Photocatalytic degradation of phenol by visible light-responsive iron-doped TiO2 and spontaneous sedimentation of the TiO2 particles.

Fe-doped TiO2 was prepared by the calcination of Fe(x)TiS(2) (x=0, 0.002, 0.005, 0.008, 0.01) and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectra. All the Fe-doped TiO2 were composed of an anatase crystal form and showed red shifts to a longer wavelength. The activity of the Fe-doped TiO2 for the degradation of phenol was investigated by varying the iron content during UV (365nm) and visible light (405nm and 436nm) irradiation. The degradation rate depended on the Fe content and the Fe-doped TiO2 was responsive to the visible light as well as the elevated activity toward UV light. The molar ratio of 0.005 was the optimum for both the UV and visible light irradiations. The result was discussed on the basis of the balance of the excited electron-hole trap by the doped Fe(3+) and their charge recombination on the doped Fe(3+) level. The Fe-doped TiO2 (x=0.005) was more active than P25 TiO2 under solar light irradiation. The suspended Fe-doped TiO2 spontaneously precipitated once the stirring of the reaction mixture was terminated.