自电再生式电控离子交换系统的构建与一步提取卤水中锂和溴过程中多尺度界面传质

To effectively extract low concentrations of lithium and bromine from saline lake or sea brine, a green, low-cost and one-step process based on electrically switched ion exchange (ESIX) technique with self-electrical energy recuperation ability was proposed, in which the potential difference between the oxidation-reduction of the two electroactive materials for selective adsorptions of lithium and bromine ions acts as the driving force to proceed the reactions as well as ion moving. Especially, this process can generate electrical energy during the extractions of lithium and bromine ions, achieving self-electrical energy recuperation. This is one of the key features of this proposal. The novel imprinted lithium ESIX material will be fabricated by hybriding co-polymer composite of amino crown ethers and anilines with manganese oxide while the novel bromine ESIX material will be obtained by inserting hybrid composites of polypyrrole and cobaltocene into two-dimensional bismuth bromide interlayers. Herein, the microstructure with ion-exchange functional units will be designed based on the special binding forces between the target ion and organic ligands, the migration of group active sites in the metastable process and hydrogen bond on the surface. The enhanced memory of imprinted passage, selectivity, ion exchange capacity and stability of the obtained materials and heterointerfaces will be improved by tuning the target ionic ligand and creating novel polymerization technique. Furthermore, in this proposal, the principle for precise fabrication of ion exchange unit, the mechanism of ESIX heavy metal ions, the multiscale coupling mass transfer mechanism in the electrode/electric double layer/flow-field multi-scale system, and the unit energy consumption in the system will be investigated in details and an effective dynamic model will be constructed and applied for the process optimization. The obtained know-how is expected to be a theoretical basis for the scale-up of such a novel process in the practical application.

为实现绿色、经济、高效的从盐湖或海水卤水中提取低浓度的锂和溴，本项目提出了自电再生式电控离子交换系统一步提取锂和溴离子的新工艺。以电活性锂、溴离子交换材料的氧化/还原电势差为推动力，通过自发反应提取锂和溴离子并放出电能，实现能量循环利用。采用氧化锰表面包覆氨基冠醚与苯胺共聚物制备印迹型锂离子交换材料，以二维溴氧铋层间插入聚吡咯和二茂钴的杂化体系制备配位型溴离子交换材料，分别获得高选择电位响应型性锂、溴离子交换材料。基于亚稳定络合过程中基团活性位点的迁移、氢键转移及目标离子与有机配体的相互作用特点，对材料和异质界面的微结构进行精密调控和优化，来增强印迹孔道的记忆并提高材料的选择性、离子交换容量和稳定性。重点研究电活性离子交换基元微结构的精密构筑原理、电控离子交换机理、电极内部-双电层-流场间的多尺度界面耦合传质机制及系统单位能耗，并构建有效的数学模型，为新工艺的工业应用提供理论依据。

传统盐湖卤水提锂（溴）的工艺技术主要包括沉淀法、萃取法、吸附法、纳滤和电化学法等，这些技术始终存在处理能力低、处理速率慢和易产生二次污染等缺点，都难以满足锂（溴）资源回收的技术和经济要求。为克服传统盐湖卤水提锂（溴）工艺的缺点，打破技术瓶颈，实现盐湖卤水中低浓度锂（溴）离子的经济、高效、绿色提取，本项目设计开发了自电再生式电控离子交换（ESIX）系统一步提取锂和溴离子的新工艺，并设计制备了具有较宽氧化还原电势差窗口的印迹型λ-MnO2锂离子交换材料，以二维溴氧铋层间插入聚吡咯杂化体系制备了配位型溴离子交换材料，分别获得系列高选择电位响应型性锂、溴离子交换纳米功能材料。同时，基于亚稳定络合过程中基团活性位点的迁移、电子转移及目标离子与无机-有机配体的相互作用特点，通过精密调控和优化材料以及异质界面的微结构增强了印迹孔道的记忆效应并提高了材料的选择性、离子交换容量和稳定性。通过原位电化学测试技术、先进材料表征以及密度泛函理论计算方法研究了电活性离子交换基元微结构的精密构筑原理、电控离子交换机理、电极内部-双电层-流场间的多尺度界面耦合传质机制及系统单位能耗，并构建了有效的数学模型。结果表明，在离子提取过程中，由于锂（溴）的嵌入，两电极间固有的电位差被平衡，同时引发了电能的产生，所产生的电能被自动存储并在离子释放过程中提供锂（溴）的解吸所需的能量，该自电再生ESIX体系具有极低的能耗和良好的选择性，证明了电活性锂、溴离子交换材料的氧化/还原电势差能够作为推动力，通过自发反应提取锂和溴离子并放出电能，实现能量循环利用。此外，随着膜电极间电势差的不断增大，锂（溴）提取效率不断提高，而且在溶液置换过程中系统没有产生或消耗能量。因此，该自电再生式ESIX系统不仅具有优良的锂（溴）提取性能，并且能耗远低于其它技术，为新工艺的工业应用提供了理论依据以及积累了丰富的经验。