongs to the NapC/NrfH family of quinol dehydrogenases. It is proposed that CymA oxidizes the quinol in the inner-membrane and transfers the released electrons to redox proteins in the periplasm. Although the periplasmic proteins receiving electrons from CymA during Fe(III) oxidation have not been identified, they are believed to relay the electrons in the periplasm to MtrA. A decaheme c-Cyt, MtrA is thought to be embedded in the trans outer-membrane and porin-like protein MtrB. Together, MtrAB deliver the electrons through the outer-membrane to the MtrC and OmcA on the outmost bacterial surface. MtrC and OmcA are the outer-membrane decaheme c-Cyts that are translocated across the outer-membrane by the bacterial type II secretion system. Functioning as terminal reductases, MtrC and OmcA can bind the surface of Fe(III) oxides and transfer electrons directly to these minerals via their solvent-exposed hemes. To increase their reaction rates, MtrC and OmcA can use the flavins secreted by S. oneidensis MR-1 cells as diffusible co-factors for reduction of Fe(III) oxides. Because of their extracellular location and broad redox potentials, MtrC and OmcA can also serve as the terminal reductases for soluble forms of Fe(III). Although our understanding of the Mtr pathway is still far from complete, it is the best characterized microbial pathway used for extracellular electron exchange. Characterizations of the Mtr pathway have made significant contributions to the molecular understanding of microbial reduction of Fe(III) oxides.
Shi, Liang; Rosso, Kevin M.; Clarke, Thomas A.; Richardson, David J.; Zachara, John M.; Fredrickson, Jim K.
Oxidation and reduction of pig skeletal muscle ryanodine receptors.
Time-dependent effects of cysteine modification were compared in skeletal ryanodine receptors (RyRs) from normal pigs and RyR(MH) (Arg(615) to Cys(615)) from pigs susceptible to malignant hyperthermia, using the oxidizing reagents 4,4'-dithiodipyridine (4, 4'-DTDP) and 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB) or the reducing agent dithiothreitol (DTT). Normal and RyR(MH) channels responded similarly to all reagents. DTNB (1 mM), either cytoplasmic (cis) or luminal (trans), or 1 mM 4,4'-DTDP (cis) activated RyRs, introducing an additional long open time constant. 4,4'-DTDP (cis), but not DTNB, inhibited channels after >5 min. Activation and inhibition were relieved by DTT (1-10 mM). DTT (10 mM, cytoplasmic or luminal), without oxidants, activated RyRs, and activation reversed with 1 mM DTNB. Control RyR activity was maintained with 1 mM DTNB and 10 mM DTT present on the same or opposite sides of the bilayer. We suggest that 1) 4,4'-DTDP and DTNB covalently modify RyRs by oxidizing activating or inhibiting thiol groups; 2) a modified thiol depresses mammalian skeletal RyR activity under control conditions; 3) both the activating thiols and the modified thiols, accessible from either cytoplasm or lumen, reside in the transmembrane region; 4) some cardiac sulfhydryls are unavailable in skeletal RyRs; and 5) Cys(615) in RyR(MH) is functionally unimportant in redox cycling.
Haarmann, C S; Fink, R H; Dulhunty, A F
Characterization of methionine oxidation and methionine sulfoxide reduction using methionine-rich cysteine-free proteins
Background Methionine (Met) residues in proteins can be readily oxidized by reactive oxygen species to Met sulfoxide (MetO). MetO is a promising physiological marker of oxidative stress and its inefficient repair by MetO reductases (Msrs) has been linked to neurodegeneration and aging. Conventional methods of assaying MetO formation and reduction rely on chromatographic or mass spectrometry procedures, but the use of Met-rich proteins (MRPs) may offer a more streamlined alternative. Results We carried out a computational search of completely sequenced genomes for MRPs deficient in cysteine (Cys) residues and identified several proteins containing 20% or more Met residues. We used these MRPs to examine Met oxidation and MetO reduction by in-gel shift assays and immunoblot assays with antibodies generated against various oxidized MRPs. The oxidation of Cys-free MRPs by hydrogen peroxide could be conveniently monitored by SDS-PAGE and was specific for Met, as evidenced by quantitative reduction of these proteins with Msrs in DTT- and thioredoxin-dependent assays. We found that hypochlorite was especially efficient in oxidizing MRPs. Finally, we further developed a procedure wherein antibodies made against oxidized MRPs were isolated on affinity resins containing same or other oxidized or reduced MRPs. This procedure yielded reagents specific for MetO in these proteins, but proved to be ineffective in developing antibodies with broad MetO specificity. Conclusion Our data show that MRPs provide a convenient tool for characterization of Met oxidation, MetO reduction and Msr activities, and could be used for various aspects of redox biology involving reversible Met oxidation.
Alkaline O2 reduction on oxide-derived Au: high activity and 4e(-) selectivity without (100) facets.
Gold films produced from gold oxide precursors ("oxide-derived Au") were compared to polyhedral Au nanoparticles for electrocatalytic alkaline O2 reduction. Despite having no detectable abundance of (100) facets, oxide-derived Au exhibited 4e(-) selectivity and surface-area-normalized activity that rivaled cubic Au nanoparticles with high (100) abundance. The activity of oxide-derived Au likely arises from active sites at the surface terminations of defects that are trapped during gold oxide reduction. PMID:24849198
Min, Xiaoquan; Chen, Yihong; Kanan, Matthew W
The high-temperature oxidation, reduction, and volatilization reactions of silicon and silicon carbide
A thermochemical analysis was made of the oxidation, reduction, and volatilization reactions which occur in the Si-O-C system. One characteristic feature is the high SiO(g) and SiO(g) + CO(g) pressures at the Si(s)-SiO2 and SiC(s)-SiO2(s) interfaces. Active oxidation with weight losses and passive oxidation with weight gains were found on oxidizing Si(s) and SiC(s) in low oxygen pressures above 1000░C.
Earl A. Gulbransen; Sven A. Jansson
Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis.
Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured ?-Mn(2)O(3) and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V and 1.0 V, a potential region between the ORR and the OER relevant conditions. Next, we perform density function theory (DFT) calculations to understand the changes in the MnO(x) surface as a function of potential and to elucidate reaction mechanisms that lead to high activities observed in the experiments. Using DFT, we construct surface Pourbaix and free energy diagrams of three different MnO(x) surfaces and identify 1/2 ML HO* covered Mn(2)O(3) and O* covered MnO(2), as the active surfaces for the ORR and the OER, respectively. Additionally, we find that the ORR occurs through an associative mechanism and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis and experimental methods offers an understanding of manganese oxide oxygen electrocatalysis at the atomic level, achieving fundamental insight that can potentially be used to design and develop improved electrocatalysts for the ORR and the OER and other important reactions of technological interest. PMID:22990481
Su, Hai-Yan; Gorlin, Yelena; Man, Isabela C; Calle-Vallejo, Federico; N°rskov, Jens K; Jaramillo, Thomas F; Rossmeisl, Jan
Pseudomonas seleniipraecipitans Proteins Potentially Involved in Selenite Reduction.
Pseudomonas seleniipraecipitans grows in the presence of high levels of selenite and selenate and reduces both oxyanions to elemental selenium (Se(0)), a property that may make P.Āseleniipraecipitans useful as an inoculant for biobarriers designed to remove selenite or selenate from ground or surface waters. An earlier study showed that P.Āseleniipraecipitans nitrate reductase reduced selenate to Se(0), but failed to identify the protein(s) involved in selenite reduction. This study used ammonium sulfate precipitation, hydrophobic interaction chromatography, and native PAGE to isolate two electrophoretic gel regions, identified as bands A and B that showed selenite-reductase-activity. Proteomics was used to identify the proteins present in those regions. Glutathione reductase (GR) was detected in the A-band; based on this information, Saccharomyces cerevisiae GR, obtained from a commercial source, was evaluated and found to have selenite-reductase-activity, confirming that GR can reduce selenite to Se(0). Proteomics was also used to detect the proteins present in the B-band and thioredoxin reductase (ThxR) was detected as a B-band protein; based on this information, E.Ācoli ThxR, obtained from a commercial source, was evaluated and found to have selenite-reductase-activity, confirming that ThxR can reduce selenite to elemental selenium. Thus, evidence presented in this study shows that S.Ācerevisiae GR and E.Ācoli ThxR can reduce SeO3 (2-) to Se(0) and strongly suggests that P.Āseleniipraecipitans GR and ThxR can also reduce SeO3 (2-) to Se(0). PMID:24604150
Hunter, William J
Reduction of Iron-Oxide-Carbon Composites: Part I. Estimation of the Rate Constants
NASA Astrophysics Data System (ADS)
A new ironmaking concept using iron-oxide-carbon composite pellets has been proposed, which involves the combination of a rotary hearth furnace (RHF) and an iron bath smelter. This part of the research focuses on studying the two primary chemical kinetic steps. Efforts have been made to experimentally measure the kinetics of the carbon gasification by CO2 and w³stite reduction by CO by isolating them from the influence of heat- and mass-transport steps. A combined reaction model was used to interpret the experimental data and determine the rate constants. Results showed that the reduction is likely to be influenced by the chemical kinetics of both carbon oxidation and w³stite reduction at the temperatures of interest. Devolatilized wood-charcoal was observed to be a far more reactive form of carbon in comparison to coal-char. Sintering of the iron-oxide at the high temperatures of interest was found to exert a considerable influence on the reactivity of w³stite by virtue of altering the internal pore surface area available for the reaction. Sintering was found to be predominant for highly porous oxides and less of an influence on the denser ores. It was found using an indirect measurement technique that the rate constants for w³stite reduction were higher for the porous iron-oxide than dense hematite ore at higher temperatures (>1423 K). Such an indirect mode of measurement was used to minimize the influence of sintering of the porous oxide at these temperatures.
Halder, S.; Fruehan, R. J.
Remote fabrication and irradiation test of recycled nuclear fuel prepared by the oxidation and reduction of spent oxide fuel
NASA Astrophysics Data System (ADS)
A direct dry recycling process was developed in order to reuse spent pressurized light water reactor (LWR) nuclear fuel in CANDU reactors without the separation of sensitive nuclear materials such as plutonium. The benefits of the dry recycling process are the saving of uranium resources and the reduction of spent fuel accumulation as well as a higher proliferation resistance. In the process of direct dry recycling, fuel pellets separated from spent LWR fuel rods are oxidized from UO2 to U3O8 at 500 ░C in an air atmosphere and reduced into UO2 at 700 ░C in a hydrogen atmosphere, which is called OREOX (oxidation and reduction of oxide fuel). The pellets are pulverized during the oxidation and reduction processes due to the phase transformation between cubic UO2 and orthorhombic U3O8. Using the oxide powder prepared from the OREOX process, the compaction and sintering processes are performed in a remote manner in a shielded hot cell due to the high radioactivity of the spent fuel. Most of the fission gas and volatile fission products are removed during the OREOX and sintering processes. The mini-elements fabricated by the direct dry recycling process are irradiated in the HANARO research reactor for the performance evaluation of the recycled fuel pellets. Post-irradiation examination of the irradiated fuel showed that microstructural evolution and fission gas release behavior of the dry-recycled fuel were similar to high burnup UO2 fuel.
Jin Ryu, Ho; Chan Song, Kee; Il Park, Geun; Won Lee, Jung; Seung Yang, Myung
Treatment of oxide spent fuel using the lithium reduction process
The wide variety in the composition of DOE spent nuclear fuel complicates its long-term disposition because of the potential requirement to individually qualify each type of fuel for repository disposal. Argonne National Laboratory (ANL) has developed the electrometallurgical treatment technique to convert all of these spent fuel types into a single set of disposal forms, simplifying the qualification process. While
E. J. Karell; R. D. Pierce; T. P. Mulcahey
Biodegradation potential of wastewater micropollutants by ammonia-oxidizing bacteria
This study examined the biodegradation potential of three wastewater micropollutants (triclosan, bisphenol A, and ibuprofen) by Nitrosomonas europaea and mixed ammonia-oxidizing bacteria in nitrifying activated sludge. N. europaea could degrade triclosan and bisphenol A, but not ibuprofen. The degradation was observed only in the absence of allylthiourea (an inhibitor for ammonia monooxygenase (AMO)), suggesting that AMO might be responsible for
Hyungkeun Roh; Nethra Subramanya; Fuman Zhao; Chang-Ping Yu; Justin Sandt; Kung-Hui Chu
Reduction of local velocity spreads by linear potentials
NASA Astrophysics Data System (ADS)
We study the spreading of the wave function of a Bose-Einstein condensate accelerated by a constant force both in the absence and in the presence of atom-atom interactions. We show that, despite the initial velocity dispersion, the local velocity dispersion defined at a given position downward can reach ultralow values and be used to probe very narrow energetic structures. We explain how one can define quantum mechanically and without ambiguities the different velocity moments at a given position by extension of their classical counterparts. We provide a common theoretical framework for interacting and noninteracting regimes based on the Wigner transform of the initial wave function that encapsulates the dynamics in a scaling parameter. In the absence of interaction, our approach is exact. Using a numerical simulation of the one-dimensional Gross-Pitaevskii equation, we provide the range of validity of our scaling approach and find a very good agreement in the Thomas-Fermi regime. We apply this approach to the study of the scattering of a matter wave packet on a double barrier potential. We show that a Fabry-Perot resonance in such a cavity with an energy width below the pK range can be probed in this manner. We show that our approach can be readily transposed to a large class of many-body quantum systems that exhibit self-similar dynamics.
Damon, F.; Vermersch, F.; Muga, J. G.; Guķry-Odelin, D.
HDR reservoir flow impedance and potential for impedance reduction
The data from flow tests which employed two different production zones in a well at Fenton Hill indicates the flow impedance of a wellbore zone damaged by rapid depressurization was altered, possibly by pressure spallation, which appears to have mechanically propped the joint apertures of outlet flow paths intersecting the altered wellbore. The rapid depressurization and subsequent flow test data derived from the damaged well has led to the hypothesis that pressure spallation and the resultant mechanical propping of outlet flow paths reduced the outlet flow impedance of the damaged wellbore. Furthermore, transient pressure data shows the largest pressure drop between the injection and production wellheads occurs near the production wellbore, so lowering the outlet impedance by increasing the apertures of outlet flow paths will have the greatest effect on reducing the overall reservoir impedance. Fenton Hill data also reveals that increasing the overall reservoir pressure dilates the apertures of flow paths, which likewise serves to reduce the reservoir impedance. Data suggests that either pressure dilating the wellbore connected joints with high production wellhead pressure, or mechanically propping open the outlet flow paths will increase the near-wellbore permeability. Finally, a new method for calculating and comparing near-wellbore outlet impedances has been developed. Further modeling, experimentation, and engineered reservoir modifications, such as pressure dilation and mechanical propping, hold considerable potential for significantly improving the productivity of HDR reservoirs.
Du Teau, Robert; Brown, Donald
HDR reservoir flow impedance and potentials for impedance reduction
The data from flow tests which employed two different production zones in a well at Fenton Hill indicates the flow impedance of a wellbore zone damaged by rapid depressurization was altered, possibly by pressure spallation, which appears to have mechanically propped the joint apertures of outlet flow paths intersecting the altered wellbore. The rapid depressurization and subsequent flow test data derived from the damaged well has led to the hypothesis that pressure spallation and the resultant mechanical propping of outlet flow paths reduced the outlet flow impedance of the damaged wellbore. Furthermore, transient pressure data shows the largest pressure drop between the injection and production wellheads occurs near the production wellbore, so lowering the outlet impedance by increasing the apertures of outlet flow paths will have the greatest effect on reducing the overall reservoir impedance. Fenton Hill data also reveals that increasing the overall reservoir pressure dilates the apertures of flow paths, which likewise serves to reduce the reservoir impedance. Data suggests that either pressure dilating the wellbore connected joints with high production wellhead pressure, or mechanically propping open the outlet flow paths will increase the near-wellbore permeability. Finally, a new method for calculating and comparing near-wellbore outlet impedances has been developed. Further modeling, experimentation, and engineered reservoir modifications, such as pressure dilation and mechanical propping, hold considerable potential for significantly improving the productivity of HDR reservoirs.
