电渗析用锂离子选择透过膜微结构调控与传递过程强化

The organic-inorganic hybrid lithium ion selective membrane was prepared by the composite membrane technology. Firstly, the cation exchange membrane was prepared as the basement membrane by mixing SPEEK and surface functionalized lithium ionic sieve with negative charge, then the positively charged layer containing functionalized lithium ionic sieve with positive charge was formed on the basement membrane through interfacial polymerization. The separation of Li+ from Na+，K+, Mg2+, Ca2+ was realized by electrodialysis from the salt lake brine. The preparation and microstructure regulation of the membrane will be investigated. The internal relations between the separation performance-membrane microstructure-preparation conditions-membrane materials will be explored to realize the controllable preparation of lithium ion selective membrane. The effect of lithium ionic sieve on membrane microstructure will be investigated in detail. The interaction mechanism between the effect of charged groups on lithium ionic sieve and those on membrane material and the interaction mechanism between the compound layer and the basement membrane will be investigated. Additionally, the influence of ion transfer process will be investigated by multi-scale synergistic effect and its mechanism of action based on the theory of mass transfer in the multicomponent mixture. Then, the theory and method for strengthen of the transfer process can be obtained. The theoretical basis and technical support was provided for the comprehensive utilization of salt lake brine and seawater.

项目以磺化聚醚醚酮和表面接枝荷负电基团的锂离子筛共混制备阳离子交换膜为基膜；然后采用界面聚合技术，在基膜表面制备含表面接枝荷正电基团的锂离子筛的荷正电复合层，制备有机-无机杂化锂离子选择透过膜，采用电渗析技术实现盐湖卤水中Li+与Na+、K+ 、Mg2+ 、Ca2+分离。项目将探索膜微结构参数的形成条件和过程机制，研究膜性能-结构-制备条件-膜材料之间的内在关系，实现锂离子选择透过膜的可控制备。项目将重点研究锂离子筛对膜微结构的影响，锂离子筛上荷电基团与膜材料荷电基团之间的相互作用机制，复合层与基膜的协同作用机制。以多组分混合物中质量传递理论为基础，探索多尺度协同效应及其作用机制对离子传递的影响规律，获得强化传递过程的理论和方法，为盐湖卤水和海水的综合利用提供理论基础和技术支持。

目前，以商业单价离子选择性膜制备的电渗析装置，已经应用于盐湖卤水提锂，实现了产业化。电渗析法能实现连续规模生产且无污染；产业化过程中发现的问题为电力消耗较高,所形成的富锂卤水中Na+、K+、Mg2+、 Ca2+、SO42-等杂质含量较高，造成整体制锂工艺成本较高。针对上述问题，项目研制了锂离子选择透过膜和单价阴离子选择性膜。（1）以磺化聚醚醚酮和表面接枝荷负电基团的锂离子筛制备基膜；然后采用界面聚合技术，在基膜表面制备含表面接枝荷正电基团的锂离子筛的荷正电复合层，制备锂离子选择透过膜；（2）以季铵化壳聚糖、季铵化氧化石墨烯和聚乙二醇共混制备基膜，然后通过界面聚合技术，在基膜表面复合上含固定荷负电基团的多孔改性层，得到单价阴离子选择性膜。项目开发的锂选择性透过膜，Li+与Mg2+的分离效果高于商业膜，特别是可以实现Li+与Na+、K+在一定程度上的分离，这是目前商业膜做不到的；项目开发的单价阴离子选择性膜，对Cl−与SO42−的分离效果也优于商业膜。项目开发的两种膜，有望提高盐湖卤水电渗析提锂的电流效率，降低电耗，同时减少后处理的难度，降低整体提锂工艺的成本。项目探索了锂离子筛、氧化石墨烯的改性方法和对膜微结构的调控作用，基膜与复合层的协同作用机理；研究了多尺度协同效应及其作用机制对离子传递的影响规律，所得到传递理论和方法对相关的研究和实践有一定的指导意义。项目的研究成果为盐湖卤水和海水中锂资源利用提供了理论基础和技术支持。