Huang Pin-Wen, Wang Cong-Zhi, Wu Qun-Yan, Lan Jian-Hui, Song Gang, Chai Zhi-Fang, Shi Wei-Qun
Zhejiang University of Water Resources and Electric Power, Hangzhou 310018, China.
Dalton Trans. 2018 Apr 17;47(15):5474-5482. doi: 10.1039/c8dt00134k.
In recent years, there has been a trend to use synergistic systems of neutral and acidic extractants into a single-solvent formulation to achieve Ln3+/An3+ extraction and separation via simplified processing schemes. In this study, geometrical structures, bonding nature, and thermodynamic stabilities of a series of possible extraction complexes of Am3+ and Eu3+ with two neutral-acid synergistic systems (CMPO-HDEHP and CMPO-HEH[EHP]) were theoretically studied using scalar-relativistic density functional theory (DFT). It is found that hydrogen bonds between neutral and acid ligands may greatly influence the Eu3+/Am3+ extraction and separation performance of the two synergistic systems. According to natural bond orbital (NBO) and energy decomposition analyses (EDA), the phosphoryl oxygen atoms of HDEHP or HEH[EHP] have higher affinity for Eu3+ and Am3+ than those of the CMPO ligand. Since weak but different extents of covalency exist in Eu- and Am-complexes, Eu3+/Am3+ separation via these two systems may be attributed to the different compositions of interactions between the metal ions and ligands. Thermodynamic analysis shows that the neutral complexes ML(NO3)2 (M = Eu and Am; L = [CMPO-DEHP]- and [CMPO-EH[EHP]]-) appear to be the most probable species in the complexation process.
近年来，出现了一种将中性和酸性萃取剂的协同体系用于单一溶剂配方的趋势，以便通过简化的工艺方案实现Ln3+/An3+的萃取和分离。在本研究中，使用标量相对论密度泛函理论（DFT）对一系列可能的Am3+和Eu3+与两种中性-酸性协同体系（CMPO-HDEHP和CMPO-HEH[EHP]）形成的萃取配合物的几何结构、键合性质和热力学稳定性进行了理论研究。结果发现，中性和酸性配体之间的氢键可能会极大地影响这两种协同体系的Eu3+/Am3+萃取和分离性能。根据自然键轨道（NBO）和能量分解分析（EDA），HDEHP或HEH[EHP]的磷酰氧原子对Eu3+和Am3+的亲和力高于CMPO配体的磷酰氧原子。由于Eu-和Am-配合物中存在弱但程度不同的共价性，通过这两种体系进行Eu3+/Am3+分离可能归因于金属离子与配体之间相互作用的不同组成。热力学分析表明，中性配合物ML(NO3)2（M = Eu和Am；L = [CMPO-DEHP]-和[CMPO-EH[EHP]]-）似乎是络合过程中最可能的物种。
