The Studies On Preparation And Properties Of Modified NaNO-TiO₂

Titanium dioxide, as a semiconductor material with wide band gap has goodphotocatalytic property. A variety of TiO₂nanostructured material is a novel functionalmaterial with size of around1-100nm, which has small crystalline size, high specificsurface area, high activity, good dispersion and so on. TiO₂shows superior chemicalstability, high refractive index, excellent photocatalytic performance and goodbiocompatibility due to its small size effect and quantum effect. As a result, it haspotential application in environment, materials, energy, medical and health fields. Inaddition, TiO₂with sterile, deodorant, antifouling and self-cleaning properties isable to oxidize micro-organisms, bacteria and so on into CO₂and H₂O, especially,modified TiO₂which appears excellent photocatalytic property under visible light.Modified TiO₂/Al₂O₃porous membrane, combining photocatalytic technology andmembrane separation technology, is utilized not only to intercept organic compounds,heavy metals in wastewater but also to remove the organic residues.Moreover, modified TiO₂/Al₂O₃porous membrane not only take advantage of lowoperation pressure of nanofiltration membrane, high selectivity of divalent andmulticharged ions, good compaction, strong anti-pollution capability, but also utilizehigh-temperature resistance of α-Al₂O₃ceramic membrane, good chemical stability,high mechanical strength and high separation efficiency. At the same time, it preventspowder TiO₂aggregation and easy inactivation.The results showed that inorganic ceramic microfiltration membrane supporter wasprepared by extrusion method in which α-Al₂O₃, carbon black and magnesium stearatewere used as aggregate, pore-forming agent and release agent, respectively. In addition,the effects of the amount of pore-forming agent, the amount of release agent, calcinationtemperature and holding time on porosity, flux of pure water and compressive strengthof supporter have been investigated by orthogonal tests. The results showed that theinfluence order was the amount of pore-forming agent, the amount of release agent,calcination temperature and holding time. Moreover, the optimum preparation condition was: the amount of pore-forming agent7%, the amount of release agent4%, calcinationtemperature1350oC and holding time120min.In this paper, modified nano-TiO₂sol has been prepared. The prepared process isas follow: Glacial acetic acid and tetrabutyl titanate were mixed to form solution A, atthe same time, nitric acid and ethanol were mixed to form solution B. Then solution Aand B were mixed quickly, and distilled water was added. At last, the sol was placed onthe electric furnace to boil for5min.Because SiO₂and Al₂O₃could form mutual peptization, silicon sol was chosen toplate film. Nano-TiO₂films with the average pore size of around2-7nm have beenprepared by dipping method and interfacial polymerization method, respectively, inwhich SiO₂/Al₂O₃composite ultrafiltration membrane was chosen as supporter, onwhich the modified TiO₂sol was coated. At last, modified TiO₂porous membrane wasused to filtrate wastewater including methyl orange and Escherichia coli. The resultsshowed that the retention rate of methyl orange reached80%, while the retention ofEscherichia coli was up to100%. Moreover, the membrane has strong anti-pollution.It is demonstrated that because of the simple synthesis method, low cost and highremoval efficiency, the composite porous membrane is a good environment-friendlymaterial.