Microwave-assisted preparation, characterization and photocatalytic properties of a dumbbell-shaped ZnO photocatalyst

A novel dumbbell-shaped ZnO photocatalyst was successfully synthesized by microwave heating in the present study. The prepared ZnO photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis absorption spectrum (UV-Vis). The results indicated that the prepared ZnO photocatalyst shows a united dumbbell shape with 2 mu m diameter and 5 mu m length. The photocatalytic activity of the prepared dumbbell-shaped ZnO photocatalyst was evaluated by the degradation of Methylene Blue (MB) in aqueous solution. The effects of pH. catalyst dosage ([ZnO]) and initial concentration of MB ([MB]) on the photocatalytic degradation efficiency of MB were investigated. An optimum condition was determined as pH 7-8, [ZnO] = 1.0 g-ZnO L-1 and [MB] = 15 mg-MB L-1. Under the optimum condition, the decolorization and TOC removal efficiencies of MB at 75 min reaction time were achieved 99.6% and 74.3%, respectively, which were higher than that by the commercial ZnO powder. In addition, the photocatalytic degradation kinetics of MB was also investigated. The results showed that the photocatalytic degradation kinetics of MB fitted the pseudo-first-order kinetics and the Langmuir-Hinshelwood model. (C) 2010 Elsevier B.V. All rights reserved.