title: Dechlorination of polychlorinated biphenyls, naphthalenes and dibenzo-p-dioxins by magnesium/palladium bimetallic particles.
abstract: The contamination of sediments with polychlorinated organics such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (Dioxins) and polychlorinated naphthalenes (PCNs) remains a significant problem in many rivers, harbors, and estuarine areas in the US and around the world. In this work, rapid dechlorination of PCBs, PCNs, and Dioxins by palladium - coated magnesium (0.01% by weight Pd) has been demonstrated in pure solvent systems (10% methanol in distilled water). This reaction was investigated with the goal of developing it as a future sediment treatment method. More than 90% of the initial single PCB congeners BZ 3 and 170 were removed in 1 to 10 minutes and about 58% of the total initial Arochlor 1260 was removed in 4 minutes. The removal of single Dioxin and PCN congeners also occurred rapidly resulting in a 69 to 95% reduction in 30 minutes. Rapid removal of biphenyl, the expected degradation end product for PCBs, was also observed (80% removal in 5 minutes). Experiments conducted with Arochlor 1260 and biphenyl did not identify significant volatile fractions. A significant amount of PCBs were extracted from the filtered Mg/Pd material suggesting that PCBs first adsorb to the surface of the bimetal and then dechlorination occurs; lesser chlorinated congeners and biphenyl were also found adsorbed to the Mg/Pd material. Experiments conducted with single PCB congeners BZ 194 and 204 demonstrated the formation of lower - chlorinated PCB congeners, indicating that dechlorination was occurring. A stepwise dechlorination process was suggested in which chlorines in the ortho position were removed last.
authors.affiliation: Environmental Research Group, University of New Hampshire, 35 Colovos Rd. Durham, NH 03824, USA.
authors.forename: Emese
authors.initials: E
authors.lastname: Hadnagy
authors.forename: Linda M
authors.initials: LM
authors.lastname: Rauch
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Gardner
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D004147:Dioxins / Q000737:chemistry*; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009281:Naphthalenes / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011078:Polychlorinated Biphenyls / Q000737:chemistry*
chemical_list: D004147:Dioxins; D009281:Naphthalenes; D002713:Chlorine; D010165:Palladium; D011078:Polychlorinated Biphenyls; D008274:Magnesium