改性超疏水聚丙烯中空纤维膜及其在膜蒸馏中的应用

发布时间：2018-08-13 09:50

【摘要】：本文用聚丙烯中空纤维膜为基材,在其表面涂覆一层多孔的超疏水涂层,将聚丙烯中空纤维膜改性为超疏水中空纤维膜。本文旨在寻找一种成本低廉,操作简单可行的方法来制备超疏水聚丙烯中空纤维膜。利用APS/TEOS的不同比例,制备出不同尺寸的二氧化硅颗粒。并通过透射电子显微镜(TEM)观察其粒径大小。然后将聚丙烯颗粒加入到二甲苯溶液中溶解后,加入二氧化硅颗粒用溶胶-凝胶法制得溶胶,加入非溶剂2-丁酮,在相分离的作用下,将溶胶涂覆与聚丙烯中空纤维膜的表面。利用聚丙烯溶液在表面形成的网状结构,将二氧化硅颗粒附着于膜的表面,以此来增加膜的表面粗糙度。最后用1H,1H,2H,2H-全氟辛基三乙氧基硅烷(POTS)修饰涂覆后的聚丙烯中空纤维膜,进过修饰后的聚丙烯中空纤维膜的表面自由能降低,然后得到接触角为158°的超疏水聚丙烯中空纤维膜。对改性后的聚丙烯中空纤维膜进行扫描电镜(SEM)和原子力显微镜的(AFM)测试观察,发现膜表面的涂层为多孔连续的涂层,并且相比较原膜,改性后的膜表面的粗糙度有了很大的提高。通过XPS和傅里叶红外光谱(FT-IR)的测试,发现POTS和二氧化硅成功的接枝在膜表面,有效的增加了粗糙度和降低了表面能。同时,讨论了二氧化硅颗粒的用量、聚丙烯颗粒用量、涂覆次数、MEK用量等方面对聚丙烯中空纤维膜的超疏水性能影响,从而确定在聚丙烯中空纤维膜超疏水改性的最佳条件。对改性后的超疏水聚丙烯中空纤维膜进行膜蒸馏的实验。利用压汞法测定改性后超疏水聚丙烯中空纤维膜的平均孔径和孔隙率。改性后膜的平均孔径有所下降,孔隙率较原膜相比,有所提高,说明超疏水涂层是多孔的。测定不同改性膜在3.5wt%NaCl溶液中的通量和截留率,得出改性后膜通量较原膜有所上升,同时截留率提高到99.9%。并且研究讨论了 NaCl溶液温度、NaCl溶液浓度、真空度等条件变化对改性超疏水聚丙烯中空纤维膜在膜蒸馏中的通量和截留率的变化。
[Abstract]:In this paper, polypropylene hollow fiber membrane was modified into super hydrophobic hollow fiber membrane by coating a porous superhydrophobic coating on its surface. The purpose of this paper is to find a cheap, simple and feasible method to prepare superhydrophobic polypropylene hollow fiber membrane. Silica particles of different sizes were prepared by using different proportion of APS/TEOS. The particle size was observed by transmission electron microscope (TEM). Then the polypropylene particles were dissolved in xylene solution and silica particles were prepared by sol-gel method. The sols were coated on the surface of polypropylene hollow fiber membrane under the action of phase separation by adding non-solvent 2-butanone. In order to increase the surface roughness of the film, silica particles are attached to the surface of the film by using the network structure formed on the surface of the polypropylene solution. Finally, the polypropylene hollow fiber membrane coated with 1H ~ 1H ~ (-1) H _ (2) H _ (2) H _ (2) H _ (2) H _ (2) H _ (2) fluorooctyl triethoxysilane (POTS) was modified. The surface free energy of the modified polypropylene hollow fiber membrane was decreased, and then the super hydrophobic polypropylene hollow fiber membrane with a contact angle of 158 掳was obtained. Scanning electron microscope (SEM) and atomic force microscopy (AFM) were used to test the modified polypropylene hollow fiber membrane. It was found that the coating on the membrane surface was porous and continuous, and compared with the original membrane. The surface roughness of the modified film has been greatly improved. The results of XPS and Fourier transform infrared spectroscopy (FT-IR) show that POTS and silica are grafted on the surface of the film effectively increasing the roughness and reducing the surface energy. At the same time, the effects of the amount of silica particles, the amount of polypropylene particles and the amount of MEK coating on the superhydrophobicity of polypropylene hollow fiber membrane were discussed, and the optimum conditions for superhydrophobic modification of polypropylene hollow fiber membrane were determined. The membrane distillation of modified superhydrophobic polypropylene hollow fiber membrane was carried out. The average pore size and porosity of modified superhydrophobic polypropylene hollow fiber membrane were measured by mercury injection method. The average pore size of the modified membrane was decreased, and the porosity was increased compared with that of the original membrane, indicating that the superhydrophobic coating is porous. The flux and retention rate of different modified membranes in 3.5wt%NaCl solution were measured. The results showed that the flux of the modified membrane was higher than that of the original membrane, and the retention rate was increased to 99.9%. The flux and retention of modified superhydrophobic polypropylene hollow fiber membrane in membrane distillation were studied.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ051.893

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