基于分离-浓缩协同机制构建选择性正渗透膜及其在深层海水资源化中的应用

The exploration and utilization of deep seawater is the forefront international research trend of deep-sea resourcezation, and the key is the efficient concentration of active substances. However, high energy consumption and low concentration efficiency seriously weaken the process economy and product value. Facing the significant demand of efficient concentration technology for deep seawater resourcezation, we proposed to establish a novel selective forward osmosis (FO) technology that integrates separation and concentration, and is expected to realize the integration, high efficiency and low energy consumption of the concentration process. Aiming at the highly selective FO membranes, we proposed a new constructing approach and performance regulation mechanism of selective FO membrane based on self-supporting carbon nanotubes (CNTs) frameworks as support layer. On the basis of finely tuned pore structure, surface properties and mechanical property of CNTs frameworks, the preparation of ultra-thin support layer and controlled skin layer can be realized, facilitating water and monovalent transport and controlling divalent salt transport with the aid of the accompanying charging effect. This approach endowed the membrane with high concentration performance and high selectivity performance. Combined with mass transfer experiments and molecular dynamics simulation, the correlation of membrane material-structure-property was obtained, and the mass transfer mechanism of synergistic separation-concentration was revealed. Furthermore, we studied the concentration of active substances in deep seawater using our selective FO technology, which can feedback for the preparation of highly efficient FO membranes and the optimization of process operation. The selective FO technology proposed in this project can also provide reference for promoting wastewater resourcezation.

深层海水开发利用是深海资源化的国际研发前沿趋势，其关键是活性物质的高效浓缩，但过程中能耗高、浓缩率低严重消弱了过程经济性和产品价值。面向深层海水资源化对高效浓缩技术的重大需求，本项目拟建立集分离与浓缩为一体的选择性正渗透（FO）技术，有望实现该过程的集成化、高效化和低能耗化。以高效选择性FO膜为研究目标，提出以自支撑碳纳米管（CNTs）薄层为支撑层构建选择性FO膜的新方法及性能调控机制。精细调变CNTs薄层孔结构、表面性质和机械性能，实现支撑层超薄化、荷电化和皮层可控化制备，利用藉此伴生的双层荷电效应，促进膜对水、一价盐传输，改善膜对二价盐等管控，赋予膜高浓缩和高选择性能。结合传质实验和分子动力学模拟，获取膜材料-结构-性能关联，探究分离-浓缩协同传质机理。进而，对深层海水活性物质浓缩过程做有益尝试，为高效FO膜制备和工艺操作优化反馈信息。本项目的选择性FO技术也为推进废水资源化提供借鉴。

面向水资源、环境和能源领域对高性能、低能耗分离膜的重大需求，本项目瞄准当前正渗透膜超薄化、可控化制备的难题，提出了基于碳纳米管（CNTs）薄层支撑的超薄正渗透膜的新思路及构建新方法。主要研究内容及结果如下：（1）成功研制了以CNTs薄层为中间支撑层的系列高效正渗透膜材料，并揭示了CNTs薄层孔结构及性质对皮层结构和分离性能的调控作用，实现了具有高度均匀、适当交联度和荷电性正渗透膜的可控制备。（2）成功研制了以CNTs薄层为自支撑层的高通量高选择性正渗透膜材料，并建立了新型自支撑界面聚合方法。在此界面聚合过程中，水相胺类单体通过CNTs薄层空隙扩散至油相，进而与酰氯单体发生反应，揭示了CNTs薄层的胺类单体扩散速度的管控机制；此外，分离性能研究表明，超薄支撑层可有效强化水传递，降低内浓差极化，从而获得具有优异正渗透性能的分离膜。（3）建立了以高效正渗透膜为核心的传质机理模型及实验室规模的浓缩工艺，实现了混合盐溶液的分盐浓缩，并归纳出不同离子的传质规律，揭示了强化水传递和有效管控盐离子传输的控制因素；（4）对深层海水活性物质浓缩过程做有益尝试，为高效FO膜制备和工艺操作优化反馈信息。以上研究工作为高效正渗透膜制备奠定理论基础和技术支撑。该正渗透膜研制技术的推广必将推进节能减排技术以及节能型膜分离技术的革新和拓展，并满足FO技术在环境、能源等领域的巨大需求，在工业污水零排放和无污染综合利用海水淡化等领域产生巨大的社会经济效益，促进我国水资、环保、能源以及国防等许多产业的快速发展。