This project addresses the challenge of separating rare earth elements (REEs) from one another and from other ions, using Nature’s solutions to this problem as guides. REEs are ubiquitous components of current technologies from permanent magnets and lasers to medical imaging agents. Separations of REEs from more abundant metals and from each other in mining and recycling applications is currently a laborious, energy- and resource-intensive process using relatively low-selectivity ligands. Increasing efficiency of these separations has the potential to lower costs, decrease waste, and allow usage of feedstocks with lower REE concentrations.
The recent discovery and characterization of lanmodulin (LanM), a highly selective REE-binding protein, forms the basis of this research. LanM has an intriguing framework in which to understand the fundamentals of the biological coordination chemistry of lanthanide ions; preliminary data also indicate that it is a protein with remarkable stability properties that enable it to quantitatively extract total REEs from industrially relevant feedstocks even under harsh experimental conditions. Although LanM displays exceedingly high selectivity for REEs versus non-REEs, its selectivity within the REEs is rather low. The present research program will utilize a multidisciplinary approach to develop LanM variants with higher intra-REE selectivities for REE separations. Whereas small molecules, materials, and whole cells have been explored for separations, effective macromolecular approaches are conspicuously absent. The promising performance, stability, affinity, and selectivity of LanM suggest that this protein and its derivatives may serve as guides for new and efficient approaches to REE separations.
