D.M. Park, P. Diep, Z. Dong, J. Seidel, W. Choi, J. Cotruvo, Y. Jiao
Lawrence Livermore National Lab,
United States
Keywords: lanmodulin, REE separation, protein-based REE separation, synthetic biology
Summary:
Rare earth element (REEs: Sc, Y, La- Lu) are irreplaceable components in many clean energy and consumer technologies. However, the extraction and subsequent separation of individual REEs from REE-bearing feedstocks remains a significant economic and environmental challenge. Here, I will discuss the development of a biology-based, all-aqueous REE extraction and separation approach as a sustainable potential alternative to conventional hydrometallurgical processes. This process leverages lanmodulin proteins, bacterial proteins that have evolved as part of lanthanide uptake pathways and exhibit exceptionally high REE binding affinity and selectivity.1, 2 Through immobilization of lanmodulin onto porous resin, we achieved selective capture and separation of REE ions from complex metal ion mixtures, including Dy/Nd separation from a range of E-waste feedstocks3, 4 and Dy, Sc, La, and Y separation from ore-derived mixed REE oxides.5 To better facilitate separation process optimization and scaling, we are developing a process model of lanmodulin separations. This includes a thermodynamic model that captured the non-intuitive separation behavior of lanmodulin, where separation factors vary widely based on feed composition, while also accurately predicting the binding distribution in feedstocks with as many as 10 REEs.6 The model also revealed intrinsic limitations of the archetypical lanmodulin from M. extorquens for separating closely spaced lanthanides, which we seek to overcome through protein engineering and bioprospecting. To this end, I’ll describe a screening platform for quantitative determination of the intra-REE selectivity profile of proteins in masse, which we have used to characterize over 1000 natural and engineered REE binding proteins to date. Finally, I will describe the deployment of newly discovered, highly selective lanmodulin variants for enhanced REE separations from electronic waste and primary ore (allanite) feedstocks over a range of scales. Collectively, these advances bolster the prospects for using REE binding proteins as a platform for organic solvent-free REE separations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DEAC52-07NA27344 (LLNL-ABS-858227).