相邻稀土元素镨钕“推拉”萃取动力学分离的界面机理研究

It is difficult for the separation of adjacent rare-earth elements praseodymium and neodymium. Only depending on discrepancy in thermodynamic properties of the complexation stability of organic extractant molecules with rare earth ions, the separation selectivity is poor and efficiency is low. "Push-pull" extraction is an effective method to increase the separation coefficients of adjacent rare-earth elements praseodymium and neodymium. However, the mechanism of the push-pull effect on enhancing the separation of adjacent rare earths, especially the essential reason of "push-pull" extraction and kinetic separation, are still unclear. In this project, from the interfacial molecular level of extraction and kinetics separation process, the stirring method and oil film flatting method are adopted to investigate the regulation rules of "push-pull" extraction and kinetic separation of praseodymium and neodymium, related with the information of interfacial molecular behaviors. By the interfacial spectral characterization, associated with the molecular dynamics simulation, the root cause of discrepancy in separation factors of adjacent rare-earth elements is revealed, during the whole process of extraction and complexation reaction between organic extractant molecules, water soluble complexing agent and rare-earth ions. The interfacial mechanism of "push-pull" extraction and kinetic separation of adjacent rare-earth elements is put forward, laying the foundation for developing the new method of enhanced separation adjacent rare-earth elements with similar properties.

相邻稀土元素镨和钕的分离十分困难，仅仅依靠有机萃取剂分子与稀土离子络合稳定性的热力学性质差异，分离选择性差，且分离效率低。“推拉”萃取是拉大相邻稀土镨、钕分离系数的有效方法。然而，对强化相邻稀土分离的推拉效应产生机制，特别是“推拉”萃取动力学分离的本质原因尚不清楚。本项目拟从萃取动力学分离过程的界面分子层次出发，采用搅拌法和平铺油膜法考察镨钕“推拉”萃取动力学分离与界面分子行为有关的调控规律。通过界面光谱表征，配合分子动力学模拟，揭示有机萃取剂分子、水溶性络合剂、稀土离子等发生萃取络合反应的整个历程中，导致相邻稀土元素分离系数差异的根本原因，提出相邻稀土“推拉”萃取动力学分离的界面机理，为发展强化分离性质相似的相邻稀土元素新方法奠定基础。

相邻稀土元素镨和钕的分离十分困难，仅仅依靠有机萃取剂分子与稀土离子络合稳定性的热力学性质差异，分离选择性差，且分离效率低。“推拉”萃取是拉大相邻稀土镨、钕分离系数的有效方法。然而，对强化相邻稀土分离的“推拉”效应产生机制，特别是“推拉”萃取动力学分离的本质原因尚不清楚。本项目采用薄层油膜萃取法，与传统搅拌法对比，研究相邻稀土镨、钕动力学分离的调控规律，盐析诱导动力学强化分离相邻稀土镨钕的界面行为研究，以及“推拉”效应强化镨钕动力学分离行为及机理，发现Pr3+和Nd3+离子的分离系数可达10以上，油膜层厚度及料液流速调控分离行为，且盐阴离子增强Pr3+/Nd3+分离能力的顺序为SCN->NO3->Cl-，阳离子Li+离子的盐析效应比Na+离子更明显，Pr3+和Nd3+离子的分离行为直接受其扩散传质速率的影响。此外，分析Pr3+、Nd3+与[A336][NO3]、DTPA络合行为的微弱差异，探明了它们之间竞争配位作用产生的机制。通过界面光谱表征，配合分子动力学模拟，揭示有机萃取剂分子、水溶性络合剂、稀土离子等发生萃取络合反应的整个历程中，界面吸附行为的差异是导致相邻稀土元素分离系数差异的根本原因，提出相邻稀土“推拉”萃取动力学分离的界面微观机理。本研究可望将“推拉”萃取动力学分离方法应用到其他稀土元素分离中，为开发一些物理化学性质极其相似的目标元素的强化提取和分离方法做出贡献，也为开发高效、绿色分离相邻稀土的新方法、实现稀土资源清洁高效利用提供了理论指导，也可以应用于具有挑战性的物理和化学性质极为相似的的金属离子回收与分离其他相关领域。