The enhancement of adsorption and photocatalytic activity of rare earth ions doped TiO2 for the degradation of Orange I

Rare earth ions (Sm3+, Nd3+, Pr3+) doped TiO2 (RE3+–TiO2) catalysts were prepared by the sol–gel method, and characterized by X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS). The adsorption abilities and photocatalytic activities of RE3+–TiO2 were evaluated by isothermal adsorption and Orange I degradation under UV light and visible light illumination. The adsorption results showed that RE3+–TiO2 had higher saturated adsorption amounts and higher adsorption equilibrium constants than pure TiO2. The adsorption equilibrium constants (Ka) and the saturated adsorption amount (Qmax) of RE3+–TiO2 would increase with the increase of dosage. In the meantime, the photocatalytic activity of RE3+–TiO2 for Orange I degradation under both UV and visible light irradiations were higher than that of TiO2. The optimal dosage was 1.5% for Orange I degradation under UV light and 1.0% under visible light. The higher photoactivity might be attributable to the transitions of 4f electrons of RE3+.