DuTeau, R.; Brown, D.
Enhanced wastewater treatment efficiency through microbially catalyzed oxidation and reduction: synergistic effect of biocathode microenvironment.
Microbially catalyzed treatment of wastewater was evaluated in both the anode and cathode chambers in dual chambered microbial fuel cell (MFC) under varying biocathode microenvironment. MFC operation with aerobic biocathode showed significant increment in both TDS (cathode, 90.2▒1%; anode, 39.7▒0.5%) and substrate (cathode, 98.07▒0.06%; anode, 96.2▒0.3%) removal compared to anaerobic biocathode and abiotic cathode operations (COD, 80.25▒0.3%; TDS, 30.5▒1.2%). Microbially catalyzed reduction of protons and electrons at cathode will be higher during aerobic biocathode operation which leads to gradual substrate removal resulting in stable bio-potential for longer periods facilitating salts removal. Bio-electro catalytic behavior showed higher exchange current density during aerobic biocathode operation resulting in induced electrochemical oxidation which supports the enhanced treatment. Anaerobic biocathode operation depicted relatively less TDS removal (anode, 16.35%; cathode, 16.04%) in both the chambers in spite of good substrate degradation (anode, 84%; cathode, 87.39%). Both the chambers during anaerobic biocathode operation competed as electron donors resulting in negligible bio-potential development. PMID:21920735
Mohan, S Venkata; Srikanth, S
Analytical model for reduction of deep levels in SiC by thermal oxidation
NASA Astrophysics Data System (ADS)
Two trap-reduction processes, thermal oxidation and C+ implantation followed by Ar annealing, have been discovered, being effective ways for reducing the Z1/2 center (EC - 0.67 eV), which is a lifetime killer in n-type 4H-SiC. In this study, it is shown that new deep levels are generated by the trap-reduction processes in parallel with the reduction of the Z1/2 center. A comparison of defect behaviors (reduction, generation, and change of the depth profile) for the two trap-reduction processes shows that the reduction of deep levels by thermal oxidation can be explained by an interstitial diffusion model. Prediction of the defect distributions after oxidation was achieved by a numerical calculation based on a diffusion equation, in which interstitials generated at the SiO2/SiC interface diffuse to the SiC bulk and occupy vacancies related to the origin of the Z1/2 center. The prediction based on the proposed analytical model is mostly valid for SiC after oxidation at any temperature, for any oxidation time, and any initial Z1/2-concentration. Based on the results, the authors experimentally achieved the elimination of the Z1/2 center to a depth of about 90 ?m in the sample with a relatively high initial-Z1/2-concentration of 1013 cm-3 by thermal oxidation at 1400 ░C for 16.5 h. Furthermore, prediction of carrier lifetimes in SiC from the Z1/2 profiles was realized through calculation based on a diffusion equation, which considers excited-carrier diffusion and recombination in the epilayer, in the substrate, and at the surface.
Kawahara, Koutarou; Suda, Jun; Kimoto, Tsunenobu
TiO2-graphene nanocomposites. UV-assisted photocatalytic reduction of graphene oxide.
Graphene oxide suspended in ethanol undergoes reduction as it accepts electrons from UV-irradiated TiO(2) suspensions. The reduction is accompanied by changes in the absorption of the graphene oxide, as the color of the suspension shifts from brown to black. The direct interaction between TiO(2) particles and graphene sheets hinders the collapse of exfoliated sheets of graphene. Solid films cast on a borosilicate glass gap separated by gold-sputtered terminations show an order of magnitude decrease in lateral resistance following reduction with the TiO(2) photocatalyst. The photocatalytic methodology not only provides an on-demand UV-assisted reduction technique but also opens up new ways to obtain photoactive graphene-semiconductor composites. PMID:19206319
Williams, Graeme; Seger, Brian; Kamat, Prashant V
Electrocatalytic potentialities of silver as a cathode for organic halide reductions
The peculiar halide affinity for silver results in an extraordinary electrocatalytic activity for the reduction of halides (either glycosyl halides or, more generally, aryl and alkyl halides). The most striking features are: (a) a reduction potential shift in the positive direction of about 1000 mV with respect to glassy carbon and 500 mV with respect to mercury; (b) a cage
Sandra B. Rondinini; Patrizia R. Mussini; Federico Crippa; Guido Sello
Energy conservation via electron bifurcating ferredoxin reduction and proton/Na(+) translocating ferredoxin oxidation.
The review describes four flavin-containing cytoplasmatic multienzyme complexes from anaerobic bacteria and archaea that catalyze the reduction of the low potential ferredoxin by electron donors with higher potentials, such as NAD(P)H or H(2) at ? 100 kPa. These endergonic reactions are driven by concomitant oxidation of the same donor with higher potential acceptors such as crotonyl-CoA, NAD(+) or heterodisulfide (CoM-S-S-CoB). The process called flavin-based electron bifurcation (FBEB) can be regarded as a third mode of energy conservation in addition to substrate level phosphorylation (SLP) and electron transport phosphorylation (ETP). FBEB has been detected in the clostridial butyryl-CoA dehydrogenase/electron transferring flavoprotein complex (BcdA-EtfBC), the multisubunit [FeFe]hydrogenase from Thermotoga maritima (HydABC) and from acetogenic bacteria, the [NiFe]hydrogenase/heterodisulfide reductase (MvhADG-HdrABC) from methanogenic archaea, and the transhydrogenase (NfnAB) from many Gram positive and Gram negative bacteria and from anaerobic archaea. The Bcd/EtfBC complex that catalyzes electron bifurcation from NADH to the low potential ferredoxin and to the high potential crotonyl-CoA has already been studied in some detail. The bifurcating protein most likely is EtfBC, which in each subunit (??) contains one FAD. In analogy to the bifurcating complex III of the mitochondrial respiratory chain and with the help of the structure of the human ETF, we propose a conformational change by which ?-FADH(-) in EtfBC approaches ?-FAD to enable the bifurcating one-electron transfer. The ferredoxin reduced in one of the four electron bifurcating reactions can regenerate H(2) or NADPH, reduce CO(2) in acetogenic bacteria and methanogenic archaea, or is converted to ??H(+)/Na(+) by the membrane-associated enzyme complexes Rnf and Ech, whereby NADH and H(2) are recycled, respectively. The mainly bacterial Rnf complexes couple ferredoxin oxidation by NAD(+) with proton/sodium ion translocation and the more diverse energy converting [NiFe]hydrogenases (Ech) do the same, whereby NAD(+) is replaced by H(+). Many organisms also use Rnf and Ech in the reverse direction to reduce ferredoxin driven by ??H(+)/Na(+). Finally examples are shown, in which the four bifurcating multienzyme complexes alone or together with Rnf and Ech are integrated into energy metabolisms of nine anaerobes. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems. PMID:22800682
Buckel, Wolfgang; Thauer, Rudolf K
The effects of freeze-thaw and sonication on mitochondrial oxygen consumption, electron transport chain-linked metmyoglobin reduction, lipid oxidation, and oxymyoglobin oxidation.
Mitochondria potentially influence Mb redox stability in meat by (1) decreasing partial oxygen pressure via oxygen consumption, (2) mitochondrial electron transport chain (ETC)-linked reduction of MetMb, and/or (3) oxidation of mitochondrial membrane lipid. The objective of this study was to investigate the effect of freeze-thaw and sonication treatments on mitochondrial oxygen consumption, ETC-dependent MetMb reducing activity, lipid oxidation, and Mb redox stability. Mitochondria were frozen and thawed (-18░C for 2h and 4░C for 0.5h) for 3 cycles, or sonicated for 30s with a sonic dismembrator. State III oxygen consumption rate (OCR) was decreased by both treatments at pH 7.2, and by sonication only at pH 5.6 (P<0.05). There was no effect on state IV OCR (P>0.05). Respiratory control ratio (RCR) was decreased by freeze-thaw and sonication at pH 7.2 and 5.6 (P<0.05). Sonication increased mitochondrial lipid oxidation and MetMb formation (P<0.05); a similar effect was observed in sonicated samples in the presence of ascorbic acid and ferric chloride (P<0.05). Sonication also decreased mitochondrial ETC-dependent MetMb reduction (P<0.05). These results suggested that sonication treatment had the potential to affect Mb stability via mitochondrial lipid oxidation and/or ETC-mediated MetMb reduction, but the effect on myoglobin stability by freeze-thaw treatment was minimal. PMID:22063055
Tang, Jiali; Faustman, Cameron; Mancini, Richard A; Seyfert, Mark; Hunt, Melvin C
Attention Reduction and Suppressed Direct-Current Potentials in the Human Brain
Distraction suppresses direct-current potentials (contingent negative variation) recorded from the human scalp. This reduction is accompanied by retarded reaction time. Contingent negative variation and reaction time appear to reflect a common process, attention.
Joseph J. Tecce; Neil M. Scheff
Potential Impacts of Reductions in Refinery Activity on Northeast Petroleum Product Markets. Updated May 11, 2012.
National Technical Information Service (NTIS)
This report updates and expands upon a December 2011 U.S. Energy Information Administration (EIA) report, Reductions in Northeast Refining Activity: Potential Implications for Petroleum Product Markets.1 To date, the market transition following the closin...
Potential Impacts of Reductions in Refinery Activity on Northeast Petroleum Product Markets.
National Technical Information Service (NTIS)
This report updates and expands upon a December 2011 U.S. Energy Information Administration (EIA) report, Reductions in Northeast Refining Activity: Potential Implications for Petroleum Product Markets.1 To date, the market transition following the closin...
Temperature-programmed reduction and oxidation of metals supported on. gamma. -alumina
Quantitative measurements of temperature-programmed reduction and oxidation (TPR\\/TPO) at temperatures up to 1200┬░C were used to characterize 2% metal on ╬│-alumina catalysts. The TPR\\/TPO results were also compared with the redox behavior of the bulk compounds. It was found that supported FeŌOŌ, MoOŌ, and NiO could be reduced to metal only at temperatures near 1100┬░C. In all cases reduction of
A. Kadkhodayan; A. Brenner
Kinetics of cobalt sulfide reduction in the presence of calcium oxide
Kinetic measurements have been made on the hydrogen reduction of solid cobalt sulfide in the presence of calcium oxide. The\\u000a cobalt metal yield was compared with that of the direct reduction reaction over the temperature range 600 to 800░C at various\\u000a hydrogen flow rates, and calcium oxde to cobalt sulfide mixing ratios. It was found that the presence of calcium
J. D. Ford; M. A. Fahim
Kinetics of chromium oxide reduction from a basic steelmaking slag by silicon dissolved in liquid iron
The reduction of chromium oxide from a basic steelmaking slag (45 wt pct CaO, 35 wt pct SiO2, 10 wt pct MgO, 10 wt pct A12O3) by silicon dissolved in liquid iron at steelmaking temperatures was studied to determine the rate-limiting steps. The reduction\\u000a is described by the reactions: (Cr2O3) + Si = (SiO2) + (CrO) + Cr [1] and
James W. Robison; Robert D. Pehlke
Impact of Iron Oxide Structure on Fe(II)-Catalyzed Reductive Biomineralization
Due to the reactivity of ferrous Fe, the fate of Fe(II) following dissimilatory iron reduction will have a profound bearing on biogeochemical cycles. Ferric (hydr)oxides vary from well-ordered phases in mature environments to short-range order minerals such as ferrihydrite in those subject to varying redox conditions. Structural order may have appreciable impacts on the extent and rate of Fe(III) reduction
C. M. Hansel; S. G. Benner; S. Fendorf
Evidence of alloy formation during reduction of platinized tin oxide surfaces
NASA Technical Reports Server (NTRS)
Ion scattering spectroscopy, Auger electron spectroscopy, and electron spectroscopy for chemical analysis have been used to examine a platinized tin oxide catalyst surface before, during, and after reduction by annealing under vacuum at 250 to 450 C. These techniques were then used to examine the reduced surface after a room-temperature, low-pressure oxygen exposure. The spectral results and the behavior of the reduced surface toward oxygen exposure both indicate that a Pt/Sn alloy is produced during reduction.
Gardner, Steven D.; Hoflund, Gar B.; Davidson, Mark R.; Schryer, David R.
Selection of oxygen reduction catalysts for rechargeable lithium¢air batteriesŚMetal or oxide?
Carbon-supported Pd and PdO nanocatalysts were synthesised using either chemical reduction or thermal synthesis procedures and were used as model metal and oxide catalysts for oxygen reduction in rechargeable lithium¢air batteries. The Pd metal catalyst showed excellent initial performance, e.g. a discharge capacity of 855mAh (gsolids)?1. However, the PdO catalyst displayed superior capacity retention to the Pd catalyst, producing a
H. Cheng; K. Scott
Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions.
Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400?░C (designated as LT-LiCoO2) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800?░C (designated as HT-LiCoO2) for the oxygen evolution reaction. Although LT-LiCoO2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li1-xCoO2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LT-Li0,5CoO2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co4O4 cubane subunits and a pinning of the Co(3+/4+):3d energy with the top of the O(2-):2p band. PMID:24862287
Maiyalagan, Thandavarayan; Jarvis, Karalee A; Therese, Soosairaj; Ferreira, Paulo J; Manthiram, Arumugam
Reductive Dissolution of Biogenic Manganese Oxides in the Presence of a Hydrated Biofilm
The chemical reactivity of the biogenic Mn oxide produced by Pseudomonas putida strain MnB1 was assessed in the presence of bacterial cells and biofilm through reductive dissolution experiments at pH 4.4, 5.2, and 6.0. The reactivity of the biogenic Mn oxide was compared to that of a synthetic (chemically produced) birnessite at pH 6.0. In addition, the effect of bacterial
Brandy Toner; Garrison Sposito
Reduction of nitrogen oxides with catalytic acid resistant aluminosilicate molecular sieves and ammonia
Noxious nitrogen oxides in a waste gas stream such as the stack gas from a fossil-fuel-fired power generation plant or other industrial plant off-gas stream is catalytically reduced to elemental nitrogen and/or innocuous nitrogen oxides employing ammonia as reductant in the presence of a zeolite catalyst in the hydrogen or sodium form having pore openings of about 3 to 10 A.
Pence, Dallas T. (Idaho Falls, ID); Thomas, Thomas R. (Idaho Falls, ID)
Catalytic reduction of nitric oxide by methane over CaO catalyst
The selective catalytic reduction of nitric oxide by methane was studied over CaO catalyst in a bubbling fluidized bed in\\u000a the temperature range of 800¢900 ░C, in which NO cannot be reduced by CH4 without CaO catalyst. The nitric oxide conversion was found to depend on oxygen and CH4 feed concentration, and also on temperature. In addition, the presence of
Wei Xu; Huiling Tong; Changhe Chen; Xuchang Xu
Reductive acid leaching of manganese dioxide with glucose: Identification of oxidation derivatives of glucose
The oxidation of glucose during the reductive leaching of pure MnO2 and manganese ore in sulphuric acid at 90 ░C MnO2 was investigated. The aim was to identify the derivatives and the chemical pathway of glucose oxidation. Organic derivatives were monitored by HPLC using an Aminex HPX-78H column and UV detection. Chromatographic patterns of leaching solutions showed that major compound
G. Furlani; F. Pagnanelli; L. Toro
Solid-state Water-mediated Transport Reduction of Nanostructured Iron Oxides
The Fe2+\\/Fe3+ ratio in two-dimensional iron oxide nanosructures (nanolayers with a thickness of 0.3¢1.5 nm on silica surface) may be precisely controlled using the transport reduction (TR) technique. The species =¢O¢Fe(OH)2 and (=Si¢O¢)2¢FeOH forming the surface monolayer are not reduced at 400¢600░C because of their covalent bonding to the silica surface, as demonstrated by M÷ssbauer spectroscopy. Iron oxide microparticles (microstructures)
Vladimir M. Smirnov; Vladimir G. Povarov; Gennadii P. Voronkov; Valentin G. Semenov; Igor' V. Murin; Viktor N. Gittsovich; Boris M. Sinel'nikov
Identifying prospective antifouling coatings for venturis: Zeta potential measurements of oxides at elevated temperatures
This report describes the results of research to determine the zeta potential of oxides responsible for fouling of heat transfer, venturi, and other flow measurement device surfaces. Fouling deposits formed on these surfaces reduce mass flow rates of water, causing power reductions of as much as 3 to 4%. There is considerable evidence that deposit formation can be prevented by coating the critical surfaces with a coating material that electrostatically repels the suspended fouling particulates. The zeta potential can be used as a parameter to identify and determine the best coating material to be employed for fouling prevention. The research entailed the development of the equipment necessary for zeta potential measurements, measurement of zeta potentials of oxides and coatings of interest to nuclear power plant applications, and evaluation of candidate coating materials to prevent fouling of surfaces. By this approach, numerous metals and oxides have been identified as potential coating materials. Fouling studies revealed that magnetite does not deposit on tungsten and palladium surfaces, indicating the potential use of these metals for coating venturi surfaces used in nuclear power plants.
