不同粒径分布的纳米二氧化钛在醋酸纤维素超滤膜中的分散性能研究

在醋酸纤维素(CA)基料中添加不同浓度经表面改性的不同粒径的纳米二氧化钛(TiO_2)粒子,其中包括平均粒径10、40nm以及这两种粒子的质量比2∶1的级配混合粒子,利用相分离法制备了无机-有机纳米复合CA超滤膜,通过测定膜的孔隙率、孔径分布、渗透性能以及膜表面的电镜扫描(SEM)表征进而研究不同粒径分布对纳米粒子在铸模液中分散性能.结果表明:在不引起纳米粒子团聚的前提下,在CA中添加的纳米粒子粒径越小,复合膜的性能越好;而级配粒子的添加量高于单一粒径粒子的添加量.当膜的渗透性能达到最佳值时,上述3种不同粒径分布的粒子添加量分别为4%、3%、5%(质量分数),而成膜后孔隙率均可达到70%以上,纯水的透水量可分别达到527、443、591L/(m~2·h).这说明颗粒级配分布促进了纳米粒子在铸模液中的分散性能.由于两种粒子混合均匀后存在粒径带双峰分布颗粒级配,在剪切条件下,纳米粒子不易因粒子表面作用引起团结,而团聚在一起的级配颗粒却容易受剪切剥离分散,从而起到促进纳米粒子在聚合物溶液中的分散作用.

Study on the dispersibility of different size of titanium dioxide (TiO_2) nanoparticle in cellulose acetate(CA) ultrafiltration(UF) membranes

The organic-inorganic composite UF membrane that used CA as base material was successfully prepared by phase-inversion method,in which different concentration of TiO_2 nanoparticle with different particle size distribution were added including mean particle size distribution of 10,40nm and grain composition ,which was blended by the first two types of particle with weight proportion of 2:1.The influence of different partisize distribution on dispersibility of TiO_2 nanoparticle had been characterized via measurement of the porosity,pore size distribution,SEM observation,and permeability of the nanoparticle-CA composite membrane.The results showed that the dispersibility of the grain composition particles was better than that of particles with single particle-size distribution in CA casting solution,and the TiO_2 nanoparticle addition amount of former was larger than that of latter without nanoparticle aggregation.When the permeability of membrane was up to the optimum value,the addition amounts of three types of particle-size distribution particle were 4,3 and 5wt% respectively;the porosity of them all were up to more than 70%;the flux of permeation of water respectively reach to 443,527,591L/(m~2·h).The reason why membrane performance with addition of TiO_2 nanoparticle of grain composition distribution was the best was that grain composition distribution enhanced the dispersibility of TiO_2 nanoparticle in casting solution.On the function of fluid shear,the aggregation nanoparticles were easy to disperse in casting solution due to the shear stress,thus,the dispersibility of TiO_2 nanoparticle in casting solution was enhanced.