Magnetic Field Directed Rare‐Earth Separations

The separation of rare‐earth ions from one another is challenging due to their chemical and physical similarities. Nearly all rare‐earth separations rely upon small changes in ionic radii to direct speciation or reactivity. Herein, we show that the intrinsic magnetic properties of the rare‐earth ions impact the separations of light/heavy and selected heavy/heavy binary mixtures. Using TriNOx3− ([{(2‐tBuNO)C6H4CH2}3N]3−) rare‐earth complexes, we efficiently and selectively crystallized heavy rare earths (Tb–Yb) from a mixture with light rare earths (La and Nd) in the presence of an external Fe14Nd2B magnet, concomitant with the introduction of a concentration gradient (decrease in temperature). The optimal separation was observed for an equimolar mixture of La:Dy, which gave an enrichment factor of EFLa:Dy=297±31 for the solid fraction, compared to EFLa:Dy=159±22 in the absence of the field, and achieving a 99.7 % pure Dy sample in one step. These results indicate that the application of a magnetic field can improve performance in a molecular separation system for paramagnetic rare‐earth cations. Subtle differences: Rare‐earth separations generally rely on small differences in the ionic radii of the trivalent oxidation state. A process for the separation of rare‐earth elements has been developed which is enhanced by the presence of an external magnetic field.