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.