| In recent years, photocatalytic oxidation technology used semiconductor, which was applied in the degradation of dye wastewater and organic pollutant, has gained a great deal of attention from research workers. TiO2, as a kind of photocatalytic materials, has its unique advantages, but the large forbidden band width (Eg=3.2eV), low utilization rate of solar energy and narrow band width of visible light has limited its wide application, so the development of the new high-efficiency catalysts with narrow band has been a hotspot.The structure of bismuth system photocatalyst have a good catalytic performance, especially the obvious absorption range of visible light, hence the development of bismuth system photocatalyst has become the research focus of the topics gradually. Bismuth tungstate (Bi2WO6) as the simplest oxide of Aurivillius type layer structure, researchers has paid more ettention to its potential value in terms of degradation in wastewater, Since Kudo reported Bi2WO6has a better photocatalytic activity under visible light irradiation(λ>420nm) in1999s. In this paper, the influence about preparation conditions on its photocatalytic propertie has been studied, the metal-doped Bi2WO6has also been studied in order to further improve the photocatalytic performance. The catalysts were characterized by modern characterization techniques such as XRD、SEM、BET、DRS、FT-IR, then the photocatalytic performance was studied by the degradation of simulative RhB solution. The concrete research content is as follows:(1) The sample Bi2WO6was preparaed by hydrothermal synthesis and coprecipitation method, The structure and properties of the catalyst characterized by X-ray diffraction (XRD). The results indicated that the sample preparaed by hydrothermal synthesis was the orthorhombic phase structure, however, another was amorphous type. Then the Bi2WO6catalyst was prepared by hydrothermal synthesis method, and the influence of different preparation conditions on the structure and properties of Bi2WO6photocatalyst were studied, The single factor was the predecessore pH, Temperature(T) and time(t) respectively. The results showed that the pH value of precursor suspensions has a more effective impact on the photocatalytic performance of Bi2WO6compared to the other two conditions. The related characterization showed the pH value of precursor suspensions have a greatly effect on crystal particle, morphology and specific surface area etc.The catalyst has a better photocatalytic activity about pH value4.5, which has a fluffy-inserted layer structure, high crystallinity as well as larger specific surface area.(2) The different metal-doped catalysts (3.0%Ni-Bi2WO6,3.0%Co-Bi2WO6,3.0%Zr were obtained at the optimized technology conditions of synthesis (pH=4.5, T=160, t=12h). The results indicated that the photocatalytic activity of Bi2WO6was improved by the Zr、Co-doped, what’s more, it was highly effective when the Zr-doped concertration was1.0%, however, the photocatalytic activity was restrained by the Ni-doped. Then the Bi2WO6of different Zr-doping amount was further studied, the results implied the photocatalytic activity of Bi2WO6was greatly effected by concertration of meatal-doped, and the1.0%Zr-Bi2WO6has better photocatalytic activity, the degradation was increased6.0%compared to the purity Bi2WO6under the condition of the same reaction process.(3) The technology conditions of the degradation were optimized and confirmed with the1.0%Zr-Bi2WO6being as the catalyst, the conditions were respectively catalyst dosage, initial pH and concentration of RhB solution. The kinetics research indicated that the reaction activation was submited to first-order reaction kinetic mode, and the reaction rate constant reduced with the increasing of initial concentrations. |
PDF Full Text Request