Demonstration of a continuous counter-current extraction process based on a non-heterocyclic N-donor ligand NTAamide(n-Oct) for trivalent actinides/lanthanides separation

Abstract

To achieve the effective separation of trivalent lanthanides and actinides, a novel NTAAMIDE process based on a non-heterocyclic N-donor NTAamide(n-Oct) extraction system has been developed. It was shown that NTAamide(n-Oct) could extract Am3+ and Eu3+ rapidly to achieve equilibrium within 10 min and has a large loading capacity of 0.75 mol Eu3+/mol NTAamide(n-Oct) in pH = 3.0 HNO3 solution. Meanwhile, relatively high nitrate concentration and low temperature are beneficial for increasing the distribution ratios of metal ions. Further back extraction experiment indicated that both 3.00 mol/L HNO3 and 0.50 mol/L glycollic acid with pH = 4.0 HNO3 could quantitative strip Am3+ and Eu3+ at three stages, while 5 mmol/L TEE-BisDGA was able to selective strip Eu3+. In addition, total organic carbon analysis, FT-IR, 1H NMR, ESI-MS, and extraction measurements revealed that NTAamide(n-Oct) with extremely low solubility in the aqueous phase showed outstanding acid tolerance and irradiation stability. Finally, an enlarged bench test performed by mixer-settler enabled isolating 96.13% Am3+ from macro amount of rare earth elements with decontamination factor of Am3+/Eu3+ as 1320, demonstrating good application prospect for the NTAAMIDE process in the areas of An3+/Ln3+ separation.