Study On The Preparing Technics Of Supported TiO₂ Separation Membranes

TiO₂ asymmetric membranes were prepared by sol-gel technics in this study, some measuring and testing techniques such as TG-DTA,XRD, SEM,TEM had been used to analyze and characterize the composition and microstructure of the substrates,sol and membranes. The relationship among the performance,composition and structure had been studied.Al₂O₃ ceramic substrates had been prepared usingα-Al₂O₃,calcined Suzhou kaoline, MgO,TiO₂,and BaCO3 as raw materials and were formed by pressure. Discuss the affection on aperture, porosity and rupture strength by granularity of powder, molding pressure, the mount of pore-forming materials and sintering temperatures. Finally, we prepared the porous Al₂O₃ substrate whose average aperture was about 1.1μm, the porosity was about 41% and rupture strength was about 35Mpa by using 5.2μm powder and 6% (wt%) starch, formed under the pressure of 60kN and fired at 1350℃for 2h.TiO₂ sols were synthesized by fractional hydrolyze used titanium ethoxide as starting materials. Discuss the affection to sol stability and gelating time by factors such as titanium concentration, water quantity, pH value, mixing method, hydrolyzing temperature, aging time and addition of polyvinyl alcohol. Finally, TiO₂ sol was prepared by this method: mixing the H2O,HNO3 and fractional C2H5OH and dipping into the continuously stirred mixture of Ti(OC4H9)4, Acac and another part of C2H5OH. Soluble and light brown TiO₂ sol was prepared by controlling the titanium concentration, the ratio of water and Ti(OC4H9)4, pH value and addition of polyvinyl alcohol. The pH value of the sol prepared by this method is between 3 and 4 and the sols have the good stability.Gel film was coated on the substrate by dip-painting method, crackfree TiO₂ ceramic membranes were made by controlling some processing parameters, such as the addition of polyvinyl alcohol, the viscidity of sol, coating times, drying and heat treatment processes. The main crystalline phase of the membranes is anatase;The aperture range is approximately from 30nm to 150nm and average aperture is about 70～80nm.