title: Degradation of γ-HCH spiked soil using stabilized Pd/Fe0 bimetallic nanoparticles: pathways, kinetics and effect of reaction conditions.
abstract: This study investigates the degradation pathway of gamma-hexachlorocyclohexane (γ-HCH) in spiked soil using carboxymethyl cellulose stabilized Pd/Fe(0) bimetallic nanoparticles (CMC-Pd/nFe(0)). GC-MS analysis of γ-HCH degradation products showed the formation of pentachlorocyclohexene, tri- and di-chlorobenzene as intermediate products while benzene was formed as the most stable end product. On the basis of identified intermediates and final products, degradation pathway of γ-HCH has been proposed. Batch studies showed complete γ-HCH degradation at a loading of 0.20 g/L CMC-Pd/nFe(0) within 6h of incubation. The surface area normalized rate constant (k(SA)) was found to be 7.6 × 10(-2) L min(-1)m(-2). CMC-Pd/nFe(0) displayed ≈ 7-fold greater efficiency for γ-HCH degradation in comparison to Fe(0) nanoparticles (nFe(0)), synthesized without CMC and Pd. Further studies showed that increase in CMC-Pd/nFe(0) loading and reaction temperature facilitates γ-HCH degradation, whereas a declining trend in degradation was noticed with the increase in pH, initial γ-HCH concentration and in the presence of cations. The data on activation energy (33.7 kJ/mol) suggests that γ-HCH degradation is a surface mediated reaction. The significance of the study with respect to remediation of γ-HCH contaminated soil using CMC-Pd/nFe(0) has been discussed.
authors.affiliation: Ecotoxicology Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow 226 001, UP, India.
authors.forename: Ritu
authors.initials: R
authors.lastname: Singh
authors.forename: Virendra
authors.initials: V
authors.lastname: Misra
authors.forename: Mohana Krishna Reddy
authors.initials: MK
authors.lastname: Mudiam
authors.forename: Lalit Kumar Singh
authors.initials: LK
authors.lastname: Chauhan
authors.forename: Rana Pratap
authors.initials: RP
authors.lastname: Singh
mesh_terms: D000327:Adsorption; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods; D005290:Ferric Compounds / Q000737:chemistry*; D001556:Hexachlorocyclohexane / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013696:Temperature
chemical_list: D005290:Ferric Compounds; D012989:Soil Pollutants; C000499:ferric oxide; D001556:Hexachlorocyclohexane; D010165:Palladium; D002266:Carboxymethylcellulose Sodium