Effects of structural variation of glycolamide extractants in the treatment of high-level waste solutions

The amide derivatives of diglycolic acid having long carbon chains, usually C8 or higher, have attracted the interest of separation chemists working for nuclear waste management applications since last 2-3 decades. a monoglycolamide ligand was identified as a better solvent having similar extraction properties as diglycolamide ligands. The stripping of extracted metal ions from monoglycolamide ligand was possible without the use of complexing agents and third phase splitting was prevented for this ligand due to its minimal aggregation. The structure of commonly used octyl derivative of diglycolamide ligand, N,N,N',N'-tetraoctyl diglycolamide (TODGA) and the corresponding monoglycolamide N,N-di-octyl-2-hydroxyacetamide (DOHyA) are shown in the article. The consequences of structural variation of glycolamide ligands on various aspects such as aggregation behavior and complexation behavior during the extraction of trivalent metal ions were studied in detail by a comparison of TODGA and DOHyA ligands. The better compatibility of DOHyA-Eu complex in the non-polar diluent, n-dodecane could be attributed to the improved hydrophilicity of DOHyA due to the presence of hydroxyl groups in DOHyA molecule. The properties of the diglycolamide TODGA was tuned in an effective way by changing to the simpler monoglycolamide structure and the studies showed the promising nature of the monoglycolamide derivative, DOHyA for solvent extraction of trivalent metal ions