Chlorinated Byproducts from the TiO sub(2)-Mediated Photodegradation of Trichloroethylene and Tetrachloroethylene in Water

The by-products of trichloroethylene (TCE) and tetrachloroethylene (PCE) in water during the titanium dioxide photocatalysis process were examined. Analysis was performed by gas chromatography with electron-capture detection. The by-products of PCE were found to be dichloroacetic acid and trichloroacetic acid. For TCE, the products formed were dichloroacetaldehyde, dichloroacetic acid, trichloroacetaldehyde, and trichloroacetic acid. The results suggested that dichlorinated by-products are formed by a process in which the first step is reduction of the chloroalkene by conduction-band electrons. Dichloroacetic acid is a known animal carcinogen that is more potent than either TEC or PCE. The carcinogenicity of dichloracetalkehyde is unknown.