Water treatment efficacy of various metal oxide semiconductors for photocatalytic ozonation under UV and visible light irradiation

We have investigated a photocatalytic ozonation system of seven metal oxide semiconductors, TiO2 (P25), Nb2O5, SnO2, WO3, Fe2O3, In2O3, and BiVO4, under visible light both with and without UV irradiation for their efficacy in removing total organic carbon (TOC) from aqueous oxalic acid solution for water treatment. The investigation revealed that all the metal oxide samples functioned as photocatalysts for the photocatalytic ozonation system. TiO2 exhibited the highest activity under UV irradiation, and also exhibited a little activity under visible light irradiation. WO3, Fe2O3, In2O3, and BiVO4 functioned as visible-light-responsive photocatalysts and Fe2O3, In2O3, and BiVO4 were newly identified as active photocatalysts under visible light irradiation for the photocatalytic ozonation system. It is suggested that WO3 is a promising material for the photocatalytic ozonation system due to its activity in the wavelength range of solar energy. (C) 2014 Elsevier B.V. All rights reserved.