Photoassisted heterogeneous catalysis: The degradation of trichloroethylene in water

The complete mineralization of trichloroethylene (Cl2CCClH), in dilute aqueous solutions, to HCl and CO2 is demonstrated with heterogeneous photoassisted catalysis using illuminated titanium dioxide (TiO2). An intermediate, dichloroacetaldehyde, is identified, and a photoassisted reaction sequence is proposed. A simple Langmuirian rate equation satisfactorily represents both the disappearance of initial reactant, trichloroethylene, and intermediate, dichloroacetaldehyde, as well as the inhibitory influence of product HCl. The present paper and two related reports (A. L. Pruden and D. F. Ollis, Environ. Sci. Technol., in press; C.-Y. Hsiao, C.-L. Lee, and D. F. Ollis, J. Catal. 82, 418 (1983)) establishing mineralization of chloromethanes, indicate some potential for removal of the two most common chlorocarbon contaminants from water via heterogeneous photocatalysis.