Studies On TiO₂ In Situ Supported On Sepiolite And Tourmaline

A kind of novel composite photocatalyst was prepared through hydrolysis of TiCl4, in order to solve the separation problem of photocatalyst in application, and the problems of low quantum yield and low solar energy conversion efficiencies. Sepiolite with strong physical adsorption function and tourmaline with spontaneous polarity were used as carriers. The preparation, crystalline phase and surface morphology of the materials were studied. Besides, the photocatalytic activities and mutual interactions mechanism between TiO₂ and mineral were also investigated.TiO₂ grew successfully on the surface of sepiolite and tourmaline through hydrolysis of TiCl4 under boiling reflux condition. The photocatalysts'crystalline phase and surface morphology were characterized by means of X-ray diffraction(XRD),scanning electron microscope(SEM), and X-ray photoelectron spectrum (XPS). The photocatalytic performances were evaluated through study on the ability of generating hydroxyl radical (·OH ) by electron spinning resonance (ESR) and the decomposition of methyl orange in aqueous solution. It shows that TiO₂ is rutile-anatase mixing type while the composite prepared by the same method is rutile crystal. The average diameter of the TiO₂ ball which grow on sepiolite fibre is 2μm, and TiO₂ granules grow into clusters on the surface of tourmaline particles. The binding energy of Ti2p becomes 0.2eV lower with the presence of the mineral. The composite can produce more·OH free radicals than TiO₂ under the irradiation both visible light and ultraviolet light. The two minerals can improve the photocatalytic activity of TiO₂, furthermore they can expand its photoexciting spectra into visible light.The mechanism of two minerals promoting TiO₂'s photocatalytic performance was investigated respectively. It is found that the strong adsorption of sepiolite can increase the substance concentration near the photocatalysts and make higher efficiency. In the TiO₂ and tourmaline system, the surface electric field of tourmaline particle makes the photo-generated electrons and photo-generated holes move towards reverse direction, which reduces their re-combination and enhances the production of·OH. Meanwhile the two minerals have similar surface hydroxy which can capture the photo-generated electron and enhance the·OH producing.