Photocatalytic oxidation of NOx using composite sheets containing TiO2 and a metal compound

The photocatalytic oxidation of nitrogen oxides (NOx) over titanium dioxide (TiO2) sheets containing metal compounds (MCs) had been studied. Calcium oxide (CaO), magnesium oxide (MgO), calcium carbonate (CaCO3), aluminium oxide (Al2O3) and ferric oxide (Fe2O3) were used as MCs. Al2O3 and Fe2O3 added to the TiO2 sheet did not affect the photooxidation of nitrogen oxides (NOx). The CaO sheet treated with TiO2 sol had the greatest efficiency as a NOx remover under UV irradiation. It is believed that CaO has a high adsorptivity for nitrogen dioxide (NO2) and nitric acid (HNO3). The amount of NOx removed by a TiO2 sheet including MC showed a tendency to increase with increasing pH of the MC suspension, i.e. there is a good correlation between the alkalinity of the MC and the retention of NO2 and HNO3.