(374b) Dechlorination of Polychlorinated Biphenyls in Sediment Slurries by Palladium Modified Zerovalent Iron

Polychlorinated biphenyls (PCBs) are one group of persistent organic pollutants (POPs) of international concern because of global distribution, persistence, and toxicity. Removal of these compounds from the environment presents a very tough challenge because they are highly hydrophobic and have very low solubility in water and because they are recalcitrant to chemical and biological degradations. Although there are several methods which are developed to treat PCBs quite effectively under specific conditions, but there is not one that can be applied effectively to remediate PCB in the contaminated soils and sediments. Zerovalent iron has been applied to quite effectively remediate groundwater and soil contaminated by halogenated aliphatic compounds, but not those contaminated by PCBs (except in ethanol/water solutions using nanoscale ZVI iron). It has been reported that palladized iron particles dechlorinate PCBs in water-solvent solutions, but use of Fe/Pd for the remediation of PCBs in sediment systems has not been reported. This paper presents experimental results of Fe/Pd catalyzed dechlorination of PCBs in sediment slurries amended by solvents, because solvents are likely used in the remediation of PCB contaminated soils and sediments to enhance the solubility of the contaminants. The rate of dechlorination of 2-chlorobiphenyl (a target PCB compound) in sediment slurries was significantly slower than the values observed in water and water-solvent solutions, and the catalytic dechlorination in sediment slurries was likely inhibited after an initial phase of dechlorination.