The Muscovite-Water Interface in Electrolyte and Fulvic Acid Solutions as Observed Using In-situ X-ray Reflectivity

抄録

High-resolution in-situ X-ray reflectivity measurements were used to characterize the sorption of K, Cs, Ca, and Ba from chloride solutions, Zn from chloride, nitrate, and trifluorosulfonate (triflate) solutions, and fulvic acid in the presence and absence of BaC1₂ onto the basal surface of muscovite. X-ray reflectivity data were collected through the specular reflection condition and converted to electron density profiles perpendicular to the interface by applying atomistic structural models that included surface relaxation, sorbate concentration and position, water structure, and surface roughness. Interpretations of the electron density profiles indicated that cations were attached to the basal surface dominantly in the first and second adsorbed layers, anions did not cosorb in large amounts with divalent cations, and fulvic acid sorbed as approximately 8-Å thick layers. All derived profiles imply that no separate water layer exists between the sorbates and mineral surface. Water layering above the sorbed cation layers and minimal relaxation of the bulk muscovite were observed.