Preparation And Photocatalytic Activities Evaluation Of Modified TiO₂Photocatalyst

Environmental pollution and energy crisis are becoming a serious problem. Recently, the use of semiconductor photocatalysts has been much noticeable to solve some environmental pollution. In the number of various semiconductors, which were used; titanium dioxide (TiO2) was one of the most important photocatalyst for the degradation of environmental contaminants. This is because of its high photocatalytic activity, non-toxicity, chemical stability under different conditions, and relative inexpensive. TiO2is an effective material for the degradation of dyes from wastewater. However, because of its large band gap (3.2eV); it cannot absorb sunlight, successfully. To reduce the band gap and increase the photoactivity of semiconductor, various ways have been tested, which one of them is its doping with different metal oxides.The ZnO/TiO2was prepared with sol-gel method and was characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and BET. Several key factors, such ZnO doping amount, calcination temperature and calcination time in the preparation process, were analysed in the degradation of the Reactive Brilliant Blue KN-R solution under UV or simulated sunlight. The results showed that, the prepared TiO2existed in the form of anatase. ZnO/TiO2composites exhibited pronounced red-shift and strong absorption in visible light region. The optimized preparation condition of ZnO/TiO2photocatalyst was obtained:the ZnO doping amount was8%(molar ratio of Zn to Ti), the calcination temperature was450℃, the calcination time was2h. Under the conditions of the dosage of ZnO/TiO2was1g/L and the initial concentration of dye was50mg/L, the degradation rate of Reactive Brilliant Blue KN-R reached55%.Under the optimized preparation condition of ZnO/TiO2photocatalyst, the sol-gel method was used to prepare the NiO/ZnO/TiO2. And the samples were characterized by XRD, UV-Vis DRS, TEM and XPS. Several key factors, such as ZnO doping amount, calcination temperature and calcination time in the preparation process, the dosage of NiO/ZnO/TiO2and the initial concentration of dye in the reaction process, were analysed in the degradation of the Reactive Brilliant Blue KN-R solution under simulated sunlight. The results showed that, the prepared TiO2existed in the form of anatase. NiO/ZnO/TiO2composites exhibited more pronounced red-shift and stronger absorption in visible light region, compared with that of ZnO/TiO2photocatalyst. The optimum conditions were as follows:the NiO doping amount was0.4%, the calcination temperature was450℃, the calcination time was2h, the dosage of NiO/ZnO/TiO2was1g/L, the initial concentration of dye was30mg/L. Under the optimal conditions, the degradation rate of Reactive Brilliant Blue KN-R reached73.5%, which were both higher than the ZnO/TiO2. The results indicated that doping with NiO further increase the photocatalytic activity of the ZnO/TiO2. Furthermore, there was also no obvious decrease of the photocatalytic activity of the catalyst after repeating the same experiment for four times.