Title: "Unconventional Resources: The New Conventional for Critical Element Recovery"

Dr. Young-Shin Jun, Anna McKelvey Professor

Washington University in St. Louis, Department of Energy, Environmental & Chemical Engineering, McKelvey School of Engineering

Host: Levi Stanley

Abstract: Critical elements, including rare earth elements (REEs), nickel (Ni), and cobalt (Co), are crucial in modern technologies and advanced materials, such as magnets, batteries, catalysts, electronic devices, and defense systems. Due to the limited global supply chains of these elements, alternative sources are urgently needed. This talk will present my group’s discovery for recovering critical elements from two unconventional resources: coal-based resources for REEs and low-quality ores and alkali waste for Ni and Co.

First, to extract REEs from coal-based materials, we developed a supercritical fluid-assisted extraction and multistage stripping process using tributyl phosphate-nitric acid (TBP-HNO₃). We demonstrated recovery of REEs direct from the solid matrix of unburned coals as well as coal fly ashes. We tested carbon dioxide (scCO2), nitrogen (scN₂), and air (scAir) as potential supercritical fluids and evaluated their effects on REE extraction selectivity and efficiency. With scCO₂, REEs were recovered with nearly 100% purity achieved by the fifth stripping stage. This technology is also useful for other unconventional resources such as old electric and acid mine wastes.

Second, to effectively recover nickel and cobalt from low-quality ores such as ultramafic rocks, we investigated the carbonation and sulfidation of these silicate minerals and examined the release of Ni and Co during these processes. In the concurrent carbonation-sulfidation system, Ni and Co were extracted in sulfide forms and did not contribute to carbonation, resulting in only magnesium (Mg) forming Mg carbonate solids. These distinctive solid formation behaviors will allow us to design more effective recovery methods for Ni and Co from Mg-rich waste and ores. Additionally, the product materials can be directly used as pseudo-supercapacitor materials for energy storage.

Both examples clearly demonstrate the amazing potential of unconventional resources to secure critical elements when nanoscale interfacial processes and solid nucleation are deeply understood and effectively controlled.

Bio: Dr. Young-Shin Jun is Anna McKelvey Professor in the Department of Energy, Environmental & Chemical Engineering at Washington University. She received her bachelor’s and master’s degrees from Ewha Womans University (Seoul, South Korea), holds master’s and PhD degrees at Harvard University, MA, and conducted postdoctoral research at the University of California-Berkeley/Lawrence Berkeley National Laboratory in CA. Dr. Jun advances the understanding of nanoscale interfacial chemistry and solid nucleation to tackle key challenges in energy and the environment. She currently focuses on three critical areas: CO₂-energy-chemical systems; novel technologies to recover critical elements, nutrients, and valuable salts from unconventional resources; and nanomaterials synthesis and nanotechnologies for improving the quality of water and soil. Professor Jun has received numerous awards, including the 2008 Ralph E. Powe Junior Faculty Award, the 2011 U.S. NSF CAREER award, the 2020 James Lee Award, the 2022 Jackson Award, a 2022 AEESP Distinguished Service Award, and an IUPAC 2025 Distinguished Women in Chemistry or Chemical Engineering Award. She was named a 2015 Kavli Fellow by the U.S. National Academy of Sciences, a 2016 Frontier of Engineering Fellow by the U.S. National Academy of Engineering, a 2018 Fellow of the Royal Society of Chemistry, a 2019 Fellow of the American Chemical Society (ACS), and a 2024 Fellow of the American Association for the Advancement of Science (AAAS). Dr. Jun is an Editorial Board Member of ACS ES&T: Engineering, RSC Advances, and Current Opinion in Chemical Engineering.