The Magnetic Visible-light-active TiO₂-based Photocatalyst:Synthesis And Catalyzing

Photocatalytic degradation is an advanced oxidation process for treating wastewater with complex organic pollutants. Nano-scale semiconductors have placed themselves in an important position in a variety of advanced oxidation methods. Among the employed semiconductors, TiO2is very attractive in heterogeneous photocatalysis due to its high photocatalytic activity, non-toxic nature, low cost, excellent chemical and mechanical stability, and so on. However, the industrial application of TiO2was impeded by some drawbacks such as narrow absorption spectrum, low quantum efficiency and recycling difficulty in the suspension system. To overcome the drawbacks above, reasonable and feasible methods should be proposed to modify TiO2.In this paper, the magnetic Fe3O4powder was prepared by hydrothermal and coprecipitation methods. The magnetic TiO2/Fe3O4photocatalyst was synthesized by sol-gel technology. The morphology, structure and optical properties of samples were characterized by XRD, TEM and UV-Vis. Several key factors, such Fe3O4adulterant proportion, calcination temperature and calcination time in the preparation process, were analysed in the degradation of the Reactive Brilliant Red X-3B solution under UV or simulated sunlight. The results showed that, the prepared TiO2existed in the form of anatase, and the magnetic property of TiO2/Fe3O4photocatalyst was well preserved. The Fe3O4magnetite particles were coated by one layer of TiO2, and the particle size range of TiO2/Fe3O4composites was about200-250nm. The optimized preparation condition of TiO2/Fe3O4photocatalyst was obtained: Fe3O4adulterant proportion:6%(molar ratio of Fe to Ti), calcined temperature:300℃; calcined time:2h.The TiO2/Fe3O4photocatalyst prepared at optimized preparation condition was coupled with CdS by impregnation method, thus the CdS-TiO2/Fe3O4composite photocatalyst was prepared. The samples were characterized by XRD, UV-Vis, TEM and XPS. Several factors, such as CdS adulterant proportion, calcination temperature, and calcination time in the preparation process, were also analyzed in the degradation of the Reactive Brilliant Red X-3B solution under simulated sunlight. The results showed that, the Fe3O4were coated by a loose layer of CdS-TiO2clusters, and the average diameter of the particles in CdS-TiO2/Fe3O4composites was about250nm. CdS-TiO2/Fe3O4composites exhibited more pronounced red-shift and stronger absorption in visible light region, compared with that of pure TiO2or TiO2/Fe3O4photocatalyst. The optimized preparation condition of CdS-TiO2/Fe3O4composites was obtained:CdS adulterant proportion:1%, calcined temperature:300℃; calcined time:1h. The degradation rate of Reactive Brilliant Red X-3B (50mg/L) is88.59%by the optimized CdS-TiO2/Fe3O4photocatalyst under simulated sunlight irradiation for120min. The CdS-TiO2/Fe3O4photocatalyst is highly recyclable due to preserved magnetism, and the high activity can also be maintained even after several experimental runs. In specific, the degradation rate of Reactive Brilliant Red X-3B was still up to78.9%after five runs.