Photocatalytic decolorization of methylene blue dye by zinc oxide powder


Photocatalytic decolorization of methylene blue dye (MB) in water has been investig -ated in an immersed UV light irradiation slurry photoreactor using zinc oxide (ZnO) as a semiconductor photocatalyst. The effects of different parameters such as initial dye concentration, photocatalyst loading, and pH of solution on the decolorization rate of MB have been systematically investigated. A two-stage photocatalytic decolo -rization of MB, the first stage of fast decolorization rate and the subsequent second stage of rather slow decolorization rate, was found. The efficiency of decolorization of MB increased as initial MB concentration decreased. There was the optimal ZnO concentration being around 1500 mg L−1. The optimal pH was around 7 where reaction rate decreased above and under this pH value.