Electrochemical degradation mechanism of trichloroethylene in grass beads mock soil

抄録

Electrochemical degradation of trichloroethylene (TCE) in grass beads mock soil was investigated. Various organochlorine compounds have been used in metal parts rinse and dry cleaning, for their characteristics as solvent and chemical stability. With careless handling, these chemicals caused contamination of soil and underground water, in Japan, United States and other countries. As the toxicity to central nerve system and carcinogenicity of TCE was recognized, remediation of TCE contamination became an urgent issue. However, technologies, such as removal of soil or aeration in deep ground water need large amount of expenditure. To cope with the TCE contamination issue, we explored quick and cost-efficient technique of in situ TCE degradation in soil. We studied the electrochemical TCE degradation assisted by Fe ion catalysis in Fenton reaction. Electrochemical degradation mechanism of TCE is not well known. In this study, TCE solution was contained in a semi sealed vessel with 1 mmφ grass beads to avoid evaporation. Directive current (DC) voltage of 10 V was applied with iron electrodes, placed 8.6 cm apart. Reaction vessel was kept at 15ºC during voltage application by immersing in water. As the DC voltage applied, Fe ion was dissolved into the solution from positive and negative electrodes, and moved to the other electrode by electrophoresis. These ion species are expected to promote TCE degradation. Remaining TCE concentration after reaction was measured by GC-ECD. TCE concentration was decreased by 2-10% around the surface of the electrodes in 120 min. TC, TOC, IC were also measured after 120 min. Chloride ion concentration was measured by liquid chromatography. Almost all the reacted organic carbon was converted to carbon dioxide, and little intermediate product was observed in GC-MS analysis. These results suggest the possibility of TCE degradation with low cost ion electrode by application of DC voltage to the soil.