(467e) The Surface Rheology of Interacting Peptide Surfactants and Rare Earth Elements at Air-Water Interfaces

We study peptide-based surfactants (PEPS) at air-water interfaces for selective binding of rare earth elements (REEs). PEPS comprise a hydrophilic amino acid sequence based on lanthanide binding tags that selectively bind REEs and a hydrophobic sequence that confers amphiphilicity. We envision a REE separation process based on interfacial foam fractionation (IFF) using high affinity and highly selective REE-binding peptide surfactants (PEPS) at air-water interfaces. PEPS added to REE feedstocks will associate selectively with REE cations and adsorb to air water interfaces for recovery. The proposed process would be green in comparison to solvent extraction.

We use particle tracking methods to study the interface of soluble solutions of PEPS as a function of bulk REE concentration to probe for the formation of surface domains. we also characterize the interfacial rheology using correlated displacement velocimetry (CDV). In this method, we study the flow field around Brownian colloids at the interface by measuring their correlated displacements at short lag times. The thermally induced flow can be decomposed into interfacial hydrodynamic multipoles which reveal information about the interface’s compressibility, providing fundamental insights on the mechanical response of PEPS monolayers. This study guides the design of PEPS/fluid system essential to the envisioned separation processes.