共萃剂作用下中性磷类溶剂从高镁锂比盐湖卤水中分离提取锂盐研究

Lithium is a strategic resource of the 21st century for social sustainable development. There are rich resources of salt lake brine in China, but the majority of them show the characteristics of high magnesium/lithium ratio. The separation of lithium and magnesium is an important technical problem unsolved yet in the salt lake brine, which relates to the development of lithium resources and the success or failure of extracting lithium..This project adopts new lipophilic anions as co-extraction reagent (perchlorate radical, thiocyanate radical, nitrate radical, etc) and neutral phosphorus extractants (tributyl phosphate, trioctyl phosphate, di-(1-methyl-heptyl) methyl phosphonate, trialkyl phosphine oxide, etc), and carries out the research of lithium and magnesium separation through reverse micelle in microemulsion phase of the high selective extraction of lithium ion. In the aspects of screening of extraction solvent, determination of optimal extraction-process scheme, kinetics of extraction process, thermodynamic properties, mechanism of extracting action, etc, systematic researches are developed, the structural essence of microemulsion extraction is elucidated, and their change laws of extractive effect-structure are revealed..In the project, atomic absorption spectrometer, nuclear magnetic resonance spectrometer, fluorescence probe, quick-freeze deep-etch electron microscopy, etc, are used to analyze and characterize the extraction process, the preparation methods of LiCl, LiClO4 and Li2CO3 are researched, influences of extractant and co-extraction reagent on environmental pollution are eliminated, and a solvent extraction method of the most promising industrialization is provided. This technology has the advantages of reasonable production economy, mild operating condition, small corrosion of equipment, reversed phase extraction with water, etc, being a new bright spot of study in this field.

锂是21世纪社会可持续发展的战略资源。我国盐湖卤水资源丰富，但大部分呈高镁锂比特征，在高镁锂比盐湖卤水中进行锂镁分离是一项尚未解决的重大技术难题，关系到锂盐资源的开发和提锂的成败。本项目采用新的亲油性阴离子作共萃剂(高氯酸根、硫氰酸根、硝酸根等)和中性磷类萃取剂(磷酸三丁酯、磷酸三辛酯、甲基膦酸二甲庚酯、三烷基氧膦等)，通过微乳相中反胶团对锂离子的高选择性萃取进行锂镁分离研究。在萃取溶剂筛选、最佳萃取工艺方案确定、萃取过程的动力学、热力学性质和萃取作用机理等方面开展系统研究，阐明微乳相萃取结构本质，揭示其萃效-结构变化规律。使用原子吸收光度计、核磁共振谱仪、荧光探针、速冻深蚀电子显微术等分析和表征萃取过程，研究LiCl、LiClO4、Li2CO3的制备方法，消除萃取剂和共萃剂对环境污染的影响，提供最有希望工业化的提锂方法。它具有生产经济性合理、操作条件温和等优点，是该领域中新的研究亮点。

随着锂离子电池在电动汽车、能量储存和3C产品上的广泛应用，锂盐需求量迅速增长，市场价格暴涨，这充分体现了我国盐湖锂资源开发的必要性和紧迫性。针对柴达木盆地盐湖老卤我们采用溶剂萃取法开展工作，详细研究了中性磷类溶剂在锂镁分离中的作用，与磷相连的烷基越多，其官能团磷酰氧P=O上的碱性越强，其顺序为(RO)3P=O<(RO)2RP=O<(RO)R2P=O<R3P=O，导致Li+、Mg2+与萃取剂结合力有所增强但选择性下降，用水从负载有机相中脱出程度亦降低。同类溶剂分子烷基越长萃取容量越小。. 对亲油性的阴离子共萃剂进行全面筛选评价，与其他阴离子比较高氯酸根具有良好的共萃作用，不需要酸性环境，能在中性或弱酸性条件下直接萃取卤水。用磷酸三丁酯(TBP)分别考察了Li+、Na+、Mg2+和Ca2+高氯酸盐的萃取行为和热力学萃取机理。在TBP和NaClO4共萃体系中，发现甲基异丁基酮和3,5-庚二酮对Li+的萃取呈现较好的正协同效应，而对Mg2+的萃取呈现相反的负协同效应。通过合成和萃取详细研究了磷酸三正戊酯和磷酸三异戊酯的锂镁分离行为。. 对实验中发现的固液萃取法提锂新途径进行了深入研究。用磷酸三烷酯或磷酸三烷酯和一元饱和醇混合溶剂萃取卤盐：(1)发现有机溶剂在不用共萃剂时对含锂卤盐仍有良好的萃取性能，打破了现有溶剂萃取法中必须使用共萃剂的认识；(2)发现低锂卤水浓缩结晶时，经过多个实验反复证明，确有相当部分锂盐富集于卤盐表层，这有利于使用有机溶剂进行萃取；(3)发现改用醇酯混合萃取剂后，固液萃取体系中Mg2+萃取率显著降低，镁锂质量比下降10倍以上。该项技术已经申请中国发明专利和PCT国际专利。. 使用AA-7000型原子吸收分光光度计分析实验过程中Li+含量，使用红外光谱、核磁共振谱、扫描电子显微镜和X-射线衍射谱表征了样品萃取前后的变化，用ESCALAB 250Xi 型X-射线光电子能谱仪测定了卤盐表层离子含量，特别是用JEM-2100型高分辨透射电子显微镜在萃取后负载有机相中直接观察到了不同大小和形状的微乳相结构，为深入理解萃取过程机理提供了有力证据。