采用功能化冠醚实现极低浓度溶液中稀土高效识别与异步分离的机理研究

At present, there are still some unsolved problems such as poor selectivity, low recovery and organic pollution in the process of rare earth enrichment and separation from low concentration solution. Based on the principle of molecular recognition, the macro-cyclic functional crown ether grafted silicone resin will be prepared to achieve efficient recognition and asynchronous extraction of rare earth at extremely low concentration in complex solution. The recognition mechanism of 4NP-18C6 on light rare earth ions as well as 2N-15C5 on heavy rare earth ions and the synergistic coordination effect of side-arm group will be revealed by investigation on the coordination mechanism of functional crown with RE3+ and impurity ions. The adsorption behavior of 4NP- 18C6@SiO2 and 2N-15C5@SiO2 to RE3+ in complex solution system will be carried out to clarify the thermodynamics and kinetics of the adsorption process, meanwhile, the variety of functional crown structure during adsorption will be investigated. The results of above researches will reveal the selective adsorption mechanism of RE3+ and provide a theoretical basis for rare earth recovery from extremely low concentration solution. The successful realization of this project will bring great practical significance and scientific value for alleviating rare earth resource crisis，promotion the comprehensive utilization of rare earth resources and enriching the basis theory of rare earth organic complexes.

目前从极低浓度溶液中富集分离稀土的工艺技术尚存在选择性差、回收率低、工艺欠环保等问题。本项目基于分子识别原理，拟采用大环功能化冠醚来实现极低浓度溶液中稀土元素的高效识别与异步分离。通过对功能化冠醚与RE3+/杂质离子的配位机理研究，揭示4NP-18C6与轻稀土离子和2N-15C5与中重稀土离子的选择性识别机理；开展复杂体系下，4NP-18C6@SiO2和2N-15C5@SiO2吸附剂对RE3+的吸附行为研究，阐明吸附热力学与动力学，并结合冠醚的结构演变规律，揭示稀土离子的选择性吸附与异步分离机制，从而为从极低浓度溶液中直接富集分离稀土提供理论基础。本项目的成功实施，对于缓解日趋严重的稀土战略资源危机、开发稀土资源的高效综合利用技术和丰富稀土有机配位化学理论，具有重要的指导意义与科学价值。

功能化冠醚可用于从复杂溶液体系中选择性识别分离有价金属离子。基于密度泛函理论的反应性描述结果表明，1,7-二氮杂-15冠5醚的环上N、O原子和3个游离水分子的O原子参与稀土离子的亲核反应，形成RE：冠醚：H2O=1：1：3的8配位化合物；基于两相滴定测试结果表明，稀土冠醚配合物的稳定性受金属离子半径大小、有机溶剂极性、水相平衡阴离子种类的影响，萃合物稳定常数随着稀土原子序数的增大呈现逐渐降低得趋势，并体现出轻、中、重稀土的分组效应。直接溶剂萃取的结果表明，氮杂冠醚可从复杂硫酸体系中选择性萃取分离轻稀土离子，采用EDTA或草酸溶液反萃可得到高纯稀土化合物；将氮杂冠醚负载到硅胶树脂上制得的冠醚吸附剂，可从极低浓度稀土溶液中选择性吸附分离轻稀土离子，特别是对镧表现出较强的化学吸附分离能力，最大饱和吸附容量22-23mg·g-1，负载树脂上的稀土可采用EDTA溶液进行解吸回收。上述研究结果，对稀土冠醚有机配合物化学基础数据进行了补充，对于硫酸体系中轻稀土离子的选择性回收与痕量稀土离子分离检测新方法的建立具有重要指导意义。