Oxidative Degradation and Toxicity Reduction of Trichloroethylene (TCE) in Water Using TiO_2/Solar Light: Comparative Study of TiO_2 Slurry and Immobilized Systems

摘要

A solar-driven, photocatalyzed degradation system using TiO_2 slurry and immobilized systems was constructed and applied to the degradation of trichloroethylene (TCE) contaminated water using TiO_2 with solar light. The experiments were carried out under constant weather conditions on a sunny day. Solar photocatalytic treatment efficiency of the solar light/TiO_2 slurry system was compared with that of the solar light/TiO_2 immobilized system. The operation of the solar light/TiO_2 slurry and immobilized systems showed 100% (TiO_2 slurry system), 80% (TiO_2 immobilized system) degradation of the TCE after 6 h, with a chloride production yield of approximately 89% (TiO_2 slurry system), 72% (TiO_2 immobilized system). The oxidants such as H_2O_2 and S_2O_8~(2-) in the TiO_2 slurry and immobilized systems increased TCE degradation rate by suppressing the electron/hole recombination process. The degradation rate and relative toxicity reduction of TCE followed the order of solar light/TiO_2 slurry + S_2O_8~(2-) > solar light/TiO_2 slurry + H_2O_2 > solar light/TiO_2 immobilized + S_2O_8~(2-) > solar light/TiO_2 slurry > solar light/TiO_2 immobilized + H_2O_2 > solar light/TiO_2 immobilized. Finally, following to the toxicity result, the acute toxicity was reduced by below toxicity endpoint (EC_(50) concentration) following the treatment. It means that many of the metabolites of TCE reduction are less toxic to Vibrio fischeri than the parent compound. Based on these results, TCE can be efficiently and safely treated in a solar-driven, pho-tocatalyzed degradation system.