PHOTOCATALYTIC OXIDATION OF AQUEOUS AMMONIA (AMMONIUM ION) TO NITRITE OR NITRATE AT TIO2 PARTICLES

The photocatalytic oxidation of ammonia (ammonium ion) in the presence of air or pure oxygen at titanium(IV) oxide powder surfaces and induced by UV light was investigated. Experimental conditions were varied and the effect of pH, sparging gas, as well as the concentration of both ammonia (ammonium ion) and photocatalyst were investigated. It has been established that the principal product of photocatalytic oxidation depends on pH, and is either nitrite or nitrate. A gas-diffusion flow injection analysis system with conductivity detection was used for on-line monitoring of ammonia concentration. In addition, ion-chromatography with UV detection was utilized for off-line monitoring of nitrite and nitrate concentrations. The use of a photocatalyst such as TiO2 may prove to be a viable method for conversion of ammonia (ammonium ion) to either nitrite or nitrate.