Gravity-Driven Separation for Enrichment of Rare Earth Elements Using Lanthanide Binding Peptide-Immobilized Resin.

Rare Earth Elements (REEs) constitute indispensable raw materials and are employed in a diverse range of devices, including but not limited to smartphones, electric vehicles, and clean energy technologies. While there is an increase in demand for these elements, there is a global supply challenge due to limited availability and geopolitical factors affecting their procurement. A crucial step in manufacturing these devices involves utilizing highly pure REEs, often obtained through complex and nonsustainable processes. These processes are vital in isolating individual REEs from mixtures containing non-REEs and other REEs. There exists an urgent requirement to explore alternative techniques that enable the selective recovery of REEs through more energy-efficient processes. To overcome the limitations mentioned above, we developed a microbead-based technology featuring immobilized lanthanide binding peptides (LBPs) for the selective adsorption of REEs. This technology does not require the utilization of external stimuli but uses gravity-based separation processes to separate the bound REE from the unbound REE. We demonstrate this technology's potential by enriching two relevant REEs (Europium and Terbium). Additionally, we propose a mechanism whereby REEs bind selectively to a particular LBP, leveraging the distinctive physicochemical characteristics of both the REE and the LBP. Moreover, these LBPs exhibit no binding affinity toward other frequently encountered industrial ions. Finally, we demonstrate the recovery of REEs through a change in system conditions and assess the reusability of the microbeads for subsequent adsorption cycles. We anticipate that this approach will address the challenges of REE recovery and demonstrate the potential of biomolecular strategies in advancing sustainable resource management.