Jayaweera, P.; Hettiarachchi, S.; Pound, B.G. (SRI International, Menlo Park, CA (United States))
The anti-oxidation potential of polyphenol extract from cocoa leaves on mechanically deboned chicken meat (MDCM)
Polypenols were extracted from young cocoa leaves (CL) and analysed for their total phenols (Folin-Ciocalteau method), catechin composition (HPLC method) and reducing power (Fe3+ reduction). The extracts (at different concentrations) were tested for their anti-oxidation potential in a model meat system, based on mechanically deboned chicken meat (MDCM). The anti-oxidation characteristics were compared against a 1:1 butylated hydroxyl anisole (BHA)\\/butylated
Osman Hassan; Lam Swet Fan
Study on the Reduction Behavior of Zirconia Supported Iron Oxide Catalysts by Temperature-Programmed Reduction Combined with in SituM÷ssbauer Spectroscopy
The reduction properties of Fe2O3\\/ZrO2catalysts with various Fe2O3loading and the interactions between iron oxide and zirconia have been studied by using temperature-programmed reduction combined within situM÷ssbauer spectroscopy. This is shown that the intermediates formed during reduction depend strongly not only on the reduction temperature but also on the iron loading. Several iron species such as bulk phase ?-Fe2O3, small ?-Fe2O3particles,
Kaidong Chen; Yining Fan; Zheng Hu; Qijie Yan
Superior catalysts for selective catalytic reduction of nitric oxide. Quarterly technical progress report, January 1, 1995--March 31, 1995.
National Technical Information Service (NTIS)
During this quarter, progress was made on the following tasks: TPD techniques were employed to study the reaction mechanism of the selective catalytic reduction of nitrogen oxide with ammonia over iron oxide pillared clay catalyst; and a sulfur dioxide re...
W. B. Li R. T. Yang
Studies on Oxidation, Reduction and Adsorption of Metallic Ions in Aqueous Solutions by Activated Carbons and the Like.
National Technical Information Service (NTIS)
Activated carbons were used for oxidation, reduction and adsorption of metallic ions in aqueous solutions to separate, refine and recover them. Activated carbons promote the oxidation reaction of Fe(2+) to Fe(3+) and hexacyanoferrate (II) to hexacyanoferr...
I. Saito
Yttrium oxide/gadolinium oxide-modified platinum nanoparticles as cathodes for the oxygen reduction reaction.
Rare-earth-element (Y, Gd) modified Pt nanoparticles (NPs) supported on a carbon substrate (Vulcan XC-72) are synthesized via a water-in-oil chemical route. In both cases, X-ray diffraction (XRD) measurements show the non-formation of an alloyed material. Photoemission spectroscopy (XPS) results reveal that Y and Gd are oxidized. Additionally, no evidence of an electronic modification of Pt can be brought to light. Transmission electron microscopy (TEM) studies indicate that Pt-Y2 O3 and Pt-Gd2 O3 particles are well dispersed on the substrate-and that their average particle sizes are smaller than the Pt-NP sizes. The catalytic activity of the Pt-Y2 O3 /C and Pt-Gd2 O3 /C catalysts towards the oxygen reduction reaction (ORR) is studied in a 0.5?M H2 SO4 electrolyte. The surface and mass specific activities of the Pt-Y2 O3 /C catalyst towards the ORR at 0.9 V (vs. the reversible hydrogen electrode, RHE) are (54.3▒1.2) ?A?cm(-2) Pt and MA=(23.1▒0.5) mA?mg(-1) Pt , respectively. These values are 1.3-, and 1.6-fold higher than the values obtained with a Pt/C catalyst. Although the as-prepared Pt-Gd2 O3 /C catalyst has a lower catalytic activity for the ORR compared to Pt/C, the heat-treated sample shows a surface specific activity of about (53.0▒0.7) ?A?cm(-2) Pt , and a mass specific activity (MA) of about (18.2▒0.5) mA?mg(-1) Pt at 0.9 V (vs. RHE). The enhancement of the ORR kinetics on the Pt-Y2 O3 /C and heat-treated Pt-Gd2 O3 /C catalysts could be associated with the formation of platinum NPs presenting modified surface properties. PMID:24819164
Luo, Yun; Habrioux, Aurķlien; Calvillo, Laura; Granozzi, Gaetano; Alonso-Vante, Nicolas
Manganese sulfide formation via concomitant microbial manganese oxide and thiosulfate reduction
The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 produced ╬│-MnS (rambergite) nanoparticles during the concurrent reduction of MnOŌ and thiosulfate coupled to HŌ oxidation. To investigate effect of direct microbial reduction of MnOŌ on MnS formation, two MR-1 mutants defective in outer membrane c-type cytochromes (╬mtrC\\/╬omcA and ╬mtrC\\/╬omcA\\/╬mtrF) were also used and it was determined that direct reduction of MnOŌ was
Ji-Hoon Lee; David W. Kennedy; Alice Dohnalkova; Dean A. Moore; Ponnusamy Nachimuthu; Samantha B. Reed; Jim K. Fredrickson
Characterization study of polycrystalline tin oxide surfaces before and after reduction in CO
NASA Technical Reports Server (NTRS)
Polycrystalline tin oxide surfaces have been examined before and after reduction in 40 Torr of CO at 100 and 175 C using Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA), ion scattering spectroscopy (ISS) and electron stimulated desorption (ESD). The changes in the surface composition and chemical states of the surface species generally are subtle for the reductive conditions used. However, significant changes do occur with regard to the amounts and the chemical forms of the hydrogen-containing species remaining after both the 100 and 175 C reductions.
Drawdy, Jean E.; Hoflund, Gar B.; Davidson, Mark R.; Schryer, David R.
Multifunctional Low-Pressure Turbine for Core Noise Reduction, Improved Efficiency, and Nitrogen Oxide (NOx) Reduction
NASA Technical Reports Server (NTRS)
This work studied the feasibility of using Helmholtz resonator cavities embedded in low-pressure-turbine (LPT) airfoils to (1) reduce core noise by damping acoustic modes; (2) use the synthetic jets produced by the liner hole acoustic oscillations to improve engine efficiency by maintaining turbulent attached flow in the LPT at low-Reynolds-number cruise conditions; and (3) reduce engine nitrogen oxide emissions by lining the internal cavities with materials capable of catalytic conversion. Flat plates with embedded Helmholtz resonators, designed to resonate at either 3000 or at 400 Hz, were simulated using computational fluid dynamics. The simulations were conducted for two inlet Mach numbers, 0.25 and 0.5, corresponding to Reynolds numbers of 90 000 and 164 000 based on the effective chordwise distance to the resonator orifice. The results of this study are (1) the region of acoustic treatment may be large enough to have a benefit; (2) the jets may not possess sufficient strength to reduce flow separation (based on prior work by researchers in the flow control area); and (3) the additional catalytic surface area is not exposed to a high velocity, so it probably does not have any benefit.
Miller, Christopher J.; Shyam, Vikram; Rigby, David L.
Potential of municipal solid waste for renewable energy production and reduction of greenhouse gas emissions in South Korea.
Energy from waste (EfW) for nonrecyclable wastes is a suitable method of waste management and is important for renewable energy production. South Korea currently recycles 57% of household waste and landfills 26%. The remaining 17% is incinerated, mainly for heat production. In this study, the potential for energy production and reduction of corresponding greenhouse gas (GHG) emissions from municipal solid waste (MSW) in Korea was estimated without accounting for the lifecycle impact of waste management. The properties of the MSW were established from data available in national-scale waste surveys and reports. The potential of EfW for GHG emission reduction was calculated considering (1) the direct release of anthropogenic carbon, nitrous oxide (N2O), and methane (CH4); and (2) the reduction in indirect GHG emissions by fossil fuel displacement. CH4 emissions from landfilling were also estimated from biogenic carbon in waste. Applying the resulting emission factors to various EfW cases suggests that the current level of GHG emissions is significant but can be substantially reduced by increased use of EfW. A net reduction in GHG emissions can be achieved only by EfW with combined heat and power (CHP). PMID:20222530
Ryu, Changkook
A simple and efficient method to prepare graphene by reduction of graphite oxide with sodium hydrosulfite
NASA Astrophysics Data System (ADS)
Inspired by an ancient reducing method used in textile production, sodium hydrosulfite was used to reduce graphite oxide as an efficient reducing agent in our work. The reduced materials were characterized by x-ray photoelectron spectroscopy, thermogravimetric analysis, wide-angle x-ray scattering, Raman spectroscopy, solid state 13C NMR spectroscopy and electrical conductivity measurements, respectively. The results showed that graphite oxide can be reduced with sodium hydrosulfite in a few minutes, with a degree of reduction comparable to those achieved with hydrazine. It provides an efficient method to reduce graphite oxide and could be used as a method to prepare novel composites.
Zhou, Tiannan; Chen, Feng; Liu, Kai; Deng, Hua; Zhang, Qin; Feng, Jiwen; Fu, Qiang
Explosive thermal reduction of graphene oxide-based materials: mechanism and safety implications
Thermal reduction of graphene oxide or graphite oxide (GO) is an important processing step in the fabrication of many graphene-based materials and devices. Here we show that some bulk solid GO samples can undergo explosive decomposition when small samples are heated slowly in inert gas environments, while others do not. These micro-explosions can occur for samples as small as few milligrams and are sufficiently energetic to cause laboratory equipment damage. Thermochemical analysis methods are used to understand the factors that lead to the explosive reduction mode. The studies show that the explosive mode of reduction is caused by the exothermicity of GO reduction coupled with a threshold sample mass/size that causes heat and mass transfer limitations leading to local temperature rise and a thermal runaway reaction. The explosive mode of reduction is not caused or promoted by interstitial water, and its onset temperature can be lowered by immersion in potassium hydroxide solution. By allowing early release of internal gas pressure, the explosive mode reduces the extent of surface area development in GO exfoliation from an optimum value of 1470 m2g?1 obtained under non-explosive reduction conditions. Explosive reduction of bulk GO poses industrial safety hazards during large-scale storage, handling, and processing.
Qiu, Yang; Guo, Fei; Hurt, Robert; Kulaots, Indrek
Effect of reduction treatment on microstructure and mechanical properties of fluorite oxides
NASA Astrophysics Data System (ADS)
Ceria based materials because of their high ionic conductivity at low temperatures are potential candidates as the electrolyte component in the new generation of low temperature solid oxide fuel cells (SOFCs). The effects of operation conditions in SOFCs on microstructure and mechanical integrity of ceria-based materials are evaluated in this research. Pure ceria and gadolinium doped ceria (GDC) were selected to perform this investigation. The state-of-art electrolyte material, yttria-stabilized zirconia (YSZ), was also studied for comparison purposes. The samples were heat treated at 800░C under various oxygen partial pressures ( PO2 s) until equilibrium was reached. The defect concentrations were conserved to room temperature by fast cooling. The crystal structure and the lattice parameter were evaluated by the x-ray diffraction method. Microstructural evaluations and fractographic analyses were conducted using electron microscopy techniques. The intrinsic elastic modulus was evaluated using nanoindentation techniques. The bulk elastic modulus and fracture strength were measured using the four-point-bend testing method and fracture toughness was evaluated using chevron-notched Brazilian disc samples loaded under the mode I condition. The result of this study revealed that microcracks were formed during the reduction heat treatment in ceria and GDC when the PO2 was lower than 10-19 atm. It was also found that ceria samples upon cooling experienced phase transformation that led to the formation of several ordered pseudo-cubic phases. The intrinsic elastic modulus of both ceria and GDC decreased drastically when heat treated at very low PO2 s while the effect was insignificant in YSZ. These results correlate well with our theoretical modeling. Further analysis suggests that an increase in the point defect concentration weakens the attractive forces between atoms. The degradation of bulk elastic modulus of ceria was more pronounced at low PO2 s due to the presence of microcracks caused by the reduction treatments. The results on fracture properties of ceria showed that the flexural strength decreased significantly after reduction in very low PO2 s; however, in contrast, fracture toughness was increased by 30--40% when the PO2 was decreased to the range of 10-20--10-22 atm. Fractographic studies showed that the microcracks developed during reduction treatment are responsible for the decreased strength. In this dissertation, the enhancement in toughness was explained by crack deflection and microcrack toughening mechanisms.
Wang, Yanli
Role of oxidation-reduction processes in the solution of uranium oxides in acid media
The degree of oxidation of the components of the ore material is of decisive importance in the extraction of uranium. Since the solution of uranium is composed of various chemical processes and complicated by the presence of impurities in the ores, it is necessary to study the rules of uranium oxidation and the effect of various compounds which dissolve during
G. M. Nesmeyanova; G. M. Alkhazashvili
Pyrite oxidation and reduction - Molecular orbital theory considerations. [for geochemical redox processes
NASA Technical Reports Server (NTRS)
In this paper, molecular orbital theory is used to explain a heterogeneous reaction mechanism for both pyrite oxidation and reduction. The mechanism demonstrates that the oxidation of FeS2 by Fe(3+) may occur as a result of three important criteria: (1) the presence of a suitable oxidant having a vacant orbital (in case of liquid phase) or site (solid phase) to bind to the FeS2 via sulfur; (2) the initial formation of a persulfido (disulfide) bridge between FeS2 and the oxidant, and (3) an electron transfer from a pi(asterisk) orbital in S2(2-) to a pi or pi(asterisk) orbital of the oxidant.
Luther, George W., III
Reduction of nitric oxide by acetylene on Ir surfaces with different morphologies: comparison with reduction of NO by CO.
Reduction of nitric oxide (NO) by acetylene (C(2)H(2)) has been investigated by temperature-programmed desorption (TPD) on planar Ir(210) and faceted Ir(210) with tunable sizes of three-sided nanopyramids exposing (311), (311[overline]), and (110) faces. Upon adsorption, C(2)H(2) dissociates to form acetylide (CCH) and H species on the Ir surfaces at low C(2)H(2) precoverage. For adsorption of NO on C(2)H(2)-covered Ir, both planar and faceted Ir(210) exhibit high reactivity for reduction of NO with high selectivity to N(2) at low C(2)H(2) precoverage, although the reaction is completely inhibited at high C(2)H(2) precoverage. Coadsorbed C(2)H(2) significantly influences dissociation of NO. The N-, H-, and C-containing TPD products are dominated by N(2), H(2), CO, and CO(2) together with small amounts of H(2)O. For adsorption of NO on C-covered Ir(210) at fractional C precoverage, formation of CO(2) is promoted while production of CO is reduced. Reduction of NO by C(2)H(2) is structure sensitive on faceted Ir(210) versus planar Ir(210), but no evidence is found for size effects in the reduction of NO by C(2)H(2) on faceted Ir(210) for average facet sizes of 5 nm and 14 nm. The results are compared with reduction of NO by CO on the same Ir surfaces. As for NO+C(2)H(2), the Ir surfaces are very active for reduction of NO by CO with high selectivity to N(2) and the reaction is structure sensitive, but clear evidence is found for size effects in the reduction of NO by CO on the nanometer scale. Furthermore, coadsorbed CO does not affect dissociation of NO at low CO precoverage whereas coadsorbed CO considerably influences dissociation of NO at high CO precoverage. The adsorption sites of CCH+H on Ir are characterized by density functional theory. PMID:23273167
Chen, Wenhua; Shen, Quantong; Bartynski, Robert A; Kaghazchi, Payam; Jacob, Timo
The report describes work to demonstrate, on a utility pilot plant scale, the performance, reliability, and practicability of reducing nitrogen oxides (NOx) emissions from steam boilers by reduction of NOx with ammonia over a platinum catalyst. A utility pilot plant treating a sl...
