Photocatalytic Performance and Reaction Pathway of TiO₂ Composite Materials on Ammonia and Nitrogen Degradation in Water

The nano-TiO₂ composite photocatalysts,i.e.activated carbon supported TiO₂（TiO₂/AC）,Tween-80,Cu²⁺and Fe³⁺doped TiO₂,were separately prepared by sol-gel method,and the samples were characterized by X-ray powder diffraction（XRD） and ultraviolet-visible spectrometer（UV-VIS）.The photocatalytic performances of the modified TiO₂ materials were tested in ammonia and nitrogen solution under the irradiation of ultraviolet lamp,and the photocatalytic degradation pathways of the ammonia and nitrogen were also discussed.The results show that TiO₂ doped by Cu²⁺ or Fe³⁺ is mainly composed of anatase phase,with the average particle size of TiO₂ decreased.Obvious redshift of the absorption spectrum occurs for Cu²⁺ doped TiO₂,while it is unconspicuous for Fe³⁺ doped TiO₂.The order of photocatalytic degradation efficiency for ammonia and nitrogen by the materials（from high to low） is TiO₂/AC＞Fe³⁺/Tween-80/TiO₂ ＆ Cu²⁺/Tween-80/TiO₂＞Fe³⁺/TiO₂ ＆ Cu²⁺/TiO₂.Simultaneous doping of Cu²⁺ and Fe³⁺ can play a.synergistic effect on photocatalytic efficiency of TiO₂.The reaction pathways for photocatalytic oxidation of ammonia and nitrogen by the modified TiO₂ are basically similar to those of bio-oxidation process,with N₂ as the terminal product.