Study On Novel Visible-Light-Active Titania Photocatalysts-Prepared By TiO₂-coated FeOOH

Photocatalysis has been becoming international focus in material and chemistry fields in recent years for its properties. Application of photocatalyst in environmental protection is an important and promising attempt.TiO₂-coated goethite (α-FeOOH) was prepared through sol-gel method and following heat treatment. The TiO₂/α-Fe₂O₃ was characterized by BET,XRD,TEM,SEM and FTIR. The absorptic and photocatalytic ability were studied when treated a dye-reactive brilliant blue X-BR using TiO₂/α-Fe₂O₃ calcinied at different temperatures. The results indicate that BET surface area of TiO₂/α-Fe₂O₃ after calcination increased dramatically in comparison with the original a-FeOOH. The surface area increased from 35.4m²/g to 167.7m²/g when calcined at 350℃but decreased when calcinied at 450℃. Crystalline TiO₂ coated onα-FeOOH was from anatase to rutile and the average crystallite size increased gradually with increasing of heat-treatment temperatures. We studied the absorption and photocatalytic activity of TiO₂/α-Fe₂O₃ for reactive brilliant blue X-BR under UV irradiation. It showed that the highest photocatalytic activity and absorption of TiO₂/α-Fe₂O₃ calcined at 350℃and the decolor rate could reach to 85.19%.TiO₂/γ-Fe₂O₃, a nanosize magnetic visible-light-active photocatalyst, was prepared through sol-gel method and subsequent calcination in H₂/O₂ atmosphere. The TiO₂/γ-Fe₂O₃ was characterized with specific surface area (BET), X-ray diffraction (XRD), transmission electron microscope (TEM), magnetic susceptibility (MS) and UV-Vis diffuse reflectance. The absorptive and photocatalytic ability were evaluated by decolorization of reactive brilliant blue X-BR aqueous solution. The results indicate that calcination gives rise to a dramatic increase in the BET surface area of TiO₂/γ-Fe₂O₃, and the obtained product has a broader absorbance band (200-500nm) than pure Titania. It was found that under Xenon lamp irradiation, TiO₂/γ-Fe₂O₃ could work as the absorbent of the dye and also as the photocatalyst for the decomposition of absorbed reactive brilliant blue X-BR. According to the UV-Vis diffuse reflectance spectra, the TiO₂/γ-Fe₂O₃ displays a very broad range absorbance in 200nm-700nm. Such an extended coverage in the visible spectrum makes TiO₂/γ-Fe₂O₃ composites possible to utilize most of the energy from sunlight.