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ELECTROCHEMICAL DEGRADATION OF ORGANIC CONTAMINANTS IN WATER AND SEDIMENTS
Citation:
AlAbed*, S R. ELECTROCHEMICAL DEGRADATION OF ORGANIC CONTAMINANTS IN WATER AND SEDIMENTS. Presented at Washington University, St. Louis, MO, October 22, 2004.
Impact/Purpose:
To inform the public.
Description:
Electrochemical degradation (ECD) utilizes high redox potential at the anode and low redox potential at the cathode to oxidize and/or reduce organic and inorganic contaminants. EDC of Trichloroethylene (TCE), although theoretically possible, has not been experimentally proven. The mechanism of TCE reduction is unclear, however, the low redox potential and ample electrons available at the cathode suggest that TCE might be reduced at the surface of highly conductive material such as graphite. The focus of our current research is to study the occurrence of TCE reduction using granular graphite cathodes and to identify and quantify the reduction products of TCE. In experiments with an initial TCE concentration of less than 100 mg/l, TCE was reduced approximately by 75% in the reactor under an applied voltage of 10 V. Compounds detected from TCE dechlorination were chloride in the solution, ethane and a minimal amount of methane and ethane in the headspace gas. Chloromethane (CM) and trace amounts of dichloroethylene (cis-1, 2-DCE) were also present in solution and in headspace gas. The mass balance of chlorine showed that the amount of chloride converted from TCE was much less than the amount of chlorine in TCE that had been reduced. The chloride yield decreased as a higher cell voltage was applied. We concluded that CM might be a direct product of chloride oxidation at the graphite anode and not a product of TCE dechlorination. To prove the latter, adding bromide in the reactor increased chloride yield significantly and inhibited CM generation. Our results confirmed the effectiveness of ECD to dechlorinate TCE with the potential of using this technology to remediate contaminants other than TCE such as PAHs, PCBs, fuels, and arsenic in contaminated sediments and groundwater.