The Study Of Photocatalytic Activity And Modify Of Nano Titanium Dioxide Powder

The titanium dioxide nanopowders were prepared with tetrabutyltitanate (TNB) as raw material by the sol-gel process.The samples were characterized by mean of TG-DTA, XRD, SEM, IR and FS techniques respectively. The effects of the ratio of reaction material, the pH value of reaction system, the stiring velocity, the total material volume, the hydrolyze temperature, the dried ways of the wet gel and the calcined temperature of the dry gel were discussed on the particle size, particle size distributing, the composing of crystal phase and the photocatalytic property by the experimental design. The most suitable praparation conditions should controlled as follows: hydrolyze temperature was about 20-30℃; the ratio of TNB and water and solvent was 1:4:15; the pH value of reaction system was 2; the stiring velocity was 300r/min; temperature would be increased slowly and length by length in the dry process; the calcined temperature was about 400℃.The product was anatase TiO₂ and its mean dimention was about 8nm.The transition metal ions such as Mn2+, Fe3+, Cu2+ and the rare earth element metal ions such as Y3+ and La3+ were selected with different ratio doping in TiO₂ to study the photocatalyst modifying in this paper for the sake of improving the quantum-sized efficience of photocatalitic reaction of nano-TiO₂. The samples were employed as catalysts for phenol photocatalytic oxidation degradation in aqueous suspension, used as probe reactions. The experiments showed that doping could improve the photocatalytic activity of nano-TiO₂ efficently and the improving of photocatalytic activity were quantitatively correlated with the factors such as metal ion radii, their electronic configuration, the oxide and reduce potential and the dopant concentration. Iron-doped nano-TiO₂ showed the best catalytic efficence when the moral ratio was 0.5% under the experimental conditions in this paper.Others,TiO₂/FeMnCuO4 composite photocatalyst was studied ,but obvious improving of photocatalytic activity was not be found in the experiments of degradation phenol.The phenol of photocatalytic degradation was affected by many factors. In this paper, react conditions included intensity of light, pH value of solution , concentration of calalyst , initio concentration of phenol solution and air quantity of aeration were modified to study the influence of degradation of phenol.The result indicated that efficience of degradation was best when pH value of solution was 9 and concentration of calalysts was 2.50g/L. The efficience was more high when the initio phenol solution concentration was increased on the condition that the concentration was below 70mg/L.The quantum-sized effect and modifying effect were studied by model chemistry method with ab initio and DFT theory to probe the relationship between the micro structure of TiO₂ and photocatalytic property. The calculation by selecting cluster model with different size showed that the quantum-sized effect was more prominent with the decrement of model size and the energy distance was bigger near Fermi energy level. The calculation of transition metal ions doped model indicated that energy levers of impurity were brought in by doping. It led to red shift of absorption light and the absorption frequency of spectrum of annatise TiO₂ was extended. It was also one reason that photocatalytical activity was capable of improving efficiently by doping of the transition metal ions.