Photocatalytic Reduction of Nitrate by Ag/TiO2 Catalyst

Ag/TiO2 catalysts were prepared by a simple chemical reduction method and characterized by TEM, XRD, XRF and UV-Vis and further tested for photo-catalytic nitrate reduction under germicidal UV (254 nm) and visible light irradiation. The effects of Ag content, hole scavengers (such as formic acid, acetic acid, ethanol and oxalic acid, sodium oxalate), concentration of formic acid on N removal were investigated. Best catalytic activity for photocatalytic reduction of nitrate (100 mgN·L-1) with the presence of formic acid was obtained when the content of Ag was 1.0wt%, the concentration of formic acid was 0.030 mol·L-1. Best nitrate conversion after 2 h UV irradiation, reached 98.43% and N2-N selectivity was 79.24%, no nitrite was detected, and 20.76% converted nitrate existed in NH4-N form. A higher selectivity for N2 (92%) was obtained by using visible light illumination (300 W), although the nitrate conversion was only 37.9%.