2 </ Sub> Preparation And Photocatalytic Properties Of Iron, Lanthanum-doped Nano Tio <sub>

In recent years,much attention has been paid for heterogeneous photocatalysis owing to its potential application in many areas,especially the treatment of environmental pollution.TiO₂ is paid the extensive attention at home and abroad,beause it is stable,cost effectiveandnon-corrosive.However,TiO₂ as photocatalyst has some disadvantage,the photocatalytic activity of TiO₂ is limited by fast charge-carrier recombination and its low quanta efficiency,the pure TiO₂ absorbs only the small ultraviolet part(3-5%) of solar light due to its wide band-gap of 3.2ev.The lower quanta efficiency and wide bandgap are the main factors to restrict the practicality and industrialization of photocatalytic oxidation.Therefore, reducing the recombination of electron-cavity pairs,any improvement of photocataly -tic efficiency and utilization of visible light will have a profound effect.In our study,we modify the TiO₂ by metal doping to improve the photocatalic ability and utilization of visible light.Fe³⁺,La³⁺ single doped TiO₂ and Fe-La co-doped TiO₂ were prepared by sol-gel method. Factors affecting TiO₂ crystal composition,particle size and photocata -lyitc activity such as the raw material ratio,calcination temperatures. The structure shape and spectrum characteristic were characterized by XRD, XPS,FSand UV-Vis. The photocatalytic activities were evaluated by degradation of methyl orange.At the same time,we investigated the effect of doping on photocatalytic activity of TiO₂ under ultraviolet and visible light.Furthermore,we analyed the reaction kinetic of organics photocatalytic degradation process.Nano-TiO₂ was prepared by sol-gel method with C16H36O4Ti as forerunner body, glacial acetic acid as inhibitor,the doped samples calcined at 500℃presented anatase structure,the patricle size of Fe³⁺,La³⁺ doped TiO₂ is smaller than pure TiO₂ and the average size of the Fe³⁺,La³⁺ co-doped TiO₂ is about 6.1nm. We consider that metal co-doped restrain the growth of crystal.Fe³⁺,La³⁺ co-doped changed the binding energy peaks of Ti and O,and Fe³⁺ doped into the TiO₂ lattice,and the existence of La ion is in the form of La2O3,this also description that the sol-gel method can be effective to doped some Fe³⁺,La³⁺ into TiO₂.UV-Vis results show that the absorption sideband of Fe³⁺,La³⁺ doped TiO₂ has red-shift and widen the spectrum absorption range.The little fluorescence intensity,the lower recombination of electron-cavity pairs,and the better catalyze effect of the catalyst.The results show that the photocatalytic of Fe³⁺,La³⁺ doped TiO₂ has been highly improved under ultraviolet or visible light,the optimal doping of La³⁺ is 0.6%,Fe³⁺ is 0.01%,and annealing temperature is 500℃.The co-doping of rare-earth and metal show a synergistic effect for photocatalyic activity of TiO₂.The co-doped TiO₂ show higher photocatalytic activity in degradation of methyl orange than that of single doped TiO₂.Titania co-doped with Fe-La for n(La):n(TiO₂)=0.6%, n(Fe):n(TiO₂) =0.01% have higher photocatalytic efficiency. Fitting cuve of methyl orange photocatalytic degradation show that the reaction kinetics of rare-earth doped TiO₂ is according with the first order reaction equation of Langmuir-hinshelwood.