Debye Visiting Chair Lecture 3 by Kathleen Stebe

Peptide surfactants (PEPS) for the Green Separation of Rare Earth Elements

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There is a tremendous drive to replace petrochemically derived amphiphiles with naturally derived amphiphiles for formulations. As this (r)evolution occurs, there is opportunity to consider more broadly the ability to design functional surfactants for interfacial processes that exploit biology’s rich tool kit. In this talk, I will share an example of the design of a functional peptide surfactant (PEPS) for selective capture of rare earth elements. This work is performed by a team of researchers spanning four institutions supported by Basic Energy Sciences at the Department of Energy grant number DE-SC0022240. Rare earth elements (REEs) are crucial to modern technologies. These elements are notoriously difficult to separate from each other, owing to the similar diameters of the REE cations and the fact that they are typically present in the +3-oxidation state.

We are developing an environmentally friendly REE separation process which exploits PEPS that bind selectively to REEs to form PEPS:REE complexes that adsorb to the air-water interface for recovery via a froth flotation process. PEPS are ‘green’ molecules amenable to design for REE selectivity, interfacial activity, and scalable production. This approach requires that PEPS’ ability to bind selectively to REE cations is retained in the highly anisotropic environment of the fluid interface. As an initial PEPS structure, we have studied a known surface-active lanthanide binding tag peptide designed to coordinate via multidentate interactions with REE cations in a binding loop inspired by the highly conserved EF-hand binding sequence in calcium binding proteins. Progress to date, challenges and ongoing work are described.

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Witte Hal, Marinus Rupert Building
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