新型正渗透仿生分离膜的制备及应用基础研究

The high energy requirement for current desalination membranes necessitates a new class of forward osmosis membranes to produce fresh water and clean energy through a low-cost, efficient and eco-friendly way. Carbon nanotube-based biomimetic FO membranes are attracting numerous attentions due to its proven excellent water permeability and solute rejection. Despite several studies have attempted to incorporate carbon nanotubes into polymeric membranes, it is challenging to align carbon nanotubes vertically in a large scale and to achieve such robust and defect-free membranes for desalination and clean energy. Here, we propose a novel approach to pattern carbon nanotubes into nano-channels of block copolymer and achieve such FO biomimetic membranes by "Bottom-up" method, using block copolymer and carbon nanotubes as building blocks. This project will focus on the mechanism study of water and ions transporting through FO membrane, investigate the microstructure-property relationship of biomimetic membrane using the advanced techniques including microscopy, spectroscopy and chromatography, reveal the major factors influencing the membrane structure, properties, and stability, and test the performance of this novel FO membranes such as water permeability, salt rejection and membrane structure parameter. This novelty is of great benefits to its versatile platform for the study of co-assembly of nano-materials and its universal application in the scaling-up production of other functional membranes such as bioreactor and biosensors.

开发高效节能环保的正渗透膜是当今分离膜领域的前沿课题，对低污染低能耗又高效地获取淡水资源和清洁能源具有重要的科学意义和应用价值。此课题以提高FO膜的水通量和盐截留效率，降低膜的内浓差极化为目标，通过"自下而上"的方式，以碳纳米管为仿生功能单元，以嵌段共聚物为模板，通过界面作用力的调控，实现碳纳米管的大面积定向排列，制得一种全新高效的仿生FO分离膜。课题紧紧围绕"FO分离膜水分子传输与盐组分截留的微界面机制"这一关键科学问题展开，使用现代化的显微术、能谱、光谱、色谱等高级分析检测手段追踪仿生分离膜在形成过程中的组分与结构动态变化规律，识别对成膜过程起关键作用的影响因子和机制，进而对仿生分离膜在FO体系中的水通量、反向盐通量（比盐通量）及盐截留效率等性能进行评价测试。本课题的研究成果将丰富高效仿生分离膜的制备和应用基础理论，为其它仿生功能器件的制备提供借鉴。

正渗透膜技术可以高效地用于处理复杂水质和加工浓缩食品，发展成为当今分离膜领域的重点研究方向。为了提升正渗透膜的水通量和盐截留效率，降低正渗透膜的内浓差极化，本课题从正渗透膜的结构设计与性能优化出发，利用嵌段共聚物和碳纳米管等新型膜材料，成功制备出系列高通量和高选择性的正渗透膜，并考察了所研制的正渗透膜在水处理和果汁浓缩中的应用。主要成果体现在以下几个方面：（1）合成了系列不同组成与分子量的双亲性嵌段共聚物PS-b-PEO和PSF-b-PEG，并成功实现公斤级放大化制备PSF-b-PEG膜材料，其中亲水PEG嵌段含量可在7.5 wt.%-35.5 wt.%范围内调控；（2）选择合适溶剂体系，调控嵌段共聚物在铸膜液中的自组装行为，利用SNIPS一步成功制备了通量高于25 LMH/bar的PS-b-PEO和PSF-b-PEG嵌段共聚物膜，显著优于传统高分子膜材料的渗透选择性；（3）将碳纳米管加入PS-b-PEO嵌段共聚物铸膜液中，制得混合基质膜，并使水通量增加到63 LMH/bar；（4）以PSF-b-PEG嵌段共聚物膜为基膜，通过界面聚合制备正渗透复合膜，创新应用了退火后处理手段调控嵌段共聚物基膜的微观结构，显著提升了正渗透复合膜的渗透选择性，其A/B值高达19.56 bar-1，高于HTI公司商业化正渗透复合膜A/B值的3倍；（5）以碳纳米管（CNT）层为中间层，通过界面聚合制备出一系列具有不同CNT厚度的复合正渗透膜，研究结果发现：在1 M NaCl作为汲取液，AL-DS模式下，最优样的水通量达到37.9 LMH，反向盐通量低于0.5 gMH，性能显著优于目前文献报道的复合正渗透膜；（6）为了进一步优化正渗透膜结构，首次直接以超薄CNT膜作为支撑层，制备出超薄正渗透复合膜，研究结果发现：在1 M NaCl作为汲取液，AL-DS模式下，最优样CNT-PA复合膜的水通量超过150 LMH，为目前文献报道中的最高值；水渗透系数A达到9.22 ± 1.14 LMH/bar，膜结构参数S仅为38 μm; （7）采用正渗透（FO）-膜蒸馏（MD）膜集成系统浓缩果汁和市政污水处理，开发新型汲取液山梨酸钾溶液，实现苹果汁的浓缩倍数高达4.25倍；并可极大提高市政污水处理的出水水质。