Uranyl-modified TiO2 for complete photocatalytic oxidation of volatile organic compounds under UV and visible light

Three commercially available TiO2 powder photocatalysts and additional one synthesized in laboratory via the modification of anatase TiO2 with uranyl nitrate (5 wt%) have been studied in the complete oxidation of several VOCs under UV (367 nm) and visible (450 nm) light. The kinetic curves for VOC removal, intermediate formation, and final product accumulation are presented in the paper and discussed in detail. The TiO2 modification with uranyl ions (UO22+) provides the ability for photocatalyst to absorb visible light with wavelength up to 500 nm. The photocatalytic activity of the uranyl-modified TiO2 under visible light was up to 56 times higher than the activity of one of the best visible light sensitive commercial photocatalysts, KRONOClean® 7000 from Kronos Worldwide Inc. The complete oxidation of all the tested pollutants occurred over UO22+/TiO2 both under UV and visible light. The formation of gaseous intermediates was observed for certain types of VOC, but the intermediates were further completely oxidized to carbon oxides and water under long-term irradiation. The kinetic regularities of PCO process under visible light were similar to the process under UV except somewhat prolonged kinetics due to lower photonic efficiency of light utilization in the visible spectral range.