Photocatalytic Degradation of Tri- and Tetrachloroethylene on Porous TiO₂ Pellets

Abstract

The photo-assisted catalytic degradations of trichloroethylene (TCE) and tetrachloroethylene (PCE) were studied in a tubular photoreactor packed with TiO₂ pellets prepared by sol-gel method. The experiments were performed at 32°C in a non-circulating mode. Comparison with the ethylene degradation reveals that TCE and PCE were degraded more efficiently than ethylene. However, only 48% of TCE or 57% of PCE was converted to HCl and CO₂ whereas 95% of ethylene was mineralized. Phosgene, CHCl₃ and dichloroacetic acid were detected from the photodegradation of TCE while that of PCE yielded phosgene, CCl₄ and trichlroacetic acid. Phosgene in the effluent gas stream was completely removed by passing through water. The reaction mechanism to form these chlorinated products is discussed.