Reduction of nitric oxide by isobutene over Cu-Mn alloys
Cu-Mn alloys with various bulk compositions have been used in the catalytic reduction of NO by i-C{sub 4}H{sub 8} at 500 C. The gas-phase reactions were monitored by mass spectroscopy (MS) and the catalyst surfaces were characterized by X-ray photoelectron spectroscopy (XPS) at certain stages of the reactions. The compositions and oxidation states of the alloy surfaces are strongly dependent on the bulk composition and the oxygen pressure, and eventually influence the reaction kinetics, product distribution, as well as mechanism of NO reduction. On a Cu-Mn (atomic 8%) alloy surface, with a medium oxygen pressure (reducing conditions), the reaction of NO with partially oxidized products of i-C{sub 4}H{sub 8} is suggested to be the main mechanism of NO reduction. However, too low or too high an oxygen pressure leads to direct decomposition of NO with the production of N{sub 2} or N{sub 2}O, depending on reducing or oxidizing reaction conditions. On high-manganese-concentration alloy surfaces (55%, 92% atomic), under strong reducing conditions, the main path of NO reduction is via the reaction of adsorbed NO{sub 2} with i-C{sub 4}H{sub 8}, which gives rise to N{sub 2} production. When the reaction conditions pass from reducing to oxidizing, NO decomposition leads to the formation of N{sub 2}O.
Lu, H.; Karlsson, U.O. [Royal Inst. of Tech., Stockholm (Sweden)] [Royal Inst. of Tech., Stockholm (Sweden); Pradier, C.M. [Ecole Nationale Superieure de Chimie, Paris (France). Lab. de Physico-Chimie des Surfaces] [Ecole Nationale Superieure de Chimie, Paris (France). Lab. de Physico-Chimie des Surfaces
Control of combustion-generated nitrogen oxides by selective non-catalytic reduction
Controlling nitrogen oxides (NOx) emissions is becoming a daunting technical challenge as increasingly strict emission limits are being imposed. The stringent regulations have prompted the innovation and characterization of NOx control technologies suitable for various applications. This paper presents a review on NOx removal techniques with particular reference to selective non-catalytic reduction (SNCR) technology. This includes initially how SNCR emerged
M. Tayyeb Javed; Naseem Irfan; B. M. Gibbs
The paper gives results of studies of the applicability and effectiveness of fuel/air staging (variously called In-furnace NOx Reduction, reburning, or biased firing) in controlling nitrogen oxide (NOx) emissions from refinery process heaters and cement kilns. The studies were co...
Temperature-programmed reduction and oxidation of bimetallic catalysts Rh?Ag\\/Al 2 O 3
Investigations of temperature-programmed reduction and oxidation of bimetallic catalysts Rh?Al2O3 seem to indicate that there are no strong interactions between rhodium and silver. Bimetallic catalysts rather show the additive properties of individual components, i. e. rhodium and silver.
T. Paryjczak; J. G¾ralski; K. W. J¾?wiak
Automatic apparatus for catalyst characterization by temperature-programmed reduction\\/desorption\\/oxidation
An apparatus is described for the automatic quantitative registration of reduction, desorption\\/adsorption, and oxidation phenomena which occur when a catalyst sample is heated or cooled under temperature programming in a flowing gas that contains either hydrogen or oxygen as the reactive component. The design considerations and the automation scheme are fully discussed. A typical example of the characterization of a
H. Boer; W. J. Boersma; N. Wagstaff
An analysis of results from the Regional Oxidant Modeling for Northeast Transport (ROMNET) study (U.S. EPA, 1991, EPA-450/4-91-002a) has investigated the chemical conditions under which air quality was predicted to improve with reductions in ROG and/or NOx emissions, or with chan...
As an exercise in model sensitivity, the Environmental Protection Agency's Regional Oxidant Model (ROM) was run for several simulations to study the impact of across-the-board reductions in anthropogenic VOC and NOx emissions on the photochemical environment of the eastern United...
Electrolytic Reduction of Spent Oxide Fuel ¢ Bench-Scale Test Results
A series of tests were performed to demonstrate the electrolytic reduction of spent light water reactor fuel at bench-scale in a hot cell at the Idaho National Laboratory Materials and Fuels Complex (formerly Argonne National Laboratory - West). The process involves the conversion of oxide fuel to metal by electrolytic means, which would then enable subsequent separation and recovery of actinides via existing electrometallurgical technologies, i.e., electrorefining. Four electrolytic reduction runs were performed at bench scale using ~500 ml of molten LiCl -- 1 wt% Li2O electrolyte at 650 ║C. In each run, ~50 g of crushed spent oxide fuel was loaded into a permeable stainless steel basket and immersed into the electrolyte as the cathode. A spiral wound platinum wire was immersed into the electrolyte as the anode. When a controlled electric current was conducted through the anode and cathode, the oxide fuel was reduced to metal in the basket and oxygen gas was evolved at the anode. Salt samples were extracted before and after each electrolytic reduction run and analyzed for fuel and fission product constituents. The fuel baskets following each run were sectioned and sampled, revealing an extent of uranium oxide reduction in excess of 98%.
S. D. Herrmann; S. X. Li; M. F. Simpson
Flash Reduction and Patterning of Graphite Oxide and Its Polymer Composite
Graphite oxide (GO) is a promising precursor for the bulk production of graphene-based materials due to its relatively low cost of synthesis. The superior solvent processability of GO makes it particularly attractive for making composites by premixing with other materials. Typically, the reduction of GO has relied on either chemical agents or high temperature treatment. Here we report a room
Laura J. Cote; Rodolfo Cruz-Silva; Jiaxing Huang
CO Oxidation and NO Reduction on Metal Surfaces: Density Functional Theory Investigations
This article reviews the accumulated theoretical results, in particular density functional theory calculations, on two catalytic processes, CO oxidation and NO reduction on metal surfaces. Owing to their importance in automotive emission control, these two reactions have generated a lot of interest in the last 20 years. Here the pathways and energetics of the involved elementary reactions under different catalytic
Zhi-Pan Liu; P. Hu
Electro-catalytic reduction of nitrogen oxides: Topical report for May 17, 1987June 30, 1988
This study is aimed at investigating the use of intense electric fields and discharges resulting from the application of such fields to electrodes of small dimensions (such as points or wires) in conjunction with various material surfaces to bring about the reduction of nitric oxides without the aid of other reducing agents such as NHŌ, CO, etc. Two important observations
Metals, nitrides, and carbides via solar carbothermal reduction of metal oxides
We have examined the thermodynamics of the carbothermic reduction of metal oxides in either nitrogen or argon atmospheres. The reaction, which is given generally by (where the M denotes metal) MxOy + C (+ N2;) ? {Mx?Ny?, Mx?Cy?, M} + CO, is highly endothermic and proceeds at temperatures from 1300 to 2350 K for the systems considered. Exploratory experimental studies
Edward A. Fletcher
Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles
The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant. - Graphical abstract: Reduction of iron oxide nanoparticles by carbon black at 1200 deg. C yields well crystallized carbon-encapsulated iron nanoparticles. Highlights: > Carbon-encapsulated iron nanoparticles were synthesized by carbothermal reduction of iron oxide nanoparticles. > The process has the highest selectivity at 1200 C. > Lower temperatures result in iron oxide nanoparticles wrapped in carbon matrix. > The encapsulation rate of Fe at 1200 deg. C was found to be 15%.
Bystrzejewski, M., E-mail: email@example.com [Dept of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw (Poland)
Natural-Gas Catalytic Reduction of Nitric Oxide Tail Gases from Nitric Acid Production.
National Technical Information Service (NTIS)
Tests were conducted on natural-gas catalytic reduction of tail-gas nitric oxides from nitric acid production; they took place at atmospheric pressure in a combined installation. In operation over 710 hrs the nickel-chromium foil showed sufficient thermal...
A. D. Tikhonenko M. N. Nabiev
In-Situ Chemical Reduction and Oxidation of VOCs in Groundwater: Groundwater Treatability Studies
NASA Technical Reports Server (NTRS)
This paper presents NASA Marshall Space Flight Center's treatability studies for volatile organic compounds in groundwater. In-Situ groundwater treatment technologies include: 1) Chemical Reduction(Ferox); 2) Chemical Oxidation (Fenton Reagents, Permanganate, and Persulfate); and 3) Thermal (Dynamic Underground Stripping, Six-Phase Heating). This paper is presented in viewgraph form.
Keith, Amy; Glasgow, Jason; McCaleh, Rececca C. (Technical Monitor)
The objectives of this research project were to refine existing models of microbiological and geochemical controls on Fe(III) oxide reduction, using laboratory reactor systems which mimic to varying degrees the physical and chemical conditions of the subsurface. Novel experimenta...
Potential toxicity of superparamagnetic iron oxide nanoparticles (SPION)
Superparamagnetic iron oxide nanoparticles (SPION) are being widely used for various biomedical applications, for example, magnetic resonance imaging, targeted delivery of drugs or genes, and in hyperthermia. Although, the potential benefits of SPION are considerable, there is a distinct need to identify any potential cellular damage associated with these nanoparticles. Besides focussing on cytotoxicity, the most commonly used determinant of toxicity as a result of exposure to SPION, this review also mentions the importance of studying the subtle cellular alterations in the form of DNA damage and oxidative stress. We review current studies and discuss how SPION, with or without different surface coating, may cause cellular perturbations including modulation of actin cytoskeleton, alteration in gene expression profiles, disturbance in iron homeostasis and altered cellular responses such as activation of signalling pathways and impairment of cell cycle regulation. The importance of protein-SPION interaction and various safety considerations relating to SPION exposure are also addressed.
Singh, Neenu; Jenkins, Gareth J.S.; Asadi, Romisa; Doak, Shareen H.
Advanced experimental analysis of controls on microbial Fe(III) oxide reduction. First year progress report
'The authors have made considerable progress toward a number of project objectives during the first several months of activity on the project. An exhaustive analysis was made of the growth rate and biomass yield (both derived from measurements of cell protein production) of two representative strains of Fe(III)-reducing bacteria (Shewanellaalga strain BrY and Geobactermetallireducens) growing with different forms of Fe(III) as an electron acceptor. These two fundamentally different types of Fe(III)-reducing bacteria (FeRB) showed comparable rates of Fe(III) reduction, cell growth, and biomass yield during reduction of soluble Fe(III)-citrate and solid-phase amorphous hydrous ferric oxide (HFO). Intrinsic growth rates of the two FeRB were strongly influenced by whether a soluble or a solid-phase source of Fe(III) was provided: growth rates on soluble Fe(III) were 10--20 times higher than those on solid-phase Fe(III) oxide. Intrinsic FeRB growth rates were comparable during reduction of HF0 and a synthetic crystalline Fe(III) oxide (goethite). A distinct lag phase for protein production was observed during the first several days of incubation in solid-phase Fe(III) oxide medium, even though Fe(III) reduction proceeded without any lag. No such lag between protein production and Fe(III) reduction was observed during growth with soluble Fe(III). This result suggested that protein synthesis coupled to solid-phase Fe(III) oxide reduction in batch culture requires an initial investment of energy (generated by Fe(III) reduction), which is probably needed for synthesis of materials (e.g. extracellular polysaccharides) required for attachment of the cells to oxide surfaces. This phenomenon may have important implications for modeling the growth of FeRB in subsurface sedimentary environments, where attachment and continued adhesion to solid-phase materials will be required for maintenance of Fe(III) reduction activity. Despite considerable differences in the rate and pattern of FeRB growth with different Fe(III) forms, a roughly consistent long-term biomass yield of 5 to 15 mg protein per mmol Fe(III) reduced was observed during growth on different forms of Fe(III). These results should prove useful for quantitative modeling of FeRB growth and metabolism in various types of experimental and in situ anaerobic sedimentary systems.'
Roden, E.E.; Urrutia, M.M.
Scenario analysis on CO 2 emissions reduction potential in China's iron and steel industry
The international climate community has begun to assess a range of possible options for strengthening the international climate change effort after 2012. Analysis of the potential for sector-based emissions reduction and relevant mitigation options will provide the necessary background information for the debate. In order to assess the CO2 abatement potential of China's steel industry, a model was developed using
Ke Wang; Can Wang; Xuedu Lu; Jining Chen
Basic Nickel Carbonate: Part I. Microstructure and Phase Changes during Oxidation and Reduction Processes
NASA Astrophysics Data System (ADS)
A significant industrial problem associated with the production of nickel from basic nickel carbonate has been identified. Fundamental studies of the change of phase, product surface, and internal microstructures taking place during oxidation and reduction processes at temperatures between 110 ░C and 900 ░C have been carried out. The various elemental reactions and fundamental phenomena that contribute to the change of the physical and chemical characteristics of the samples during the processes taking place in Ni metal production through gas/solid-reduction processes have been identified and thoroughly investigated. The following phenomena affecting the final-product microstructure were identified as follows: (1) chemical changes, i.e., decomposition, reduction reactions, and oxidation reactions; (2) NiO and Ni recrystallization and grain growth; (3) NiO and Ni sintering and densification; and (4) agglomeration of the NiO and Ni particles.
Rhamdhani, M. A.; Jak, E.; Hayes, P. C.
A one-step, solvothermal reduction method for producing reduced graphene oxide dispersions in organic solvents.
Refluxing graphene oxide (GO) in N-methyl-2-pyrrolidinone (NMP) results in deoxygenation and reduction to yield a stable colloidal dispersion. The solvothermal reduction is accompanied by a color change from light brown to black. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images of the product confirm the presence of single sheets of the solvothermally reduced graphene oxide (SRGO). X-ray photoelectron spectroscopy (XPS) of SRGO indicates a significant increase in intensity of the C=C bond character, while the oxygen content decreases markedly after the reduction is complete. X-ray diffraction analysis of SRGO shows a single broad peak at 26.24 degrees 2theta (3.4 A), confirming the presence of graphitic stacking of reduced sheets. SRGO sheets are redispersible in a variety of organic solvents, which may hold promise as an acceptor material for bulk heterojunction photovoltaic cells, or electromagnetic interference shielding applications. PMID:20586422
Dubin, Sergey; Gilje, Scott; Wang, Kan; Tung, Vincent C; Cha, Kitty; Hall, Anthony S; Farrar, Jabari; Varshneya, Rupal; Yang, Yang; Kaner, Richard B
Synthesis of graphene nanosheets via oxalic acid-induced chemical reduction of exfoliated graphite oxide
Preparing high-quality graphene through reduction of graphene oxide (GO) by oxalic acid is demonstrated in this paper. Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffraction and Raman spectrometry were taken to confirm the reduction of GO and the formation of graphene under these mild conditions. Thermogravimetric analysis and conductivity measurements further testify the excellent thermal stability and conductivity of the obtained graphene. A possible mechanism for the reduction process was also proposed. Furthermore, a Pt-graphene composite was fabricated on a glassy carbon electrode and excellent electrocatalytic activity towards methanol oxidation was observed. With advantages of low toxicity, simple purification process and high quality of the product, oxalic acid provides a feasible route to prepare graphene from GO under mild conditions, thus facilitating the use of graphene-based materials for large-scale applications.
