Promising Lipophilic PyTri Extractant for Selective Trivalent Actinide Separation from High Active Raffinate

Abstract

Within a spent nuclear fuel recycling strategy, in the past few years, the pyridine-bis-triazole unit was found to be rather effective and selective in minor actinide (MA) separation from synthetic high active raffinate (HAR). In this research work, the main features of the recently studied PTEH ligand were investigated in order to evaluate its potentialities in SANEX-like processes. Its applicability in advanced separation processes was demonstrated, even at process temperatures. It manifested satisfactory extraction properties for a successful selective An separation from Ln, easy cation release, and adequate extraction kinetics as well as outstanding hydrolytical and radiolytical stability. All the results collected in this work allowed the scientists on the committee of the H2020 GENIORS project to promote PTEH as a concrete alternative to the reference CyMe4-BTBP ligand.

Insights into the Complexation Mechanism of a Promising Lipophilic PyTri Ligand for Actinide Partitioning from Spent Nuclear Fuel

“…Following these experimental activities, a difference of 2 orders of magnitude between the stability constants of the [Cm­(PTEH) 3 ] 3+ and [Eu­(PTEH) 3 ] 3+ complex species was observed. This yields a theoretical separation factor = 126 ± 4, in good agreement with the SF Cm(III)/Eu(III) ∼ 140 obtained in extraction experiments …”

“…16−18 In particular, the lipophilic 2,6-bis(1-(2-ethylhexyl)-1H-1,2,3-triazol-4-yl)pyridine (PyTri-Ethyl-Hexyl�PTEH) ligand proved to be an excellent candidate for the SANEX-like processes (Figure 1, top right), endowed with a good solubility in the mixtures of organic diluents used, a satisfactory extraction efficiency, a remarkable An selectivity, a fast extraction kinetics and a good radiochemical stability. 19,20 Given this promising experimental evidence and the prospective of an industrial application of such a PyTri family, the complexation behavior of the PTEH ligand has been investigated in details in the present work by means of different techniques. Indeed, fundamental studies on the complexation properties, together with the better understanding of the molecular reason for their remarkable selectivity, are paramount for the systematic improvement of such extracting agents toward the industrial application.…”

“…Following these experimental activities, a difference of 2 orders of magnitude between the stability constants of the [Cm(PTEH) 3 ] 3+ and [Eu(PTEH) 3 ] 3+ complex species was observed. This yields a theoretical separation factor SF Cm(III)/Eu(III) 20 Extraction Tests. To determine the stoichiometry of the Cm(III) and Eu(III) complexes involved in the extraction process, TRLFS analysis was performed on organic phases from extraction experiments.…”

“…Besides the widely investigated BTP, BTBP, and BTPhen ligands (Figure , bottom), recently, the pyridine-bistriazole (PyTri) chelating unit (Figure , top left) was found to be similarly promising for the selective An­(III) separation under SANEX conditions. − In particular, the lipophilic 2,6-bis­(1-(2-ethylhexyl)-1H-1,2,3-triazol-4-yl)­pyridine (PyTri-Ethyl-HexylPTEH) ligand proved to be an excellent candidate for the SANEX-like processes (Figure , top right), endowed with a good solubility in the mixtures of organic diluents used, a satisfactory extraction efficiency, a remarkable An selectivity, a fast extraction kinetics and a good radiochemical stability. , …”

“… 16 − 18 In particular, the lipophilic 2,6-bis(1-(2-ethylhexyl)-1H-1,2,3-triazol-4-yl)pyridine (PyTri-Ethyl-Hexyl—PTEH) ligand proved to be an excellent candidate for the SANEX-like processes ( Figure 1 , top right), endowed with a good solubility in the mixtures of organic diluents used, a satisfactory extraction efficiency, a remarkable An selectivity, a fast extraction kinetics and a good radiochemical stability. 19 , 20 …”