Simultaneous photocatalytic removal of ammonium and nitrite in water using Ce³⁺-Ag⁺modified TiO₂

Simultaneous photocatalytic removal of both ammonium and nitrite from water via coupled oxidation and reduction for N2formation was studied, using TiO2loaded with different ratios of Ce3+and Ag+. The catalysts were prepared using a sol-gel method with PEG or P123 as soft template. The catalysts with the highest activity (cerium and silver loading both at 0.1%) in N removal were characterized by TEM, XRD and UV-vis spectra. The crystalline TiO2was mainly anatase type, its size averaged at 8.8-9.6 nm. Contents of Ce and Ag and ratios of ammonium to nitrite (NH4-N/NO2--N) in the reaction solution affected either the catalyst activity or the nitrogen removal efficiency. The best removal rates were 69.9% NH4+-N, simultaneously 59.9% NO2--N, and 64.9% TN (total nitrogen) in annular reactor, after 2 h UV (254 nm, 20 W) irradiation when ratio of NH4-N/NO2--N was 1. Using solar light, the same solution after 2 h reaction using the same Ce and Ag co-modified TiO2, removal of NH4-N, NO2-N and TN was 44.8%, 45.3% and 45.1% respectively using a tubular reactor.