Song, Peng; Zhang, Xiao-Yan; Sun, Mingxun; Cui, Xiao-Li; Lin, Yuehe
Reversible oxidation/reduction of silver supported on silica aerogel: Influence of the addition of phosphate
NASA Astrophysics Data System (ADS)
Ag/SiO2 and Ag3PO4/SiO2 systems supported on silica aerogel were investigated using temperature-programmed reduction (TPR), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and infrared spectroscopy. The formation of highly dispersed silver particles, uniformly distributed along the surface and stabilized with silanol groups, was observed for Ag/SiO2 system. Phosphate and silanol groups produce two states of silver localization in phosphate-containing system. The addition of phosphate onto the silica surface leads to the reversible oxidation/reduction of silver in the temperature range of 100-300░C with transitions of silver (particles 10-30 nm in size) to charged states (ions, clusters stabilized by phosphate groups). This reversible behavior of silver is stable, and the amount of silver involved in these processes remained constant (ś50%) for the series of consistent cyclic oxidation/reduction treatments.
Mamontov, G. V.; Izaak, T. I.; Magaev, O. V.; Knyazev, A. S.; Vodyankina, O. V.
Reduction phases of thin iron-oxide nanowires upon thermal treatment and Li exposure
NASA Astrophysics Data System (ADS)
Iron oxide nanostructures, a promising alternative to carbon-based anode in lithium-ion batteries, can be produced using a hard template route. This procedure guarantees the formation of Fe2O3 nanowires with comparable diameter and size (average diameter 8 nm) with a dominant cubic ?-phase at the surface. Lithium exposure of the iron oxide nanowires in ultra-high-vacuum (UHV) conditions induces reduction of the Fe ion, leading to a Fe3O4 and then to a Fe2+ phase, as determined by means of core-level photoemission spectroscopy. Mild annealing of Fe2O3 in UHV determines an oxygen content reduction for the nanowires at lower temperature with respect to the bulk phase. The morphology and the evolution of the electronic properties upon reduction have been compared to those of micro-sized bulk-like grains, to unravel the role of the reduced size and surface-volume ratio.
Angelucci, Marco; Frau, Eleonora; Hassoun, Jusef; Hong, Inchul; Grazia Betti, Maria; Panero, Stefania; Scrosati, Bruno; Mariani, Carlo
Degradation of diclofenac by advanced oxidation and reduction processes: kinetic studies, degradation pathways and toxicity assessments.
Many pharmaceutical compounds and metabolites are found in surface and ground waters suggesting their ineffective removal by conventional wastewater treatment technologies. Advanced oxidation/reduction processes (AO/RPs), which utilize free radical reactions to directly degrade chemical contaminants, are alternatives to traditional water treatment. This study reports the absolute rate constants for reaction of diclofenac sodium and model compound (2, 6-dichloraniline) with the two major AO/RP radicals: the hydroxyl radical (ĢOH) and hydrated electron (e(aq)(-)). The bimolecular reaction rate constants (M(-1) s(-1)) for diclofenac for ĢOH was (9.29 ▒ 0.11) ū 10(9), and for e(-)(aq) was (1.53 ▒ 0.03) ū10(9). To provide a better understanding of the decomposition of the intermediate radicals produced by hydroxyl radical reactions, transient absorption spectra are observed from 1 - 250 ?s. In addition, preliminary degradation mechanisms and major products were elucidated using (60)Co ?-irradiation and LC-MS. The toxicity of products was evaluated using luminescent bacteria. These data are required for both evaluating the potential use of AO/RPs for the destruction of these compounds and for studies of their fate and transport in surface waters where radical chemistry may be important in assessing their lifetime. PMID:23384514
Yu, Hui; Nie, Er; Xu, Jun; Yan, Shuwen; Cooper, William J; Song, Weihua
Palladium and gold nanotubes as oxygen reduction reaction and alcohol oxidation reaction catalysts in base.
Palladium (PdNTs) and gold nanotubes (AuNTs) were synthesized by the galvanic displacement of silver nanowires. PdNTs and AuNTs have wall thicknesses of 6?nm, outer diameters of 60?nm, and lengths of 5-10 and 5-20??m, respectively. Rotating disk electrode experiments showed that the PdNTs and AuNTs have higher area normalized activities for the oxygen reduction reaction (ORR) than conventional nanoparticle catalysts. The PdNTs produced an ORR area activity that was 3.4, 2.2, and 3.7?times greater than that on carbon-supported palladium nanoparticles (Pd/C), bulk polycrystalline palladium, and carbon-supported platinum nanoparticles (Pt/C), respectively. The AuNTs produced an ORR area activity that was 2.3, 9.0, and 2.0?times greater than that on carbon-supported gold nanoparticles (Au/C), bulk polycrystalline gold, and Pt/C, respectively. The PdNTs also had lower onset potentials than Pd/C and Pt/C for the oxidation of methanol (0.236?V), ethanol (0.215?V), and ethylene glycol (0.251?V). In comparison to Pt/C, the PdNTs and AuNTs further demonstrated improved alcohol tolerance during the ORR. PMID:24757078
Alia, Shaun M; Duong, Kathlynne; Liu, Toby; Jensen, Kurt; Yan, Yushan
Redox Potentials, Laccase Oxidation, and Antilarval Activities of Substituted Phenols
Laccases are copper-containing oxidases that are involved in sclerotization of the cuticle of mosquitoes and other insects. Oxidation of exogenous compounds by insect laccases may have the potential to produce reactive species toxic to insects. We investigated two classes of substituted phenolic compounds, halogenated di- and trihydroxybenzenes and substituted di-tert-butylphenols, on redox potential, oxidation by laccase and effects on mosquito larval growth. An inverse correlation between the oxidation potentials and laccase activity of halogenated hydroxybenzenes was found. Substituted di-tert-butylphenols however were found to impact mosquito larval growth and survival. In particular, 2,4-di-tert-butyl-6-(3-methyl-2-butenyl)phenol (15) caused greater than 98% mortality of Anopheles gambiae larvae in a concentration of 180 nM, whereas 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-methylpropanal oxime (13) and 6,8-di-tert-butyl-2,2-dimethyl-3,4-dihydro-2H-chromene (33) caused 93% and 92% mortalities in concentrations of 3.4 and 3.7 ?M, respectively. Larvae treated with di-tert-butylphenolic compounds died just before pupation.
Prasain, Keshar; Nguyen, Thi D. T.; Gorman, Maureen J.; Barrigan, Lydia M.; Peng, Zeyu; Kanost, Michael R.; Syed, Lateef U.; Li, Jun; Zhu, Kun Yan; Hua, Duy H.
Potential of front-face fluorescence to monitor OM reduction in drinking water during potabilization process
NASA Astrophysics Data System (ADS)
Elimination of OM in drinking water represents a great challenge for municipalities and technical actors to ensure that it can be safely used for consumption purposes. Indeed, current indicators such as Total Organic Carbon (TOC), turbidity or UV-Absorbance at 254 nm (UVA254) enable only non-specific overview of the amount of organic residuals in water. Fluorescence EEMs are a potent tool for discrimination and deep analysis of OM detailed composition and behaviour. It has been shown that several forms of OM co-exist in raw water, and come from various origins (bacteria, humic compoundsģ). Potabilization operation is composed of different steps that aim at decreasing all forms of OM using chemical as well as physical methods (ozone oxidation, filtration on activated carbon or sand, flocculation etc.). Unfortunately, it has been observed that reduction of OM during this process was not identical for all the forms, and the process showed a particular lack of efficiency during raining periods. 130 samples of water at various stages of potabilization were analyzed using home-made compact fluorometer, an apparatus composed of UV excitation LEDs. Using chemometrical treatment of spectral data, we put into highlight 5 different forms of OM that were identified according to litterature data. We evidenced the critical steps of the purification on OM reduction, as well as the relative content of each form from raw to product water. In particular, we showed that two forms were less reduced than the other three, so that progressive enrichment of total OM in the former was observed throughout the process. Moreover, a study was carried out in order to establish calibration models over conventional analyses using the spectral information. Highly satisfying models were thus obtained over TOC, turbidity and UVA254, with average RMSEC values of 13%, 7% and 16% respectively. These results demonstrate the potential of the fluorescence analyzer to simultaneously predict three major OM-related quality parameters of water. Finally, study of relationships between the different OM forms, climate parameters (temperature, raw water flow, rainfall) and coagulant amounts showeds that each OM form was specifically linked to these parameters. In particular, we were able to pinpoint one of the five forms that was most associated with the water flow, and also the most flocculated by the coagulant. In conclusion, this work demonstrates that our fluorescence analyzer helps to get improved knowledge of OM behavior during potabilization process. Five different OM forms were identified and their respective evolution was characterized. Furthermore, we evidenced a potential use of a compact and small-size analyzer to monitor water purification steps through simultaneous prediction of quality parameters related to OM content.
Lacotte, Pierre
Biomineralization Associated with Microbial Reduction of Fe3+ and Oxidation of Fe2+ in Solid Minerals
Iron- reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so they play an important role in geochemical cycling of iron in a wide range of environments. This study was undertaken to investigate iron redox cycling in the deep subsurface by taking an advantage of the Chinese Continental Scientific Deep Drilling project. A fluid sample from 2450 m was collected and Fe(III)-reducing microorganisms were enriched using specific media (pH 6.2). Nontronite, an Fe(III)-rich clay mineral, was used in initial enrichments with lactate and acetate as electron donors under strictly anaerobic condition at the in-situ temperature of the fluid sample (65oC). Instead of a monotonic increase in Fe(II) concentration with time as would have been expected if Fe(III) bioreduction was the sole process, Fe(II) concentration initially increased, reached a peak, but then decreased to a minimum level. Continued incubation revealed an iron cycling with a cycling period of five to ten days. These initial results suggested that there might be Fe(III) reducers and Fe(II) oxidizers in the enrichment culture. Subsequently, multiple transfers were made with an attempt to isolate individual Fe(III) reducers and Fe(II) oxidizers. However, iron cycling persisted after multiple transfers. Additional experiments were conducted to ensure that iron reduction and oxidation was indeed biological. Biological Fe(II) oxidation was further confirmed in a series of roll tubes (with a pH gradient) where FeS and siderite were used as the sole electron donor. The oxidation of FeS occurred only at pH 10, and goethite, lepidocrocite, and ferrihydrite formed as oxidation products. Although molecular evidence (16S rRNA gene analysis) collectively suggested that only a single organism (a strain of Thermoanaerobacter ethanolicus) might be responsible for both Fe(III) reduction and Fe(II) oxidation, we could not rule out the possibility that Fe(III) reduction and Fe(II) oxidation may be accomplished by a consortia of organisms. Nonetheless, our data were definitive in showing that iron redox cycling exists in the deep subsurface.
Zhang, Gengxin; Dong, Hailiang; Jiang, Hongchen; Kukkadapu, Ravi K.; Kim, Jinwook; Eberl, Dennis D.; Xu, Zhiqin
Biostimulation of Iron Reduction and Subsequent Oxidation of Sediment Containing Fe-silicates and Fe-oxides: Effect of Redox Cycling on Fe(III) Bioreduction
Microbial reduction of iron has been shown to be important in the transformation and remediation of contaminated sediments. Re-oxidation of microbially reduced iron may occur in sediments that experience oxidation-reduction cycling and can thus impact the extent of contaminant remediation. The purpose of this research was to quantify iron oxidation in a flow-through column filled with biologically-reduced sediment and to compare the iron phases in the re-oxidized sediment to both the pristine and biologically-reduced sediment. The sediment contained both Fe(III)-oxides (primarily goethite) and silicate Fe (illite/vermiculite) and was biologically reduced in phosphate buffered (PB) medium during a 497 day column experiment with acetate supplied as the electron donor. Long-term iron reduction resulted in partial reduction of silicate Fe(III) without any goethite reduction, based on M÷ssbauer spectroscopy measurements. This reduced sediment was treated with an oxygenated PB solution in a flow-through column resulting in the oxidation of 38% of the biogenic Fe(II). Additional batch experiments showed that the Fe(III) in the oxidized sediment was more quickly reduced compared to the pristine sediment, indicating that oxidation of the sediment not only regenerated Fe(III) but also enhanced iron reduction compared to the pristine sediment. Oxidation-reduction cycling may be a viable method to extend iron-reducing conditions during in-situ bioremediation.
Komlos, John; Kukkadapu, Ravi K.; Zachara, John M.; Jaffe, Peter R.
Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water.
Food safety issues and increases in food borne illnesses have promulgated the development of new sanitation methods to eliminate pathogenic organisms on foods and surfaces in food service areas. Electrolyzed oxidizing water (EO water) shows promise as an environmentally friendly broad spectrum microbial decontamination agent. EO water is generated by the passage of a dilute salt solution ( approximately 1% NaCl) through an electrochemical cell. This electrolytic process converts chloride ions and water molecules into chlorine oxidants (Cl(2), HOCl/ClO(-)). At a near-neutral pH (pH 6.3-6.5), the predominant chemical species is the highly biocidal hypochlorous acid species (HOCl) with the oxidation reduction potential (ORP) of the solution ranging from 800 to 900mV. The biocidal activity of near-neutral EO water was evaluated at 25 degrees C using pure cultures of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Treatment of these organisms, in pure culture, with EO water at concentrations of 20, 50, 100, and 120ppm total residual chlorine (TRC) and 10min of contact time resulted in 100% inactivation of all five organisms (reduction of 6.1-6.7log(10)CFU/mL). Spray treatment of surfaces in food service areas with EO water containing 278-310ppm TRC (pH 6.38) resulted in a 79-100% reduction of microbial growth. Dip (10min) treatment of spinach at 100 and 120ppm TRC resulted in a 4.0-5.0log(10)CFU/mL reduction of bacterial counts for all organisms tested. Dipping (10min) of lettuce at 100 and 120ppm TRC reduced bacterial counts of E. coli by 0.24-0.25log(10)CFU/mL and reduced all other organisms by 2.43-3.81log(10)CFU/mL. PMID:17993375
Guentzel, Jane L; Liang Lam, Kang; Callan, Michael A; Emmons, Stuart A; Dunham, Valgene L
Chemical Oxygen Demand (COD) For Monitoring Reduction-Oxidation (Redox) Equilibrium During High Level Waste (HLW) Vitrification
High-level nuclear waste is being immobilized at the Savannah River Site by vitrification into borosilicate glass at the Defense Waste Processing Facility. Control of the REDuction/OXidation (REDOX) equilibrium in the DWPF melter is critical for processing high level liquid wastes. Based upon previous research, an acceptable iron REDOX ratio was defined for the DWPF melts as 0.09 Fe2/SFe 0.33. Controlling the DWPF melter at a REDuction/OXidation (REDOX) equilibrium ofFe2/SFe 0.33 prevents the potential for metallic and metallic sulfide species to form and accumulate on the floor of the melter. Control of foaming due to deoxygenation of manganic species is achieved by converting 66-100 of the MnO2 or Mn2O3 species in a waste feed to MnO before the waste is fed to the DWPF melter. At the lower redox limit of Fe 2/SFe 0.09 about 99 of the Mn 4/Mn 3 is converted to Mn 2. Therefore, the lower REDOX limit eliminates melter foaming from deoxygenation. Organic and nitrate concentrations in the DWPF melter feed are the major parameters influencing melt REDOX. Organics such as formates act as reductants while nitrates, nitrites, and manganic (Mn 4 and Mn 3) species act as oxidants. During melting, the REDOX of the melt pool cannot be measured. Therefore, the Fe 2/SFe ratio in the glass poured from the melter must be related to melter feed organic and oxidant concentrations to ensure production of a high quality glass without impacting production rate (e.g., from foaming) or melter life (e.g., from metal formation and accumulation).
Wet air oxidation pretreatment of biomethanated distillery effluent: Mapping pretreatment efficiency in terms color, toxicity reduction and biogas generation.
