Photocatalytic decolorization of methylene blue in the presence of TiO 2/ZnS nanocomposites

Abstract

The synthesis of distinct nanocrystalline TiO 2 capped ZnS samples was carried out using a chemical deposition method. The materials characterization showed that the presence of ZnS onto TiO 2 surface results in a red shift of the material band edge when compared with the initial semiconductor. The photocatalytic activity of the prepared nanocomposites was tested on the decolorization of methylene blue (MB) aqueous solutions. The dye photodecolorization process was studied considering the influence of experimental parameters such as catalyst concentration, TiO 2/ZnS ratio, pH and methylene blue adsorption rate. The material with the best catalytic activity towards the methylene blue photodecolorization was the TiO 2 doped with 0.2% of ZnS. The complete photodecolorization of a 20 ppm methylene blue solution, at natural pH was achieved in less than 20 min, nearly 70 min faster than the TiO 2 photoassisted process.