Lanthanide Separation via Selective Precipitation Under Neutral Aqueous Conditions With a Functionalized EDTA Chelator

In this study, we report a precipitation-based strategy for recycling and refining neodymium (Nd) from permanent magnet e-waste in neutral aqueous solution using a functionalized ethylenediaminetetraacetic acid (EDTA) chelator. A hydrophobic substituent, carbostyril 124, was introduced onto the EDTA framework to yield EDTA-cs124, which exhibited a solubility profile of the ensuing lanthanide complexes capable of differentiating the lighter and heavier lanthanides. The lighter lanthanide complexes precipitated markedly faster than the heavier ones, enabling efficient separation of Nd from a Nd/Dy/Tb mixture derived from waste hard disk drive (HDD) magnets. The recycled Nd could be refined by repeated precipitations to afford 99.3% Nd purity and 77% recovery yield. Using recyclable EDTA-cs124 provides an operationally simple and organic-solvent-free approach for lanthanide separation.