Ligand structure and diluent nature in defining improved Am³⁺ and Cm³⁺ separation using diglycolamides: a combined solvent extraction and DFT study

Abstract

Combined effect of marginal Am3+ selectivity of T2EHDGA and Cm3+ selectivity of SO3PhBTP is exploited for the improvement in Am/Cm separation.

Remarkable Improvement in Am3+ and Cm3+ Separation Using a Cooperative Counter Selectivity Strategy by a Combination of Branched Diglycolamides and Hydrophilic Polyaza-heterocycles

“…Organic diluents have a significant effect on the extraction behavior of metal ions. , A number of organic diluents of varying polarity were chosen to study the Am 3+ and Cm 3+ separation from a 0.2 M HNO 3 medium containing 1 mM SO 3 PhBTPhen (Figure S1). TODGA and T2EHDGA were chosen as representative DGA derivatives for the diluent variation studies because of their higher solubility in a wide range of organic diluents as compared to other DGA derivatives having shorter alkyl chains. , In our previous report, we observed that among the three aromatic hydrocarbon diluents toluene, t Bu-benzene, and tri iso -propylbenzene, the highest selectivity was observed in the case of toluene, and therefore, in this study, toluene was chosen. Out of the five diluents, namely, n -octanol, iso -decanol, toluene, n -dodecane, and Solvesso-100 (a high solvency C9 aromatic solvent manufactured from petroleum products), the highest extraction efficiency was observed in the case of n -octanol.…”

“…26 In the case of SO 3 PhBTP, however, the dependence was found to be ∼2 in our previous study. 28 Comparison of Different DGA Derivatives and Aqueous Complexants. The aqueous complexants SO 3 PhBTP, SO 3 PhBTBP, and SO 3 PhBTPhen (Figure 1h,i,j, respectively) were studied for the Am 3+ /Cm 3+ separation along with the seven DGA derivatives as listed in Figure 1; the results are shown in Figures 4 and S3.…”

“…In our previous work, we also observed a higher Am 3+ selectivity using T2EHDGA as compared to its straight-chain analogue TODGA, where the extraction was carried out even in n-dodecane medium in the presence of SO 3 PhBTP as the aqueous complexant. 28 The exact reason for this selectivity reversal of the DGA derivatives having straight and branched alkyl chains in the presence of SO 3 PhBTP as the aqueous complexant is not yet clearly understood. In the cases of the tetradentate aqueous complexants SO 3 PhBTBP and SO 3 PhBTPhen, on the other hand, the extraction of Cm 3+ was always higher than that of Am 3+ in the case of all of the DGA derivatives studied except for TsBDGA.…”

“…value of 2.4. 28 Chapron et al evaluated the role of the position of branching in several DGA derivatives with butyl substituents, viz., TBDGA, TiBDGA, and TsBDGA, and observed that all of them show marginal selectivity toward Cm 3+ over Am 3+ with S.F. values in the range of 1.1−1.5.…”

“…27 Recently, we have shown that N,N,N′,N′-tetrakis-2-ethylhexyl diglycolamide (T2EHDGA), a lipophilic branched DGA derivative, shows selective extraction of Am 3+ over Cm 3+ in the presence of SO 3 PhBTP in the aqueous phase due to the marginal Cm 3+ selectivity of this aqueous soluble ligand. 28 However, no study on the Am/Cm separation is known that systematically varies the ligands in both organic and aqueous phases to get a clear understanding of the selectivity, resulting in an appropriate combination of ligands. Therefore, it will be of interest to systematically study different lipophilic DGA derivatives along with the hydrophilic aqueous complexants SO 3 PhBTP, SO 3 PhBTBP, or SO 3 PhBTPhen for the separation of Am 3+ and Cm 3+ .…”