基于活性层重构处理的超高通量纳滤膜制备及其处理苦咸水的效能与机制

Exploitation and utilization of brackish water with nanofiltration (NF) technology is a significant way to alleviate the water demand-supply conflict and promote economic and social development. However, there is a typical trade-off effect between the water flux and salt rejection of NF membrane. How to improve the water flux while ensuring the desalination performance is a bottleneck problem for brackish water treatment with NF technology. In view of this, our proposal proposed a novel technical idea based on the reconstruction process of NF membrane active layer. The reconstruction process will be proceeded via the immersion and activation of nascent NF membrane by a specific reconstruction solution, which is expected to simultaneously regulate multiple active layer structure parameters and obviously promote the membrane filtration performance. On the one hand, basic experiments will be systematically conducted to reveal the corresponding relationship between the NF membrane macroscopic filtration performance and the microstructure of the active layer under different reconstruction conditions. On the other hand, the formation mechanism and controllable method of specific active layer microstructure will be explained, followed by the establishment of controllable membrane fabrication theory via the accurate data analysis. Finally, a NF membrane with ultra-high flux which can be used in the desalination of brackish water will be prepared with the guidance of the above proposed theory. The treatment efficiency and mechanism of this membrane will also be preliminarily explored via the continuous operation. The implementation of the current proposal is expected to provide scientific theory guidance for the controllable preparation of NF membrane, as well as strong technical support for the effective treatment of brackish water.

采用纳滤技术对苦咸水进行开发与利用，是缓解水资源供需矛盾和促进经济社会发展的重要途径。然而，纳滤膜的水通量与脱盐率之间存在典型的trade-off效应。如何在保证脱盐性能的同时大幅提高纳滤膜的水通量，是目前苦咸水纳滤处理技术面临的一个瓶颈问题。针对此，本项目提出了一种基于纳滤膜活性层重构处理的新型技术思路，通过特定重构溶液对新生纳滤膜进行浸润活化，以求同步优化多项活性层结构参数，从而有效提升纳滤膜的过滤性能。一方面要通过系统的基础实验揭示不同重构处理条件下纳滤膜宏观过滤性能与活性层微观结构之间的对应关系；另一方面要阐释特定活性层微观结构形成机理与控制方法，并通过准确的数据分析建立膜材料可控制备理论；最终以此为指导制备能够应用于苦咸水脱盐处理的超高通量纳滤膜，并通过连续运行初步探究其处理效能与运行机制。项目的实施将为纳滤膜的可控制备提供科学的理论指导，为苦咸水的有效处理提供有力的技术支持。

采用纳滤（NF）技术对苦咸水进行脱盐是缓解我国水资源供需矛盾和促进经济社会发展的重要举措，然而纳滤膜产水通量与盐离子截留之间存在典型的trade-off效应。如何在保证脱盐率的基础上大幅提高其产水通量是纳滤技术领域亟待解决的一个关键技术难题，对于降低运行能耗与制水成本至关重要。为此，本项目首次根据纳滤过程中的传质特征将纳滤膜功能层划分为溶解扩散区（SDR）、水分子透过区（WMR）、部分透盐区（PSR）和完全透盐区（ASR），并从传质区域调整的角度阐述了纳滤膜制备过程中协调透水性与脱盐率之间trade-off效应的基本原理与技术方法。在深入解析纳滤膜活性层微观结构参数与宏观过滤效能之间相互制约关系的基础上，提出了基于纳滤膜活性层重构处理的新型技术思路。在调控界面聚合反应过程与优化支撑层选用的基础上，结合乙醇、水、氢氧化钠的三元复合物（EWN）后处理可以有效地重构新生纳滤膜中的聚酰胺分离层，实现了包括分离层厚度、亲水性、荷电性和孔径分布等多项活性层结构参数的同步优化，从而有效协调了水通量与脱盐率之间的trade-off矛盾，制备出多种具有不同功能特色的复合纳滤膜，例如针对重金属高效去除的纳滤膜（纯水通量高达14.6 L/m2·h·bar，且对镍离子、铜离子和锌离子保持98%以上的去除率）、基于“双界面厚度控制理论（DITC）”理论的超高通量复合纳滤膜（纯水通量高达46.6 L/m2·h·bar，Na2SO4 截留率超过98%）、以PTFE为支撑层的耐干燥复合纳滤膜以及兼具高通量、高离子选择性和抗污染能力的超支化聚酯改性复合纳滤膜（纯水通量高达50.62 L/m2·h·bar，且对Na2SO4的截留率超过98%）等。通过本项目的执行，深入阐明了超高通量复合纳滤膜的合成原理，实现了其制备策略的灵活构建，且相关研究中提出的各类方法均有简便、可控和成本低的技术特征，便于实际的工业化生产，具有重要的产业化前景。