锂离子筛中空纤维膜吸附剂制备及膜吸附技术卤水提锂研究

Salt-lake brines are considered as great potential and valuable resources of the development of lithium industry in our country. The concentration brine form from salt lake after potassium extraction in Xinjiang has abundant resources of lithium. But the concentration brine contains many coexisting ions, and the Mg/Li molar ratio is above of 400, which must lead to be difficult to recovery lithium. In this project, the hollow fiber membrane-type absorbents of lithium manganese oxides (LMO) should study and be used to recovery lithium from concentration brine with high Mg/Li molar ratio. The membrane adsorption separation coupling technology should develop. The content of this project as follows: (1) the fabrication of PAN (or EVAL)- H1.6Mn1.6O4 hollow fiber membrane-type absorbents with high loading of LMO. (2) The diffusion ability of Li+ in intercrystalline and the hollow fiber membrane should enhance by regulation the lithium ion sieve morphology and the structure of LMO hollow fiber membrane-type absorbents respectively. (3) The effect of physical and chemical properties of polymer matrix, the forming method and the preparation condition on the loading content of LMO, LMO utilization rate and the stability between LMO and polymer matrix should study. (4) Composite adsorbent functionalized modification to improve the selectivity of Li+. To develop the membrane adsorption technology considering environmental protection should be efficient extracting lithium and promote the process of concentration brine-based lithium industry. The study results should provide theoretical and technical support for recycle and high-value use of lithium from concentration brine in Xinjiang.

盐湖卤水锂资源是我国今后发展锂盐工业最重要的资源基础。新疆盐湖卤水提钾后的浓缩卤水富含锂资源、储量大，但浓缩卤水共存离子多、镁锂比高达400，锂的提取难度大。为此本项目研究开发适用于高镁锂比浓缩卤水提锂的中空纤维膜状锂离子筛复合吸附剂，膜吸附技术。项目开展如下研究：（1）制备锂离子筛负载量高的PAN（或EVAL）-H1.6Mn1.6O4中空纤维膜状复合吸附剂；（2）以强化成型吸附剂中锂离子筛体相内和体相外Li+的快速传质为切入点，系统研究锂离子筛形态、复合吸附剂结构对Li+扩散传质影响；（3）以提高锂离子筛的负载量、负载利用率和负载稳定性，系统研究成型基质物理化学性能、成型方法及制备条件对锂离子筛与基质间作用的影响；（4）复合吸附剂功能化改性提高Li+选择性。实现高效提锂、环保、可工业化推广的膜吸附技术，为新疆盐湖卤水中锂资源回收及高附加值利用提供科学理论和技术支持。

本项目结合新疆盐湖提钾后浓缩卤水富含锂资源的情况，以H1.6Mn1.6O4（LIS）锂离子筛为吸附材料，选择聚氯乙烯、聚丙烯腈、乙烯-乙烯醇聚合物（EVOH）为成型基质，采用干湿相转化法、低温溶剂结晶法、静电纺丝法制备适用于高镁锂比（大于400）浓缩卤水提锂的LIS复合吸附剂。研究了Li1.6Mn1.6O4离子筛前驱体形貌、高分子基质亲疏水性和功能基团改性对LIS负载、负载稳固性、复合吸附剂结构、锂吸附性能和循环稳定性的影响。基于LIS-EVOH中空纤维膜复合吸附剂，开发了膜吸附耦合技术和吸附-解吸动态循环膜设备。主要成果如下：（1）LIS形貌对其结构（比表面积、孔体积、孔隙率）、锂吸附选择性、锂传质和循环稳定性有明显影响。高比表面积LIS提供了更多的锂吸附位点，高孔隙率LIS降低了Li+在晶相内和复合吸附剂中的传质阻力，但不稳定的晶体结构和低价态锰的存在降低LIS的循环稳定性。（2）LIS为亲水性物质，适宜亲水性高分子基质与LIS的界面作用力较好，可以提高LIS负载量、在基质中分散均匀性和负载稳固性；适宜亲水性的高分子基质在复合成型过程形成好的孔结构、高的孔隙率和LIS暴漏率；适宜亲水性高分子基质利于锂液传质、Li+与LIS吸附位点的充分接触，从而明显提高锂吸附性能、吸附速率和吸附-解吸循环稳定性。研究确定了乙烯基含量为38%的EVOH是合适的LIS负载基质。（3）设计制备了中空纤维膜吸附-解吸动态提锂装置，系统研究了LIS-EVOH中空纤维膜膜组件结构（组件长度、膜丝填充量）、进料（解吸液）流量、进料液锂浓度（解吸液浓度）等因素对吸附解吸锂性能、膜吸附解吸穿透曲线、溶液用量，循环稳定性的影响，确定了膜吸附解吸工艺条件，并初步建立了简化毛细管传质模型。其中LIS复合吸附剂设计制备方法，膜吸附耦合技术为从复杂卤水体系高效、环保提锂的工业化应用提供了科学依据和理论支持。