面向盐湖卤水锂离子提取的耐溶剂、嵌段高分子膜萃取膜材料的结构和性能调控研究

We aim to develop a novel solvent resistant, high lithium ion flux block copolymer based membrane material for the extraction of lithium ions from the salt lake brine with high magnesium/lithium ratio. The main target is to unravel the relationship between the membrane porous structure and the ion diffusion performance in the membrane extraction process. Based on ethylene vinyl alcohol block copolymer (EVAL), immersion precipitation technology will be selected for membrane preparation. Due to the high flexibility, the meso-scale demixing of the hydrophilic and hydrophobic chains of EVAL will be investigated in relating to the macro-scale liquid-liquid/solid-liquid phase separation; the phase separation thermodynamic and kinetic behaviors of EVAL solution will be analyzed. The porous structure will be analyzed and pore formation mechanism will be described. To increase the lithium ion diffusion rate, sulfonated EVAL will be synthesized; sulfonated polyether ether ketone and sulfonated graphene oxide (SGO) will be added into EVAL. Effect of the anion charges in the membrane porous structure will be related to the lithium ion diffusion rate. Special focus will be the effect of two dimensional SGO on the membrane structure and performance of the membrane for lithium ion diffusion in membrane extraction. The transport model of lithium based on a stable operation will be used for comparing the mass transport resistant of the membrane in relating to the extraction reaction and external concentration polarization. The results and fundamental understanding in this proposal will result in a smart solution to the lithium extraction from salt lake brine of high Mg/Li ratio, leading to a breakthrough in production of high purity lithium salt and provide solid theoretical and technical basis for highly efficient exploitation of the resources from The Salt Lake of Qinghai.

项目以高镁锂比青海盐湖卤水锂离子提取为目标，以TBP/煤油为萃取体系，针对新型锂离子膜萃取提取技术的核心耐溶剂膜材料材料，研究嵌段高分子膜结构的调控与锂离子扩散性能之间定量关系。以聚乙烯-乙烯醇（EVAL）共聚物为核心材料，采用浸没沉淀法，通过高分子溶液微观分析、相分离热力学和动力学等手段，研究亲水-疏水柔性链段在成膜过程中介观（链段尺度）和宏观（液-液和液-固相分离）的相互关联, 为调控孔结构提供理论依据；通过将EVAL磺化、EVAL与磺化聚醚醚酮、二维磺化氧化石墨烯材料杂化，研究均匀荷负电膜和有机-无机杂化二维荷负电纳米材料对膜结构、离子扩散的影响机制；建立稳态传质模型，定量分析膜萃取过程锂离子在膜材料中扩散对传质过程的影响，提供量化扩散阻力的工具。项目研究将为高镁锂比青海盐湖卤水中锂离子提取提供低能耗、高效率的膜技术，为突破青海盐湖卤水锂提取的世界性难题提供新的思路和技术。

本项目以高镁锂比盐湖卤水锂离子提取为目标，NaFeCl4*2TBP为萃取体系，对新型环境友好的膜萃取提锂技术的核心耐溶剂膜材料进行优化研究，探索研究嵌段高分子膜结构的调控与锂离子扩散性能之间的关键科学问题。项目研究工作以聚乙烯-乙烯醇（EVAL）共聚物为核心材料，采用浸没沉淀法，通过高分子溶液微观分析、相分离热力学和动力学，研究亲水-疏水柔性链段在成膜过程中微观（链段尺度）和宏观（液-液和液-固）两种相分离机理的相互关联, 发现乙烯基、材料结晶温度对膜材料孔结构、结晶度以及传质性能等的影响规律，为调控孔结构提供理论依据；研究工作合成了磺化EVAL，磺化聚醚醚酮，磺化氧化石墨烯，并通过将EVAL磺化、磺化聚醚醚酮与EVAL进行共混制备膜材料以及与二维磺化氧化石墨烯杂化，研究表明荷负电基团的引入对膜材料结构具有明显的影响，并且有利于离子扩散的影响；此外，研究工作还对膜传质过程进行了定量分析，提供量化了锂离子的传质阻力。本项目研究成果将为高镁锂比卤水锂提取提供新的低能耗、高效率的膜技术，为膜萃取设备提供核心的膜材料，为下一步膜萃取在盐湖卤水锂提取的应用提供了基础。