DECHLORINATION OF POLYCHLORINATED-BIPHENYLS BY ELECTROCHEMICAL CATALYSIS IN A BICONTINUOUS MICROEMULSION

A stable, conductive, bicontinuous microemulsion of surfactant/oil/water was evaluated as a medium for catalytic dechlorination of PCBs at constant current on lead cathodes. Biphenyl and its reduced alkylbenzene derivatives were the major products. Zinc phthalocyanine provided better catalysis than nickel phthalocyanine tetrasulfonate. Maximum current efficiency was 20 % for 4,4'-DCB but increased to 42 % overall for the most heavily chlorinated PCB mixture. Nearly complete dechlorination of 100 mg of Aroclor 1260 (60 % Cl) in 20 mL of microemulsion was achieved in 18 h, equivalent to the best previous result for Aroclor 1016 (48 % Cl) on Hg cathodes in buffered surfactant dispersion. Advantages of the method include avoidance of added salts and buffers, decreased toxicity of the medium compared to polar organic solvents, and the use of lead cathodes in place of environmentally unacceptable Hg.