Bifunctional Amidophosphonate Molecules for Uranium Extraction in Nitrate Acidic Media

Abstract

Bifunctional amidophosphonate derivatives, already known as efficient ligands in uranium extraction from phosphoric media, have been evaluated and compared to the conventional trin-butyl phosphate (TBP) for uranium extraction from nitric medium. The efficiency of U extraction and its selectivity towards competing elements such as Th, Zr, Mo, Fe and V was evaluated with various ligand structures. It was found that extractant molecules containing a monosaponified phosphonate moiety instead of phosphonate moieties are less effective and selective. Furthermore, it was observed that alkylation of the methylene bridge linking the two functional groups prevent the formation of precipitates during the uranium loading. Effects of acidity as well as ligand concentration were also investigated to estimate the loading capacity of the molecules. More detailed stoichiometry and transfer energy were further determined by the slope analysis method and a thermodynamic study. The possible uranium recovery from the organic phase has finally been demonstrated thanks to stripping steps at low nitric acid concentration.

Aggregation Behavior of Nitrilotriacetamide (NTAmide) Ligands in Thorium(IV) Extraction from Acidic Medium: Small-Angle Neutron Scattering, Fourier Transform Infrared, and Theoretical Studies

“…The values of "a" can be easily determined by determining the D Th at varying concentrations of the ligand at a fixed nitrate ion concentration. 65 The total ligand (L total ) added in the system is present as the sum of free ligand (L free ), ligand− acid adduct (L acid ), and ligand−Th(IV) complex (L Th(IV) ) at given experimental conditions (eq 5). The L Th(IV) terms can be neglected from eq 5 as we are using 10 −12 M Th(IV) for the extraction studies to get eq 6 and 7.…”

“…Eq gives the linear dependence of log D Th with the free ligand concentration at a given nitric acid concentration and temperature. The values of “a” can be easily determined by determining the D Th at varying concentrations of the ligand at a fixed nitrate ion concentration . The total ligand (L total ) added in the system is present as the sum of free ligand (L free ), ligand–acid adduct (L acid ), and ligand–Th­(IV) complex (L Th(IV) ) at given experimental conditions (eq ).…”

Extraction of Uranium in Nitric Media with Novel Asymmetric Tetra-Alkylcarbamide

“…Typical slope analysis of the extraction equilibrium data was used to estimate the extracted stoichiometry of complexes [ 30 ]. The D values of U(VI) were shown as a function of ligand concentration at 5 mol/L nitric acids.…”

Solvent extraction of uranium from an acidic medium for the front-end of nuclear fuel cycle: from mechanisms understanding to innovative process design

“…In addition, the bifunctional extractant was found to improve the uranium loading capacity by a factor of about 1.3 compared to TBP and to have a slightly lower solubility in the aqueous phase. As with TBP, uranium extraction is favoured in high nitric acid concentrations, suggesting that backextraction at low acidity is also possible [113].…”