Foamable Protein-Ligand Conjugates: A Sustainable Approach to Rare-Earth Metal Harvesting and Separation by Ion Flotation

High Resolution Image Download MS PowerPoint Slide The growing demand for rare-earth elements motivates sustainable alternatives to solvent extraction. Here, we report a new paradigm of coordination-active surfactants for lanthanide ion flotation, protein-ligand conjugates, that combine strong inner-sphere chelation with intrinsic protein foamability. Bovine serum albumin functionalized with diethylenetriamine-pentaacetate binds up to 25 equivalents of Eu III per protein and directly enriches lanthanides from aqueous solution by flotation. This platform achieves selective separation of Eu III from La III and maintains high capture efficiency under high ionic strength conditions where conventional collectors fail. By coupling multivalent coordination chemistry with amphiphilic macromolecular surface activity, this approach eliminates organic solvents, solid resins, and acid regeneration, establishing a scalable new archetype for rare-earth separations.