ChBE Fall 2023 Seminar: “Phase Transitions and Mesoscale Aggregation in Liquid-Liquid Extraction”

The Department of Chemical and Biological Engineering presents the fall 2023 seminar series with guest speaker Michael J. Servis, a scientist in the Heavy Element and Separation Science group at Argonne National Laboratory, who will present a lecture on “Phase Transitions and Mesoscale Aggregation in Liquid-Liquid Extraction.” This event will take place on Wednesday, September 20, from 3:15–4:30 p.m. in the Perlstein Hall Auditorium (room 131).


Understanding the molecular-scale origins of structure and phase transitions in multicomponent, hierarchically structured liquid phases is a fundamental challenge. One important application affected by these phenomena is liquid-liquid extraction, a predominant low-energy separations technique. This technique is a go-to process for metal ion separations, including recovery and recycling of f-elements. A fundamental limitation of liquid-liquid extraction is the undesirable liquid-liquid phase transition, called third phase formation, that occurs upon sufficient loading of metal ions into the extractant-containing organic phase. In this seminar, we present ongoing work showing how solution structure and phase transitions are fundamentally connected through critical fluctuations resulting from the critical point associated with this phase transition.

By combining small angle x-ray scattering with molecular dynamics simulations, we demonstrate how organic phase structure over a wide range of process-relevant compositions is dominated by critical fluctuations. Scaling relations provided by critical point theory provide a quantitative connection between aggregation and phase behavior. Broadly, we are working to close the gap between experiment and simulation in liquid-liquid critical phenomena. Advances in coherent synchrotron x-ray flux and detector design are enabling measurements at smaller and shorter length scales and timescales. Meanwhile, we are applying coarse-grained molecular dynamics models to simulate mesoscopic aggregation for larger systems and at longer timescales. Overall, this work will deepen our understanding of the relationship between molecular-scale solution structure and mesoscopic aggregation, enabling the design of more efficient separation processes.


Michael Servis received a B.A. in physics from Carleton College in Northfield, MN, followed by a Ph.D. in nuclear science and engineering from the Colorado School of Mines in Golden, CO. He is currently a scientist in the Heavy Element and Separation Science group at Argonne National Laboratory. There, he studies chemical separation processes applied to nuclear fuel reprocessing and critical materials recycling. By combining molecular simulation with experimental techniques—including small angle scattering and x-ray photon correlation spectroscopy performed at the Advanced Photon Source at Argonne—his research seeks to connect a molecular perspective of complex solutions and their interfaces to their macroscopic performance in separations applications.