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 PBBs. 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 center around optimizing experimental design factors to attain significantly faster dehalogenation rates. Electrode surfaces will be coated with dynamic surfactant bilayers and multilayers to concentrate reactants. Reaction media will employ micelles and microemulsions in water-based systems, where pollutants are likely to be found in nature. Ultrasonic mass transport and photoexcitation of visible- light harvesting catalysts will be used to further enhance reaction rates. Development of visible light rate enhancement will facilitate eventual use of sunlight to help decompose organohalides. New surfactant/catalyst systems will be tailored specifically for complete decomposition of commercial PCB and PBB mixtures and other organohalides bound to particulate matter and industrial oils. New bicontinuous water/oil/surfactant microemulsions with 6-30% water will be evaluated as media for detoxifying contaminated oil. Catalysts include aromatic hydrocarbons and highly efficient metal macrocycles. Lifetimes of reactive PCB and PBB anion radical intermediates will be measured in organic solvents and in surfactant bilayers. Combined with previously estimated standard reduction potentials, these results should lead to improved insight into environmental and toxicological interactions of halobiphenyls. Fundamental data accumulated on PCBs and PBBs will be useful in correlating structure with toxic and microbiological reactivities. This research is expected to yield significant contributions to an eventual solution of the public health problem of contamination of our environment with organohalide chemicals. It promises to generate new approaches to permanently effective cleanup of contaminated materials such as sediments, soils, and industrial oils. It is hoped that our fundamental results will aid in research aimed at uncovering mechanisms of environmental degradation and toxicity of ubiquitous and persistent organohalide pollutants.