Oxidative Degradation and Toxicity Reduction of Trichloroethylene (TCE) in Water Using TiO₂/Solar Light: Comparative Study of TiO₂ Slurry and Immobilized Systems

A solar–driven, photocatalyzed degradation system using TiO₂ slurry and immobilized systems was constructed and applied to the degradation of trichloroethylene (TCE) contaminated water using TiO₂ with solar light. The experiments were carried out under constant weather conditions on a sunny day. Solar photocatalytic treatment efficiency of the solar light/TiO₂ slurry system was compared with that of the solar light/TiO₂ immobilized system. The operation of the solar light/TiO₂ slurry and immobilized systems showed 100% (TiO₂ slurry system), 80% (TiO₂ immobilized system) degradation of the TCE after 6 h, with a chloride production yield of approximately 89% (TiO₂ slurry system), 72% (TiO₂ immobilized system). The oxidants such as H₂O₂ and S₂O₈ ^{2 –} in the TiO₂ 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/TiO₂ slurry+ S₂ O₈ ^{2 –}> solar light/TiO₂ slurry+ H₂ O₂> solar light/TiO₂ immobilized+ S₂ O₈ ^{2 –} > solar light/TiO₂ slurry> solar light/TiO₂ immobilized+ H₂ O₂> solar light/TiO₂ immobilized. Finally, following to the toxicity result, the acute toxicity was reduced by below toxicity endpoint (EC₅₀ 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, photocatalyzed degradation system.

Key Words :

• TCE
• Solar light
• TiO₂ slurry
• TiO₂–immobilized system
• H₂O₂
• S₂O₈ ^{2 –}
• Relative toxicity
• Chloride ion
• CO₂