The effluents from molasses-based distilleries after biomethanation are beset with problems of intensified dark brown color, high residual COD, low biodegradability index (BOD/COD ratio <0.2) and toxicity issues for possible land application as a potential fertilizer. Wet air oxidation (WAO) pretreatment of biomethanated distillery effluent resulted in substantial enhancement in the biodegradability index (BI) (up to 0.8). WAO pretreated effluent on anaerobic digestion indicated favorable biogas generation with methane content up to 64% along with concomitant COD reduction up to 54.75%. The HPLC analysis indicated that the pretreatment facilitated degradation of major color containing compounds-namely melanoidins, up to 97.8%. The pretreated effluent with enhanced biodegradability along with substantially reduced color also indicated positive effect on seed germination (up to 100%), implying toxicity reduction of the effluent post WAO pretreatment. PMID:24583914
Sarat Chandra, T; Malik, S N; Suvidha, G; Padmere, M L; Shanmugam, P; Mudliar, S N
Oxidation potential and state of some vanadium ores and the relation of woody material to their deposition
Oxidation potential studies with a multiple pH-potential recorder designed and constructed for this purpose demonstrated that some uranium-vanadium ores in the Colorado Plateau were in a reduced state when deposited. Any oxidation which took place occurred after deposition. Experimental and theoretical reducing studies on fresh wood, wood degraded by burial for 450 years, and lignite, indicate that such ores may have been deposited by reduction of oxidized vanadium solutions by woody material. A vanadium (III) mineral, V2O(OH)4, was prepared synthetically by reduction of a vanadium (V) solution with wood. This is the only reported synthesis of any reduced vanadium mineral by any method. It was shown that the origin of almost all vanadium deposits currently of commercial importance involves life processes and products.
Pommer, Alfred Michael
Nitrite reduction with hydrous ferric oxide and Fe(II): stoichiometry, rate, and mechanism.
Fe(II)/Fe(III) oxide is an important redox couple in environmental systems. Recent studies have revealed unique characteristics of Fe(II)/Fe(III) oxide and reactions with oxidizing or reducing agents. Nitrite was used as an oxidizing agent in this study in order to probe details of these reactions and hydrous ferric oxide (HFO) was used as the Fe(III) oxide phase. Abiotic nitrite reduction is a significant global producer of nitric oxide (a catalyst for production of tropospheric ozone) and nitrous oxide (a greenhouse gas and contributor to stratospheric ozone depletion). All experiments were conducted at pH 6.8 using a strictly anoxic environment with mass-balance measurements for Fe(II). Oxidation of Fe(II) was negligible in the absence of HFO. The reaction was fast in the presence of HFO and was described by d[Fe(II)]/dt=-k(overall)[Fe(II)(diss)][Fe(II)(solid-bound)][NO(2)(-)] (k(overall)=2.59x10(-7)microM(-2)min(-1)) for Fe(II)/Fe(III) molar ratios less than 0.30. The reaction was inhibited for higher Fe(II)/HFO ratios. The concentration of solid-bound Fe(II) was constant after an initial equilibration period and the reaction stopped when dissolved Fe(II) was depleted even though substantial solid-bound Fe(II) and nitrite remained. The results regarding rate-dependence and conservation of solid-bound Fe(II) and inhibition of reaction at high Fe(II)/Fe(III) ratios were similar to our earlier results for the Fe(II)/HFO/O(2) system [Park, B., Dempsey, B.A., 2005. Heterogeneous oxidation of Fe(II) on ferric oxide at neutral pH and a low partial pressure of O(2). Environmental Science and Technology 39(17), 6494-6500.]. PMID:19081595
Tai, Yuan-Liang; Dempsey, Brian A
Real-time monitoring of graphene oxide reduction in acrylic printable composite inks
NASA Astrophysics Data System (ADS)
This work reports the electrical characterization of a water-based graphene oxide/acrylic composite material, which was directly inkjet printed to fabricate dissipative patterns. The graphene oxide filler, which is strongly hydrophilic due to its heavily oxygenated surface and can be readily dispersed in water, was reduced by UV irradiation during photo-curing of the polymeric matrix. The concurrent polymerization of the acrylic matrix and reduction of graphene oxide filler was demonstrated by real-time resistance measurements during UV light irradiation. The presence of graphene filler allowed decreasing the resistance of the pure polymeric matrix by nearly five orders of magnitude. This was explained by the fact that clusters of reduced graphene oxide inside the polymer matrix act as preferential pathways for the mobility of charge carriers, thus leading to an overall decrease of the material's resistance.
Porro, S.; Giardi, R.; Chiolerio, A.
Sequential reduction-oxidation for photocatalytic degradation of tetrabromobisphenol A: kinetics and intermediates.
C-Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC-MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N(2)-saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a two-stage reductive debromination/subsequent oxidative decomposition process in the UV-TiO(2) system by changing the reaction atmospheres. PMID:23046696
Guo, Yaoguang; Lou, Xiaoyi; Xiao, Dongxue; Xu, Lei; Wang, Zhaohui; Liu, Jianshe
Modeling electron competition among nitrogen oxides reduction and N2O accumulation in denitrification.
Competition for electrons among different steps of denitrification has previously been shown to occur, and to play an important role in the accumulation and emission of N2O in wastewater treatment. However, this electron competition is not recognized in the current denitrification models, limiting their ability to predict N2O accumulation during denitrification. In this work, a new denitrification model is developed for wastewater treatment processes. It describes electron competition among the four steps of denitrification, through modeling the carbon oxidation and nitrogen reduction processes separately, in contrast to the existing models that directly couple these two types of processes. Electron carriers are introduced to link carbon oxidation, which donates electrons to carriers, and nitrogen oxides reduction, which receives electrons from these carriers. The relative ability of each denitrification step to compete for electrons is modeled through the use of different affinity constants with reduced carriers. Model calibration and validation results demonstrate that the developed model is able to reasonably describe the nitrate, nitrite, and N2O reduction rates of a methanol-utilizing denitrifying culture under various carbon and nitrogen oxides supplying conditions. The model proposed, while subject to further validation, is expected to enhance our ability to predict N2O accumulation in denitrification. PMID:24001217
Pan, Yuting; Ni, Bing-Jie; Yuan, Zhiguo
The Reduction of Aqueous Metal Species on the Surfaces of Fe(II)-Containing Oxides: The Role of Surface Passivation
The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The rates of metal reduction on natural oxides is strongly dependent on the extent of surface passivation and redox conditions in the weathering environment. Synchrotron studies show that surface oxidation of Fe(II)-containing oxide minerals decreases their capacity for Cr(VI) reduction at hazardous waste disposal sites.
White, A. F.; Peterson, M. L.
Oxidation-reduction processes in ground water at Naval Weapons Industrial Reserve Plant, Dallas, Texas
Concentrations of trichloroethene in ground water at the Naval Weapons Industrial Reserve Plant in Dallas, Texas, indicate three source areas of chlorinated solvents?building 1, building 6, and an off-site source west of the facility. The presence of daughter products of reductive dechlorination of trichloroethene, which were not used at the facility, south and southwest of the source areas are evidence that reductive dechlorination is occurring. In places south of the source areas, dissolved oxygen concentrations indicated that reduction of oxygen could be the dominant process, particularly south of building 6; but elevated dissolved oxygen concentrations south of building 6 might be caused by a leaking water or sewer pipe. The nitrite data indicate that denitrification is occurring in places; however, dissolved hydrogen concentrations indicate that iron reduction is the dominant process south of building 6. The distributions of ferrous iron indicate that iron reduction is occurring in places south-southwest of buildings 6 and 1; dissolved hydrogen concentrations generally support the interpretation that iron reduction is the dominant process in those places. The generally low concentrations of sulfide indicate that sulfate reduction is not a key process in most sampled areas, an interpretation that is supported by dissolved hydrogen concentrations. Ferrous iron and dissolved hydrogen concentrations indicate that ferric iron reduction is the primary oxidation-reduction process. Application of mean first-order decay rates in iron-reducing conditions for trichloroethene, dichloroethene, and vinyl chloride yielded half-lives for those solvents of 231, 347, and 2.67 days, respectively. Decay rates, and thus half-lives, at the facility are expected to be similar to those computed. A weighted scoring method to indicate sites where reductive dechlorination might be likely to occur indicated strong evidence for anaerobic biodegradation of chlorinated solvents at six sites. In general, scores were highest for samples collected on the northeast side of the facility.
Jones, S. A.; Braun, Christopher L.; Lee, Roger W.
Reinterpretation of reduction potential measurements done by linear sweep voltammetry in silicate melts
NASA Technical Reports Server (NTRS)
The equilibrium concentrations of Ni between silicate melt and Pt were determined experimentally as a function of oxygen fugacity. The results demonstrate that metallic species derived in linear sweep voltammetry experiments in silicate melts are diffusing into Pt electrodes and not into the melt, as was concluded by previoius studies. This requires reinterpretation of previous linear sweep voltammetry results and recalculation and correction of reported reduction potentials. This paper reports these corrected reduction potentials. Also reported are the activity coefficients for Ni in synthetic basalt and diopsidic melts and for Co in diopsidic melt.
Colson, R. O.; Haskin, L. A.; Keedy, C. R.
Optical Degradation of Indium Tin Oxide Thin Films Induced by Hydrogen-Related Room Temperature Reduction
NASA Astrophysics Data System (ADS)
The optical degradation of indium tin oxide (ITO) thin films due to a hydrogen-related room temperature reduction reaction was reported. The thin films were treated in an electrolysis process. Significant decrease in the optical transmission of the treated samples was observed. Compositional and structural changes in ITO caused by the reaction related to atomic hydrogen generated in the electrolysis of water was found to be responsible for the degradation. X-ray diffraction and scanning electron microcopy (SEM) observations were employed in the analysis of the products yielded in the reduction reaction.
Wang, Yu; Chen, Wan Ping; Cheng, Kei Chun; Chan, Helen Lai Wah; Choy, Chung Loong
Bacterial Reduction of Copper-Contaminated Ferric Oxide: Copper Toxicity and the Interaction Between Fermentative and Iron-Reducing Bacteria
.ĀĀ Fe(III) oxide is an important heavy-metal sink, and bacteria are responsible for much of the Fe(III) reduced in nonsulfidogenic\\u000a aquatic environments, yet factors governing the bacterial reduction of heavy metal¢contaminated iron oxide are largely unknown.\\u000a In this study with a stabilized bacterial consortium enriched from metal-contaminated sediments, we demonstrate that Cu toxicity\\u000a impedes anaerobic carbon oxidation and bacterial reduction
J. T. Markwiese; P. J. S. Colberg
The reactions of 5,5-dimethyl-2-phenyl-1,2-oxaphosphol-3-ene 2-oxide (1a) with a variety of reducing agents have been studied. Catalytic hydrogenation of 1a (Pd\\/C) resulted in reduction of the C=C bond, giving 5,5-dimethyl-2-phenyl-1,2-oxaphospholane 2-oxide (6). By contrast, hydroboration with excess BH3-THF left the double bond intact, and reduced the P=O group. The product, 5,5-dimethyl-2-phenyl-l,2-oxaphosphol-3-ene (7), is itself unstable, but it can be isolated as
Maher Mualla; Roger S. Macomber
Thermogravimetric study of the reduction of oxides of nickel and chromium
NASA Technical Reports Server (NTRS)
The effectiveness of hydrogen, carbon and hydrogen-carbon in reducing NiO, Cr2O3, mixed NiO-Cr2O3 and oxidized Ni-20Cr was evaluated by thermogravimetry. NiO was effectively reduced by all three atmospheres, Cr2O3 only by hydrogen-carbon, NiO-Cr2O3 by hydrogen and hydrogen-carbon and oxidized Ni-20Cr by hydrogen, hydrogen-carbon and partially by carbon alone. The results indicate that nickel and carbon promote the reduction of Cr2O3.
Herbell, T. P.
Reduction of charge injection barrier by 1-nm contact oxide interlayer in organic field effect transistors
NASA Astrophysics Data System (ADS)
The enhancement of the charge injection process by the insertion of an ultrathin (~1 nm) contact oxide interlayer (COI) at the metal/organic material interface in organic field effect transistors (OFETs) is reported. Six different oxides were used as COI, and Al2O3 was found to exhibit the highest OFET mobility with a reduction in the average contact resistance (Rc) from 19.9 to 1.9 k?.cm. Photoelectron yield spectroscopy analysis revealed that the insertion of COI increases the work function of an Au contact and reduces the charge injection barrier at the interface, which lowers Rc and, therefore, results in enhanced device performance.
Darmawan, Peter; Minari, Takeo; Kumatani, Akichika; Li, Yun; Liu, Chuan; Tsukagoshi, Kazuhito
Solid-phase electrochemical reduction of graphene oxide films in alkaline solution
Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.
Nitric Oxide is a Potential Diagnostic Marker for Hepatocellular Carcinoma
Hepatocellular carcinoma (HCC) is the fifth most common cancer in men and the seventh most common in women. This cancer varies widely in incidence throughout the world, with rising incidence in Egypt. HCC is considered the second most frequent cause of cancer incidence and mortality among men in Egypt. This study aimed to estimate the serum levels of nitric oxide (NO) and glutathione reductase in order to evaluate their role as oxidative status markers in HCC development and progression. For this purpose, serum levels of these parameters were assessed in 50 HCC patients, and 30 cirrhotic patients in addition to 15 healthy subjects as a control group. In the present study, glutathione reductase activity showed a significant increase in HCC as compared to the control group (P= 0.019). On the other hand, no significant difference was observed between the cirrhotic and HCC patients (P= 0.492). Serum NO was significantly higher in patients with HCC than in cirrhotic patients (P= 0.001) or the control group (P= 0.001), with a sensitivity of (74%) and specificity of (88.89%) at a cut-off level of 614.1 ?mol/l. While AFP, alpha-fetoprotein, at a cutoff level of 200 ng/ml had a sensitivity of (52%), the specificity was (100%). Indeed, nitric oxide was high in 62.5% of AFP-negative HCC patients. In conclusion, glutathione reductase has no role in HCC diagnosis. However, nitric oxide is a potential diagnostic marker for HCC. The simultaneous determination of serum nitric oxide and AFP gave significant improvement in the detection of HCC patients compared to that of AFP alone.
Eissa, Laila A.; Eisa, Nada H.; Ebrahim, Mohamed A.; Ragab, Maha; El-Gayar, Amal M.
Modeling of metal¢oxide semiconductor: Analytical bond-order potential for cupric oxide
NASA Astrophysics Data System (ADS)
Atomistic potentials for cupric element and cupric oxide are derived based on the analytical bond-order scheme that was presented by Brenner [Brenner D W, ōErratum: Empirical potential for hydrocarbons for use in simulating the chemical vapor deposition of diamond filmsö, Phys. Rev. B 1992, 46 1948]. In this paper, for the pure cupric element, the energy and structural parameters for several bulk phases as well as dimmer structure are well reproduced. The reference data are taken from our density functional theory calculations and the available experiments. The model potential also provides a good description of the bulk properties of various solid structures of cupric oxide compound structures, including cohesive energies, lattice parameters, and elastic constants.
