The University of Pennsylvania, Philadelphia, announces that its researchers have discovered a separation process that could make purifying recycled rare earth elements much less expensive. By developing a new organic compound (H3TriNOx) for binding rare earth cations, this group formed 15 different rare earth compounds.
Solution studies revealed that the “early” rare earth compounds (containing lanthanum, cerium, praseodymium, neodymium, samarium, or europium) preferred to aggregate and form dimeric species. The team observed no such aggregation for “late” rare earth compounds (containing gadolinium, terbium, dysprosium, yttrium, holmium, erbium, thulium, ytterbium, or lutetium). As a result, the solubility difference of these compounds was large enough to enable efficient separation for all early/late rare earth combinations through a single filtration step.
Optimization of the separation conditions was used to improve the effectiveness of specific combinations, most notably the neodymium/dysprosium and europium/yttrium pairs. These pairs are widely used in permanent magnets and compact fluorescent light bulbs, respectively. The TriNOx separations system is expected to contribute to the recycling of these and other end-of-life rare-earth-containing products, providing a cheap and green new source for these critical raw materials.
Publication: J.A. Bogart, B.E. Cole, M.A. Boreen, C.A. Lippincott, P.J. Carroll, and E.J. Schelter ([email protected]). “Accomplishing simple, solubility-based separations of rare earth elements with complexes bearing size-sensitive molecular apertures.” Proceedings of the National Academy of Sciences USA 113(52), 14887-14892 (2016). [DOI: 10.1073/pnas.1612628113]
