Visible-light-induced photocatalytic oxidation of nitric oxide and sulfur dioxide: Discrete kinetics and mechanism

A new photocatalyst was prepared using doped titanium dioxide (TiO2) with active species for the removal of nitric oxide (NO) and sulfur dioxide (SO2) under visible light irradiation. Nitrogen (N-), zirconium (Zr-), and nickel (Ni-) tridoped TiO2 was found to possess higher photocatalytic activity than single Ni-doping, single Zr-doping, bimetallic doping or un-doping TiO2. X-ray diffraction patterns and ultraviolet visible spectra suggest that N-, Zr-, and Ni-tridoped TiO2 is a mixed-crystal structure that enhances absorption in the visible light region. Kinetic experiments on the removal of NO and SO2 by N-, Zr-, and Ni-tridoped TiO2 under visible light irradiation were carried out in a self-designed photocatalytic reactor respectively. The effects of various operation factors on the reaction rates were evaluated. The reaction rates were successfully expressed by Langmuir-Hinshelwood model. Based on ion chromatography analysis, a visible light induced photocatalytic removal mechanism has been proposed based on N-, Zr-, and Ni-tridoped mixed-crystal TiO2. (C) 2015 Elsevier Ltd. All rights reserved.