Photocatalytic abatement of trichlorethylene over Au and Pd–Au supported on TiO2 by combined photomineralization/hydrodechlorination reactions under simulated solar irradiation

Abstract

The present work investigates the photocatalytical abatement of trichlorethylene (TCE) under simulated solar irradiation (AM 1.5). The employed catalytic materials, Au and Pd–Au nanoparticles supported on TiO2, were prepared by incipient wetness and by deposition–precipitation methods. It is found out that TCE is converted efficiently (>80%) to Cl− and CO2 over all scrutinized catalysts. Typically, the metal addition enhances to some extent the photooxidation activity of TiO2 via photogenerated OH radicals, electrons, and holes. The photocatalytic abatement of TCE over the same catalytic materials was examined in the presence of small amount of methanol. The idea was to convert TCE to Cl− and C2 (ethane and ethylene) over Au and Pd–Au/TiO2 catalysts by the H2 generated photocatalytically in situ. The experimental results evidenced that, over Pd–Au/TiO2 catalysts, hydrodechlorination (HDC) and photomineralization reactions of TCE occurs simultaneously. In contrast, Au/TiO2 is inactive to catalyze the hydrogenation of TCE. The results of TCE abatement by combined photooxidation/HDC reactions in presence of methanol are corroborated with H2 photocatalytic generation results, over the same catalytic materials, from water/methanol mixture. A reaction mechanism is advanced in light of experimental results. The photogenerated OH radicals, electrons, and holes participate in a complex reaction pathway to formation of oxygenated organic intermediates, Cl−, CO2, and H2.