ELECTROCATALYTIC REDUCTION OF HALOGENATED BIPHENYLS

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The broad long-term objectives of this project are to develop new electrocatalytic approaches for clean, permanently effective destruction of halogenated organic pollutants such as PCBs and to provide new insights into toxic and environmental interactions of these compounds by establishing fundamental details of their electron-transfer reactions. Techniques will be applicable to related toxic halogenated chemicals in our environment like chlorinated dibenzodioxins, dibenzofurans, ethylene dibromide (EDB), and chlorinated pesticides. Specific aims for the next five years include optimizing catalytic systems to attain faster dehalogenation rates while decreasing cost and energy input. Electrodes will be coated with catalytic surfactant films which preconcentrate reactants. Since pollutants are found with water in natural environments, bulk reaction media will employ organized water-based fluids called microemulsions. Surfactant/catalyst systems will be tailored specifically for complete decomposition of commercial PCB and PBB mixtures and other organohalides bound to soils and sediments and in industrial oils. New conductive water/oil/surfactant microemulsions with low surfactant content will be evaluated as low cost reaction media which avoid alternative toxic solvents. We will employ metal macrocyclic complexes to catalyze decomposition reactions with very low energy input and high catalytic efficiency. We will also investigate catalysis by proteins in surfactant films. In addition to providing low energy dehalogenations, redox protein- surfactant films may provide insight into toxic interactions of pollutants with microorganisms and mammals. Anion radicals are key intermediates in biological, chemical, and photochemical dechlorinations of PCBs. These reactive species may be partly responsible for genetic damage. Lifetimes and standard potentials for PCB anion radicals will be measured in microemulsions. Results should lead to improved insight into environmental interactions of halobiphenyls in an organized medium which mimics possible environments of the radicals in living systems. These fundamental data on organohalides will be useful in correlating structure with toxic and microbiological reactivities. This research is expected to yield significant contributions to a solution of the public health problem of contamination of our environment with organohalide chemicals, which in turn will improve the future health of our citizens. It promises to generate new approaches to permanently effective cleanup of contaminated materials such as sediments, soils, and industrial oils. Our fundamental results will aid in research aimed at uncovering mechanisms of toxicity and environmental interactions of ubiquitous and persistent organohalide pollutants.