基于离子液体萃取体系宏观超分子组装的锶分离

    Strontium Extraction Based on Macroscopic Supramolecular Assembly in Ionic Liquid System

    • 摘要: Sr的分离在放射性资源的回收利用领域有着重要意义。离子液体萃取Sr的体系得到了极大的拓展,但是很难实现Sr、Cs之间的完全分离。放射性废液的问题也关系着离子液体体系在乏燃料后处理领域的应用。本工作研究了Sr在离子液体萃取体系中的界面宏观超分子组装,并开展了其在锶铯分离领域的应用基础研究。首先发现并研究了Sr2+在离子液体萃取体系中界面上的宏观超分子组装(MSA)行为,可实现宏观超分子组装的离子液体为CnOHmimNTf2(n=2、3),萃取剂为正辛基苯基-N,N-二异丁基胺基甲酰基甲基氧化膦(CMPO)和N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)。通过质谱、核磁、红外、理论计算等方法分析了Sr宏观超分子组装体(Sr-MSA)的结构,提出了形成Sr-MSA过程的三级组装机理,即Sr2+与CMPO配体形成配合物并与C2OHmim+发生阳离子交换,进入离子液体相;配合物通过相互间的静电吸引、氢键、疏水作用、长碳链等非共价作用形成纳米尺度组装体,并可生长至介观;介观组装体逐渐转移至界面并进一步生长至宏观尺度的中间体;多个宏观中间体在Marangoni效应产生的界面牵引作用下发生MSA,最终组装为单个Sr-MSA。最后,开发了Sr的选择性分离方法,成功实现了水溶液中Sr2+的一步法选择性提取和固化。形成的Sr-MSA可用镊子夹出从而简单实现Sr2+从水溶液中的选择性分离。该法在高酸度环境下仍可适用,在高酸度场景如乏燃料后处理中有潜在应用价值。

       

      Abstract: The separation of strontium is important in the recovery of radioactive resources. Ionic liquids(ILs) based extraction systems of Sr have been greatly expanded, but the separation of Sr and Cs remains a problem. In addition, the problem of radioactive waste affects the application of IL systems in the field of spent fuel reprocessing. In this work, the macroscopic supramolecular assembly(MSA) of strontium at the interface of IL extraction systems and its basic research on the extraction of Sr were reported. The MSA behavior of Sr2+ in ionic liquid based extraction systems was studied and the structure of Sr-MSA was analyzed by mass spectrometry, 13C NMR, infrared spectroscopy and theoretical calculation. Sr-MSA was formed by using CnOHmimNTf2 (n=2, 3) as the ILs and CMPO, TODGA as the extractants. The three-step mechanism of MSA process is proposed: complexes formed by Sr2+ and CMPO are extracted to IL phase. The complexes and IL assemble into nanoparticles driven by non-covalent interactions such as electrostatic attraction, hydrogen, hydrophobic interaction. The nanoparticles aggregate into mesoscopic assemblies. The mesoscopic assemblies move to the interface and grow further into macroscopic intermediates. The intermediates finally generate into Sr-MSA under the traction from Marangoni effect. A new method for the selective extraction and one-step solidification of Sr2+ from aqueous solutions was developed. The Sr-MSA can be taken out with tweezers easily from aqueous solution. The method can still be used in high acidity environment.

       

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