Thermodynamics governing the formation of extraction complexes provides the basis for fundamental understanding of ion recognition in separations by solvent extraction. The importance of both inner- and outer-sphere interactions makes a predictive modeling of even the trends in the biphasic extraction of ions to be a daunting task. I will review our recent work to probe the coordination environment around the trivalent f-block metal cations in solution using a combination of extended X-ray absorption spectroscopy (EXAFS), density functional theory (DFT), and classical molecular dynamics (MD) simulations. Next, I will describe how the DFT calculations can rationalize the enhanced Cs<sup>+</sup> versus Na<sup>+</sup> extraction in the presence of a greasy alkylphenol cation exchanger and calix[4]pyrrole anion receptor. Finally, I discuss additional challenges to characterize the solution complexes of oxoanions and the importance of inclusion of explicit solvent molecules to reproduce the extraction trends in anion binding strength and selectivity.

Predictive modeling of ion selectivity in liquid-liquid extraction

2019 Spring National Meeting

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