Synthesis Of ZnS/Bi-TiO₂Photocatalyst And Studies Of Its Photocatalytic Activities

The excellent performance of semiconducting oxide materials in photocatalytic oxidation realm attracts a large number of ongoing research. Among various oxide semiconductor photocatalysts, TiO2has been widely considered as the most promising photocatalyst due to its high photocatalytic activity, good chemical and biological stability, non-toxicity, and low cost, etc. However, because of its large energy band gap of3.2eV, TiO2could only be excited under UV irradiation, which accounts for only about5%of solar energy. In recent years, great interests have been focused on the development of photocatalysts with visible light response. Doping TiO2with metal, nonmetal ion and coupling TiO2with different semiconductor have been regarded as the effective method of modifying TiO2/The single method of doping or coupling with TiO2affects a little. Therefore this paper will modify TiO2through the method of doping with metal ion and coupling with other semiconductor.On the one hand, through single doping with Bi, the Bi-TiO2was prepared with sol-gel method and was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS),UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and Fourier transform infrared spectroscopy (FT-IR). Methyl orange (MO), which is a common pollutant in the industry effluents, was chosen to test the photocatalytic ability of Bi-TiO2using the xenon Jamp as the simulated sunlight. The factors that affect the degradation of MO, such as doping amounts, calcination temperature, calcination time, dosage of catalyst, pH of solution and initial concentration of solution were evaluated. Meanwhile, the kinetics of MO removal was investigated. The results showed that, the optimum conditions were as follows:the Bi-Ti molar ratio was0.6%, the calcination temperature was400℃. the calcination time was5h, the dosage of Bi-TiO2was1g/L, the pH of the solution was3.0and the initial concentration of MO was20mg/L, the decolorization rate of MO was75.1%and the kinetic constant was0.0113min-1, which was3.8times as great as that TiO2. The stability of Bi-TiO2was tested by repeating the same experiment for four times and there was no significant decrease of photocatalytie activity of the catalyst found in the result.On the other hand. ZnS was further coupled on the basis of doping with Bi. The sol-gel method was used to prepare the ZnS/Bi-TiO2. And the samples were characterized by XRD. XPS, TEM. UV-vis DRS and PL. The photocatalytie ability of ZnS/Bi-TiO2was evaluated by the same way. The results showed that, the optimum conditions were as follows:the ZnS-Ti molar ratio was0.5%. the calcination temperature was400C, the dosage of ZnS/Bi-TiO2was1g/L. the pH of the solution was3.0and the initial concentration of MO was20ing/L. Under the optimal conditions, the decolorization rate of MO reached84%and the kinetic constant was0.0147rnin"1, which were both higher than the Bi-TiO2. The results indicated that coupling with ZnS further increase the photocatalytie activity of the Bi-TiO2. Furthermore, there was also no obvious decrease of the photocatalytie activity of the catalyst after repeating the same experiment for four times.