Sonophotocatalytic degradation of 4-chlorophenol using Bi2O3/TiZrO4 as a visible light responsive photocatalyst

The oxidative degradation of 4-chlorophenol (4-CP) by sonolytic, photocatalytic and sonophotocatalytic processes was studied in aqueous solutions using Bi2O3/TiZrO4 as a visible light driven photocatalyst and with 20 kHz ultrasound. The results reveal that Bi2O3/TiZrO4 is an efficient photocatalyst capable of degrading 4-CP by both photocatalytic and sonophotocatalytic processes. During the sonolysis of 4-CP solutions, HPLC results showed the formation of a number of intermediate products, whereas, no such intermediates were formed during the sonophotocatalytic degradation of 4-CP. TOC results showed rapid mineralization of 4-CP during the sonophotocatalytic degradation process, relative to that observed with sonolysis alone. The results reveal a clear advantage in using a coupled method for the oxidation of 4-CP and a cumulative effect was observed. Further, the solution pH had no specific influence on the sonophotocatalytic degradation of 4-CP, unlike the situation for sonolysis alone where the degradation rate decreased as the pH was raised from acidic to basic conditions. The combined sonophotocatalytic degradation process was found to be simple to apply and has the potential to be a powerful method for the remediation of organic contaminants present in water and wastewater. (C) 2010 Elsevier B.V. All rights reserved.