Kinetic and mechanism study on photocatalytic detoxification of Cr(VI) ions on TiO2 catalyst

Abstract

The adsorption, kinetics and mechanism of photocatalytic reduction and detoxification of Cr(VI) ions on TÍO2 catalyst are studied in this paper. The results show that Cr(VI) adsorption is mainly dependent on the system acidity and Cr(VI) concentration. Competitive adsorption is observed between Cr(VI) and phosphate ions. The presence of oxygen has no interference on Cr(VI) reduction. Kinetic study shows that the photocatalytic reduction of Cr(VI) ion on TiO2 under UV irradiation is in accord with the Langmuir‐Hinshelwood equation. It is pointed out that Cr(VI) is either indirectly reduced by getting electrons from Ti3+ or directly reduced by capturing conduction band electrons. The inhibition of Cr(VI) reduction in the presence of phosphate ions indicates that Cr(VI) adsorption is a primary step in photocatalytic reaction process. Photocatalytic reduction of Cr(VI) ion under the sunlight irradiation and the reactivation of TiO2 catalyst after the reaction revealed the possibility of application of photocatalytic decontamination to the treatment of real pollution systems.