Bridging Hydrometallurgy and Biochemistry: A Protein-Based Process for Recovery and Separation of Rare Earth Elements

Abstract

The extraction and subsequent separation of individual rare earth elements (REEs) from REE-bearing feedstocks represent a challenging yet essential task for the growth and sustainability of renewable energy technologies. As an important step toward overcoming the technical and environmental limitations of current REE processing methods, we demonstrate a biobased, all-aqueous REE extraction and separation scheme using the REE-selective lanmodulin protein. Lanmodulin was conjugated onto porous support materials using thiol-maleimide chemistry to enable tandem REE purification and separation under flow-through conditions. Immobilized lanmodulin maintains the attractive properties of the soluble protein, including remarkable REE selectivity, the ability to bind REEs at low pH, and high stability over numerous low-pH adsorption/desorption cycles. We further demonstrate the ability of immobilized lanmodulin to achieve high-purity separation of the clean-energy-critical REE pair Nd/Dy and to transform a low-grade leachate (0.043 mol % REEs) into separate heavy and light REE fractions (88 mol % purity of total REEs) in a single column run while using ∼90% of the column capacity. This ability to achieve, for the first time, tandem extraction and grouped separation of REEs from very complex aqueous feedstock solutions without requiring organic solvents establishes this lanmodulin-based approach as an important advance for sustainable hydrometallurgy.

Engineering lanmodulin's selectivity for actinides over lanthanides by controlling solvent coordination and second-sphere interactions

“…First, as the ionic radii of Nd 3+ and Am 3+ are nearly identical, 18 the higher stability of the Am–LanM complexes indicates that the metal ion size is not the only driver for LanM's binding affinity. In prior studies, 7,33,35,48 LanM's affinity trend along the lanthanide series was found to not follow the lanthanide contraction (contrary to what is generally observed for small ligands 1,12,70,71 ), which further suggests that effects other than size match and pure ionic interactions are at play in LanM's binding mechanism and preference for actinides. Second, the 3D 9 A and 3D 9 N variants retain strong affinity for actinides and lanthanides, akin to WT LanM.…”

Repeated Recovery of Rare Earth Elements Using a Highly Selective and Thermo‐Responsive Genetically Encoded Polypeptide

“…As an alternative to RELP, it was recently reported that LanM can be immobilized to recover and separate REEs from model solutions as well as a low‐grade fly ash leachate. [ 38 ]…”

A Natural Lanthanide-Binding Protein Facilitates Separation and Recovery of Rare Earth Elements

“…In this issue of ACS Central Science , Dan Park and co-workers focus on such an ecofriendly method using a natural protein. 2 …”

“… (A) In this work, 2 a natural Ln-binding protein (LanM) was immobilized on agarose beads. (B) Immobilized LanM was packed in fixed-bed columns for the evaluation of REE extraction and separation from either low-grade REE sources or of industrially important REE pairs.…”

“…While not yet optimized for separations on an industrial scale, the process described by Park et al does have the exciting potential to extract REE from low-grade leachate solutions as well as from EoL products (e.g., magnets). 2 …”