Chemical separations are central to our energy, environment, and security needs. 10-15% of all the energy consumption in the world is due to separation processes. The increasing demand in electronic display, battery, and magnet technologies require better refinery and recycling processes for rare earths and other critical materials. The contaminated underground waters from nuclear waste leaks still wait to be cleaned. Our group address these challenges by studying molecular-scale structures and energy drivers in heavy element separations. My talk will summarize two of our projects.<br/>Liquid-liquid extraction (LLE) is one of the go-to methods in heavy element separations. In LLE, metal ions are transferred from an aqueous phase into an organic phase with the help of amphiphilic extractant molecules. The aqueous phase speciation, interfacial interactions, and the organic phase structures create a complex free-energy landscape that require a detailed investigation. I will give examples from rare earth separations to demonstrate our approach. We use small angle x-ray scattering to investigate the complex fluids formed after the extraction. We pay special attention to interfaces. We combine multiple surface sensitive techniques to investigate extractant-metal interactions and interfacial water structures. I will emphasize the connections and correlations between the interfacial structures and the nanoscale organic phase structures.<br/>Graphene based membrane and sorbent materials have been extensively studied in recent years, due to their mechanical stability, unique structural and functional properties, tunability, and high surface area. Graphene based materials, alone or as additives, can be very useful under harsh conditions of heavy element separations, where the stability of polymer based materials fail. In spite of their popularity, molecular scale details of ion adsorption at graphene and graphene oxide interfaces are poorly understood. Especially, understanding the interplay between the ion hydration and adsorption is very challenging at these interfaces. We utilize <i>in situ</i> synchrotron X-ray scattering and vibrational sum frequency generation (VSFG) spectroscopy techniques to study trivalent ion adsorption at graphene and graphene oxide surfaces. Our initial studies focus on the two end points of the broad graphene based materials spectrum. High quality pristine graphene and graphene oxide.

Molecular scale understanding of rare earth separations

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.