Solar photocatalytic decolorization of C.I. Basic Blue 41 in an aqueous suspension of TiO2–ZnO

Nanosized, bicomponent TiO2–ZnO powders of varying Ti/Zn ratio, were prepared using an ultrasonic precipitation method and their crystalline structure and surface area were determined using X-ray diffraction and N2 physical adsorption. The nanosized TiO2–ZnO powders displayed high photocatalytic activity towards the decolorization of C.I. Basic Blue 41 in water under solar irradiation and a Ti/Zn molar ratio of 1:1 showed highest photocatalytic activity. The effects of various parameters such as photocatalyst loading, initial solution pH, initial dye concentration and irradiation time on decolorization rate were systematically investigated. The optimal TiO2–ZnO concentration range was around 6–10 g/L. Optimal pH was ∼6.21 which was the natural pH of a 20 mg/L aqueous solution of the dye. Approximately 100% color removal was achieved in about 1 h; the addition of a surfactant and an antistatic agent hindered photocatalytic decolorization, which obeyed pseudo-first-order kinetics.