高镁锂比卤水中硼酸根的“离子液体-醇类”协同萃取体系

Qinghai salt lake brines bear complex compositions featuring high magnesium and rich lithium and boron salts. Due to the interference of rich boron to extraction lithium and magnesium, so far only basic lithium and magnesium products are produced from those salt lakes. . A more applicable method for extraction boron from Qinghai salt lake brines is the traditional acidification-solvent extraction process. However, this process suffers from extracting agent loss dissolution and low extraction efficiency. Key solutions to these problems are the adoption of green and highly efficient solvents and highly efficient extraction equipment. Substantive research in centrifugal extraction has been conducted in recent years, but the extraction mechanism of ionic liquid systems in centrifugal extractors is still unknown. . The present study deals highly efficient boron extraction by acidification and centrifugal solvent extraction. The extraction mechanism of ionic liquid systems as well as strengthened solvent extraction with an external field will be investigated, aiming at reducing the usage and loss of organic solvents, minimizing environmental pollution by the volatilization of the solvents, insomuch as deep boron extraction from salt lake brines will be achieved in a highly efficient manner. . The successful implementation of this study may achieve the extraction mechanism and research achievement of ionic liquid and alcohol synergy extraction systems, resolve the issue of borate interference in the utilization of high value magnesium and lithium products, lead to theoretical and technological innovations in the comprehensive exploitation of salt lake magnesium, lithium and boron resources, and lay a foundation for highly efficient deep boron extraction from salt lake brines.

青海盐湖卤水有高镁富含锂、硼的特点，成份复杂。其中大量的硼对分离提取锂、镁产品有很大影响，现阶段青海盐湖只有初级锂、镁产品。 传统酸化-萃取联合分离提取硼酸在青海盐湖卤水中适应性更强。但存在醇类萃取剂溶损和提硼效率低的问题，绿色高效萃取体系的选择制备和高效萃取设备的应用是解决问题的关键和技术支持。课题组有离心萃取提硼的研究基础，但对离子液体萃取体系的萃取机理目前尚不明了。本项目设想以醇类和离子液体组成协同萃取体系，进行酸化后母液的离心萃取分离提取硼酸，对离子液体萃取体系在外场强化条件下进行深入机理、试验研究，以降低有机萃取介质的使用和损耗，减少因有机溶剂挥发而产生的环境污染，达到盐湖卤水高效深度提取硼酸之目的。本研究的实施将得到离子液体-醇类协萃体系的萃取机理和实验研究成果。实现盐湖卤水中硼的高效分离，解决硼的存在影响镁、锂高值化应用的关键科学问题，为盐湖卤水高效深度提取硼酸提供应用基础。

青海盐湖卤水普遍具有高镁富含锂、硼的特点，成份复杂。传统酸化-萃取联合分离提取硼酸在青海盐湖卤水中提硼中适应性强。但存在醇类萃取剂溶损和单级萃取率低的问题，绿色高效萃取体系的选择制备和高效萃取设备的应用是解决问题的关键。.本项目围绕这一关键问题开展研究，完成了“酸化沉淀－离心萃取-热溶结晶”分离提取硼的全流程试验；着重在传统的醇类/磺化煤油萃硼体系的改进优化方面做了大量的探索性工作，取得了一定的成果。.制备了双取代基咪唑类六氟磷酸盐离子液体，与异辛醇和磺化煤油组成萃取体系，研究了对酸化提硼母液中硼的分离萃取性能。虽然离子液体的加入没有起到预想的协萃作用，但是与传统异辛醇/磺化煤油萃取体系相比有机相的溶解损失减小了1/3。.建立了疏水性离子液体[P4,4,4,6][NTf2]/异辛醇/乙酸丁酯的萃取体系。所选用体系更适合高镁卤水中的硼、镁分离。[P4,4,4,6][NTf2]的加入也仅取代了部分有机溶剂，循环性能较好，对溶剂萃取法提取硼酸的过程稳定性具有一定指导意义。.构建了疏水性季鏻盐类离子液体Cyphos IL 104萃取体系。单独用CyphosIL104/甲苯对硼有一定的萃取能力， CyphosIL104/异辛醇萃取体系没有呈现出协同萃取的作用，但替代部分稀释剂，减少其用量。甲苯挥发性强，毒性大，难以推广。.重点选取了疏水性羟基功能化离子液体三种, [OHEtN1,1,1][NTf2]， [HOEMIm]NTf2，[HOEMMIm]NTf2。单独与稀释剂组成萃取体系时，离子液体阳离子上具有的羟基官能团与水相中硼酸分子之间发生了酯化反应，对硼都有一定的萃取能力，且硼萃取率随着羟基功能化离子液体体积分数的增大而增大，随水相pH的增大而减小，随着温度的降低而增大。.但是，与传统的醇类（一元醇、二元醇）萃取剂构建成“离子液体-醇类”萃取体系时，目前没有表现出有协同萃取的作用。一方面会降低传统醇类萃取体系的萃取效率，另一方面对萃取体系的稳定性和循环利用率有提高，二者之间要有综合平衡的考虑。另外在指导应用时，离子液体粘度高、价格贵，且相容性好、低挥发、疏水性的稀释剂的选择比较困难，在萃取工艺中的应用受到一定限制。