Influence of operating parameters on photocatalytic degradation of phenol in UV/TiO2 process

The use of hydrogen peroxide (H2O2) for improved photocatalytic degradation of phenol in aqueous suspension of commercial TiO2 powders (Degussa P-25) was investigated. Photodegradation was compared using direct photolysis (UV alone), H2O2/UV, TiO2/UV. and H2O2/TiO2/UV processes in a batch reactor with high-pressure mercury lamp irradiation. The effects of operating parameters such as catalyst dosage, light intensity. pH of the solution, the initial phenol, and H2O2 concentrations on photodegradation process were examined. It was shown that photodegradation using H2O2/TiO2/UV process was much more effective than using either H2O2/UV or TiO2/UV process. The effect of the initial phenol concentration on TOC removal was also studied, demonstrating that more than 8 h was required to completely mineralize phenol into water and carbon dioxide. For all the four oxidation processes studied, photodegradation followed the first-order kinetics. The apparent rate constants with 400-W UV ranged from 5.0 x 10(-4) min(-1) by direct photolysis to 1.4 x 10(-2) min(-1) using H2O2/TiO2/UV process. The role of H2O2 on such enhanced photodegradation of phenol in aqueous solution was finally discussed. (C) 2007 Elsevier B.V. All rights reserved.