Preparation And Application Of Titanium Dioxide Photocatalyst By Sol-gel Method

TiO₂ is the most important semiconductor in common use in the domain of photocatalysis,which can be used to degrade the polluted gas and organic compound in the waste water,because TiO₂ produces photoexcited electrons(e^-) and holes(h⁺) which have the ability of strong oxidation.Thus TiO₂ is hopeful to be widely used in the domain of environmental protection.In this work,the TiO₂ photocatalyst is prepared by the sol-gel method.Stable sol is prepared with the monomer Ti(OBu)₄.After the cross linking reaction,polymer of TiO₂ gel is synthesized. Nanometer TiO₂ powder,TiO₂ thin film coated with ground glass(TG) and TiO₂ grain coated with actived carbon(TA) are prepared and photocatalytic equipments are designed and fabricated whose photocatalytic activity is studied.Effect of components of sol on the gelation time is studied.Stable sol whichi is acidic or alkaline is coated on the glass slides and photocatalytic activity of TiO₂ thin films made from acidic sol is better.Effect of iron impurity in TiO₂ thin films on photocatalytic activity is studied and 0.1%Fe-doped TiO₂ has the best photocatalytic activity.Two kinds of TiO₂ powder is prepared by supercritical drying and vacuum drying.The TiO₂ powder obtained in the anterior way has shorter diameter of 15～30nm,larger specific surface area and slighter agglomeration,higher temperature of crystal phase transformation than that obtainted in the latter way.TiO₂ powder made from areogel after heating treatment at 700℃has the best photocatalytic activity.TG is prepared by the dip-coated method.The number of coated layers is 5 and the heating treatment temperature is 500℃.The photocatalytic equipment is fabricated with ten pieces of ground glass of dimensions of 20cm×20cm whose gradient is 5°.When the velocity of flow of MO solution is 8～10ml per minute,the degradation rate is 55%.Glass fiber cloth with different thickness coated with TiO₂ increases the photocatalytic activity of TG.Glass fiber cloth with the thickness of 0.2mm plays the most important role.TA is prepared by the dipped way which is heat treated in the air and N₂ in different temperature ranges.TiO₂ grains with the diameter of 20～50nm are distributed on the surface of activated carbon.The photocatalytic equipment of TA depurates the MO solution in 60 hours and the degradation rate is about 90%.Effect of the concentration of TA on the efficiency of photocatalyst is studied.The kinetics of the photodegradation of MO is studied and effect of the concentrations of MO on the reaction rate constant is analysed.The photocatalytic equipment of two tubes in series is fabricated and the photodegradation of MO is studied.The photocatalytic equipment of numbers of tubes in series is designed preliminarily in order to depurate more waste water in shorter time.