Selective photodegradation of phenol in the presence of a commercial humic acid

Abstract

Preferential oxidation of certain pollutants has been a major challenge in photocatalysis, since normal source water contains low concentrations of highly toxic substances along with high concentrations of natural organic matter. Pure TiO2 and doped with cerium (0.1 nominal at.%) by the sol-gel method under different conditions were synthesized. In one of the synthesis conditions, a nonionic surfactant was used as a pore-directing agent along with an acetic acid-based sol-gel route without addition of water molecules. The effect of the presence of a surfactant, the doping with cerium, the light absorption, the adsorption and the degradation of phenol and a commercial humic acid, as well as the structural properties of the synthesized materials, were investigated in this study. It can be demonstrated that by controlling the porous structure of TiO2, the access of large size natural organic matter to the TiO2 can be suppressed, thus improving the selective oxidation of small size target contaminants. Phenol as a target contaminant was successfully decomposed even in the presence of a commercial humic acid as competing natural organic matter. Under UV irradiation, highly porous catalysts prepared with polyoxyethylene (20) sorbitan monooleate surfactant exhibited a higher photocatalytic activity for the degradation of phenol in the presence of a commercial humic acid than the materials prepared without this surfactant. Under visible irradiation, the material prepared with the surfactant and doped with Ce presented the best performance, probably due to the red shift of the electronic absorption band induced by cerium incorporation to TiO2.