Enhanced photoactivity of N-doped TiO2 for Cr(VI) removal: Influencing factors and mechanism

To further enhance the photoactivity of virgin TiO2, we prepared N-doped TiO2 (N-TiO2) by sol-gel method and used it to remove Cr(VI) ions from water under visible light. The catalysts were characterized by TEM, XRD, BET and UV-vis techniques. Better crystalline structure, larger specific surface area and decreased band-gap width were obtained after the insertion of N atoms into TiO2 lattice. Several influencing factors were also investigated. The removal efficiency of Cr(VI) increases with the decrease of initial Cr(VI) concentration or the increase of catalyst dosage. Addition of glucose or some inorganic ions (Mg2+, Al3+) can promote the photoreduction process by improving the quantum efficiency. The kinetics and mechanism were discussed as well.