Core-shell nanoparticles bearing Schiff base ligand for the selective extraction of uranium from REE leach liquors

The synthesis of core-shell (Fe3O4@SiO2) magnetic nanoparticles (MNP) functionalized using a Schiff base ligand (bis(3-methoxysalicylaldehyde)-o-phenylenediimine; MeOSalophen) for uranium extraction is reported. Extractive performances with respect to pH, adsorption kinetics, chemical nature of the equilibration phase, and elemental selectivity were evaluated and a maximal adsorption capacity of 92 mg g−1 at pH 6 in presence of sulfate ions for an equilibration time of 4 h was determined. The functionalized MNP offer very high affinity for uranyl ion (Kd > 11,000 mL g−1) as well as a high degree of selectivity for this element over several metal ions present in leach liquors containing rare earth elements. While Th was also extracted with the functionalized MNP, equivalent extractive performances were achieved with the non-functionalized counterpart, suggesting that this element is most likely adsorbed on the surface of the silica coating layer. The Schiff base-functionalized core-shell nanoparticles also exhibited a high degree of reusability in the conditions tested.