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

A stable, conductive, bicontinuous microemulsion of surfactant/oil/wat er was evaluated as a medium for catalytic dechlorination of PCBs at c onstant current on lead cathodes. Biphenyl and its reduced alkylbenzen e derivatives were the major products. Zinc phthalocyanine provided be tter catalysis than nickel phthalocyanine tetrasulfonate. Maximum curr ent efficiency was 20 % for 4,4'-DCB but increased to 42 % overall for the most heavily chlorinated PCB mixture. Nearly complete dechlorinat ion 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 1 016 (48 % Cl) on Hg cathodes in buffered surfactant dispersion. Advant ages of the method include avoidance of added salts and buffers, decre ased toxicity of the medium compared to polar organic solvents, and th e use of lead cathodes in place of environmentally unacceptable Hg.