Preparation、Modification And Photocatalytic Performance Of Nanometer TiO₂ Based On Microemulsion Method

Semiconductor photocatalytic technology is an emerging approach for wastewater treatmen in recent years.The basic principle is to use semiconductor photocatalytic materials,combined with certain energy of light,electron-hole pairs were inspired,and the water and pollutant molecules adsorbed on the surface of semiconductor accept the electronic-hole pair,causing a serious of oxidation-reduction reaction,degrading the toxic and colored pollutants into non-toxic or low toxicity products.Among various catalysts,TiO2 photocatalyst is the most active studied due to its lowcost,non-toxic,highchemical stability,high photocatalytic activity.In this paper,we prepared nanometer TiO2 precursors based on microemulsion method and obtained the nanometer TiO2 samples by calcination and hydrothermal method and then characterize by XRD、SEM、TEM、FTIR、UV-vis and so on.The main research content and results are as follows:(1)Preparation of nanometer TiO2 precursors:In a typical procedure,n-hexanol,CTAB and deionized water at a weight ratio of 8:4:1 were mixed under magnetic stirring,obtaining transparent microemulsion solution.Titanium solution was prepared by adding TBOT into n-hexanol,which the amount of TBOT was decided by deionized water(the molar ratio of water to TBOT is 15:1).Then,titanium solution was added drop wise into microemulsion solution under magnetic stirring and the mixed solution turned gradually from transparent to milk white.The final nanometer TiO2 precursors were obtained by centrifugation,washing,drying and grinding processes.(2)High-temperature calcination of nanometer TiO2 precursors:The nanometer TiO2 precursors were calcined at 450℃,500℃,550℃,600℃,650℃,and 700 ℃ in air for 3 h and obtained nanometer TiO2 samples by grinding processes.The experimental results show that when the calcination temperature was 450℃,the size of nanometer TiO2 sample was minimum and its photocatalytic activity was best which the degradation of RhB solution was 98.9%within 60 min ultraviolet light irradiation.(3)Low-temperature hydrothermal of nanometer TiO2 precursors:The nanometer TiO2 precursors were scatter in water,and then transferred into a 50 ml Teflon-lined stainless-steel autoclave.In this part,we study the effect of different hydrothermal times(12h、18h、24h、30h)and hydrothermal temperature(120℃,180℃,200℃)on the property of TiO2.The experimental results show that when the hydrothermal temperature was 160℃ and hydrothermal time was 12h,the photocatalytic activity of nanometer Ti02 sample was best which the degradation of RhB solution was 99.9%within 40 min ultraviolet light irradiation.(4)Modification of nanometer TiO2:We use the advantage of surfactants in nudear suface water,surfactants was used as the surfactant and modifier at the same time.Not only the nanometer TiO2 particle size was co ntro led by surfactant modification,but also can control the dynamic process on interface transmission of light raw charge,so that the nanometer TiO2 can response to the light area.The preparation process of modified nanometer TiO2 was carried out as follows:In a typical procedure,n-hexanol,CTAB and nitric acid solution at a weight ratio of 8:4:1 were mixed under magnetic stirring,and then,titanium solution was added dropwise into microemulsion solution under magnetic stirring and the mixed solution was transferred into a 50 ml Teflon-lined stainless-steel autoclave.Last,the modified nanometer TiO2 was obtained by centrifugation washed and drying.In this part,we study the effect of different molar concentrations of nitric acid aqueous solution(1 mo 1/L.1.3mol/L、2mol/L、3mol/L)and hydrothermal temperature(120℃,180℃,200℃)on the property of TiO2.The experimental results show that the nitrate concentration and hydrothermal temperature have a different influence on the size and photocatalytic activity of modified nanometer TiO2.When the hydrothermal temperature at acertain temperature,with the nitrate concentration increase from lmol/L to 3mol/L,the particle size of TiO2 samples decrease gradually from 5nm to 3.4nm and its photocatalytic activity was increased fist,then decreased,the best concentration of nitric acid is 2mol/L.When the nitrate concentration is invariant,with the hydrothermal temperature increase from 80℃ to 200℃,the particle size of TiO2 samples increase gradually from 3.8nm to 6.2nm and its photocatalytic activity was increased fist,then decreased,the best hydrothermal temperature is 120℃.The photocatalytic experiment results showed that when then nitrate concentration is 2mol/L and hydrothermal temperature at 160℃,TiO2 sample have a best photocatalytic performance which when the visible illumination time is 60min,the degradation rate of RhB pollutants reached 99.7%.