Application of Complex-Forming Reaction to Separation of Rare Earth element by Ionic Exchanger

为了提高稀土金属离子在溶剂萃取过程中的分离效果，研究了在水相中加入络合剂对Ce、Pr、Nd的分离效果。萃取剂为D2EHPA(二(2-乙基己基亚磷酸)和HEH(EHP)(2-乙基己基膦酸氢))，并在水相中加入螯合剂DTPA(二乙基三胺五乙酸酯)。在D2EHPA体系中，萃取剂的存在对萃取剂的影响很小，可能是由于D2EHPA与金属离子之间存在较强的亲和力所致。稀土金属离子在水相中形成DTPA络合物，显著地促进了HEH(EHP)溶剂萃取液中离子的分离。在较高pH条件下，Ce、Pr、Nd离子的萃取量按Ce、Pr、Nd的顺序依次增加，在较高的pH范围内，离子从水相向有机相的迁移受到不同程度的抑制；在水相中加入络合剂，使Ce、Pr、Nd离子在萃取平衡时相互分离，并向有机相迁移。

In order to improve the separation of rare earth metal ions in the solvent extraction, the addition of a chelating reagent in the aqueous phase was investigated for Ce, Pr, and Nd. The extractants considered in this work were D2EHPA (di(2-ethylhexyl phosphorous acid) and HEH (EHP) (2-ethylhexyl hydrogen 2-ethylhexyl phosphonate) and a chelating reagent DTPA (diethylene triamine pentaacetate) was added into the aqueous phase. In such systems the extraction is considered to be depending on the relative strength between complex-forming in aqueous phase and the combination of the ion with the extractant in the organic phase.In the extraction with D2EHPA, the extraction was onli slightly affected by the presence of the chelating reagent, DTPA over the whole range of pH probably due to strong affinity between D2EHPA and metal ions in question.The formation of DTPA complex of the rare earth metal ions in the aqueous phase significantly enhanced the separation of the ions in the solvent extraction using HEH (EHP). At higher pH, the extractoin of the ions was higher in the order of Ce, Pr and Nd and the separation was promoted in high pH range.Also in the transfer of the extracted ions from the aqueous phase to the organic was found to be suppressed to different extent according to the stability of the complex ions in the aqueous phase.The addition of chelating reagent in the aqueous phase was shown to be effective in mutual separation of Ce, Pr and Nd ions both in equilibrium of extraction and in the transfer of the ions into the organic phase.