The Research Of Photocatalytic Removal Of Nitrogen By Titanium Dioxide Supported On Zeolite

It has been widely studied to photocatalytically degrade and mineralize pollutants in wastewater using semiconductors at normal temperature and pressure. Photocatalysis has become one of the most effective methods to degrade various kinds of pollutants. Titanium dioxide, an important photocatalyst for its higher stability, activity and cheapness, did not dissolve in the acid and alkali conditions. There are two main disadvantages that seriously limit the application of titanium dioxide. First powder catalysts are difficult to reuse. Second, large scale application of titanium dioxide as photocatalyst is hampered by the fact that it absorbs only a very small part of solar light (ultraviolet only 3-4%) due to its wide band-gap of 3.2eV.To overcome these two disadvantages, this paper studied preparation of titanium dioxide photocatalyst supported on zeolites with tetrabutyl titanate as titanium source by a sol-gel method. The chemical bond interaction was achieved between titanium dioxide and zeolites. This facilitated an easy recovery and resue of the catalyst. Photocatalytically deposited Pt on TiO₂/ZSM-5surface and the Nitrogen-doped TiO₂ were prepared to increase the catalyst activity in visible light area, and the efficiency in solar light utilization. The activity of these catalysts in photocatalytic oxidation and removal of ammonia from water were investigated. The influence factors such as the amount of supported TiO₂, the calcinating temperature and the dosage of photocatalyst were further studied. The results showed that the best amount of TiO₂ was about 30.4wt.%, the best calcinating temperature 450℃(anatase.was formed), and the best dosage of photocatalyst was 1g/L. Pt photocatalytically loaded on the TiO₂/ZSM-5 surface prevented the recombination of photo-induced electrons and holes, besides widening the responding range to light in visible area, and enhanced the photocatalytic activity with an optimal value at 1.5wt.%. Pt(1.5wt.%) /TiO₂(30.4wt.%) /ZSM-5 had high photocatalytic activity. The best ammonia and TN removal (120min) under solar light with air sparging reached 56.9% and 37.4% respectivelyTypical mesoporous silica MCM-41 and nitrogen doped TiO₂/MCM-41 was prepared by a sol-gel method then charactered using XRD, IR and UV-VIS. Activity of TiO₂/MCM-41 was stable after five times reuse;nitrogen-doped TiO₂/MCM-41 had high photocatalytic activity under solar irridation. The best ammonia and TN removal (120min) under solar light with air sparging reached 49.78% and 36.04% respectively.