(334i) Harnessing Nanoparticle–Peptide Interactions to Improve Foam Stability in Rare Earth Element Recovery

Rare earth elements (REEs) are vital to modern technologies due to their unique chemical properties but separating them from raw materials or end products remains difficult because of their similar physicochemical traits. Conventional separation methods, such as solvent extraction, are complex, energy-intensive, and environmentally harmful due to the use of organophosphate-based solvents. This study presents a sustainable, bioinspired method that combines lanthanide-binding tag peptides (LBTs) with foam fractionation to achieve selective REE recovery. LBT1, a peptide engineered for high-affinity binding to terbium (Tb³⁺), exhibits amphiphilic properties that promote its migration to the air–water interface upon metal coordination. However, limited foam stability and a high liquid content in the foam hinder separation performance. To address this, positively charged silica nanoparticles were introduced to electrostatically interact with the negatively charged LBT1:REE complexes, thereby enhancing foam stability and improving separation efficiency.

Surface tension and interfacial elasticity measurements confirmed improved foam characteristics in the presence of nanoparticles, while GISAXS revealed ordered nanoparticle structuring at the interface. X-ray fluorescence measurements demonstrated that LBTs retained their REE selectivity under these conditions. Foam fractionation experiments using a custom-built lab-scale column showed that nanoparticle addition led to drier, more stable foam and significantly enriched Tb³⁺ recovery, as confirmed by ICP-MS analysis.

This work highlights a novel approach to REE separation, leveraging peptide specificity and nanoparticle-enhanced interfacial behavior to offer an energy-efficient and environmentally friendly alternative to conventional extraction methods.