TiO₂ Co-doped With Metal Ions And Photocatalytic Nitrogen Removal From Water

The nanometer TiO₂ has been the focus of photocatalyst studies because of its non-poisonous feature high activity, security, stability(able to bear chemical corrosion, did not dissolve in the acid alkali conditions), low cost and other advantages.The application prospect is extremely good. At present, the nanometer TiO₂ is often used as a catalyst for the organic pollution. Recently the nanometer TiO₂ is also used as a catalyst for the inorganic pollution control. The inorganic nitrogen in the water contains ammonium nitrogen, nitrite nitrogen and nitrate nitrogen. Ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the water are the main environmental pollutants from industrial, domestic and agricultural waste waters, also from landfilling leachates, aminal farms. This research aimed at removal of inorganic nitrogen (the target pollutant) from water using photocatalysis and metal ion doped nano- TiO₂, that were prepared by a sol-gel method. It is realized via coupled ammonia oxidation and nitrite reduction, which is the main content of this study. The photocatalysts were characterized with XRD, TEM, UV-VIS, XPS, the influences of several key factors for nitrogen removal were investigated.(1) TiO₂ thin film photo-catalysts doped with Ce³⁺ La³⁺, (Ce³⁺+Ag⁺) were prepared. The results of XRD and TEM showed that the crystal structure of catalysts were of anatase type, and the average size of TiO₂ particles was about 10nm. The oxidation and reduction capability of the thin film have been studied comprehensively from some important factors of the photo-catalytic nitrogen removal in the reaction, such as different kinds and concentration of doped metal ions, dipping times(thickness of catalyst films), addition of Fe²⁺to the solution, different substrate (glass or stainless steel mesh), different designs of reactor and different light sources (UV or solar light) on photo-catalytic N removal efficiency. After 2 hours UV irradiation, simultaneous removal of ammonium and nitrite could be achieved. The removal efficiency for TN was about 30% when TiO₂ film was used.(2) TiO₂ photo-catalysts co-doped with Ce³⁺ and Ag⁺ were prepared. The results of XRD and TEM showed that the crystal structure of catalysts were of anatase type, and the average size of TiO₂ particles was 10nm. XPS spectra indicated the effect of doped ions on the binding energy of Titanium. The oxidation and reduction capability of the thin film have been studied...