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In this article Part II, we consider the application of ienaic modeling for solvent extraction of rare earths in the case of the mixed DMDOHEMA/HDEHP extractant system. The system exhibits a synergistic extraction effect depending on the acid concentration and the extractant mole fraction, as demonstrated in the experimental article Part I. In this work, we directly compare experimental findings with theoretical predictions of the droplet model. The model considers the effective free energy of transfer as a combination of competing molecular forces, but contrary to previous micelle models that focus only on the dominant stoichiometry, it allows calculations of free energies of every possible spherical aggregate. The resulting image of the extraction process is that different behaviors can be obtained depending on the acidity and mole fraction of extractants, which are associated with different aggregation regimes in a complex free energy landscape of the system. Nevertheless, self-assembly is tuned by the extraction of all solutes, and not only the target metal cations. [ABSTRACT FROM AUTHOR]

We describe here the formulation of a new synergistic extractant system for the extraction of rare earth elements from aqueous phosphoric acid solution containing large quantities of impurities currently found in urban mines and secondary deposits. This new synergistic system is original in its concept as it contains the association of the bifunctional extractant amido-phosphonate, known for its high efficiency in the recovery of uranium from phosphate rocks, with the(Bis(2-ethylhexyl) sulfosuccinate sodium) (AOT) surfactant molecule known to form reverse micelles in aliphatic diluents. The mixture was found to extract synergistically rare earth elements with high distribution coefficients (D), and exhibits a high separation factor (S.F.) toward iron (III) from phosphoric acid solution. A complete thermodynamic study of its extraction properties is also presented, showing this system has the ability to extract Rare Earth Elements (REEs) from a wide range of phosphoric acid concentrations, which is often the case in industrial processes. [ABSTRACT FROM PUBLISHER]

The extraction of rare earth elements (REEs) from nitric acid solution with a triphosphine trioxide (TPO) is presented. Performances of such a ligand in ionic liquids vs. a classical solvent (benzyl ether) are compared. TPO seems to be 10 to 100 times more efficient when it is dissolved in ionic media whatever the concentration of nitric acid involved. Mechanistic investigations reveal that cation exchange classically observed in ionic liquids is not consistent with the experimental data. Moreover, clear differences in the TPO/Ln complexes between classical and ionic media are highlighted. A stable complex of 1 lanthanide for 3 TPO is formed in an ionic liquid whereas a complex of 1 lanthanide for 6 to 9 TPO is formed in benzyl ether. Back extraction is also studied and good recovery of REEs could be obtained. The TPO/ionic liquid system shows remarkable performances i.e. efficiency and selectivity towards lanthanides in a simulated leaching solution of a Nd/Fe/B/Dy magnet. [ABSTRACT FROM AUTHOR]