Rare earth elements (REE) are essential for high-tech, low-carbon technologies, such as magnets for wind turbines and electric motors. China currently controls the REE supply chain, which hinders growth of renewable energy technologies in the U.S. and Europe and creates risk in defense industry supply chains. Rare earth production schemes from both primary ores and secondary sources involve a series of chemically intense and environmentally taxing procedures with separating individual REEs from each other representing the most challenging steps. Solvent extraction, while effective for industrial scale operations, is not effective for low-grade feedstock and poses a severe environmental burden. Ion exchange chromatography presents an alternative approach for achieving high-purity REEs but is generally cost-prohibitive for scaling. The goal of this project is to develop novel REE-binding ligands coupled with materials design to enable cost-effective and organic solvent–free REE recovery and separation from electronic wastes (E-wastes). If successful, the project expects to achieve REE separation with efficiency similar to traditional ion exchange chromatography but with reduced cost and environmental footprint.

Recently discovered REE-recognizing peptides exhibit extraordinary REE binding properties. Coupled with ease of production/handling, these peptides represent a promising new class of highly selective ligands for REE purification. This project will characterize and improve these biological ligands for REE recovery from E-wastes through formation of insoluble complex. The project team will employ molecular simulation to guide peptide design to improve binding selectivity among lanthanides, which is expected to improve separation among lanthanides. To extend the lifetime of these biological ligands, the project team will integrate the peptides with protein polymers for added control on mineralization and capacity. These peptide-polymer assemblies will serve as building blocks for producing mechanically robust and dynamic membranes in follow-on work to this project.

This consolidated biological platform presents several attractive benefits to the Department of Defense’s missions in securing a domestic REE supply chain and ensuring REE availability for national defense. The project team expects a significant gain in cost savings and a reduced carbon footprint compared to the traditional hydrometallurgical processes. By targeting E-wastes, the process has the potential to enable a circular economy and to support a domestic supply chain of critical REEs needed for the growth of green energy and defense technologies, thereby reducing the dependence on foreign imports. Results from the project will not only supply an environmentally friendly and economical method for selective recovery of REEs from waste streams but will also help further the understanding of REE biomineralization mechanisms. While this project focuses on E-waste in this project, this platform is readily adaptable to other low-grade feedstocks, such as mine tailings and coal byproducts. Thus, this application has potential both to help decouple the U.S. REE supply chain from foreign control and to generate more affordable alternatives to fossil fuel–based energy production.