Aqueous Solution Structure at the Cleaved Mica Surface: Influence of K+, H3O+, and Cs+ Adsorption

Abstract

Monte Carlo simulations of the interface between the cleaved surface of muscovite mica and aqueous solution containing K+, Cs+, and/or H3O+ ions compensating negative charge of muscovite and Cl− ions at ambient conditions are reported. Simulation results reveal that, in dependence on surface concentration, K+ is preferentially adsorbed above ditrigonal cavity centers or substituted tetrahedrons ∼1.7 A or ∼2.15 A from the surface, respectively, whereas Cs+ is preferentially adsorbed above ditrigonal cavity centers ∼2.0−2.2 A from the surface. Adsorption of K+ and Cs+ in excess of the surface concentration compensating the negative charge of muscovite leads to a coadsorption of Cl− as an outer sphere complex on the solution side of the Stern layer. This study also suggests that H3O+ is the only species adsorbing as close as ∼1.3 A from the mica surface in contact with deionized water and contributing to the first adsorbed layer observed recently with X-ray reflectivity. On the basis of available experimenta...