b'Investigating the mobilityFundamental cation, anion, and ligand effects influence the separation of rare earth element ligandof rare earth ions in an electric field under aqueous media conditions.complexes in an electric fieldR are earth elements are vital to modern clean technologies such as electric vehicle batteries and windmill turbine magnets. To be used in those for selective separation technologies, the rare earth elements must be of high purity, but the separation of individual rare earth elements from complex aqueous mixtures remains challenging. This is due in large part to the similar chemical properties of rare earth elements, which renders many conventional methods ineffective. In this work we examined electrophoretic methodology that separates ionic constituents based on their transport in an electric field. We first studied fundamental interactions PROJECT NUMBER:occurring between lanthanides and ligands within an electrophoretic system. It was 22A1059-096FP determined that nitrate provided the least variability in diffusion coefficient between adjacent lanthanides and was therefore used for subsequent studies. INITIATIVE:Emerging Core Capabilities Chemical andSolutions of formate, acetate, benzoate, iminodiacetate, oxalate, and citrate, each of Molecular Science different size and denticity, were prepared in concentrations ranging from 0 mM5 mM to observe their effect on the mobility of equimolar (0.1 mM) concentration of TOTAL APPROVED AMOUNT: lanthanum (La), samarium (Sm), dysprosium (Dy), and lutetium (Lu) in solution.$740,000 over 2 years Iminodiacetate maximized mobility differences between the four lanthanides. PRINCIPAL INVESTIGATOR:Fluorescence experiments on samples containing Sm/iminodiacetate and Dy/Robert Fox iminodiacetate elucidated the coordination environment of each lanthanide at increasing iminodiacetate concentration. At 5 mM, one iminodiacetate molecule CO-INVESTIGATORS: coordinates in a tridentate fashion with Sm but in a bidentate fashion with Gorakh Pawar, INL Dy. Density functional theory calculations arrived at the same conclusion. We Caleb Hill, University of Wyoming conclude that the electrophoretic mobility difference arising from the preferential conformation of iminodiacetate between light and heavy lanthanides causes the observed separation improvements. The effect of the electron donating atom present within the ligand and the ligand size was investigated. Oxygen, nitrogen, sulfur, and phosphorus atoms were the electron donating atom present within groups of ligands that differed in size by adding a methyl group onto their existing alkyl chains. We found that oxygen donors interact the strongest with the four lanthanide samples, evidenced by decreasing electrophoretic mobility with increased ligand concentration as well as enhanced separation factors. Size trends within ligand groups indicate a steric limit where ligands that contain butyl groups are too hydrophobic for adequate complexation with lanthanides in aqueous solution.130'