Study On The Preparation Modification And Photocatalytic Property Of N-doped TiO₂

Pure titania, N-doped TiO₂, co-doped with transition metal Fe3+ and rare earth metal La3+ were prepared by sol-gel method. The catalysts obtained were characterized by XRD, DRS and FTIR. And activated carbon fibers (ACFs) as the support for N-doped TiO₂ loading, N-doped TiO₂ loaded ACFs (TN/ACF)samples were prepared, also. The dye molecules were chosen as the model to evaluate the photocatalytic activity of all samples.The N single-doping could restrain the increase of grain size and refine grains. Besides, the results showed that adding N could led to distortion and promote the crystal transformation form anatase to rutile. It could also broad light absorption range of TiO₂, which could improve the ability of reduction-oxidation. It was found that the samples calcined at 400℃and doped with 30% N(in mole) possessed the highest photocatalytic activity among of all the prepared samples under UV-light irradition, and calind at 600℃, doped with 5% N(in mole) under Visible-light irriadiation.The optimal doping amount (in molar ratio) for Fe and La was Fe:N:TiO₂ =0.1%:30%:1 and La:N:TiO₂ =0.1%:30%:1 respectively. The optimal temperature of heat treatment for Fe-N co-doped TiO₂ and La-N co-doped TiO₂ was 400℃and 600℃respectively. The photocatalysis properties of co-doped TiO₂ prepared under this condition can be enhanced largely than N-doped TiO₂ and pure TiO₂ . The result of XRD showed that doping of Fe and doping of La both restrained the growth of the grains, promoted forming of nanoparticles and prevented the crystalline transformation of TiO₂ from anatase to rutile. The result of DRS showed that doping of Fe and doping of La both changed the spectrum absorption in ultraviolet light region and visible light region.In immobilization system, N-doped TiO₂ film covered on the surface of ACFs. N-doped TiO₂ composite oxide film located groove in ACFs easy to crase and the crack was the combination weakness of support system. Organic pollutants in water could be degraded fleetly because of the dual function of adsorption and photocatalysis. Pore structure of immobilized samples influenced the photocatalytic activity. When molecular size of pollutants matched with the pore size of immobilized samples, pollutants could be absorbed into pores of immobilized samples; when molecular size of pollutants was larger than the pore size of immobilized samples, pollutants couldn't be caught effectively by immobilization system because of pore screening. So the photocatalytic activity of immobilization system was influenced.