Preparation Of Nano-TiO₂ Via Microemulsion And Its Photocatalytic Activity

Photocatalytic technology can be applied to air purification,wastewater treatment,and so on.Titania（TiO₂）is used as photocatalyst,due to its non-toxic,cheapness and high stability.In order to prepare TiO₂ photocatalyst with excellent properties,In this paper,nano-titania（nano-TiO₂）was prepared via microemulsion method and modified.The prepared nano-TiO₂ and modified composite photocatalysts were characterized by X-ray diffraction（XRD）,transmission electron mocroscopy（TEM）,Fourier transform infrared（FT-IR）,X-ray photoelectron spectroscopy（XPS）,Raman spectroscopy（Raman）,ultraviolet-visible diffuse reflectance spectroscopy（UV-Vis）and fluorescent spectra.The photocatalytic activity of nano-TiO₂ and composite photocatalysts were investigated by photodegradation of 40 mg?L^-1methylene orange solution under UV light.This paper mainly includes the following three aspects:Preparation of nano-TiO₂ photocatalyst via microemulsion method.Tetrabutyl orthotitanate was used as titanium source.Cyclohexane,trimethylstearylammonium chloride（OTAC）and n-butanol were used as oil phase,surfactant and cosurfactant in the microemulsion system,respectively.The molar ratio of water/OTAC was 20.The prepared nano-TiO₂ had a diameter of 6⁸ nm.Furthermore,the effects of calcination temperature and calcination time on the photocatalytic activity of TiO₂ were investigated.The TiO₂ calcined for two hours at 450℃has the highest photocatalytic activity.Preparation of TiO₂-graphene composite photocatalyst via solvothermal method.Graphene oxide（GO）was prepared from natural flake graphite via Hummers’method,and TiO₂-graphene（TiO₂-RGO）composite photocatalyst were synthesized via solvothermal method.In the process of solvothermal reaction,graphene oxide was reduced to graphene,due to rapid electronic transmission and excellent adsorption performance of graphene,and the prepared TiO₂-RGO composite photocatalyst exhibit higher photocatalytic activity than pure TiO₂.Furthermore,the effects of the amount of doping graphene and the solvothermal reaction time on the photocatalytic activity of TiO₂-RGO were investigated.The TiO₂-RGO composite photocatalyst present the highest photocatalytic activity with 5%doping graphene,reacting for five hours at 120℃.Preparation of TiO₂ photocatalyst with exposed{001}facets via microemulsion-solvothermal method.TiO₂ with exposed{001}facets was synthesized via microemulsion-solvothermal method,NH₄F was used as the morphology-controlling agent.By changing the molar ratio of F/Ti and the solvothermal reaction time,the optimum conditions for the preparation of TiO₂ with highly active{001}facets were investigated.The TiO₂ photocatalyst show the highest photocatalytic activity when the solvothermal reaction time is forty-two hours at 180℃and the molar ratio of F/Ti is 0.25.Under the conditions,the prepared TiO₂ had a diameter of ca.15.6nm,the percentage of exposed{001}facets was calculated to be ca.19.1%.