超支化阳离子纳滤膜的制备及其性能研究

发布时间：2019-06-18 17:53

【摘要】：因其独特的结构特点,超支化聚合物受到了众多研究者们的青睐。然而,目前关于使用超支化聚合物制备分离膜的报道还非常有限；同时,尚未发现有关采用层层(LBL)自组装方法制备超支化纳滤(NF)膜的研究报道。针对目前商品化纳滤膜通量普遍较低问题,本研究设计并合成了一种新型超支化阳离子型聚丙烯酰氧乙基三甲基氯化铵(b-PDAC)分子；然后,通过层层自组装技术制备了具有优异分离性能的超支化聚合物复合纳滤膜并将其用于结晶紫染料的分离。首先,采用半连续可逆-加成断裂链转移(RAFT)方法合成了具有超支化结构的大分子链转移剂b-PAM和聚合产物b-PDAC。然后,采用红外、核磁以及多角度激光光散射凝胶色谱系统对聚合物的结构、分子量和分布情况进行表征和分析,当[AM]/[DAC]=4:5,[AM]/[CTA]/[APS]=600/1/0.5,[MBA]/[CTA]=20,MBA滴加时间为2h,DAC扩链反应时间为4h时所制备的超支化阳离子聚合物b-PDAC最适合用于制备复合物纳滤膜。该超支化阳离子聚合物的重均绝对分子量Mw=1.828x 106,分散指数PDI=1.959,支化度BD=0.664。最后,分别以PSS为阴离子聚电解质,b-PDAC为阳离子聚电解质,采用LBL自组装方法制备超支化纳滤膜。并对从ATR-IR、SEM、AFM、CA以及分离性能方面对所制备的超支化纳滤膜进行了研究。结果表明：当聚电解质b-PDAC和PSS浓度分别为25g·L-1,组装层数为2.5层时,所制备的[b-PDAC25/PSS25]2/b-PDAC复合纳滤膜膜表面粗糙度为12.2nm,略高于DL商品膜；且该复合纳滤膜对0.5mg·L-1结晶紫染料的截留率可达到94.23%,略低于NF270膜,而通量却是NF270膜的1.5倍。因此,与传统纳滤膜相比,拥有超支化结构的纳滤膜在截留率略微降低的情况下显著提高了膜通量。
[Abstract]:The hyperbranched polymer is favored by many researchers because of its unique structural characteristics. However, the present report on the use of hyperbranched polymers for the preparation of separation membranes is also very limited; at the same time, studies have not been found on the preparation of hyperbranched nanofiltration (NF) membranes using a layer-by-layer (LBL) self-assembly process. in that light of the low flux of the currently commercialized nano-filtration membrane, a novel hyperbranched cationic polypropylene (b-PDAC) molecule is designed and synthesized, and then, The hyperbranched polymer composite nanofiltration membrane with excellent separation performance is prepared by the layer-by-layer self-assembly technology and used for separating the crystal violet dye. First, a macromolecular chain transfer agent b-PAM and a polymerization product b-PDAC having a hyperbranched structure were synthesized by a semi-continuous reversible-addition-break chain transfer (RAFT) method. then, the structure, molecular weight and distribution of the polymer are characterized and analyzed by using an infrared, a nuclear magnetic and a multi-angle laser light scattering gel chromatographic system, and when[AM]/[DAC] = 4:5,[AM]/[CTA]/[APS] = 600/1/ 0.5,[MBA]/[CTA] = 20, the time for dropping the MBA is 2 hours, The hyperbranched cationic polymer b-PDAC, which was prepared at a time of 4 h, was most suitable for the preparation of the composite nanofiltration membrane. The hyperbranched cationic polymer has a weight average absolute molecular weight Mw = 1.828 x 106, a dispersion index PDI = 1.959, a degree of branching BD = 0.664. And finally, using the PSS as the anionic polyelectrolyte, the b-PDAC as the cationic polyelectrolyte, and adopting the LBL self-assembly method to prepare the hyper-branched nanofiltration membrane. The prepared hyperbranched nanofiltration membrane was studied from the aspects of ATR-IR, SEM, AFM, CA and separation performance. The results show that when the concentration of the polyelectrolytes b-PDAC and PSS is 25 g 路 L-1 and the number of assembly layers is 2.5, the surface roughness of the[b-PDAC25/ PSS25] 2/ b-PDAC composite nanofiltration membrane is 12.2 nm, which is slightly higher than that of the DL commercial film, and the entrapment efficiency of the composite nanofiltration membrane for 0.5 mg 路 L-1 crystal violet dye can reach 94.23%. Below the NF270 membrane, the flux is 1.5 times the NF270 membrane. Therefore, the nanofiltration membrane with the hyperbranched structure significantly improves the membrane flux in the case of a slight decrease in the retention rate compared to the conventional nanofiltration membrane.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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