FORMAL REDUCTION POTENTIALS AND REDOX CHEMISTRY OF POLYHALOGENATED BIPHENYLS IN A BICONTINUOUS MICROEMULSION

Microemulsions are clear, stable fluids which contain water, oil, and monolayers of surfactant. Redox studies of pollutants in such microheterogeneous fluids containing water may be more relevant to environmental interactions than studies in organic solvents. In this paper, cyclic and square wave voltammetry on a mercury-film electrode were used to estimate the formal potentials of the first reduction peak and to investigate the rate-determining step in the reduction of polychlorinated and polybrominated biphenyls. Slow kinetics of the initial electron transfer to form a halobiphenyl anion radical was the rate-determining step. Formal potentials in the microemulsion were shifted considerably positive relative to values in homogeneous organic solvent, with the more heavily halogenated congeners showing the largest shifts. Implications of the results with respect to PCB toxicity and anaerobic degradation are discussed.