Zwitterion-containing polymer additives for fouling resistant ultrafiltration membranes
Zwitterion-containing polymer additives for fouling resistant ultrafiltration membranes
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DOI：
10.1016/j.memsci.2017.03.034
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发表时间：
2017-07-01
影响因子：
9.5
通讯作者：
Asatekin, Ayse
中科院分区：
文献类型：
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作者：
Kaner, Papatya;Rubakh, Emil;Asatekin, Ayse
污垢可能是在许多应用中使用膜的最重要障碍，特别是在进料含有高浓度有机物（如油和生物大分子）的那些应用中。两性离子，定义为具有相等数量的带正电荷和带负电荷的官能团的分子，显示出优异的抗污性和亲水性。这些特征可以在超滤（UF）膜的制造过程中通过将商品聚合物如聚偏二氟乙烯（PVDF）与含有两性离子基团的共聚物共混而并入超滤（UF）膜中。这种方法可以直接用于现有的膜生产系统，无需后处理。然而，迄今为止的研究并没有提供任何用于设计或选择含两性离子的聚合物以实现最佳可能性能的指导。在这项工作中，我们合成了甲基丙烯酸甲酯（MMA），其均聚物与PVDF相容，与两种不同的两性离子共聚物，磺基甜菜碱甲基丙烯酸酯（SBMA）和磺基甜菜碱-2-乙烯基吡啶（SB 2 VP）。这些共聚物以前没有被研究作为膜制造中的表面分离添加剂。我们研究了不同的共聚物性质，如两性离子化学，共聚物组合物（即两性离子/疏水单体的比例），和共混物组合物对膜的性能的影响，从他们的共混物与PVDF。我们报告如何改变这些变量影响膜的形态，选择性，渗透性和耐污染性，并将这些数据与设计规则选择有利的共聚物。我们的研究表明，与以前的文献相比，增加添加剂共聚物中的亲水性/两性离子单体的量并不总是导致膜性能的改善。相反，在通过非溶剂诱导相分离（NIPS）形成膜的过程中，具有高两性离子含量（51-52重量%）的共聚物添加剂经历与PVDF的宏观相分离，并且所产生的膜显示出差的性能。另一方面，使用含有18- 19wt%两性离子单体的适当共聚物，即使使用非常少量的添加剂共聚物，也可以获得具有显着更高渗透性和显着耐污染性的膜。PVDF中两性离子添加剂含量低至5wt%可导致膜具有加倍的水通量（高达99 L/m（2）h bar）和对油悬浮液和蛋白质溶液的完全不可逆的抗污染性。只有10重量%的添加剂可以产生膜甚至更高的通量（高达165 L/m（2）h巴），并完全抵抗不可逆的污染的油悬浮液在24小时死端污染实验。据我们所知，这种程度的耐污染性以前没有报道过PVDF基膜，并表明这种膜改性方法在广泛应用中的前景。
Fouling is likely the most important obstacle to the use of membranes in many applications, especially in those that the feed contains high concentrations of organics such as oil and biomacromolecules. Zwitterions, defined as molecules with equal numbers of positively and negatively charged functional groups, show excellent fouling resistance and hydrophilicity. These features can be incorporated into ultrafiltration (UF) membranes during their manufacture by blending a commodity polymer like polyvinylidene fluoride (PVDF) with a copolymer containing zwitterionic groups. This approach can be used directly in existing membrane production systems, with no need for post-processing. Research to date, however, does not provide any guidelines for designing or selecting a zwitterion-containing polymer for this purpose to achieve the best possible performance. In this work, we synthesized copolymers of methyl methacrylate (MMA), whose homopolymer is compatible with PVDF, with two different zwitterionic copolymers, sulfobetaine methacrylate (SBMA) and sulfobetaine-2-vinylpyridine (SB2VP). These copolymers were not previously investigated as surface segregating additives in membrane manufacture. We investigate the impact of different copolymer properties such as zwitterion chemistry, copolymer composition (i.e. zwitterionic/hydrophobic monomer ratio), and blend composition on the performance of membranes manufactured from their blends with PVDF. We report how changing these variables affect the morphology, selectivity, permeance and fouling resistance of membranes, and associate this data with design rules for selecting favorable copolymers. Our study showed that, in contrast to previous literature, increasing the hydrophilic/zwitterionic monomer amount in the additive copolymer does not always result in improved membrane performance. Instead, during membrane formation by non-solvent induced phase separation (NIPS), copolymer additives with high zwitterion content (51-52 wt%) undergo macrophase separation from PVDF, and the membrane produced shows poor performance. On the other hand, with the appropriate copolymers that contain 18-19 wt% zwitterionic monomer, membranes with significantly higher permeance and remarkable fouling resistance can be attained even with very small amounts of additive copolymer. Zwitterionic additive contents as low as 5 wt% in PVDF can lead to membranes with doubled water flux (up to 99 L/m(2) h bar) and complete irreversible fouling resistance against oil suspensions and protein solutions. Only 10 wt% additive can yield membranes with even higher flux (up to 165 L/m(2) h bar), and complete resistance to irreversible fouling by an oil suspension in 24-h dead-end fouling experiments. This degree of fouling resistance have not previously been reported for PVDF-based membranes, to our knowledge, and indicates the promise of this membrane modification approach for a wide range of applications.