Bifunctional hydrophobic deep eutectic solvents for selective recovery of Sm and Co from waste SmCo permanent magnets

The application of hydrophobic deep eutectic solvent (HDES) to single-use separation of valuable metal ions in waste samarium-cobalt permanent magnets has been a significant challenge. Trioctylphosphine oxide and 3-benzoyl-1,1,1-trifluoroacetone were combined to prepare a bifunctional HDES that was investigated for green, efficient and safe recovery Sm and Co. Firstly, internal hydrogen bond interaction was verified by DSC, TGA, NMR, FT-IR and molecular dynamics study. Then, a various of optimization experiments were carried out to discovery extraction behaviors on different metal ions. The findings indicated that the acidity has a significant impact on the effectiveness of the extraction process. The maximum extraction capacities were measured as 98.8 g/L Sm(III), 64.8 g/L Co(II), 52.4 g/L, Fe(III) and 75.1 g/L Cu(II), respectively. After that, combined with UV-vis, FT-IR and XPS, the neutral complex extraction mechanism was proposed. Finally, the competitive extraction experiments at different acidity provided the theoretical underpinnings for a three-stage separation strategy that, through acidity control and the use of various stripping agents, was able to efficiently recover 97.8% Sm(III), 99.1% Co(II), 99.5% Fe(III) and 95.6% Cu(II). The whole recycling process has no need additional organic solvents, enabling cleaner and sustainable engineering production.(c) 2023 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.