Dechlorination of polychlorinated biphenyls, naphthalenes and dibenzo-p-dioxins by magnesium/palladium bimetallic particles

J Environ Sci Health A Tox Hazard Subst Environ Eng. 2007 May;42(6):685-95. doi: 10.1080/10934520701326222.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chlorine / chemistry*
  • Dioxins / chemistry*
  • Kinetics
  • Magnesium / chemistry*
  • Microscopy, Electron, Scanning
  • Naphthalenes / chemistry*
  • Palladium / chemistry*
  • Polychlorinated Biphenyls / chemistry*

Substances

  • Dioxins
  • Naphthalenes
  • Chlorine
  • Palladium
  • Polychlorinated Biphenyls
  • Magnesium