Preparation Diatomite Loaded TiO₂ Photocatalyst And Degradation Of Methyl Orange

Photocatalytic oxidation technology is a new wastewater treatment technology who has a high processing efficiency, simple processing equipment, operating conditions, easy control and no selective degradation of organic pollutants, but also has some disadvantages. Take sewage treatment for example, TiO₂ has weak adsorption capability for organic compound by itself. If we introduce adsorptive carriers to load TiO₂. Photocatalytic efficiency will increase obviously. It is adsorptive carriers’ s maximum advantage that they can adsorb organic compound around semiconductor particle, improve local concentration and avoid middle materials volatile or escape. Such behavior can accelerate reaction.Using traditional sol- gel method, titanium source with tetrabutyl titanate, organic solvent with ethanol, with glacial acetic acid inhibitor, using diatomaceous earth carrier prepared having a nanocrystalline grain and high catalytic activity the supported catalyst TiO₂/diatomite, and decolorization rate of methyl orange dye adsorption and photocatalytic decolorization rate as the evaluation of the catalytic activity, and a sol- gel process optimization, crystallization level, load and conditions aspects of a more systematic research to prepare a dye having set adsorption-degradation in one of the complex catalyst. We can draw the following conclusions:（1） determining the preferred preparation conditions of TiO₂: V[Ti（OC4H9）4]:V[H2O]:V[HAC ]:V[C2H5OH]=10:4:4:40, and calcined at 500℃ for 2 hours. The intensity of hydrolysis reaction is affected by amount of the water, glacial acetic acid acts as an inhibitor, and TiO₂ particle size would increase with the rise of calcination temperature, and TiO₂ would transform from amorphous form to anatase phase at 500℃. Under this condition, obtained TiO₂ photocatalyst had uniform particle size, and particle size is about 20 nm, methyl orange dye decolorization rate could reach at 86.1%.（2） Preparation of TiO₂/diatomite composite catalyst was: TiO₂ fixed amount during the preparation of the precursor, that is V[Ti（OC4H9）4]:V[H2O]:V[HAC ]:V[C2H5OH]=10:4:4:40, changed the dosage of diatomite, we could obtain different TiO₂ composite catalyst loading by calcining 2 hours at 500℃, and the adsorption and catalytic activity was best when TiO₂ theoretical loading was 40%.（3） With the loading of TiO₂ increased, the pore structure of diatomite would change from clear to disappear; and the infrared absorption peak of celite, bound water and organic impurities decreased successively; we could see from the composite catalyst X-ray powder diffraction pattern that characteristic peaks of the SiO2 weakened gradually, instead of TiO₂ anatase phase spectrum peak appeared and gradually enhanced.（4） Explored different loadings of TiO₂/diatomite composite effect of catalyst, divided into two phases: phase adsorption and photocatalytic stage. With the increasing of TiO₂ loadings, adsorption first increased then decreased; Although photocatalytic decolorization rate has been increased but the amplitude is leveling off. Combination of two stage adsorption and degradation effect, theoretical loading of TiO₂ was 40%, that is when the actual loading was 37.64% the catalytic effect is best, and the decolorization ratio of methyl orange dye could reach 93.1%.（5） Comparative tests we could konw that UV had a certain degradation to methyl orange solution. In the absence of UV irradiation, catalyst occurred adsorption only. Joining the homemade TiO₂, the photocatalytic effect is better than not to join. TiO₂/diatomite composite catalyst decolorization was best, setting adsorption and degradation in one.