High-throughput screening for discovery of benchtop separations systems for selected rare earth elements

Rare earth (RE) elements (scandium, yttrium, and the lanthanides) are critical for their role in sustainable energy technologies. Problems with their supply chain have motivated research to improve separations methods to recycle these elements from end of life technology. Toward this goal, we report the synthesis and characterization of the ligand tris[(1-hydroxy-2-oxo-1,2-dihydropyridine-3-carboxamido)ethyl]amine, H31·TFA (TFA = trifluoroacetic acid), and complexes 1·RE (RE = La, Nd, Dy). A high-throughput experimentation (HTE) screen was developed to quantitatively determine the precipitation of 1·RE as a function of pH as well as equivalents of H31·TFA. This method rapidly determines optimal conditions for the separation of RE mixtures, while minimizing materials consumption. The HTE-predicted conditions are used to achieve the lab-scale separation of Nd/Dy (SFNd/Dy = 213 ± 34) and La/Nd (SFLa/Nd = 16.2 ± 0.2) mixtures in acidic aqueous media. Rare earth elements are critical components of clean energy technologies, but less than 1% are recycled due to high costs of recovery. Here the authors develop a ligand that selectively precipitates rare earth elements from aqueous media as a function of pH to facilitate the separation of binary rare earth mixtures.