T.G. Levitskaia, D.H. Altavilla, N.P. Bessen, S. Jansone-Popova, B. O'Kelly
Pacific Northwest National Laboratory,
United States
Keywords: rare earth, DGA, organophosphorus acids
Summary:
The separation of rare earth elements (REEs) remains a significant scientific and industrial challenge, contributing to the primary cost of producing purified individual REEs from ores and secondary feedstocks. The current industrial standard for REE separations relies on solvent extraction using lipophilic phosphorus-based acidic reagents. While effective at partitioning bulk REEs into organic aliphatic diluents, these reagents lack selectivity for distinguishing individual REEs. Nevertheless, their well-established chemistry serves as a foundation for exploring innovative applications and new separation approaches grounded in the principles of liquid-liquid solvent extraction. Our research revisits the widely known (2-ethylhexyl)phosphonic acid mono-2-ethylhexyl ester (HEHEHP) extractant, revealing exciting possibilities for refining separation techniques and enhancing the efficiency of REE recovery. By coupling the foundational chemistry of HEHEHP with neutral diglycolamide (DGA) extractants, we have opened new pathways for addressing current challenges in REE separations. This novel combination provides fresh insights, enabling higher selectivity and efficiency while promoting technology-critical rare earth metal reuse and advancing sustainability goals. This approach represents a promising step toward overcoming the inefficiencies of established REE separation methods and achieving breakthroughs in environmentally responsible resource recovery.