Photocatalytic Degradation of Gaseous Chloroethylene Mixtures Using UV-illuminated Titanium Dioxide

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Abstract
The gas-phase photocatalytic decomposition of individual- and two-component mixtures of chloroethylenes using near-UV-illuminated TiO2 was studied. The apparent quantum efficiencies for the degradation of cis-1,2-dichloro- (0.42), trichloro- (9.6), and tetrachloroethylene (10.6) were found to increase with the number of chlorine substituents. cis-1,2-Dichloro- and trichloroethylene in the presence of tetrachloroethylene decomposed with higher quantum efficiency, specifically, 1.6 and 11.7, respectively. The decomposition of cis-1,2-dichloroethylene in the mixtures was remarkably promoted, while the apparent quantum efficiency of tetrachloroethylene to function as an accelerator showed a decrease for the decomposition with cis-1,2-dichloroethylene (3.6) or with trichloroethylene (9.1). These findings were explained in terms of the presence of chlorine atoms in photochemical and photocatalytic reactions.