Abstract:

The confined mass transfer separation membrane is mainly for the high-precision separation process at the molecular/ion level, which is of great significance to solve the application needs of CO₂ separation, azeotrope separation, lithium extraction from salt lake, desalination of seawater and so on. However, at present, the research of the confined mass transfer mechanism of this kind of membrane is lagging behind, and the theoretical models of confined mass transfer are lacking, which can no longer meet the needs of the rapid development of materials and chemical engineering. From the perspective of meso-science, the abnormal phenomenon of high flux and high selectivity of the confined mass transfer separation membrane is considered, that is, breaking through the trade-off effect, which is governed by compromise-in-competition between the selectivity mechanism and the flux mechanism. It is found that the fluid molecules will preferentially adsorb at the interface and form a stable adsorption layer. Based on this, the hypothesis of “secondary confinement” is put forward, that is, the surface induced new solid-like interface will have confinement effect on the intermediate fluid again. By comparing the pore size and the secondary confined size of the confined mass transfer separation membrane, the selective mechanism of the secondary confinement is further confirmed, and the quantitative prediction of the membrane flux and selectivity is preliminarily explored by combining the selective mechanism and the flux model, which may provide a theoretical basis for the precise construction of the limited area mass transfer membrane.

Key words: secondary confinement, confined mass transfer, membranes, separation

摘要：

限域传质分离膜主要面向分子/离子水平的高精度分离过程，对解决CO₂分离、共沸物分离、盐湖提锂、海水淡化等重大应用需求具有重要意义。然而目前，这类膜的限域传质机制研究滞后，理论模型缺乏，已不能满足材料和化工等学科高速发展的需求。用介科学观点思考限域传质分离膜同时具有高通量和高选择性这一反常现象，即突破Trade-off效应，这是选择性机制与通量机制之间的竞争与协调导致的。纳微固液界面处流体分子在界面处会优先吸附，形成稳定的吸附层，基于此本文提出了“二次限域”的假说，即界面诱导的类固态新界面会对中间流体再次产生限域效应。通过对比限域传质分离膜的孔道尺寸与二次限域尺寸，进一步认知了二次限域的选择性机制，并结合选择性机制与通量模型对膜通量和选择性的定量预测进行了初探，以期为精密构建限域传质膜提供理论基础。

关键词: 二次限域, 限域传质, 膜, 分离