The effect of Praseodymium on the adsorption and photocatalytic degradation of azo dye in aqueous Pr3+-TiO2 suspension

Praseodymium ion-doped TiO2 (Pr3+-TiO2) were prepared by the sol–gel method. The catalysts were characterized structurally by X-ray diffraction (XRD) and diffusive reflectance spectra (DRS) methods. The XRD results show that doped Pr ion could stabilize the anatase phase of TiO2 and also inhibit the increase of the crystallite size. The DRS results show that the optical absorption edge slightly shifted to red direction owing to praseodymium ion doping, and Pr3+ doped TiO2 (Pr3+-TiO2) catalysts had higher absorption peaks in the ultraviolet region. Pr3+-TiO2 had better adsorption capacities and photocatalytic abilities for dye removal than that of pure TiO2. The optimum proportion of doped Pr ion for degradation of azo dye was 1.5% under UV light and 1.0% under visible light, at which best for dye photocatalytic degradation. The red shift of the optical adsorption edge of TiO2 and visible light adsorption by Pr3+ doping were the key factors that enhanced the photocatalytic activity of the catalysts when irradiated with visible light.