多级非对称结构膜制备及传质过程强化

The complexity of the feed mixture and mass transfer process in the membrane separation of organic mixtures put forward higher requirements for the design, construction and regulation of membrane structure. Inspired by the various composite materials with intriguing hierarchical asymmetric architecture in nature which can prominently facilitate the mass transport efficiency, a novel strategy is proposed to design and fabricate hierarchically-structured asymmetric membranes from the viewpoint of enhancing the sorption and diffusion simultaneously. Pervaporative alcohol dehydration is set as the model example. An ultrathin layer is fabricated using hydrophilic materials for selective liquid permeation, mainly aiming to enhance sorption mechanism and thus increasing selectivity. Beneath the sorption layer, another thin layer is fabricated to facilitate the transport of water molecules, mainly aiming to enhance diffusion mechanism by reducing the transport resistance and thus increasing permeation flux. A physical blending-phase inversion-surface segregation coupled method is utilized to fabricate a kind of gradient-structured composite membrane with a gradient distribution of nanoparticles in polymer matrix. A vacuum assisted filtration-bioadhesion-spin coating coupled method is applied to fabricate a kind of multi-layer-structured composite membrane consisted of a polymer thin layer, an adhesive thin layer and a two-dimensional materials layer. The structural properties of the above composite membranes, including the surface structure, interfacial structure, interlayer structure and main matrix free volume property, are tuned and optimized by reasonable choice and modification of nanoparticles, bioadhesive and polymers as well as optimization of fabrication conditions. The membranes are used for pervaporative alcohol dehydration and the structure-performance relationship is to be revealed by correlating the sorption factor and diffusion factor with structure parameters. The strategy for the design and fabrication of novel high-performance dense membranes with hierarchical structure will be investigated and verified to achieve a simultaneous improvement in both selectivity and permeability.

用于小分子有机物分离的膜技术因其物系和传质过程的复杂性，对膜结构设计、构筑和调控提出了更高要求。受自然界中广泛存在的多级非对称功能结构启发，面向渗透蒸发有机物脱水过程，提出设计并制备多级非对称杂化膜，获得与溶解-扩散传质机制相适应并可促进传质的膜结构。采用“物理共混+相转化+表面偏析”法，以亲水性纳米粒子和疏水性高分子为填充剂和膜基质，构筑填充剂呈渐变分布的梯度结构杂化膜；采用“真空辅滤+仿生粘合+旋涂”法，以亲水高分子、仿生粘合剂和二维材料为组装单元，构筑具有高分子层-粘合层-二维材料层的多层结构杂化膜。膜上部是与水具有强亲和性的溶解渗透薄层，主要强化溶解机制，提高膜的选择性；下部是有利于水分子扩散的扩散渗透薄层，主要强化扩散机制，提高膜的渗透性。优化制膜条件，调控梯度分布、膜表界面结构和自由体积特性；揭示构效关系，阐明非对称膜结构对溶解-扩散的协同强化机制，实现选择性和渗透性同时提升。

用于小分子有机物分离的膜技术因其物系和传质过程的复杂性，对膜结构设计、构筑和调控提出更高的要求。受自然界中广泛存在的多级非对称功能结构启发，面向渗透蒸发有机物脱水、废水处理、质子传递、碳捕集和化工气体混合物纯化等过程，制备了基于功能性高分子、共价有机框架、氧化石墨烯、蛭石等材料的具有梯度结构和多层结构的多级非对称结构薄膜。通过纳米材料复合在膜基质中形成梯度分布结构，或通过构建高分子层-粘合层-二维材料层的多层结构，解耦溶解和扩散传质过程，从而在不牺牲选择性的同时实现快速传质。通过优化制膜条件调控梯度结构、膜表界面结构和自由体积特性，实现传质过程强化，突破选择性和通量之间彼此制约的博弈效应，所制备的多级结构膜在选择性、通量、抗污染等性能指标上显著提高，为膜分离过程高效强化提供了新思想与新途径。