High-Performance Solid Phase Extraction Chromatography as Part of a Process for Recycling NdFeB Magnet Waste

The increasing demand for rare earth elementsRare earth elements (REEs) in renewable energy technologies and advanced materials has driven a rapid rise in both their economic importance and supply risk. Complementing the supply of REEs through recyclingRecycling of waste streams is therefore becoming increasingly significant. This study investigated the recyclingRecycling of NdFeB magnetsNdFeB magnet by separating the REEs (Pr, Nd, Sm, Dy) from impurities (Fe, Co, B) using solvent extractionSolvent extraction. The subsequent purification of REEs into individual fractions was investigated using high-performance solid phase extraction chromatographyExtraction chromatography. With solvent extractionSolvent extraction, more than 99.5% REEs could be separated in three counter-current stages using D2EHPAD2EHPA. The REEs were stripped using a 1.25 M H2SO4 solution, and finally separated into Nd and Pr, Sm, and Dy fractions from the loaded stripping solution in a single chromatographic stage using a D2EHPA-impregnated column and elution with H2SO4-gradients. This study found that the column performs well in separating any residual Fe, Co, and B impurities present in the loaded strip liquor fed to the column. The performance of the chromatographic separation is however limited by the column loading capacity at higher metal feed concentrations, where HREEs such as Dy can significantly reduce the separation efficiency of impurities and LREEs which are eluted earlier.