[Photocatalytic reduction of nitrate using metal-doped titania].

Metal Fe or Cu doped P25 titania was prepared using the photodeposition method and characterized by TEM, ICP, XRD and UV-Vis, further tested for photocatalytic nitrate reduction and TN removal, under 20 W UV lamp irradiation. The influencing factors such as the pH values of solution, stirring gas, metal loadings, hole scavenger formic acid amount and co-doped Ag-Cu/TiO2 are investigated and discussed in detail. The experimental results after 2 h reaction indicated that with the increase of Cu loadings, nitrate conversion increases too, while a loading of 0.5% is optimal for highest N2 selectivity and TN (total nitrogen) removal. Using N2 as stirring gas and under acidic conditions, the N2 selectivity is lower (62%), but the highest conversion of nitrate and removal of TN can reach 36.9% and 23.2% respectively. Using CO2 as stirring gas, the highest selectivity for nitrogen 88.4% is obtained with 0.5% Cu/TiO2, 0.06 mol/L formic acid. Under the same conditions, using the prepared bimetallic titania (1%, 1:1 Ag/Cu), the conversion of nitrate and removal of TN are 48.1%, 34.2%, and N2 selectivity is 72.2%.