Bis(ethylhexyl)amido diethylenetriaminepentaacetic acid, denoted as modified DTPA here, has recently emerged as an outstanding ligand for extracting rare-earth elements on a solid-phase media, while the microscopic mechanism for the binding between rare-earth elements and the modified DTPA is still unknown. In this work, we fill this knowledge gap by employing first-principles density functional theory to study the binding mechanism of rare-earth elements with the modified DTPA at different pH values. We first compute the pKa values of the modified DTPA and study the binding between hydrated cations of rare-earth elements and the dominating modified DTPA species at different pH values. Our calculations of the Gibbs free energy explain the qualitative trends observed experimentally in the extraction of rare-earth elements. Our study provides insight into the thermodynamics of binding and separation of rare-earth elements using such materials and guides the future design of ligands for the extraction of rare-earth elements.

Density functional study of binding mechanism of rare-earth elements with bis(ethylhexyl)amido diethylenetriaminepentaacetic acid

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