Investigation of the photodecomposition of phenol in near-UV-irradiated aqueous TiO2 suspensions. I: Effect of charge-trapping species on the degradation kinetics

The effects of charge-trapping species on the kinetics of phenol decomposit ion were studied in near-UV-irradiated aqueous TiO2 (anatase) suspensions i n a batch photoreactor. The influence of catalyst loading, initial phenol c oncentration, dissolved O-2 concentration, Ag+ content and H2O2 concentrati on on the rate of phenol degradation is reported. The observed heterogeneou s degradation of phenol followed apparently zero-order kinetics up to ca. 7 0% conversion. The Langmuir-Hinshelwood kinetic model successfully describe d the influence of the initial phenol concentration and dissolved O-2 conce ntration on the rate of heterogeneous photooxidation of phenol. The data ob tained by applying the Langmuir-Hinshelwood treatment are consistent with t he available kinetic parameters. The results of the experiments in the pres ence of Ag+ indicated that the phototransformation of phenol can proceed vi a direct electron transfer, neither dissolved O-2 nor its reduction forms p laying a significant role in the degradation mechanism. (C) 1994 Elsevier S cience B.V. All rights reserved.