Modeling the adsorption of metal ions at clay minerals/water interfaces

Clay minerals represent a large fraction of the Earth's surface and show superior adsorption and catalytic performances. Adsorption of metal ions at clay minerals/water interfaces that occurs ubiquitously is closely associated with a wide spectrum of geochemical, environmental and engineered processes; However, microscopic understanding of such complicated and instantaneous processes remains difficult for current experimental techniques while falls within the power of molecular dynamics (MD) simulations. Significant progresses for adsorption of metal ions at clay interfaces benefit greatly from the development of force fields, and when compared to classical theories, MD simulations are apparently superior to model the structure and properties of electrical double layers. These issues are briefly described, and then the chapter elaborates on the adsorption of single metal ions at clay interfaces, associated mechanisms and influencing factors (e.g., clay structure, surface charge, charge location, confinement effects, and water relevant effects), as well as competitive adsorption of binary metal ions, as well as thermodynamics and kinetics of ion exchange. Future directions as posed in the end indicate that there remains a long way to comprehend thoroughly the microscopic mechanisms for adsorption/exchange of metal ions at clay interfaces.