基于“自由孔隙”的均孔膜纳米分离通道构建及其成孔机制

The controllable preparation of isoporous membrane (IPM) suitable for the precision separation of amino acids and other small size maters is still a major challenge in the field of separation membrane. In this project, a novel huge nuclear star-shape composite particles (HSCP) with micellar-like structure and monodispersed size are self-made and will be used as membrane-forming materials. Monodispersed colloidal particles from HSCP solution on the solution membrane surface will be quickly formed in the meta-stable zone with the good-solvent evaporation, and in-situ assembled into close packed colloid-crystal particle layer. Then HSCP solution below colloid particle layer will be cured through nonsolvent induced phase separation (NIPS) to form support. Finally, a IPM with a nano-channel from the "free space" among the colloid particles and a pore support will be obtained. The effects of the physical/chemical structure and the charges of HSCP and the thermodynamic and kinetic factors on the formation, self assembly process and dense packing of colloidal particles in separation layer will be studied in detail. The formation process of the support through NIPS and its synergic enhance effect on the separation layer will be investigated. The regulation and semi-quantitative relationships between colloid particle size and the free space with monodispersed size will be clear. The pore-forming mechanism will be clarified. And the structure-performance relationship between the membrane structure and the separation and mechanic properties will be investigated. In the end, a new method for preparing IPMs with a uniform pore size is developed based on the new membrane material, which will expand the membrane application in the fields of biomedicine and others for precision separation and enrich basic theory of separation membrane.

适于氨基酸等高附加值物质精准分离的均孔膜的可控制备仍是分离膜领域的研究难点。本项目设计合成一种具有类胶束状结构的尺寸单一的“大核星形复合粒子”（HSCP），通过调控成膜过程，驱动HSCP铸膜液在亚稳区快速形成HSCP单分散胶体颗粒并原位自组装成“类胶体晶”功能表层，接着通过液-固相分离过程形成多孔支撑层，构建以表层胶体颗粒之间“自由孔隙”为分离通道的非对称结构均孔膜。着重研究HSCP的物理/化学结构和表面荷电性、铸膜液亚稳态条件等对胶体颗粒原位自组装构建分离层纳米分离通道过程的影响规律，探究支撑层形成过程对分离通道构建的协同强化效应，明晰分离通道尺寸单分散性与HSCP胶体颗粒尺寸之间的调控和半定量关系，阐明均孔膜的成孔机制；明晰膜结构与服役性能的构效关系。本课题将不仅发展一种均孔膜纳米通道可控制备和结构调控的新方法，而且将拓展分离膜在生物医药等精准分离领域的应用和丰富分离膜基础理论。

孔径窄分布的高性能分离膜是被认为是“能显著提高分离效率和实现可控分离的颠覆性技术”。本项目采用颗粒沉积辅助制膜方法，成功制备出高性能纳滤膜，并探索镁锂高效分离新方法。主题研究结果如下：.1.纳米颗粒自沉积和铜离子（Cu(II)）增强制备壳聚糖基复合纳滤膜。将壳聚糖纳米颗粒（CSP）通过静电吸附到碱化的聚丙烯腈（mPAN）基膜表面，利用颗粒堆积形成的纳米水通道（颗粒自由孔隙）制得纳滤膜分离层（CSPM），孔径尺寸在0.76-1.04 nm范围内调控，并将制得CSPM/mPAN纳滤膜浸入CuSO4溶液中进行螯合交联，得到CSPM-Cu(II)/mPAN膜。结果发现与CSPM/mPAN膜相比，CSPM-Cu(II)/mPAN膜的纯水通量和Na2SO4截留率同时提高，具有良好稳定性、抗污染性能和抗菌性能。.2. 壳聚糖颗粒辅助界面聚合法制备超高分离性能复合纳滤膜。在上述工作基础上，利用纳米颗粒与界面聚合活性单体在扩散系数及其反应活性之间的差异，辅助界面聚合，成功制备出超高通量和高截留性能的新型纳滤膜，孔径尺寸在0.62-0.96nm范围内。结果发现当壳聚糖浓度为0.5%、陈化时间为6 h所制备的PIP-CSP6/TMC复合纳滤膜纯水渗透性达45.2 L·m-2·h-1·bar-1，对Na2SO4截留率为99.3%，其渗透性相当于对照组PIP/TMC复合膜的5倍，远优于目前文献报道和商业纳滤膜性能。其优异的性能主要归因于超薄的分离层、更高的有效分离面积以及更多水通道的构建。同时发现，该膜具有pH响应特性，可用于有机大分子和盐的高效分离。本工作为低压大通量高性能纳滤膜制备提供了一条便捷可行的新方法。.3. 考虑到盐湖提锂中镁锂高效分离的世界性难题，本项目利用高性能纳滤膜并耦合电场强化技术，开展了电纳滤镁锂分离研究，发现在电流密度为2.12-2.83 mA/cm2和跨膜压差为5bar的情况下，Mg2+几乎完全被截留（高于99.99%），而Li+渗透性高达0.55 molm-2h-1)，且溶液通量为75±2 Lm-2h-1。分离性能远远优于现有报道的结果。这种高效分离性能与电场作用下纳滤膜表面荷正电重构有关。这项工作为Mg2+/Li+高效分离和高纯锂盐制备提供了一条可行的途径，在盐湖提锂具有巨大的应用潜力。该工作被JMS杂志选中制作公众号重点推介工作。