PNNL

Abstract

The extraction and subsequent separation of individual rare earth elements (REEs) starting from crude REE-bearing feedstocks represents 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 bio-based, all-aqueous REE extraction and separation scheme using the REE-selective lanmodulin (LanM) protein. LanM was conjugated onto porous support materials using thiol-maleimide click chemistry to enable REE purification and separation under flow-through conditions. Immobilized LanM maintains the attractive properties of the free protein, including remarkable REE selectivity, the ability to bind REEs at low pH, and high stability over multiple low-pH adsorption/desorption cycles. We further demonstrate the ability of immobilized LanM to achieve high-purity separation of the clean energy critical REE pairs Nd/Dy and Nd/Y, and to transform an industrially relevant low-grade leachate (0.043 mol% REEs) into separate heavy and light REE fractions in a single column run while using ~90% of the column capacity. This ability to achieve 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 tool for sustainable hydrometallurgy.