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

The photocatalytic oxidation of nitrogen oxides (NO(x)) over titanium dioxide (TiO(2)) sheets containing metal compounds (MCs) had been studied. Calcium oxide (CaO), magnesium oxide (MgO), calcium carbonate (CaCO(3)), aluminium oxide (Al(2)O(3)) and ferric oxide (Fe(2)O(3)) were used as MCs. Al(2)O(3) and Fe(2)O(3) added to the TiO(2) sheet did not affect the photooxidation of nitrogen oxides (NO(x)). The CaO sheet treated with TiO(2) sol had the greatest efficiency as a NO(x) remover under UV irradiation. It is believed that CaO has a high adsorptivity for nitrogen dioxide (NO(2)) and nitric acid (HNO(3)). The amount of NO(x) removed by a TiO(2) 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 NO(2) and HNO(3).

Removal of indoor pollutants under UV irradiation by a composite TiO2-zeolite sheet prepared using a papermaking technique.

Toluene and formaldehyde are malodorous and cause indoor pollution. These materials have received much attention as hazardous and malodorous substances. It is well known that long-term exposure to even fairly low levels of toluene and formaldehyde brings about the risk of asthma and eczema. In this study, a composite TiO2-zeolite (ZE) sheet prepared using a papermaking technique was applied to remove toluene and formaldehyde under UV irradiation. The optimum composition of the TiO2 (Ti)-ZE sheet was studied in detail with regard to the effective removal of various indoor pollutants. Gaseous toluene and formaldehyde were removed by a composite TiO2-ZE sheet with different efficiencies depending upon the ratio of Ti/ZE in the composite sheet. The composite sheets could decompose formaldehyde and toluene repeatedly after being recharged. It was shown that the sheets are potentially applicable as highly functional materials to be placed on walls and ceilings of houses for the removal of various indoor pollutants.