The diamide type extractants (N, DMDHOPDA, N, DHTPDA, and N, DHOPDA) were synthesized and tested for the extraction of the lanthanide and actinide elements. The elements, Eu3+, Am3+, Th4+, NpO2+ and U022+, when extracted by DMDHOPDA, showed no pH-dependence. The relationships between log[DMDHOPDA] and log D under different ionic strengths were investigated in order to clarify the extraction reactions. The separation factor for Eu3+/Am3+ is 8.64. KeywordsSolvent extraction, diamide, actinide element, separationStudy of the solvent extraction of lanthanide and actinide elements using monoamides and diamides has continued over the last 20 years. l-5 Daamides have several advantages in extraction, such as strong complexation and the ability to extract metal ion from low pH solutions. The extraction behavior of lanthanide and actinide elements3'5, the loading capacity of the extraction solvent3, the extraction reaction with water and anions6 and the extent of radiolytic degradation' have been studied for diamides of various structures.Previously, Stephan et al.8'9 and Yao et al.10 designed and synthesized ether type diamides, in which the oxygen or nitrogen is introduced into carbon chain connecting the amide groups. These studies focused on the extraction of divalent9 and trivalent10 metal ions with these diamides.In this research, N, N'-dimethyl-N, N'-dihexyl-3-oxapentanediamide, DMDHOPDA (CH3(CH6H13)NCOCH2-0-CH2CONCH3(C6H13)), and 2 analogous compounds (N, N'-dihexyl-3-thiopentanediamide, DHTPDA, and N, N'-dihexyl-3-oxapentanediamide, DHTPDA) were synthesized. These compounds offer the possibility of two or even three oxygen and/or sulfur donors that can be associated with the metal ion. The extraction of lanthanide and actinide elements was studied to test the separation value achieved by these diamides. The difficulty of separation of analogous 4f and 5f trivalent cations is well known and has attracted many researchers.lo-15 The separation of Eu and Am has been a focus in this study.In Fig. 1, the possible modes of complexation of these cations with the diamide are shown. In mode (A), the metal ion associates with two oxygen atoms of NC=O and NC=O to make an eight-membered ring. In (B) mode, it associates with two oxygen atoms of NC=O and CH2-0-CH2 to make a five-membered ring. While in mode (C), the metal ion associates with 3 oxygen atoms of two NC=O and CH2-0-CH2 to form 2 five-membered rings.
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