Solvent Extraction of Dy(III) and Nd(III) with an Unsymmetrical Pentanediamide Extractant
Recovery of rare-earth elements (REEs), especially those of Dy and Nd, from Nd–Fe–B permanent magnets is crucial for sustainable development. Herein, an unsymmetrical pentanediamide extractant, N,N′-dimethyl-N,N′-didecyl-3-oxapentanediamide (DMDDOPDA), was synthesized and characterized for the effective extraction of Dy(III) and Nd(III). DMDDOPDA can form coordination bonds with metal ions because of the strong electron-donating abilities of the N and O atoms. The coordination sites might be inclined toward one side during the extraction. DMDDOPDA exhibited superior extraction performance in the HNO3 system than it did in the HCl system. The highest extraction efficiencies of Dy(III) and Nd(III) under optimal conditions were 99.9% and 99.5%, respectively, while their optimum stripping efficiencies were 100% and 85.3%, respectively. DMDDOPDA extraction of Dy(III) and Nd(III) in the four investigated diluents involved the formation of a neutral coordination complex. This study provides new insights into REE extraction using pentanediamide extractants.
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