One-pot green synthesis of polymeric nanocomposite: Biodegradation studies and application in sorption-degradation of organic pollutants.
The research work proposes the synthesis of a nanocomposite hydrogel which is a dual combination of binary interpenetrating network (BIPN) and bismuth ferrite nanoparticles. BIPN synthesized from binary graft copolymer (BGC) used as starting material. The cross-linked network of BGC is interpenetrating the newly synthesized cross-linked network of poly(acrylic acid) and the product is named as BIPN. Binary graft copolymer had been synthesized from grafting of guggul aqueous extract with copolymeric chains of acrylamide (primary monomer) and acrylic acid (secondary monomer) crosslinked by N,N'-methylene bisacrylamide (MBA). The maximum percentage swelling was evaluated for BGC through optimization of various reaction parameters: amount of water, binary ratio of acrylamide to acrylic acid, concentrations of MBA, ammonium persulphate, pH, temperature and time. Considering pre-optimized parameters for BGC synthesis, BIPN formation required optimization of only acrylic acid. Maximum percentage swelling obtained was 1497.79% and 308.15% for BGC and BIPN, respectively. Maximum percentage biodegradation of 90.64% and 82.38% were calculated for BGC and BIPN, respectively using composting method. Degradation efficiency of brilliant blue (BB) and fuchsin basic (FB) dyes was in the order: Nanocomposite ≫ BIPN > BGC. Maximum percentage degradation observed in case of nanocomposite was 94.1% and 99.3% in sunlight for BB and FB, respectively. The interaction of dyes with the nanocomposite involved mainly ionic interactions. The adsorption models Freundlich and Langmuir were applicable to overall adsorption and degradation process of BB and FB, respectively. Maximum adsorption capacities corresponding to minimum concentration i.e. 10 mg L-1 for BB and FB were calculated as 0.409 mg g-1 and 0.439 mg g-1, respectively. Second order and first order kinetics were found to be suitable for BB and FB adsorption-degradation pathways, respectively. Intraparticle diffusion mechanism was favorable to both dyes and adsorption followed three steps. Gas chromatography coupled with mass spectrometric analysis could give the degraded products which was helpful in drawing degradation pathway. The degradation process involved active radical species (O2-., OH.) and they carry out oxidation-reduction reactions on dyes to give decolorized solution containing mineral ions.