Rare-Earth Element Adsorption to Membranes Functionalized with Lanmodulin-Derived Peptides

Rare-earth elements (REEs) are important components of modern technology and require highly selective separation for recovery and purification. Biosorbents are an emerging class of materials for REE separation that take advantage of the natural affinity and selectivity of proteins or peptides for REE metals. Increasing the capacity while maintaining selectivity is an important practical challenge for the adoption of this technology. This contribution presents a peptide-functionalized membrane adsorber and characterizes peptide loading, REE affinity, and REE binding capacity. A hydrophilic monomer, 2-hydroxyethyl methacrylate, was copolymerized with hydrophobic allyl methacrylate and grafted from poly(vinylbenzyl chloride) electrospun membranes. Hydrophilicity, membrane morphology, and equilibrium adsorption isotherms for La and Nd in pH 5.2 solutions were measured to compare the grafted allyl methacrylate homopolymer and the copolymer containing 2-hydroxyethyl methacrylate. Ultimately, the addition of a hydrophilic comonomer improves the accessibility for peptide loading and increases the level of REE binding in aqueous solutions; however, it reduces the selectivity from 2.3 to 1.1 for Nd/La.