Electrochemical Separations for Securing Critical Minerals

Abstract

A 2019 National Academies Report highlighted that Chemical Separations account for 10–15% of the overall US energy use. Because of their large energy footprint, there is a need to innovate new separation mechanisms and technologies that are more energy efficient while being environmentally benign. Electrochemical processes are enticing for chemical separations because of their low-exergy nature. They are also an emerging technology for securing critical minerals (CMs) without generating copious amounts of chemical waste. However, further adoption of electrochemical platforms requires additional improvements in the selectivity and permeability of the targeted ionic species with membranes, chelating ligands, and adsorbents.  

This talk commences with our work on understanding ionic activity in polymeric ion-exchange membranes. Activity coefficients govern partitioning behavior and ionic selectivity. We use Manning’s theory of counterion condensation, molecular dynamics simulations, machine learning, and x-ray scattering to understand how molecular architecture and chemistry influence ionic species solvation that dictate activity coefficient values. The second part of the talk discusses our research to influence the speciation of the target ion of interest by exploiting its Pourbaix behavior and/or interaction with selective electrodes or resin materials. To that end, we have demonstrated pH-assisted electrochemical separations of copper and lithium using bipolar membranes in electrosorption cells. Selective capture of lithium occurred from geothermal brines while concurrently producing lithium hydroxide. The talk concludes with mixed matrix anion exchange membranes for selective phosphate recovery over other competing anions. Incorporating manganese oxide particles into polym(phenylene alkylene) anion exchange membranes amplified phosphate anion partitioning leading to improved phosphate selectivity. Overall, mixed matrix membranes, in-situ pH adjustment, and selective electrodes were amalgamated to facilitate selective ion separations. 

Biography

Chris Arges, Principal Chemical Engineer in the Applied Materials Division at Argonne National Laboratory, is a CASE Senior Scientist Affiliate in the Pritzker School of Molecular Engineering at the University of Chicago. He was an Associate Professor in Chemical Engineering at Penn State. Arges's research interests are at the intersection of chemical separations, polymer science, and electrochemistry. He earned his BS in chemical engineering at the University of Illinois at Urbana-Champaign and a PhD in chemical engineering at the Illinois Institute of Technology. Arges was a postdoc in the Materials Science Division at Argonne and the Pritzker School of Molecular Engineering at the University of Chicago. He is the recipient of the NSF CAREER Award, the Electrochemical Society-Toyota Young Investigator Fellowship, and the 3M Non-Tenured Faculty Award.