Degradation of γ-HCH spiked soil using stabilized Pd/Fe0 bimetallic nanoparticles: Pathways, kinetics and effect of reaction conditions

• Published in: Journal of hazardous materials Vol. 237-238; pp. 355 - 364
• Main Authors: Singh, Ritu, Misra, Virendra, Mudiam, Mohana Krishna Reddy, Chauhan, Lalit Kumar Singh, Singh, Rana Pratap
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.10.2012
• Subjects: Adsorption; Carboxymethylcellulose Sodium - chemistry; Degradation/degradation products; Environmental Restoration and Remediation - methods; Ferric Compounds - chemistry; Gas chromatography/mass spectrometry; Hydrogen-Ion Concentration; Lindane - chemistry; Metal Nanoparticles - chemistry; Palladium - chemistry; Remediation; Soil Pollutants - chemistry; Stabilized bimetallic iron nanoparticles; Temperature; γ-HCH; Degradation/degradation products; Remediation; γ-HCH; Gas chromatography/mass spectrometry; Stabilized bimetallic iron nanoparticles
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2012.08.064

[Display omitted] ► This study explores the potential of CMC-Pd/nFe0 to degrade γ-HCH in spiked soil. ► Sorption–desorption characteristics and partitioning of γ-HCH is investigated. ► Three degradation pathways has been proposed and discussed. ► γ-HCH degradation mechanism and kinetics is elucidated. ► Activation energy reveals that γ-HCH degradation is a surface mediated reaction. This study investigates the degradation pathway of gamma-hexachlorocyclohexane (γ-HCH) in spiked soil using carboxymethyl cellulose stabilized Pd/Fe0 bimetallic nanoparticles (CMC-Pd/nFe0). 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 0.20g/L CMC-Pd/nFe0 within 6h of incubation. The surface area normalized rate constant (kSA) was found to be 7.6×10−2Lmin−1m−2. CMC-Pd/nFe0 displayed ∼7-fold greater efficiency for γ-HCH degradation in comparison to Fe0 nanoparticles (nFe0), synthesized without CMC and Pd. Further studies showed that increase in CMC-Pd/nFe0 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 (33.7kJ/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/nFe0 has been discussed.