Characteristics on the determination of dissolved organic nitrogen compounds in natural waters using titanium dioxide and platinized titanium dioxide mediated photocatalytic degradation

The oxidation of dissolved organic nitrogens (DONs) in natural waters using the photocatalytic degradation with titanium dioxide (TiO2) and platinized titanium dioxide (Pt/TiO2) is applied to the conventional determination of DONs in natural waters. By the photocatalytic degradation with TiO2 and Pt/TiO2, DONs were effectively converted to inorganic nitrogens such as ammonium, nitrate and nitrite within a shorter reaction time compared with the simple photooxidation method without catalyst. The photocatalytic activity of Pt/TiO2 was superior to that observed with simple TiO2. The ammonium generated from DONs was oxidized to nitrite and nitrate under the aerobic condition with catalyst. The results of initial formation rates of inorganic nitrogens suggested that the nitrate and nitrite were directly generated from DONs, in addition to the formation route of nitrate and nitrite via ammonium. DONs in natural waters were effectively decomposed to inorganic nitrogens, and the concentration of DON in natural waters determined by the photocatalytic degradation method was good agreement with that determined by the wet oxidation method using persulfate as an oxidizing agent. The blank values observed in the photocatalytic degradation method were negligibly small in comparison with the wet oxidation method. The oxidation procedure using the TiO2 and Pt/TiO2 was powerful method for the determination of DON in natural water.