(304f) Enhanced Lanthanide Recovery with Cross-Linked Glutaraldehyde-Lanthanide Binding Peptides for Foam-Based Separations

Rare earth elements (REEs) possess unique chemical and physical properties that are applicable in a wide range of industrial applications, such as electronics, catalysis, clean energy, batteries and magnetics. Unfortunately, the separation of REEs is not currently environmentally friendly. Lanthanide Binding Tag (LBT) peptides that coordinate selectively with Ln³⁺ ions can be used to replace the energy intensive processes used for the separation and purification of these valuable metals. These surface-active biomolecules once selectively complexed with the trivalent REE cations adsorb to air/aqueous interfaces of bubbles for foam fractionation and recovery. This work aims to design a stable ion-containing foam complex for a LBT-REE separation based on mixed polymer-surfactant solutions. In order to achieve an efficient separation process, we use glutaraldehyde, an organic compound that has high affinity for proteins and peptides, to control the foam stabilization of Lanthanide-bound peptides. The use of glutaraldehyde as a foam stabilizer was quantified with dynamic tension and interfacial elasticity measurements of interfacial layers with and without glutaraldehyde. X-ray reflectivity and x-ray fluorescence near total reflection measurements on adsorbed layers were used to compute the surface concentration of the Ln³⁺ cation and to determine the thicknesses and electron density profiles of the adsorbed species. Furthermore, transmission electron microscopy (TEM), and anomalous small angle x-ray scattering (ASAXS) studies of structures in bulk solution showed structural changes with the introduction of aldehydes without changing the number of cations per peptide, which indicates stability of the binding pocket. The foam stabilization and REEs extraction enhancement by the LBT peptides presented in this work provide an approach to use peptide-glutaraldehyde conjugates for the recovery of rare earth elements.