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

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 O2 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 O2 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 O2 nor its reduction forms playing a significant role in the degradation mechanism.