A facile process for enhanced rare earth elements separation from dilute solutions using N, N-di(2-ethylhexyl)-diglycolamide grafted polymer resin

Separation of rare earth elements (REEs) from dilute solutions using liquid-liquid extraction is often plagued by third phase formation and multiple sequential extraction steps. A new system based on the N, N-di(2-ethylhexyl)-diglycolamide (DEHDGA) grafted polymer resin, used for the efficient separation of RE(III) are proposed. Upon grafting of DEHDGA ligand, the resulting polymer resin was evaluated for its RE(III) adsorption performance. By using a combination of pH-dependent adsorption, kinetics and equilibrium adsorption isotherms experiments, the results suggest that adsorption behavior of the resin for RE(III) is mainly influenced by pH, and thus a competitive adsorption model is proposed to simultaneously describe the adsorption of RE(III) and protons. The proposed resin demonstrates enhanced selectivity towards RE(III) in the presence of Al(III) and Fe(III) compared to the DGA-normal resin at pH 3.0. These results establish that the polymer skeleton could provide a favorable geometry of DEHDGA ligand for complexing RE(III) through the carbonyl and ether groups, which is supported by the FT-IR and XPS analysis of prepared RE(III)-loaded resin. Furthermore, the polymer resin could be reused after four consecutive cycles without substantial loss of adsorption ability, offering a facile process for highly efficient REEs separation from a low concentration of leaching solution.