Li, Kun; Yang, Wen; Wei, Ji-Lin; Du, Shi-Wen; Li, Yong-Tang
Two Oxidation Sites for Low Redox Potential Substrates
Versatile peroxidase shares with manganese peroxidase and lignin peroxidase the ability to oxidize Mn2+ and high redox potential aromatic compounds, respectively. Moreover, it is also able to oxidize phenols (and low redox potential dyes) at two catalytic sites, as shown by biphasic kinetics. A high efficiency site (with 2,6-dimethoxyphenol and p-hydroquinone catalytic efficiencies of ?70 and ?700 s?1 mm?1, respectively) was localized at the same exposed Trp-164 responsible for high redox potential substrate oxidation (as shown by activity loss in the W164S variant). The second site, characterized by low catalytic efficiency (?3 and ?50 s?1 mm?1 for 2,6-dimethoxyphenol and p-hydroquinone, respectively) was localized at the main heme access channel. Steady-state and transient-state kinetics for oxidation of phenols and dyes at the latter site were improved when side chains of residues forming the heme channel edge were removed in single and multiple variants. Among them, the E140G/K176G, E140G/P141G/K176G, and E140G/W164S/K176G variants attained catalytic efficiencies for oxidation of 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonate) at the heme channel similar to those of the exposed tryptophan site. The heme channel enlargement shown by x-ray diffraction of the E140G, P141G, K176G, and E140G/K176G variants would allow a better substrate accommodation near the heme, as revealed by the up to 26-fold lower Km values (compared with native VP). The resulting interactions were shown by the x-ray structure of the E140G-guaiacol complex, which includes two H-bonds of the substrate with Arg-43 and Pro-139 in the distal heme pocket (at the end of the heme channel) and several hydrophobic interactions with other residues and the heme cofactor.
Morales, Maria; Mate, Maria J.; Romero, Antonio; Martinez, Maria Jesus; Martinez, Angel T.; Ruiz-Duenas, Francisco J.
Electronic structures of iron(III) and manganese(IV) (hydr)oxide minerals: Thermodynamics of photochemical reductive dissolution in aquatic environments
NASA Astrophysics Data System (ADS)
Sunlight-induced reduction and dissolution of colloidal Fe-Mn (hydr)oxide minerals yields elevated concentrations of Fe 2+ and Mn 2+ in natural waters. Since these elements may be biolimiting micronutrients, photochemical reactions might play a significant role in biogeochemical cycles. Reductive photodissolution of Fe (hydr)oxide minerals may also release sorbed metals. The reactivity of Fe-Mn (hydr)oxide minerals to sunlight-induced photochemical dissolution is determined by the electronic structure of the mineral-water interface. In this work, oxygen K-edge absorption and emission spectra were used to determine the electronic structures of iron(III) (hydr)oxides (hematite, goethite, lepidocrocite, akaganeite and schwertmannite) and manganese(IV) oxides (pyrolusite, birnessite, cryptomelane). The band gaps in the iron(III) (hydr)oxide minerals are near 2.0-2.5 eV; the band gaps in the manganese (IV) oxide phases are 1.0-1.8 eV. Using published values for the electrochemical flat-band potential for hematite together with experimental pH pzc values for the (hydr)oxides, it is possible to predict the electrochemical potentials of the conduction and valence bands in aqueous solutions as a function of pH. The band potentials enable semiquantitative predictions of the susceptibilities of these minerals to photochemical dissolution in aqueous solutions. At pH 2 (e.g., acid-mine waters), photoreduction of iron(III) (hydr)oxides could yield millimolal concentrations of aqueous Fe 2+ (assuming surface detachment of Fe 2+ is not rate limiting). In seawater (pH 8.3), however, the direct photo-reduction of colloidal iron(III) (hydr)oxides to give nanomolal concentrations of dissolved, uncomplexed, Fe 2+ is not thermodynamically feasible. This supports the hypothesis that the apparent photodissolution of iron(III) (hydr)oxides in marines systems results from Fe 3+ reduction by photochemically produced superoxide. In contrast, the direct photoreduction of manganese oxides should be energetically feasible at pH 2 and 8.3.
Sherman, David M.
Nitrogen oxides reduction by carbonaceous materials and carbon dioxide separation using regenerative metal oxides from fossil fuel based flue gas
NASA Astrophysics Data System (ADS)
The ever-growing energy demands due to rising global population and continuing lifestyle improvements has placed indispensable emphasis on fossil fuels. Combustion of fossil fuels leads to the emission of harmful gaseous pollutants such as oxides of sulfur (SOx) and nitrogen (NOx), carbon dioxide (CO2), mercury, particulate matter, etc. Documented evidence has proved that this air pollution leads to adverse environmental health. This dissertation focuses on the development of technologies for the control of NOx and CO2 emissions. The first part of the thesis (Chapters 2--6) deals with the development of carbon based post combustion NOx reduction technology called CARBONOX process. High temperature combustion oxidizes both atmospheric nitrogen and organic nitrogen in coal to nitric oxide (NO). The reaction rate between graphite and NO is slow and requires high temperature (>900░C). The presence of metallic species in coal char catalyzes the reaction. The reaction temperature is lowered in the presence of oxygen to about 600--850░C. Chemical impregnation, specifically sodium compounds, further lowers the reaction temperature to 350--600░C. Activated high sodium lignite char (HSLC) provided the best performance for NO reduction. The requirement of char for NOx reduction is about 8--12 g carbon/g NO reduced in the presence of 2% oxygen in the inlet gas. The second part of this dissertation (chapter 7--8) focuses on the development of a reaction-based process for the separation of CO2 from combustion flue gas. Certain metal oxides react with CO2 forming metal carbonates under flue gas conditions. They can be calcined separately to yield CO2. Calcium oxide (CaO) has been identified as a viable metal oxide for the carbonation-calcination reaction (CCR) scheme. CaO synthesized from naturally occurring precursors (limestone and dolomite) attained 45--55% of their stoichiometric conversion due to the susceptibility of their microporous structure. High surface area precipitated calcium carbonate (PCC) was synthesized that provided a mesoporous CaO structure upon calcination. This CaO structure attained more than 90% conversion towards the carbonation reaction at 650░C. The reactivity of the novel CaO structure was maintained close to 95% over two reaction-regeneration cycles at 700░C. Vacuum calcination proved beneficial in maintaining the structural integrity of the sorbent.
Gupta, Himanshu
Reduction, sulfidation, and regeneration of mixed iron-aluminum oxide sorbents
The reactions of hydrogen sulfide with various metal oxides have been investigated extensively in connection with the desulfurization of coal gas to be used in advanced power generation cycles. The reduction and sulfidation of Fe[sub 2]O[sub 3] and Fe[sub 2]O[sub 3]-Al[sub 2]O[sub 3] sorbents were investigated by thermogravimetric analysis (TGA). Mixed iron-aluminum oxides were reduced more slowly and by a more complex mechanism than pure iron oxide. Several phases that were responsible for this difference were identified by temperature-programmed reduction (TPR), x-ray diffraction (XRD), BET surface area (BET), and scanning electron microscopy (SEM). Sulfidation of reduced sorbents in the TGA at 600 C produced two crystalline phases: high-temperature, hexagonal pyrrhotite (Fe[sub 1[minus]x]S), and unreacted FeAl[sub 2]O[sub 4]. The reaction of the pure and mixed oxide with a mixture of H[sub 2]S-H[sub 2]-H[sub 2]O-N[sub 2] was studied in a tubular microreactor to evaluate the performance of these materials as high-temperature H[sub 2]S sorbents. At 650 C the mixed oxide yielded considerably lower prebreakthrough outlet H[sub 2]S levels than the pure iron oxide. Regeneration in pure SO[sub 2] and SO[sub 2] - air mixtures of sulfided samples resulted in complete conversion of iron sulfide to iron oxide and quantitative recovery of elemental sulfur.
Patrick, V.; Gavalas, G.R. (California Inst. of Tech., Pasadena (United States)); Sharma, P.K. (Jet Propulsion Lab., Pasadena, CA (United States))
Going Wireless: Fe(III) Oxide Reduction without Pili by Geobacter sulfurreducens Strain JS-1.
Previous studies have suggested that the conductive pili of Geobacter sulfurreducens are essential for extracellular electron transfer to Fe(III) oxides and for optimal long-range electron transport through current-producing biofilms. The KN400 strain of G. sulfurreducens reduces poorly crystalline Fe(III) oxide more rapidly than the more extensively studied DL-1 strain. Deletion of the gene encoding PilA, the structural pilin protein, in strain KN400 inhibited Fe(III) oxide reduction. However, low rates of Fe(III) reduction were detected after extended incubation (>30 days) in the presence of Fe(III) oxide. After seven consecutive transfers, the PilA-deficient strain adapted to reduce Fe(III) oxide as fast as the wild type. Microarray, whole-genome resequencing, proteomic, and gene deletion studies indicated that this adaptation was associated with the production of larger amounts of the c-type cytochrome PgcA, which was released into the culture medium. It is proposed that the extracellular cytochrome acts as an electron shuttle, promoting electron transfer from the outer cell surface to Fe(III) oxides. The adapted PilA-deficient strain competed well with the wild-type strain when both were grown together on Fe(III) oxide. However, when 50% of the culture medium was replaced with fresh medium every 3 days, the wild-type strain outcompeted the adapted strain. A possible explanation for this is that the necessity to produce additional PgcA, to replace the PgcA being continually removed, put the adapted strain at a competitive disadvantage, similar to the apparent selection against electron shuttle-producing Fe(III) reducers in many anaerobic soils and sediments. Despite increased extracellular cytochrome production, the adapted PilA-deficient strain produced low levels of current, consistent with the concept that long-range electron transport through G. sulfurreducens biofilms is more effective via pili. PMID:24814783
Smith, Jessica A; Tremblay, Pier-Luc; Shrestha, Pravin Malla; Snoeyenbos-West, Oona L; Franks, Ashley E; Nevin, Kelly P; Lovley, Derek R
Anion exchange membranes for electrochemical oxidation-reduction energy storage system
NASA Technical Reports Server (NTRS)
Oxidation-reduction couples in concentrated solutions separated by appropriate ion selective membranes were considered as an attractive approach to bulk electrical energy storage. A key problem is the development of the membrane. Several promising types of anionic membranes are discussed which were developed and evaluated for redox energy storage systems. The copolymers of ethyleneglycoldimethacrylate with either 2-vinylpyridine or vinylbenzl chloride gave stable resistance values compared to the copolymer of vinylbenzlchloride and divinylbenzene which served as the baseline membrane. A polyvinylchloride film aminated with tetraethylenepentamine had a low resistance but a high ion transfer rate. A slurry coated vinylpyridine had the lowest ion transfer rate. All these membranes functioned well in laboratory cells at ambient temperatures with the acidic chloride oxidant/reductant system, Fe 3, Fe 2/Ti 3, Ti 4.
Odonnell, P. M.; Sheibley, D. W.; Gahn, R. F.
Dye-sensitization-induced visible-light reduction of graphene oxide for the enhanced TiO2 photocatalytic performance.
The reduction of graphene oxide (GO) with a large-scale production has been demonstrated to be one of the key steps for the preparation of graphene-based composite materials with various potential applications. Therefore, it is highly required to develop a facile, green, and environmentally friendly route for the effective reduction of GO. In this study, a new and effective reduced method of GO nanosheets, based on the dye-sensitization-induced visible-light reduction mechanism, was developed to prepare reduced GO (rGO) and graphene-based TiO2 composite in the absence of any additional reducing agents. It was found that the dye-sensitization-induced reduction process of GO was accompanied with the formation of TiO2-rGO composite nanostructure. The photocatalytic experimental results indicated that the resultant TiO2-rGO nanocomposites exhibited significantly higher photocatalytic performance than pure TiO2 because of a rapid separation of photogenerated electrons and holes by the rGO cocatalyst. PMID:23534830
Wang, Ping; Wang, Jin; Ming, Tingsen; Wang, Xuefei; Yu, Huogen; Yu, Jiaguo; Wang, Yonggang; Lei, Ming
Cordierite as catalyst support for cobalt and manganese oxides in oxidation¢reduction reactions
Cobalt and manganese oxide samples supported on cordierite (commercial grade) were prepared by wet impregnation method using finely powdered support material and cobalt or manganese nitrate. The extent of loading was varied between 5 and 20wt.% Co3O4 or Mn2O3. The physicochemical, surface and catalytic properties of the thermally treated solids (350 and 700░C) were investigated using XRD, EDX, nitrogen adsorption
Nagi R. E. Radwan; G. A. El-Shobaky; Y. M. Fahmy
Hydrazine reduction of transition metal oxides: In situ characterization using x-ray photoelectron spectroscopy
Among the first row transition metal oxides from VŌOŌ to ZnO, CuO was found to be the most easily reduced by hydrazine. CuO surfaces exposed to hydrazine at approx.10Ōü╗ŌüČ Torr could be reduced to the metallic state at room temperature. Reduction kinetics, continuously measured at the surface using in situ x-ray photoelectron spectroscopy (XPS) at hydrazine pressures of 6 x
D. M. Littrell; B. J. Tatarchuk
Phase formation in the process of iron and titanium oxides metallothermic reduction
Phase formation in the alloys obtained during process of collective Ti and Fe oxides reduction by Al has been investigated. Thermodynamic computer simulation of the process (based on the system free energy minimizing principle) has indicated a range of possible reactions with various metallic compounds formation. Differential-thermal (DT), X-ray diffraction (XRD) methods and melting of reaction mixtures at 1773-1973 K
S A Krasikov; A L Nadolsky; A G Shapovalov; I P Pazdnikov; A Y Tashmurzin; Y Y Shurygin; M A Osokina
Superior Pillared Clay Catalysts for Selective Catalytic Reduction of Nitrogen Oxides for Power Plant Emission Control
Fe+-, Cr+-, Cu+-, Mn+-, Co+-, and Ni+-exchanged Al2O3-pillared interlayer clay (PILC) or TiO2-PILC catalysts are investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia in the presence of excess oxygen. Fe+-exchanged pillared clay is found to be the most active. The catalytic activity of Fe-TiO2-PILC could be further improved by the addition of a small amount of
R. Q. Long; R. T. Yang; K. D. Zammit
Reductive leaching of manganese oxide ore in aqueous methanol¢sulphuric acid medium
The reductive leaching of manganese oxide ore in aqueous methanol¢sulphuric acid was investigated. Studies were conducted at low (30 and 70░C) and high (120¢170░C) temperatures, using different acid (0.005¢0.30 M H2SO4) and methanol (0¢50 vol%) concentrations. Results showed that satisfactory levels of manganese extraction could be achieved during autoclave digestion at temperatures between 150 and 170░C with a reaction mixture
F. W. Y Momade; Zs. G Momade
Preparation of technical zirconium diboride by the carbothermic reduction of mixtures of zirconium and boron oxides
A study was made of the preparation of technical zirconium diboride by the reduction of mixtures of zirconium and boron oxides with carbon under industrial conditions. It is shown that the optimum conditions for the preparation of zirconium diboride by the carbothermic method are established when a charge having the composition ZrO2+1.2 B2O3+5 C (i.e., with a 20% excess of
A. I. Karasev
Catalytic systems based on fiberglass woven matrices doped with metals in reaction of nitrogen oxide reduction
The results of a study of the reactions catalyzed by nontraditional fiberglass woven catalysts activated by metals or oxides,\\u000a are presented. The catalytic activity of such catalysts, activated by implanting Pt, Pd, Co, or Cr, in NO reduction with carbon\\u000a monoxide and propane is studied. Fiberglass catalysts containing Pt and Pd are more active than traditional catalysts. The\\u000a catalysts are
V. V. Barelko; A. P. Khrushch; A. F. Cherashev; I. A. Yuranov; V. A. Matyshak; O. N. SilÆchenkova; T. I. Khomenko; O. V. Krylov
Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide
Reduction of a colloidal suspension of exfoliated graphene oxide sheets in water with hydrazine hydrate results in their aggregation and subsequent formation of a high-surface-area carbon material which consists of thin graphene-based sheets. The reduced material was characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, NMR spectroscopy, Raman spectroscopy, and by electrical conductivity measurements.
