Photocatalytic degradation of chloroform in the gas phase on the porous TiO2 pellets: effect of Cl accumulated on the catalyst surface

Abstract The photocatalytic degradation of chloroform was studied in a tubular photoreactor packed with TiO 2 pellets prepared by sol–gel method. Concentrations of chloroform and CO 2 in the gas stream and Cl − ion which was dissolved from the pellets into water after the photodegradation experiments were detected quantitatively. Chloroform was completely mineralized to CO 2 and HCl but the conversion decreased drastically with an increase in the irradiation time. Such a decrease in the catalytic activity was attributable to the accumulation of Cl − on the TiO 2 surface and was recovered by washing the pellets with water. The presence of Cu and Ca(OH) 2 increased the concentration of Cl − accumulated on the surface. The deterioration of the catalytic activity was suppressed with Ca(OH) 2 whereas no appreciable effect was observed with Cu. The TiO 2 prepared by sol–gel method exhibited a higher catalytic activity than commercially available Degussa P-25.