基于反应型筛网的界面聚合正渗透膜的设计与制备研究

Forward osmosis (FO) technology is advanced and potential in the field of water purification and desalination. FO membrane as a key technology is limited by the low flux largely due to the internal concentration polarization (ICP) in support layer. This application aims to fabricate a high-flux FO membrane through interfacial polymerization (IP) on the surface of screen mesh as a support to largely decrease ICP and significantly increase flux. In this application, screen mesh was modified by DOPA/Dopamine self-polymerization technology and further grafting to improve the surface hydrophilicity and create organic groups on surface which can react with acyl chloride. Afterwards, the modified mesh was impregnated in aqueous phase containing amine with surfactant followed by immersed in organic phase containing acyl chloride, where the polyamide active layer was formed on the mesh surface. By adjusting the mesh structure and property as well as the IP conditions, the FO membrane with a good uniform, defect-free and mechanical strength active layer will be obtained. Combined with membrane characterization and separation performance, the interrelationship of membrane fabrication process, membrane structure and membrane performance will be revealed. The mechanism of the formation of active layer on the mesh surface will also be studied to supervise and optimize the membrane design and fabrication. The resultant FO membrane will combine the advantages of screen mesh and super-thin active layer to achieve both good rejection and excellent flux. It will break a new path for the development of high-performance FO membrane fabrication.

正渗透是国际上最前沿、最具潜力的脱盐和水净化技术，其核心是正渗透膜，但膜支撑层中内浓差极化严重降低了水通量，是该技术发展和应用的瓶颈。本项目以高水通量正渗透膜为研究目标，从具有良好支撑层结构的筛网出发，拟采用多巴/多巴胺自聚-复合技术进行表面改性，以提高筛网亲水性并使其带有与酰氯反应的活性基团，然后以胺类为水相、酰氯为油相，进行界面聚合，首次制备以筛网为支撑层的聚酰胺正渗透膜。通过调整筛网结构、性质和界面聚合条件来获得完整性、均匀性和强度均优且与筛网牢固结合的皮层；根据膜结构表征和传质性能测试，揭示膜制备工艺、膜结构和膜性能的内在联系，得到较为成熟的膜制备技术；剖析筛网表面界面聚合皮层生长机制，以指导和优化膜设计和制备。本项目所研制的正渗透膜有望充分结合并发挥筛网和超薄皮层的优势，以最大程度降低内浓差极化，在保持优良脱盐率的同时显著提升水通量，其成功研制将为高性能正渗透膜的开发开辟新路径。

本项目从具有良好支撑层结构的筛网出发，围绕筛网材料优化设计、筛网与聚酰胺皮层匹配性、皮层结构与分离性能调控和强化、筛网上皮层生长机制、正渗透传质机理等方面开展了研究工作，成功获得了具有超高水通量的以筛网为支撑层的薄层复合（TFC）正渗透膜。该正渗透膜能够极大程度降低内浓差极化，在保证优良脱盐率（相同测试条件下，盐反混通量与当前商品化正渗透膜持平）的同时，显著提高水通量（相同测试条件下，比当前商品化正渗透膜提高约一个数量级）；通过筛网改性获得反应型筛网，能够大大增强筛网支撑层与皮层复合强度，提高了正渗透膜的耐久性能并延长其使用寿命；探究并获得了筛网表面皮层随界面聚合时间的形成机制以及筛网对于正渗透过程传质的促进机理。本项目所获得的正渗透膜以及较成熟的膜制备工艺，提出了一个全新的薄层复合正渗透膜概念，开辟了国内外高通量正渗透膜的新途径。此外，在筛网表面成功完成界面聚合操作，并获得性能显著提高的正渗透膜，为其他新型材料的制备提供了新思路。