A B S T R A C TOne of the major disadvantages of the application of ZnO nanoparticles as photocatalyst in photocatalytic systems is photoinstability due to the photocorrosion under UV light irradiation resulting in the significant reduction in their photocatalytic activity. Therefore, in the present study, SiO 2 nanopowders were incorporated into the ZnO nanoparticles to enhance their photocatalytic activity for the decolorization of methylene blue (MB) dye in comparison with pure ZnO/UV process. The efficiency of UV/ZnO/SiO 2 process was compared with UV/ZnO process for the decolorization of MB dye and the removal of chemical oxygen demand (COD). The effect of various amounts of SiO 2 (5, 10, and 15%) incorporated into ZnO nanoparticles was studied. At optimal SiO 2 loading of 10%, the decolorization efficiency of MB and the removal of COD were obtained to be 100 and 81%, respectively. However, using UV/ZnO process at the same operational conditions, the decolorization efficiency of MB and the removal of COD were 66 and 44%, respectively. An initial pH of 7 and initial dye concentration of 25 mg/L were chosen as optimal experimental conditions. It can be stated that the incorporation of SiO 2 nanopowders into the ZnO nanoparticles would be beneficial for enhancing their photocatalytic activity.

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