(649j) Exploring the Limits of PEG/PEO Membranes for Lithium Separation Using Molecular Simulations

Modern technology relies on an assortment of critical materials that have limited abundance in nature and require increasingly novel methods to extract them and/or recycle them from prior use. Critical ions, such as those comprised of rare earth elements (REE), Lithium, and Cobalt, present new challenges in developing efficient methods for capture and recovery from both brines and the burgeoning domain of e-waste recycling. The development and deployment of polymeric membranes, including those tailored with distinctive ligands, enabling the sequestration of these ions via host-guest interactions, are a promising platform. In this work, we focus on understanding the forces needed to purify lithium resources using ethylene oxide-rich environments. We utilize Molecular Dynamics simulations to elucidate and quantify salient properties governing ion permeation dynamics within membranes. These properties include the relative solvation free energy of metal ions in ethylene oxide-rich environments relative to aqueous solutions (ΔΔG) and a concomitant exploration of ionic mobility within the polymer-rich material. From these detailed simulations, we conclude how best to design molecular membranes for lithium separations and discuss general observations applicable to other critical applications involving ionic materials.