【作者】 黄征青；

【导师】 郭兴蓬；

【作者基本信息】 华中科技大学 ， 材料学， 2006， 博士

【摘要】 本文介绍了超滤的原理、超滤膜的分类与制备方法及影响超滤膜结构与性能的因素;综述了超滤的应用、存在的问题与发展趋势及有机/无机膜的研究进展。针对超滤膜中膜材分子取向不能根据膜微观结构需要进行人为控制的问题,首次选择磁性物质（Fe₃O₄）为无机填料,以聚丙烯腈为基材、二甲亚砜为溶剂、聚乙烯吡咯烷酮和聚乙二醇为致孔剂配制悬浮液,利用浸没沉淀相转化法在有磁场和无磁场作用下制备了PAN- Fe₃O₄超滤膜。采用DSC、DTG和DMA研究了膜的热稳定性,用浸泡法研究了膜的化学稳定性,用原子力显微镜（AFM）和电子显微镜（SEM,FESEM）观察了膜的微观结构,用错流超滤装置进行了纯水、牛血清蛋白水溶液、猪血溶液过滤实验评价了膜的分离性能。取得的主要成果与结论如下:膜材料的分子取向对超滤膜的微观结构有重要的影响。在正常的制膜条件下,用1500高斯正交磁场作用于膜的形成过程,可以控制膜材分子（Fe₃O₄）的取向,这为控制超滤膜的微观结构提供一种新的方法。对蛋白质溶液进行超滤时,超滤膜的相对渗透通量通常为20-30%。过滤猪血溶液的对比实验发现:在正交磁场作用下所制的PAN- Fe₃O₄超滤膜的渗透通量和相对渗透通量均高于相应无磁场作用下所制的PAN- Fe₃O₄超滤膜,而且,磁化膜的稳定相对渗透通量均在35%以上,个别能达到50%以上;磁化膜与非磁化对血液蛋白的截留率相近。同时,还阐明了该过程中膜的污染机理,该机理能很好地解释膜性能的变化规律。结果表明在PAN- Fe₃O₄超滤膜制备过程中使用外加磁场作用能有效提高膜的耐污染能力,这一结果为开发适用于血液处理的耐污染超滤膜提供了一种新途径;在PAN- Fe₃O₄超滤膜中,四氧化三铁与PAN在室温下没有形成化学键,也不存在官能团之间的相互作用;添加Fe₃O₄对膜的玻璃化温度没有影响,但能提高PAN环化脱氢反应的温度和分解温度;PAN- Fe₃O₄超滤膜的耐酸性强于耐碱性,在pH值为10以上的溶液中由于水解作用而溶解,使得膜失去使用价值,膜的耐酸性与酸的种类、浓度和氧化性有关。无外加磁场作用时所制得的PAN- Fe₃O₄超滤膜在结构与性能方面有以下规律:与不添加Fe₃O₄时相比,在铸膜液中添加1.1wt%的Fe₃O₄时,膜的平均孔径显著减小,表面粗糙度显著增大;随着Fe₃O₄添加量从1.1wt%增大到4.3wt%,膜的表面粗糙度逐渐减小,膜的平均孔径也基本呈现逐渐减小的趋势;随着Fe₃O₄添加量从0wt%增大到4.3wt%,膜的渗透通量和截留率呈现逐渐增大的趋势。Fe₃O₄微粒在PAN- Fe₃O₄超滤膜中的分布比较均匀,膜的矫顽力与Fe₃O₄添加量无关,均为114 Oe;膜的剩磁随着Fe₃O₄添加量增大而增大;膜样品进行饱和磁化所需的最小外加磁场强度为5400 Oe。在正交磁场作用下所制得的PAN- Fe₃O₄超滤膜在结构与性能方面有以下规律: Fe₃O₄的添加使膜的皮层厚度减小,并导致膜支撑层中的微孔由规则、整齐且垂直于膜平面的排列变为不规则、倾斜于膜平面的排列。膜的孔径、表面粗糙度随Fe₃O₄含量的增加先减小后增大;膜的纯水渗透通量、BSA溶液的渗透通量和相对抗污染性亦是随Fe₃O₄含量的增加先减小后增大。膜的截留率随Fe₃O₄含量的增加而逐渐减小,但变化范围在2%以内。与通常的结果不同,膜的渗透性能和抗污染性能与膜的表面粗糙度无关。更多还原

