(378j) Engineering Ionic Liquid Specificity for Efficient Lanthanide Extraction: A Computational Study

Sixteen of the 17 rare earth elements (REEs) have been designated critical materials by the U.S. Department of the Interior. The lanthanide chemical group (lanthanum-lutetium) accounts for 15 of the 17 REEs. The physical, chemical, catalytic, electrical, and magnetic properties of REEs make them favorable for a wide range of applications. While REEs are relatively abundant in the Earth's crust, they are not sufficiently concentrated for economical mining. Low concentrations and similar properties of REEs make it difficult to extract and purify them from each other. The goal of this work is to rationally design ionic liquids, for enhanced removal of lanthanide ions in solution covering the range of ionic radii of the lanthanide series, and thus addressing an overall goal of designing an environmentally friendly separation of lanthanides from solution. In this work, using computer simulations, we cover the range of ionic radii of the lanthanide series and examine the structure, local coordination environment, solvation energies, binding affinities and dynamics of how individual lanthanide ions bind to various ionic liquids, with the aim to identify molecular features of ionic liquids that may allow for selective binding of particular lanthanides, e.g., lanthanum ions with a radius of 1.045 Å versus ytterbium ions with a radius of 0.868 Å. Overall, the implications of this research extend to offering a sustainable and effective method for lanthanide extraction with applications in the field of material science including alloy materials, and metallurgy industry.