Photocatalytic reduction of nitrate over Ag–TiO2 in the presence of oxalic acid

This study investigates the UV assisted reduction of nitrate using Ag–TiO2 composite photocatalyst in the presence of oxalic acid as hole scavenger. Ag–TiO2 composite was prepared by photodeposition method and its physico-chemical properties were determined by HRTEM with EDAX, XRD, XPS, BET Surface area and FTIR studies. Nitrite and ammonium should not be formed as by-products during the reduction of nitrate as both are more toxic than nitrate. Hence, experimental conditions like UV irradiation time, nitrate concentration, oxalate concentration and dose of photocatalyst were optimized to convert nitrate completely into nitrogen have been scrutinized. Effective nitrate reduction with 100% nitrogen selectivity was attained within 1 h. Effect of common anions present in water like Cl−, SO42− and HCO3− on the photocatalytic reduction of nitrate was investigated. The kinetic data of oxalic acid oxidation obeyed the pseudo-first order equation. The applicability of this system for the reduction of nitrate from drinking water has been tested.