A strategy for selective extraction of lanthanides based on self-assembly with MPyEDChDGA from nitric acid solution☆

Abstract

The development of new and efficient extractants plays a key role in the separation and recovery of rare earth elements. In this paper, the extractant (N,N-methylpyridineethyl-N',N'-dicyclohexyl-3-oxadiglycolamide, MPyEDChDGA) with a new structure was synthesized, and the pyridine group was successfully grafted onto the 3-oxadiglycolamide structure. Using MPyEDChDGA for efficient enrichment of rare earth ions, the self-assembled solids were recovered by simple filtration without further back-extraction and final precipitation, achieving a one-step strategy for the recovery of rare earth ions. Several important parameters affecting the self-assembly extraction, including pH, diluent, temperature, and extractant concentration, were systematically evaluated using La(NO3)3, Tb(NO3)3, and Lu(NO3)3 as representatives. The self-assembled solids were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FT-IR), Raman, and X-ray photoelectron spectroscopy (XPS) analyses. The stoichiometry of the extraction species was characterized using the Job’s method and electrospray ionization mass spectrometry (ESI-MS). In addition, MPyEDChDGA was applied to the recovery of Sm in SmCoCu simulated liquid, and the results show that MPyEDChDGA has good selectivity of Sm from transition metals (Co, Cu). The separation factor of Sm/Co can reach 6281±117, which provides a new approach to recovering Sm from SmCoCu scrap magnets. This study presents an efficient and convenient new strategy for the recovery and separation of rare earth elements.