Decomposition of aqueous tetrachloroethylene by Fenton oxidation treatment

Flask-scale experiments were performed to elucidate the reaction mechanism in which tetrachloroethylene (PCE) in water is decomposed by Fenton oxidation treatment. Concentrations of Cl⁻, total inorganic carbon, and PCE were measured during a 24-h reaction period in which there occurred a pseudo first-order reaction (k=0.17 h⁻¹) and >95% dechlorination and mineralization. Results indicate that: (i) PCE decomposition due to Fenton oxidation is compensated throughout the experiment by increasing Cl⁻ and CO₂, and (ii) mineralization rates derived from the increase in CO₂ are nearly the same as dechlorination rates due to the increase in Cl⁻. GC/MS and GC/ECD analyses of reaction intermediates confirmed the presence of trichloroacetic acid (TCAA) only. That is, organic compounds such as dichloroacetic acid (DCAA), monochloroacetic acid, acetic acid, and formic acid were not detected, having been decomposed by Fenton oxidation although no degradation of TCAA occurred and detected TCAA only explained 1% of decomposed PCE. These findings indicate that dechlorination and mineralization proceed almost simultaneously during PCE decomposition by Fenton oxidation treatment, and not via intermediates such as acetic acid and DCAA.