The Coordination Chemistry and Stoichiometry of Extracted Diglycolamide Complexes of Lanthanides in Extraction Chromatography Materials

Industrial rare earth element (REE) separations predominantly utilize solvent extraction processes tailored toward conventional resources such as bastnäsite, monazite, and ion adsorption clays. Advances in diglycolamide (DGA) chemistry have shown effective characteristics for REE separations. However, limitations associated with traditional DGA techniques, third-phase formation gelling, hindered commercial viability. By supporting extractants on porous resins polystyrene divinyl benzene (PS-DVB), the desirable combination of selectivity ease operation sorbent columns can be achieved. To design a low-cost model solid-supported DGAs, influenced by underlying coordination must explored to achieve efficient functional systems. Within this study, we report novel resin materials, each incorporating one DGAs N,N,N’,N’-tetra-(1-octyl)-3-oxapentane-1,5-diamide (TODGA), N,N′-dimethyl-N,N′-dioctyl-3-oxapentane-1,5-diamide (DMDODGA), 2,2ʹ-oxybis(1-(3-(((2-ethylhexyl)thio)methyl)-4-methylpyrrolidin-1-yl)ethan-1-one) (DEHPDGA). The affinity across lanthanide (Ln) series was evaluated both hydrochloric acid nitric media varying Ln feed concentrations study distribution ratios loading characteristics. Focusing dysprosium, extended X-Ray Absorption Fine Structure (EXAFS) density theory (DFT) calculations were also utilized explore their effects ligand performance. general trend resulted DMDODGA having highest strength all three at concentrations. Coordination-chemistry analysis supported data, DFT calculations, EXAFS results under forced conditions posited less than expected 3:1 ligand-to-metal coordination.