Photocatalytic oxidation of toluene and trichloroethylene in the gas-phase by metallised (Pt, Ag) titanium dioxide

The photodegradation of single component and binary mixtures of toluene and trichloroethylene (TCE), on TiO2, Pt/TiO2 and Ag/TiO2 was investigated. Intermediates formed during toluene photodegradation resulted in photocatalyst deactivation. Pt deposits improved the photocatalyst lifetime, delaying toluene breakthrough by up to 2.5 times and improving mineralisation by a factor of 3.5. Ag deposits had a negligible effect on photocatalyst performance. Deactivation was not evident during TCE photodegradation by neat or metallised TiO2. Pt deposits deterred TCE photodegradation with this effect ascribed to poisoning of the metallic Pt sites by photogenerated chloride radicals. In contrast, low Ag loadings were beneficial for TCE photodegradation with this effect ascribed to the temporary interaction between metallic Ag sites and chloride radicals to form AgCl. AgCl possesses semiconductor characteristics which may assist with TCE photodegradation. Photodegradation of the binary toluene/TCE mixture was observed to merge the positive and negative interactions between the metal deposits, organics and intermediates.