Photocatalytic degradation of reactive dye RED‐3BA in aqueous TiO2 suspension under UV‐visible light

Abstract

The photo‐catalytic degradation efficiency of several commercial titania powders (Degussa P‐25 and Ishihara Sangyo ST‐01) and of TiO2 supported on diatomite were investigated in the degradation of a reactive dye (RED‐3BA) under UV‐Visible light. The observed rate constant for Degussa P‐25 was found to be higher than that achieved by using Ishihara Sangyo ST‐01 (kobs = 3.3 × 10−2min−1 for Degussa P‐25 and 4 × 10−4min−1 for Ishihara Sangyo ST‐01). This could be related to the amount of basic hydroxyl groups on the surface of TiO2 particles as shown in the IR spectra. TiO2 Degussa P‐25 supported on diatomite was prepared by dip‐coating method. The photo‐catalytic activity of supported TiO2 was twice smaller than TiO2 Degussa P‐25 (kp-25 = 3.3 × 10−2min−1;kp25/diatomite = 1.6 × 10−2min−1). The higher surface areas of ST‐01 and the TiO2/diatomite could not lead to a higher degradation rate and to a higher degree of mineralization but TiO2/diatomite could be separated more promptly and more easily from the solution. The effect of pH was investigated in the range 4–9. Acidic (pH = 4) medium was found to favor the adsorption and degradation rate with P‐25 particles.