Preparation Of Titanium Dioxide Transprent Nanodispersion By High Gravity Technology And Its Application Research

With the rapid development of nanotechnology,various nanomaterials are being explored as novel tools for a vast range of applications.Among them,TiO2 nanocrystals attract wide attentions owing to their unique optical properties,chemical stability,thermal stability,superhydrophilic and so on.So far,they have been extensively applied in many fields,including degradation of organic pollutants,semiconductor solar cells,self-cleaning,etc.However,the conventional nano-TiO2 powder is extremely easy to agglomerate itself,not completely achieving excellent nano-effects.In addition,the application properties of TiO2 significantly depend on the dispersibility,the size,and the morphology of particles.In view of this,we presented a novel synthetic approach to achieve controllable preparation of transparent dispersions of monodisperse anatase-TiO2 nanoparticles using high gravity technology combined with solvothermal or hydrothermal treatment was proposed in this thesis.Oil-soluble nano-TiO2(OSN-TiO2)and water-soluble nano-TiO2(WSN-TiO2)were prepared respectively,and can be stably dispersed in various commonly-used organic solvents and water to form transparent dispersions.The effects of various process parameters on the size,morphology and dispersity of nano-TiO2 particles were explored,then its application properties were also studied.The main contents were as follows:(1)The monodisperse OSN-TiO2 was prepared by alkoxide hydrolysis in an traditional stirring tank reactor(STR)combined with solvothermal treatment and surface modification.The obtained nanoparticles could be dispersed in various commonly used organic solvents to form transparent nanodispersions.The effects of solvothermal temperature and time,deionized water,pH,alcohol solvent,surface modification condition on the dispersibility,particle size and morphology of the nanoparticles were investigated.The optimal process parameters are as follows:solvothermal temperature of 150?;the solvothermal time of 20 h;VH2O:VCH3COOH:VTBOT=1.2:1:10.OSN-TiO2 could be stably dispersed in various polar or non-polar organic solvents such as chloroform,tetrahydrofuran and cyclohexane to form a series of transparent dispersions when the addition amounts of stearic acid were 12 wt.%.When KH570 was used as a modifier,the particles could be dispersed in methylene chloride and the dispersion was more stable.Monodisperse OSN-TiO2 nanoparticles with a decreased average size from 12 to 5 nm could be achieved by using the linear alcohol with the decreased carbon number from 2 to 8,while monodisperse TiO2 nanorods with an aspect ratio of 1-5 were prepared using alcohols with different locations of branched methyl group.(2)Based on the above research results,the monodisperse OSN-TiO2 nanorods was further prepared using high-gravity technology in the rotating packed bed(RPB).Compared with the traditional STR method,the OSN-TiO2 nanorods obtained by using high-gravity technology had higher crystallinity and narrower particle size distribution.Furthermore,the monodisperse WSN-TiO2 was prepared by alkoxide hydrolysis in the RPB combined with hydrothermal treatment and surface modification.The effects of materials composition,hydrothermal conditions,surface modification conditions,liquid flow rate and rotating speed of RPB on particles were studied.The optimum process conditions were obtained:VTBOT:VH2O:VHNO3:VC2H5OH=10:84:1:20,hydrothermal conditions of 110?and 10 h,KH792 addition amount of 30 wt.%,RPB rotation speed of 2500 rpm,and the liquid flow rate of at least 160 mL/min for A solution(vA:VB=1:3).The particle size of WSN-TiO2 prepared under optimal conditions is 5?10 nm,the specific surface area is 245 m2/g,and the Zeta potential of TiO2-H2O dispersion is 46.2 mV,which can be stably dispersed for more than 6 months.(3)The application performances of monodisperse TiO2 transparent nanodispersion in high refractive composite coating and photocatalysis degradation were studied.Firstly,the transparent TiO2-PS nanocomposite coating was prepared by solution blending,the mass fraction of OSN-TiO2 was 0?60 wt.%.The transmittace of obtained nanocomposite coating was more than 90%in a wavelength range of400 to 800 nm.And the refractive index of TiO2-PS increased with the increase of TiO2 content and could be adjusted from 1.59 to 1.79.In addition,the refractive index of the nanocomposite coating with the addition of fully crystalline anatase nano-TiO2 was obviously higher than that of partially crystallized products.The TiO2-H2O dispersion was further used for photocatalytic degradation of methyl blue.The effects of methyl blue concentration and mechanical stirring on catalytic degradation were explored.The results showed that the photodegradation efficiency of low concentration methyl blue over WSN-TiO2 reached 100%at 60 min,while over P25 reached 98%at 120 min.The photodegradation efficiency of high concentration methyl blue over WSN-TiO2 reached 100%at 105 min,while over P25 reached 69%at 120 min.Obviously,the degradation performance of WSN-TiO2 was much better than that of commercial P25.And WSN-TiO2 had more obvious advantage without stirring.The adsorption process of methyl blue on the surface of WSN-TiO2 was consistent with Langmuir isotherm adsorption model.