EFFECT OF PLATINUM ON THE PHOTOCATALYTIC DECOMPOSITION OF 2-CHLOROPHENOL IN AQUEOUS SOLUTION BY UV/TiO2

Photocatalytic decomposition of 2-chlorophenol in aqueous solutions with platinum-coated TiO2 slurry under UV irradiation was examined, utilizing various solution pH levels, dissolved oxygen levels and UV light intensities. The atomic percentage of platinum deposited on the TiO2 surfaces were identified by X-ray photoelectron spectroscopy (XPS) to be in the range of 0.12 and 0.99%. The decomposition of 2-chlorophenol in acidic aqueous solutions by UV/TiO2 was enhanced to certain extents for experiments conducted with platinum-coated TiO2 containing up to 0.82% platinum because of the formation of Schottky barrier between platinum and TiO2 to prevent the recombination of electric holes and electrons. However, for experiments conducted with TiO2 coated with higher platinum contents, the decomposition rate of 2-chlorophenol was reduced markedly, possibly because of the depression of the light absorption of TiO2 by the shielding of coated platinum. The photocatalytic decomposition of 2-chlorophenol in aqueous solution was inhibited for experiments conducted in neutral and alkaline solutions because the presence of platinum increases the repulsion between 2-chlorophenol species and TiO2 to hinder the adsorption of 2-chlorophenol species on TiO2. The decomposition rate of 2-chlorophenol in aqueous solution by UV/TiO2 was found to be improved significantly with increasing UV light intensity.