How acidity rules synergism and antagonism in liquid–liquid extraction by lipophilic extractants—Part II: application of the ienaic modelling

ABSTRACT

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.

KEYWORDS:

• droplet model
• ienaics
• synergy
• polydispersity in aggregation
• extraction landscape

Acknowledgments

The authors acknowledge the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. [320915] ‘‘REE-CYCLE’’: Rare Earth Element reCYCling with Low harmful Emissions. Research Agency for support through grant BIFR/CEA/16-18-002 and the Slovenian Research Agency for support through program P3-0388 are acknowledged. French ANR Agence Nationale de la Recherche grant ANR-18-CE29-0010 is acknowledged. The support of Laboratory Chemisyst ANR 11-01-05 is acknowledged.

Supplementary material

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