联萘酚-离子液体螯合缔合萃取分离锂同位素的研究

The separation of lithium isotopes is critical to the future civil nuclear energy development, and also puts forward higher requirements for separation coefficient, and environment friendly character, process flow and so on. This project proposed the new system of lithium isotopes separation by chelation-association extraction using binaphthol and ionic liquid. To improve the efficiency of the separation of lithium isotopes, the project will mainly focus on three aspects. Firstly, from the chelating agent synthesis and structure-properties relationship, the bonding lithium ability to lithium and hydrophobic performance of the article chelating agents will be improved, and the best chelating agents with high separation ability will be screened out. Secondly, by reducing the viscosity and water-soluble ability of the ionic liquid, different types of ionic liquids as the association and diluent on the lithium isotope separation performance will be studied, and the best chelate complex system will be found. Through depth study of the structures of the extracted species, the lithium isotope separation mechanism will be futher explored. Finally, through the establishment of the whole process of countercurrent cascade experimental model, the separation processes of industrial closure process parameters will be studied. This project will not only provide a theoretical basis for the large-scale, highly efficient separation of lithium isotopes, solve the problems of inefficiency and environmental pollution in the separation process, while promote our country's extraction separation of lithium isotopes into the international forefront, and promote international exchanges and cultivation of talents.

锂同位素分离对未来民用核能的发展至关重要，也对分离方法在分离系数、环境友好、工艺流程等方面提出了更高的要求。本项目提出基于联萘酚-离子液体螯合缔合协同萃取分离锂同位素的新体系，项目主要从三个方面研究如何提高锂同位素分离的效率：首先从螯合剂的设计合成和构效关系入手，着重改善螯合剂对锂的键合能力和疏水性能，研究并筛选出对锂同位素具有较高分离能力的螯合剂；其次通过降低离子液体的黏度和水溶性，研究不同种类的离子液体作为缔合剂和稀释剂对锂同位素分离性能的影响，筛选出最佳的螯合缔合体系，通过深入研究萃合物的结构进一步探索锂同位素分离的机理；最后通过建立逆流串级全流程实验模型，通过模型分析为工业闭合分离过程提供工艺参数。项目的研究不仅可为国家大规模、高效率分离锂同位素提供理论依据，解决分离过程中低效和环境污染等问题，同时推动我国萃取分离锂同位素进入国际前沿，促进国际交流和人才培养。

高效绿色分离锂同位素迄今仍是国际难题。项目针对锂同位素分离的低效和环境污染等问题，通过分子设计筛选螯合剂和离子液体，构建了萃取分离锂同位素的新体系。（1）建立了以2,2'-联萘-17-冠-5为萃取剂、咪唑基离子液体为萃取溶剂的液-液萃取分离锂同位素体系。从冠醚浓度、锂盐浓度、锂盐种类、初始pH、萃取温度和萃取时间等方面对液液萃取分离锂同位素的萃取能力、动力学及热力学行为进行了考察。研究表明，轻同位素6Li富集于离子液体相，而重同位素7Li富集于水相, 6Li/7Li最大单级分离系数达到1.046。（2）建立了物理负载联萘冠醚-离子液体复合材料固-液萃取分离锂同位素体系。通过溶胶-凝胶法和直接浸渍法两种物理负载以及化学键合负载离子液体的方法，制备了一系列含有离子液体的固体吸附剂进行固-液萃取分离锂同位素，进一步优化了联萘冠醚/离子液体萃取分离锂同位素体系的稳定性和分离效率。研究表明6Li富集于固体相， 7Li富集于水相，最大萃取率为15.86%，最大单级分离系数为1.048。利用X射线-单晶衍射捕获到了萃取络合物的晶体结构，阐明了固-液萃取分离的锂同位素机理。（3）建立了钙钛矿型无机离子交换剂分离锂同位素体系。基于钙钛矿型钛酸镧锂前驱体，氢化得到无机离子交换剂，探究了其离子交换性能及锂同位素分离能力， 6Li+富集于交换剂相而7Li+富集在液相，最大单级分离系数为1.045，优于已报道的无机离子交换体系。综上，项目研究推动了我国锂同位素分离的发展，为绿色环保高效率分离锂同位素提供了新的理论依据。