【Abstract】 This dissertation introduces the principle of ultrafiltration, the classification and the manufacturing methods of ultrafiltration membrane, and, the facts influencing the microstructures and performance of ultrafiltration membrane. The reviews are also given for the applications of ultrafitration, the main problems existing in the application, the development trend of ultrafiltration, and, the research advance in the organo-mineral membranes. The orientation of material molecular in the ultrafiltration membrane has not been controlled at will according to the need of membrane microstructure. In order to solve this problem, novel PAN- Fe₃O₄ ogano-mineral ultrafiltration membranes were prepared under no magnetic field or an orthogonal magnetic field by the wet phase inversion process from suspentions. These suspentions consist of polyacrylonitrile （PAN）, dimethyl sulfoxide （DMSO）, ferrosoferric oxide （Fe₃O₄）, polyvinylpyrrolidone （PVP） or polyethylene glycol （PEG）. The heat resistance and the solvent resistance of PAN-Fe₃O₄ ultrafiltration membrane were investigated by the analysis of TGA, DSC and DMA, and, the dissolving experiments, respectively. The microstructures of PAN- Fe₃O₄ ultrafiltration membrane were investigated by the Atomic Force Microscope （AFM） and the Scanning Electronic Microscope （SEM or FESEM）. The performance of membranes was also examined by the filtration tests of pure water, BSA （Bovine Serum Albumin） aqueous solution and pig blood aqueous solution in a cross-flow ultrafiltration equipment. The main achievements and results are as follows:The arrangement orientation of material mocular has an important effect on the microstructure and the performance of ultrafiltration membrane. When an orthogonal magnetic filed of 1500Gs was applied in the manufacturing process of membrane, the result indicates that the arrangement orientations of material Fe₃O₄ are consistent with the magnetic field. This result may give a new method to control the microstructure of ultrafiltration membrane.In the ultrafiltration of protein solution, the relative flux of membrane is generally 20-30%. The contrast tests of pig blood solution indicates that the flux and the relative flux of a PAN- Fe₃O₄ membrane prepared under an orthogonal field are higher than that of a corresponding PAN- Fe₃O₄ membrane prepared under no field. In addition, the stable relative fluxes of magnetized membranes are above 35%, even over 50% for individual membrane. The difference between magnetized membranes and non-magnetized membranes is very small for the rejections to pig blood proteins. At the same time, the fouling mechanism of membranes given in this thesis can give a reasonable explanation on the change of membrane performance. Our results show that the magnetization of membranes can effectively improve the anti-fouling ability of the PAN- Fe₃O₄ membrane. The obtained result may give insight to the development of new membranes with a good anti-fouling performance in the filtration of blood solution.No chemical bond was found between PAN and Fe₃O₄ in the membrane at room temperature. The addition of Fe₃O₄ can improve the temperatures of dehydrogenated reaction and decomposition of PAN but dot change the glassy transition temperature. The resistance against acid is stronger than the resistance to base for a PAN- Fe₃O₄ membrane. This membrane will lose the value in a solution with pH value of over 10. The resistance against acid for this membrane depends on the concentration and the oxidation of an acid.For the PAN- Fe₃O₄ membranes, a 1.1wt% addition of Fe₃O₄ can obviously reduce the mean pore size and increase the surface roughness. But the addition of Fe₃O₄ change from 1.1wt% to 4.3wt%, the roughness and the pore size of membrane gradually become small. In addition, the water flux and the rejection of membranes basically become high with the change of Fe₃O₄ addition amount form 0wt% to 4.3wt%.The Fe₃O₄ particles are well-distributed in the PAN- Fe₃O₄ membrane. The magnetic coercivity of the PAN- Fe₃O₄ membrane is 114Oe and don not change with the Fe₃O₄ content in a membrane. The remanent magnetizations of membranes are improved with the increase of Fe₃O₄ content. Membrane samples can reach the saturation of the magnetization when the external fields reach above 5400Oe.For the PAN- Fe₃O₄ membranes prepared under an orthogonal magnetic field, the addition of Fe₃O₄ can reduce the thickness of membrane skinlayer and result in a change of macro pores in sublayer from regular, and perpendicular to the membrane plane to irregular and oblique to the membrane plane. The pore size, the surface roughness, the pure water fluxe, and the flux of BSA solution first reduce and then increase with the increase of Fe₃O₄ addition amount in the membranes. The rejections gradually decline with the increase of Fe₃O₄ addition amount and change within 2%. Contrary to the common results, the membrane permeability and the anti-fouling performance appear to have no direct correlation to the roughness of membrane surface in our results.更多还原