Molecular-level understanding of metal ion retention in clay-rich materials

Clay minerals retain or adsorb metal ions in the Earth’s critical zone. Rocks, sediments and soils rich clay can concentrate rare earth elements (REEs) ion adsorption-type deposits (IADs) are similarly effective at metallic contaminant remediation. However, molecular-scale chemical physical mechanisms of retention remain only partly understood. In this Review, we describe nature, location energy requirements mineral surfaces. Retention originates mainly from electrostatic interactions during cation exchange low pH bonding surface complexation precipitation neutral high pH. Surface induce redox reactions including neoformation layered structures. IADs, outer-sphere adsorption is major mechanism REE ions. By contrast, use pollution control relies on various that coexist, exchange, nucleation growth. To more effectively leverage mineral–metal resource recovery remediation, complex such as must be better understood; for instance, by utilizing advances quantum mechanical calculations, close combination between synchrotron simulation techniques, upscaling molecular-level information macroscopic thermokinetic predictive models. ions, exploited industrial waste disposal. This Review discusses their importance environmental applications.