Photocatalytic degradation reactions of aquatic nitrogenous organic compounds using pure and modified titania

Photocatalytic degradation (PCD) of NH₃, alkylamines, and alkylammoniums was systematically studied in aerated and deaerated aqueous suspensions of pure or modified titania. While the slow photocatalytic oxidation of NH₃ to nitrite/nitrate was the only pathway for decomposition of NH₃ on naked TiO₂, a new pathway, that of selective oxidation of NH₃ to dinitrogen, opened up on Pt/TiO₂. The PCD of tetramethylammoniums on TiO₂ showed successive demethylation processes to generate tri-, di-, and mono-methylammonium as an intermediate and ammonium and nitrate as a final product in the presence of dissolved oxygen, but it did not take place without oxygen. However, the absence of dissolved oxygen increased the PCD rates of alkylamines on Pt/TiO₂, and generated products that were different from those formed on pure TiO₂. Alkylamine degradation using surface-fluorinated TiO₂ or silica-modified TiO₂ photocatalyst was discussed. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).