Sasha Stankovich; Dmitriy A. Dikin; Richard D. Piner; Kevin A. Kohlhaas; Alfred Kleinhammes; Yuanyuan Jia; Yue Wu; SonBinh T. Nguyen; Rodney S. Ruoff
Biogenic gases and the oxidation and reduction of carbon in Amazon River and floodplain waters
Concentrations of COZ, 02, CH4, and N,O in the Amazon River system reflect an oxidation- reduction sequence in combination with physical mixing between the floodplain and the mainstem. Concentrations of CO, ranged from 150 PM in the Amazon mainstem to 200-300 PM in aerobic environments and up to 1,000 PM in oxygen-depleted environments of the floodplain. Apparent oxygen utilization (AOU)
Application of electrolyzed oxidizing water on the reduction of bacterial contamination for seafood
For reducing bacterial contamination, electrolyzed oxidizing water (EO water) has been used to reduce microbial population on seafood and platform of fish retailer. The specimens of tilapia were inoculated with Escherichia coli and Vibrio parahaemolyticus, and then soaked into EO water for up to 10min. EO water achieved additional 0.7logCFU\\/cm2 reduction than tap water on E. coli after 1min treatment
Yu-Ru Huang; Hung-Sheng Hsieh; Shin-Yuan Lin; Shin-Jung Lin; Yen-Con Hung; Deng-Fwu Hwang
Amorphous chromia for low-temperature selective catalytic reduction of nitric oxide
This paper reports on high surface area amorphous chromia found to be a highly active and selective catalyst for the reduction of nitric oxide by ammonia in an oxygen excess. A comparison to a VŌOŌ\\/TiOŌ catalyst shows that at a space velocity of 24000 hŌü╗┬╣ in 900 ppm NO, 900 ppm NHŌ, and 1.8% OŌ, over 90% conversion occurs at
Edward Curry-Hyde; Alfons Baiker
Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups.
This study examined the effect of H2O2 on the delayed rectifier potassium current (IKDR) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H2O2. To reveal the mechanism behind H2O2-induced changes in IKDR, cells were treated with different oxidizing and reducing agents. External application of membrane permeable H2O2 reduced the amplitude and voltage-dependence of IKDR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical (OH) generation, prevented H2O2-induced reduction in IKDR. Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H2O2. Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IKDR; however, DTT and GSH reversed and prevented the H2O2-induced inhibition of IKDR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H2O2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H2O2, that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IKDR, identifies hydroxyl radical as an intermediate oxidant responsible for the H2O2-induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target. PMID:23688542
Hasan, Sonia M K; Redzic, Zoran B; Alshuaib, Waleed B
Significant work has been done by the investigators on the cerium oxide-copper oxide based sorbent/catalysts for the combined removal of sulfur and nitrogen oxides from the flue gases of stationary sources. A relatively wide temperature window was established for the use of alumina-supported cerium oxide-copper oxide mixtures as regenerable sorbents for SO{sub 2} removal. Preliminary evaluation of these sorbents as catalysts for the selective reduction of NO{sub x} gave promising results with ammonia, but indicated low selectivity when methane was used as the reductant. Since the replacement of ammonia by another reductant is commercially very attractive, in this project, four research components will be undertaken. The investigation of the reaction mechanism, the first component, will help in the selection of promoters to improve the catalytic activity and selectivity of the sorbents in the SCR with methane. This will result in new catalyst formulations (second component). If this research is successful, the combined SO{sub 2}-NO{sub x} removal process based on alumina-supported copper oxide-ceria sorbent/catalysts will become very attractive for commercial applications. The objective of the third component of the project is to develop an alternative SCR process using another inexpensive fuel, residual fuel oil, instead of natural gas. This innovative proposal is based on very scant evidence concerning the good performance of coked catalysts in the selective reduction of NO and if proven to work the process will certainly be commercially viable. The fourth component of the project involves our industrial partner TDA Research, and the objective is to evaluate long- term stability and durability of the prepared sorbent/catalysts. In the second year of the project, the catalysts were investigated for their SCR activity with methane in a microreactor setup and also, by the temperature-programmed desorption (TPD) technique. The results from the SCR experiments indicated that manganese is a more effective promoter than rhodium on the supported copper oxide-ceria catalysts under study; the effectiveness of the promoter increases with the increase in Ce/Cu ratio. The TPD profiles of the unpromoted catalyst (Cu/Ce=3) is different than those promoted with 0.1% rhodium.
Ates Akyurtlu; Jale F. Akyurtlu
Study on the oxidation and reduction of tungsten surface for sub-50 nm patterning process
The oxidation characteristics of tungsten line pattern during the carbon-based mask-layer removal process using oxygen plasmas have been investigated for sub-50 nm patterning processes, in addition to the reduction characteristics of the WO{sub x} layer formed on the tungsten line surface using hydrogen plasmas. The surface oxidation of tungsten lines during the mask layer removal process could be minimized by using low-temperature (300 K) plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WO{sub x} on the tungsten line could be decreased to 25% compared to results from high-temperature processing. The WO{sub x} layer could also be completely removed at a low temperature of 300 K using a hydrogen plasma by supplying bias power to the tungsten substrate to provide a activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40-nm-CD device processing, the complete removal of WO{sub x} formed on the sidewall of tungsten line could be observed.
Kim, Jong Kyu; Nam, Seok Woo; Cho, Sung Il; Jhon, Myung S.; Min, Kyung Suk; Kim, Chan Kyu; Jung, Ho Bum; Yeom, Geun Young [Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711, South Korea and Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711 (Korea, Republic of); Department of Chemical Engineering and Data Storage Systems Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of)
Nitrous oxide reduction in nodules: denitrification or N/sub 2/ fixation
Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor/sup +/) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor/sup -/) rhizobium strain (32H1) were incubated with 1% /sup 15/N/sub 2/O (95 atom% /sup 15/N) in the following three atmospheres: aerobic with C/sub 2/H/sub 2/ (10%), aerobic without C/sub 2/H/sub 2/, and anaerobic (argon atmosphere) without C/sub 2/H/sub 2/. The greatest production of /sup 15/N/sub 2/ occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more /sup 15/N/sub 2/ was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N/sub 2/O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase.
Coyne, M.S.; Focht, D.D.
CO 2 in the iron and steel industry: an analysis of Japanese emission reduction potentials
A new linear programming model has been developed for the analysis of CO2 emission reduction potentials in the Japanese iron and steel industry. This model is named Steel Environmental strategy Assessment Program. The model can be used to analyse the impact of CO2 taxes on technology selection, iron and steel trade and product demand for the next three decades. The
Dolf Gielen; Yuichi Moriguchi
The density-functional theory (DFT) based computational chemistry software package DMol was used to provide insight into the reductive potentials of a series of halomethanes. t is known that certain members of this series are readily reduced in vivo via catalysis by cytochrome P4...
Drag reduction potentials of turbulence manipulation in adverse pressure gradient flows
It is noted that there is no neccessary correlation between skin friction minimization and drag minimization; the latter requires that account should be taken of both friction and pressure drag, so that in adverse pressure gradient regions, both low skin friction and small shape factor should be pursued. This restricts drag-reduction potentials, since skin friction redictions often entail shape-factor increments.
B. van den Berg
Influence of metal oxide nanoparticles concentration on their zeta potential.
In an attempt to estimate the zeta potential of various metal oxide nanoparticles (NPs) dispersed in water, it is interesting to observe that both the magnitude and the sign of this property depend highly upon their concentration. For example, in the case of naked TiO2 at pH 6, the zeta potential increased from -6.7 to 8.2 mV as the particle concentration varied from 0.5 to 5 mg L(-1). As a result, the isoelectric points of naked TiO2, Fe3O4, Fe(OH)3, and Al2O3-coated TiO2 could deviate ca. one, one, two, and three pH units, respectively, depending upon the particle concentration. We showed that these behaviors arise mainly from that the dissolved ambient CO2 reacts with the particle surface functional groups to form M-OCO2(-), which neutralizes or even overcompensates the particle surface charge. The surface density of M-OCO2(-), [M-OCO2(-)](s) depends upon the particle concentration; if it is sufficiently high, [M-OCO2(-)](s) becomes negligible, so is its influence on the zeta potential. We concluded that the zeta potential measurements for the tested NPs are reliable only if their concentration exceeds a certain level. This also applies to other metal oxides or hydroxides, the surface of which reacts appreciably with dissolved CO2. The results gathered are of practical significance in estimating the surface properties of unknown and/or newly synthesized NPs since conventional measurements are usually made at dilute particle concentrations. PMID:23838331
Wang, Nan; Hsu, Chien; Zhu, Lihua; Tseng, Shiojenn; Hsu, Jyh-Ping
Probing the oxidation reduction properties of terrestrially and microbially derived dissolved organic matter
NASA Astrophysics Data System (ADS)
Dissolved organic matter (DOM) has been shown to be an integral component in biogeochemical electron transfer reactions due to its demonstrated ability to facilitate redox reactions. While the role of DOM as a facilitator of electron transfer processes has been demonstrated, greater knowledge would lead to better understanding of the structural components responsible for redox behavior, such as quinones and nitrogen and sulfur (N/S) functional groups. This investigation uses direct scan voltammetry (DSV) coupled with fluorescence and NMR spectroscopy as well as thermochemolysis gas chromatography mass spectrometry (GC-MS) and X-ray photoelectron spectroscopy (XPS) to elucidate the organic moieties responsible for facilitating electron transfer reactions. We contrast electrochemical properties and structural details of three organic matter isolates from diverse sources; Great Dismal Swamp DOM (terrestrially derived, highly aromatic), Pony Lake DOM (microbially derived, highly aliphatic) and Toolik Lake (terrestrially derived, photochemically and microbially altered) with juglone (a redox-active model quinone). Aromatic and phenolic constituents were detected (by 13C NMR) and recovered (by thermochemolysis GC-MS) from all three fulvic acid samples, highlighting the ubiquity of these compounds and suggesting that the quinone-phenol redox couple is not limited to DOM derived from lignin precursors. The range of hydroxy-benzene and benzoic acid derivatives may explain the lack of a single pair of well-defined oxidation and reduction peaks in the DSV scans. The presence of a wide-range of hydroxylated benzoic acid isomers and other redox-active aromatic residues implies that native DOM possesses overlapping redox potentials analogous to their characteristic range of p Ka values.
Fimmen, Ryan L.; Cory, Rose M.; Chin, Yu-Ping; Trouts, Tamara D.; McKnight, Diane M.
Theoretical simulation of reduction mechanism of graphene oxide in sodium hydroxide solution.
Based on a density functional theory simulation, we proposed a reduction mechanism of graphene oxide (GO) under a sodium hydroxide solution containing anions (OH(-)), cations (Na(+)) and neutral H2O molecules as main components. OH(-) anion can interact with hydroxyl in GO and transfer electrons to the graphene sheet, resulting in negatively charged GO, and these electrons obviously lower the barrier of the ring-opening reaction of epoxy. Na(+) cations can be attracted by the negatively charged GO, and this reaction is equivalent to the one between metallic Na and GO. The opened epoxy is reduced with the assistance of Na(+) cation and water molecule. In such a reduction process, NaOH can be viewed as a catalyst and more defects should be formed because of these diffused epoxies on the negatively charged graphene sheet. Our results may be helpful to understand further the nature of the reduction of GO among various reducing agents. PMID:24845648
Chen, Chu; Kong, Weixin; Duan, Hai-Ming; Zhang, Jun
Synthesis of high-performance graphene nanosheets by thermal reduction of graphene oxide
Graphical abstract: High-performance graphene nanosheets were synthesized by thermal reduction of graphene oxide under ethanol atmosphere. X-ray photoelectron spectroscopy, Raman spectroscopy and electrical transport measurements indicate that the resulting graphene nanosheets can effectively restore its graphic structure in GO and present high mobility. Highlights: {yields} Graphene nanosheets were synthesized by reduction of GO under ethanol atmosphere. {yields} Raman and XPS results indicate the reduced graphene sheets have high-performance. {yields} Graphene sheets field-effect transistors present high mobility. -- Abstract: High-performance graphene nanosheets have been synthesized by thermal reduction of graphene oxide (GO) under ethanol atmosphere. The reduced GO nanosheets were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and electrical transport measurements, respectively. The results indicated that the thermal reduction of GO under ethanol atmosphere can effectively remove the oxygen-containing functional groups and restore its graphic structure compared to the ones obtained using hydrazine or hydrogen. The electrical measurements indicated that the electrical mobility of single-layer graphene sheet reduced under ethanol atmosphere at 900 {sup o}C can reach 29.08 cm{sup 2} V{sup -1} S{sup -1}.
Wei, Ang; Wang, Jingxia; Long, Qing; Liu, Xiangmei; Li, Xingao [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications NUPT, 9 Wenyuan Road, Nanjing 210046 (China)] [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications NUPT, 9 Wenyuan Road, Nanjing 210046 (China); Dong, Xiaochen, E-mail: firstname.lastname@example.com [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications NUPT, 9 Wenyuan Road, Nanjing 210046 (China)] [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications NUPT, 9 Wenyuan Road, Nanjing 210046 (China); Huang, Wei, E-mail: firstname.lastname@example.com [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications NUPT, 9 Wenyuan Road, Nanjing 210046 (China)] [Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications NUPT, 9 Wenyuan Road, Nanjing 210046 (China)
Reduction of excess sludge production in sequencing batch reactor through incorporation of chlorine dioxide oxidation.
In this study, chlorine dioxide (ClO(2)) instead of chlorine (Cl(2)) was proposed to minimize the formation of chlorine-based by-products and was incorporated into a sequencing batch reactor (SBR) for excess sludge reduction. The results showed that the sludge disintegrability of ClO(2) was excellent. The waste activated sludge at an initial concentration of 15 g MLSS/L was rapidly reduced by 36% using ClO(2) doses of 10mg ClO(2)/g dry sludge which was much lower than that obtained using Cl(2) based on similar sludge reduction efficiency. Maximum sludge disintegration was achieved at 10mg ClO(2)/g dry sludge for 40 min. ClO(2) oxidation can be successfully incorporated into a SBR for excess sludge reduction without significantly harming the bioreactor performance. The incorporation of ClO(2) oxidation resulted in a 58% reduction in excess sludge production, and the quality of the effluent was not significantly affected. PMID:21620565
Wang, Guanghua; Sui, Jun; Shen, Huishan; Liang, Shukun; He, Xiangming; Zhang, Minju; Xie, Yizhong; Li, Lingyun; Hu, Yongyou
Reduction of thermal damage in ultrathin gate oxides after intrinsic dielectric breakdown
NASA Astrophysics Data System (ADS)
We have compared the thermal damage in ultrathin gate SiO2 layers of 5.6 and 3 nm thickness after intrinsic dielectric breakdown due to constant voltage Fowler-Nordheim stress. The power dissipated through the metal-oxide-semiconductor capacitor during the breakdown transient, measured with high time resolution, strongly decreases with oxide thickness. This is reflected in a noticeable reduction of the thermal damage found in the structure after breakdown. The effect can be explained as the consequence of the lower amount of defects present in the oxide at the breakdown instant and of the occurrence of a softer breakdown in the initial spot. The present data allow us to estimate the power threshold at the boundary between soft and hard breakdown, and they are compared to numerical simulations of heat flow.
Lombardo, S.; La Magna, A.; Crupi, I.; Gerardi, C.; Crupi, F.
Sulfide Oxidation Coupled to Arsenate Reduction by a Diverse Microbial Community in a Soda Lakeå
We characterized the arsenate-reducing, sulfide-oxidizing population of Mono Lake, California, by analyzing the distribution and diversity of rrnA, cbbL, and dissimilatory arsenate reductase (arrA) genes in environmental DNA, arsenate-plus sulfide-amended lake water, mixed cultures, and isolates. The arsenate-reducing community was diverse. An organism represented by an rrnA sequence previously retrieved from Mono Lake and affiliated with the Desulfobulbaceae (Deltaproteobacteria) appears to be an important member of the arsenate-reducing, sulfide-oxidizing community. Sulfide oxidation coupled with arsenate reduction appears to proceed via a two-electron transfer, resulting in the production of arsenite and an intermediate S compound that is subsequently disproportionated. A realgar-like As/S mineral was formed in some experiments.
Hollibaugh, James T.; Budinoff, Charles; Hollibaugh, Ryan A.; Ransom, Briana; Bano, Nasreen