Citation:

AL-ABED, S. R. AND Y. FANG. USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE. D. Grasso (ed.), ENVIRONMENTAL ENGINEERING SCIENCE. Mary Ann Liebert, Inc., Larchmont, NY, 24(6):842-851, (2007).

Description:

Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was removed and up to 75% was eliminated during TCE dechlorination; on the other hand, the chloride yield was extremely low–less than half of the amount of chlorine was recovered, and a carcinogenic, namely chloromethane (CM) was formed. These perplexing results were investigated, through experiments and theoretical analysis, to determine the true extent of dechlorination. Analysis of TCE adsorption results indicated that, in a dechlorination experiment, the adsorbed amount, which varies with the rate of decrease of the concentration of TCE in the solution, were between 7 and 25% of the initial amount of TCE. Results of the dechlorination of carbonstable isotope TCE confirmed that CM was not a product of dechlorination; in fact, it was a product of an electrode reaction of chloride in the acetate ammonium electrolyte. Extremely low yield of chloride was caused by its reaction with acetate in forming CM and by the reactions at the graphite anode; preventing these chloride-consuming reactions, by using a platinum anode and a potassium nitrate electrolyte, increased chloride yield and chlorine recovery significantly. Based on these findings, the percentage of TCE dechlorinated using a granular-graphite electrode was estimated in a range between 60 and 85%.

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