Study On The Microwave-assisted Preparation Of Modified TiO₂ And Its Photocatalytic Performance

In recent years, the photocatalysis ability of nano-TiO₂ has been larger developed in the degradation of organic pollutants, as its clean energy, facile react condition, high sustainability and little secondary pollution. However, due to the wide band gap of TiO₂（3.23eV）, the visible light energy can not be efficiently used to excited it. Except that, as the nanopowder is easy to agglomerate which makes the efficiency of photoelectron transfer is low in the reaction and hampers its practical application. In order to improve the responsiveness of TiO₂ to visible light and to wider its absorption bands and to lower its transition energy level. In this paper, Ce, Fe, Cu metal element were selected as doped source, and doped-TiO₂ nanopowder were prepared by microwave assisted hydrolysis of Ti（SO4）2. And then the photocatalytic activity of doped-TiO₂ nanopowder was tested by formaldehyde degradation test of. The main research contents and results are as follows:Firstly, According to characteristics of TiO₂ nanopowder prepared by the preparation method, solution pH（a）, microwave power（b） and calcination temperature（c） were chosen as affecting factories to its photocatalytic performance. Orthogonal experiment was designed, the degree of influence of the three factors were decided by ―range analysis‖ method, it is that solution pH > microwave power > calcination temperature, and the best preparation conditions are: A1B2C3. At the same time, on the basis of this conclusion, it is prepared that Ce, Fe, Cu doped with different amount of TiO₂ nanopowder. The photocatalytic performance tests show:the best doping amount of TiO₂ nanopowder is 1.5% Ce, 2.5% Fe and 2% Cu, the degree of the effects to photocatalytic performance of these three elements is: Ce > Fe > Cu. Analysis found that the doping ions have no significant effect on the structure of TiO₂ by X-ray diffraction（XRD） and UV-Vis diffuse reflectance（UV-Vis）, but it broadens the visible absorption range of TiO₂, and makes its absorption red edge shift to the visible light region. The element of Ce can effectively inhibit the grain growth, prevent the transformation from anatase to rutile.Secondly, Photocatalytic properties of nano-TiO₂ is easily to be reduced by agglomeration of the nanopowder which has high surface energy. For avoiding the influence of agglomeration, high-porosity doped TiO₂ micropowder was prepared by choosing microwave hydrothermal method which can change the spatial structure of nano-TiO₂. The samples are characterization analysised by means of scanning electron microscopy（SEM）, nitrogen adsorption（BET）,the results show that the micropowder has high porosity, its average pore size is 153.4nm and the specific surface area of the micropowder is 154.9m2/g. Therefore the high-porosity doped TiO₂ micropowder shows good visible light catalytic performance in low concentration of formaldehyde solution.In the end, the common decorative plaster was used as the substrate and the high-porosity doped TiO₂ micropowder was loaded on the gypsum board by using sintering method, then the research was acting for testing its light catalytic activity by degrading formaldehyde gas. The results show that the degradation effect was significant for formaldehyde gas, the valid degradation of gypsum board loading Ce-TiO₂ powder for formaldehyde gas is 3.67 times higher than blank sample in 48 hours. The formaldehyde gas degradation rate by using the photocatalysis of these modified micropowder is 18.93%.