原位氧化法构筑钛锂离子筛封装MXene用于电场辅助选择性吸附高镁锂比盐湖卤水中锂的研究

Lithium extraction from salt lake brine is an important approach for the production of lithium in the future. To selectively adsorb lithium from the salt lake brine with high Mg/Li ratio, in this proposal, titanium-based lithium ion sieves coated titanium-based MXene materials are engineer by in-situ oxidation of titanium-based MXene materials, and are further employed in electric field assisted lithium adsorption from salt lake brine with high Mg/Li ratio with high rate and excellent selectivity. By this strategy, lithium with high purity can be separated and concentrated. The adsorption capacities of the constructed materials can be rationally controlled by tuning the layers and interlayer distances of the pristine MXene materials. In addition, the thicknesses of lithium ion sieves also can be regulated by controlling the factors during the in-situ oxidation process. The structure-activity relationship between the structures of titanium lithium ion sieve encapsulated MXene and the selective adsorption performance and selectivity are determined by in-situ spectral characterization methods. The lithium ion migration mechanism driven by the electric field is studied as well. Moreover, the effects of the co-existed Mg2+, K+, Na+ are also considered. The lithium adsorption efficiency is also optimized by tuning the electric field strength and types of concentration solution, and a novel method of selective separation of lithium from salt lake brine with high Mg/Li ratio is formed. This proposal not only establishes a novel strategy for fabrication of titanium lithium ion sieve encapsulated MXene, but also provides a green and highly-efficient approach for selective separation of lithium from salt lake brine with high Mg/Li ratio.

盐湖卤水提锂是未来生产锂的重要途径。本项目针对国内盐湖卤水高镁锂比的特点，在高比表面积的钛系MXene的表层，通过原位氧化法构筑具有高锂选择性的钛锂离子筛封装层，耦合电场加速锂离子选择性吸附和分离，实现高纯度锂的富集。通过调控钛系MXene的层数和层间距，控制锂的吸附容量；通过控制原位氧化过程中的参数，调变钛锂离子筛封装层的厚度。通过原位谱学等表征方法研究钛锂离子筛封装MXene二维超薄材料与锂选择性和吸附容量之间的构效关系，研究电场驱动下锂的迁移和传递机制，考察钛锂离子筛封装MXene二维超薄材料在Mg2+、K+、Na+等金属离子共存时对锂吸附选择性的影响，调变电场强度及锂富集溶液的类型提升锂的提取效率，建立锂离子快速选择性分离的方法。该研究的开展，不仅提出构建新型钛锂离子筛封装MXene二维超薄材料的新方法，而且提供一种绿色、快速从高镁锂比盐湖卤水中提取高纯度锂的新思路。

本项目系统研究了钛酸锂在分离高镁锂比盐湖卤水中锂资源的应用。通过该课题的研究，构筑了一系列高性能提锂剂：以MXene为钛源，设计构筑了中空纳米球和多孔分级微球钛酸锂锂离子筛；采用溶胶-凝胶法耦合固相法构筑了表面润湿性可调控钛锂离子筛；通过引入Fe元素设计合成了可磁性分离的层状钛锂离子筛；通过表面活性剂的调控设计了锰酸锂锂离子筛用于电化学提锂。实现了对盐湖锂资源中锂的高选择性、高效回收的目标。本项目主要进行了以下几个方面的研究工作：.1. 以MXene为钛源，通过水热耦合高温构筑了纳米片自组装多孔分级微球钛锂离子筛、中空结构和分级微球结构，缩短了锂离子的传输路径、增加水溶液中的Li和离子筛表面接触、并促进Li-H之间的离子交换，理论吸附容量高达52.97 mg·g-1。.2. 通过溶胶-凝胶法耦合固相法构筑了润湿性可调控的钛锂离子筛，建立了不同晶相的TiO2与对应钛锂离子筛之间的润湿性及其锂吸附性能之间的规律。对沉锂母液中Li+的吸附容量达到30.11 mg·g-1，且在循环过程中Ti的溶损率始终低于0.31 wt%。.3. 通过引入Fe元素构筑了层状钛锂离子筛，建立了可磁性分离的吸附剂提锂体系，对锂的分配系数达到177.66，同时对Na+、K+和Mg2+的分离因子均大于1。提锂剂的解吸效率和吸附容量没有发生显著变化，同时Fe的溶损率随循环次数增加而逐渐降低，其溶损率维持在0.7%左右，具有优异的循环性能。.4. 建立了二维多孔圆片状锰酸锂锂离子筛电化学提锂方法，多孔结构促进了Li+扩散，平均扩散系数达到7.6×10-9 cm2∙s-1，并且在电化学提取盐湖卤水中锂的过程中表现出高选择性。进一步揭示了晶面对锂离子吸附性能的影响规律。结构优化后的提锂剂能够在保持高放电容量的同时具有高循环稳定性，建立的电化学提锂系统在放电2小时内对锂的提取量达到20.25 mg∙g-1。