Photocatalytic Reductions of Nitric Oxide in gas Phase and Nitrate ion in Water with Reducing Agents on Hollandite Catalyst

Abstract

AbstractPhotoctalysis of a unique hollandite compound was investigated for the reductions of nitric oxide (NO) in gas phase and nitrate ion (NO3) in water with reducing agents under UV irradiation. Both NO and NO3 are hazardous chemicals to human. Recently, it was reported that titanium oxide (TiO2) photocatalyst perfomaed the oxidative decomposition of NO to NO3. However, an ideal photocatalytic removal of NO would be the reductive decomposition of NO to N2 and O2 without by-products. In this study, the surface activity of the unloaded hollandite, prepared by sol-gel method, was applied to the photocatalytic reaction. The present photocatalysis was quantitatively examined by using on-line mass spectrometry and ion chromatography, and the adsorption species on the hollandite surface was analyzed by in-situ IR spectroscopy. UV-ixradiated hollandite extu'bited high selectivity for the formation of N2 in the reductive decomposition of NO. Moreover, this catalyst also showed the reductive decomposition of NO3 to NO2 and N2 in water. In particular, the photocatalytic decomposition of NO3 would be a new pathway that has not been reported for popular photo-catalysts such as unloaded TiO2. Probably, this type compound is expected to have potentialities as a new type photocatalyst.