两性离子型抗污染超滤膜表面构建及其性能研究

发布时间：2018-03-01 20:08

本文关键词： 超滤抗污染原位胺化两性离子聚电解质　出处：《天津大学》2015年硕士论文　论文类型：学位论文

【摘要】：超滤膜作为一种仅靠压力驱动的分离过程,因其节能、环保及操作简单等优点而受到广泛关注。而膜污染引起的通量降低,寿命缩短等问题却成为了超滤膜使用过程中的瓶颈。对超滤膜进行改性,增强其抗污染性能是推广超滤膜使用的关键。两性离子基团是一类具有独特的化学结构,即同时具有正负电荷,并整体呈现电中性的功能性基团。两性基团带有电荷,可以通过静电作用力结合周围的水分子。因为静电作用力强于氢键作用力,结合水分子更为牢固,而被广泛应用于材料的亲水改性。本文通过在超滤膜表面引入两性离子基团构建抗污染表面,并对其抗污染性能进行考察。首先通过原位胺化的方法制备胺化聚氯乙烯(PVC)超滤膜,具体的将三乙烯四胺(TETA)作为胺化剂,亲核取代PVC主链上的活性氯原子,一方面可以改善PVC的亲水性,另一方面可以引入活性反应位点以便进一步改性。随后在胺化聚氯乙烯超滤膜表面与氯乙酸钠反应,引入两性离子基团从而构建两性离子表面。以蛋白质为模拟污染物,两性离子化的PVC超滤膜抗污染性能得到明显提升,吸附阻力仅为0.19×1011 m-1(空白PVC超滤膜为3.61×1011 m-1)。其次,通过对超支化高分子聚乙烯亚胺(PEI)进行化学改性,即在其链段接枝两性基团,制备了两性聚乙烯亚胺(Z-PEI)。借助Z-PEI中未反应完全的胺基与水解聚丙烯腈(H-PAN)超滤膜进行反应形成共价酰胺键,从而锚定于膜表面,完成两性离子表面的构建。所制备的两性离子化超滤膜具有良好的抗污染性能。通量恢复基本达到100%,通量衰减仅为31.4%。此外由于Z-PEI的特殊枝化结构,Z-PEI可以通过多位点接枝于膜表面以增强其稳定性。最后,通过在荷负电超滤膜表面引入单一荷正电聚电解质季胺化壳聚糖,构建两性表面。一方面希望利用聚电解质的荷电基团与膜表面水分子形成水化层,达到抵御污染物的目的,另一方面正电荷聚电解质与负电荷膜表面共同构建两性表面可以减少污染物的特异性粘附。所得超滤膜通量恢复可以提高到90.2%,通量衰减降至35.6%,抗污染效果明显。
[Abstract]:As a pressure driven separation process, ultrafiltration membrane has attracted wide attention because of its advantages of energy saving, environmental protection and simple operation, while the flux caused by membrane fouling is reduced. Life shortening has become the bottleneck in the process of UF membrane use. The modification of UF membrane and the enhancement of its anti-fouling performance are the key to popularize UF membrane use. Amphoteric ion group is a kind of unique chemical structure. That is, a functional group with a positive and negative charge, and an overall electrically neutral functional group. The amphoteric group has a charge that binds the surrounding water molecules by electrostatic forces, because the electrostatic forces are stronger than the hydrogen bond forces, and the water molecules are more strongly bound. It has been widely used in the hydrophilic modification of materials. In this paper, the antifouling surface was constructed by introducing amphoteric groups on the surface of ultrafiltration membrane. The antifouling properties of the membrane were investigated. Firstly, the polyvinyl chloride (PVC) ultrafiltration membrane was prepared by in situ amination. Triethylenetetramine (TETA) was used as the amine agent to nucleophilic replace the active chlorine atoms on the main chain of PVC. On the one hand, the hydrophilicity of PVC can be improved, on the other hand, active reaction sites can be introduced for further modification. The amphoteric ion group was introduced to construct the amphoteric ion surface. The antifouling performance of the amphoteric PVC ultrafiltration membrane was obviously improved by using protein as the simulation pollutant, and the adsorption resistance was only 0.19 脳 1011 m ~ (-1) (compared with 3.61 脳 10 ~ (11) m ~ (-1) m ~ (-1) of the blank PVC ultrafiltration membrane. The hyperbranched polyimide (PEI) was chemically modified, that is, the amphoteric group was grafted in the chain segment. The amphoteric polyimide (Amphoteric polyimide) Z-PEI was prepared. The amphoteric polyimide (Amphoteric polyimide) Z-PEI was prepared by reacting with the hydrolyzed polyacrylonitrile (HPAN) ultrafiltration membrane to form a covalent amide bond, which was anchored on the surface of the membrane. The amphoteric ion surface was constructed. The amphoteric ultrafiltration membrane has good antifouling performance. The flux recovery is basically 100 and the flux attenuation is only 31.40.In addition, because of the special dendritic structure of Z-PEI, Z-PEI can pass through multiple sites. Dot grafting onto the surface of the membrane to enhance its stability. Finally, The amphoteric surface was constructed by introducing a single charged polyelectrolyte quaternary chitosan to the surface of the membrane. On the one hand, it was hoped that the charged group of the polyelectrolyte and the water molecules on the surface of the membrane would form a hydration layer to resist pollutants. On the other hand, the positive charge polyelectrolyte and negative charge membrane surface can reduce the specific adhesion of pollutants, the flux recovery of the membrane can be increased to 90.2, and the flux decay to 35.6.The antifouling effect is obvious.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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