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 decomposition were studied in near-UV-irradiated aqueous TiO2 (anatase) suspensions in a batch photoreactor. The influence of catalyst loading, initial phenol concentration, dissolved O-2 concentration, Ag+ content and H2O2 concentration on the rate of phenol degradation is reported. The observed heterogeneous degradation of phenol followed apparently zero-order kinetics up to ca. 70% conversion. The Langmuir-Hinshelwood kinetic model successfully described the influence of the initial phenol concentration and dissolved O-2 concentration on the rate of heterogeneous photooxidation of phenol. The data obtained by applying the Langmuir-Hinshelwood treatment are consistent with the available kinetic parameters. The results of the experiments in the presence of Ag+ indicated that the phototransformation of phenol can proceed via direct electron transfer, neither dissolved O-2 nor its reduction forms playing a significant role in the degradation mechanism. (C) 1994 Elsevier Science B.V. All rights reserved.