Synthesis Of The Series Of Nanosize TiO₂ Powder And Study On Its Catalytic Property

Photocatalytic oxidation technology of semiconductors is one kind of decomposition treatment techniques of organic pollutant. Because of its mineralization ability and possible application to pollution control, this environmental friendly technique have received special attention. In this thesis, the basic research achievement and advancement about the photocatalytic oxidation technique of semiconductor was reviewed including its mechanism and immobilization and modification of catalyst. Nanosize TiO₂ has many advantages as an high efficient photocatalyst. To aim at improving its activity and solving the pomblems restraining its practical application such as difficulty in recovering for circulation use, the series of TiO₂ nanopowder, including mobile and immobile, were synthesized by sol-gel method and modified by lanthanon and transition metal doping. we have studied on its photocatalytic property and biocatalytic activitity and applied immobile TiO₂ nanopowder to the photocatalytic oxidation treatment of cigarette factory wastewater.Nanosize TiO₂ was synthesized by Sol-Gel and characterized. The effect of preparing conditions such as calcination temperature and the ratio of acid and water on the physical characterization and photocatalytic activity were investigated. Moreover, Using ultraviolet lamp as experiment light source, this paper applied nanosize TiO₂ to the photodegradation of methyl orange, acid fuchsine and methyl lene blue. The effect of some factors such as initial pH value and photocatalyst dosage on photocatalyst property were also discussed. and the photodegradation dynamic equation of three kinds of dye have been established under the best degradation condition. On the basis of these research, TiO₂ nanopowder have been modified by Zn2+and La3+ doping. The influence of Zn2+and La3+ doping on the structure, UV-Vis absorption spectra and photocatalytic activity of nanosize TiO₂ were investigated in detial. The results of experiment of photocatalytic degradation of methyl orange demonstrated that after Zn2+and La3+ doping catalysts'photocatalytic property are related with the doping quantity. Appropriate doping could improv TiO₂ nanopowder's photocatalytic activity obviously because Zn2+and La3+ doping restrained the growth of grain, caused distortion and expansion of crystal lattice and enhanced TiO₂ nanopowder's absorption to ultraviolet.The effect of nano-TiO₂ on pea germination and growth was investigated under the different experiment conditions. The results indicated that the effect of TiO₂ nanoparticle is related with its size and dosage. Under the certain concentration, nano-TiO₂ could hasten the germination and growth of pea, While nano-TiO₂ has obvious restraint influence under higher dosage of nano-TiO₂.In order to resolve the problem of difficulty of separation and circulation use of the suspended catalyst , the immobilization of nano-TiO₂ have been studied. We selectived bleaching clay , active carbon and artificial zeolite as carrier and immobilized nano-TiO₂ on carriers by sol method.Titanium dioxide pillared bleaching clay composite material was characterized by using XRD, BET, SEM,TG-DTA techniques. Results of structural characteristic analysis indicated that the TiO₂ particles have inserted into the interlayer of bleaching clay. and since these particles enlarged the interlayer distance of bleaching clay, composite catalyst have larger surface area. The optimal conditions for the preparation were obtained by adjusting the ratio of TiO₂ in composite catalyst and the calcination temperature. Experimental results show that composite catalyst have higher photocatalytic activity than nano-TiO₂, TiO₂/AC and TiO₂/zeolite composite catalysts because of its high specific surface area,high acidity and cooperation of nano-TiO₂ with carrier bleaching clay. Under the optimal photocatalytic degradation experimental condition, the decoloration ratio of methyl orange solution is above 90 % and COD removal of cigarette factory wastewater is 75.1%. In addition, composite catalysts can be easily recovered for its good sedimentation ability and exhibited high stability for circulation use in treatment of wastewater. To improve titanium dioxide pillared bleaching clay composite material's photocatalytic activity, lanthanon (Sm3+,Tm3+,Ho3+,Nd3+)doping titanium dioxide pillared bleaching clay were synthesized and characterized by X-ray diffraction(XRD), BET, UV-Vis, TG-DTA techniques. The photocatalytic activity of titanium dioxide pillared bleaching clay increased markedly after lanthanon doping ,especially after Thulium doping. Under the optimal doping quantity(0.1%) and photocatalytic degradation experimental conditions, Thulium doping titanium dioxide pillared bleaching clay composite material has good performance in treatment of cigarette factory wastewater-- COD removal of wastewater is 79.6%. All in all, after pilot study titanium dioxide pillared bleaching clay composite material has revealed the application value in photocatalytic oxidation treatment of actual industry wastewater and our studies provided important information for the practical application of photocatalytic oxidation technique.