Changes in the Si−O Vibrations of Smectite Layers Accompanying the Sorption of Interlayer Water

Abstract

The frequencies of Si-O stretching, νSi-O, in layers of montmorillonite and of H-O-H bending, ν2, in the interlayer water were investigated by infrared spectroscopy. Oriented gels of Li-and Na-montmorillonite equilibrated at different water contents, mw/mc, were obtained by using a miniature pressure membrane apparatus. One part of each gel was used for the gravimetric determination of mw/mc. The other part was transferred to an FTIR spectrometer where the spectrum of the gel was measured by attenuated total reflectance. Thus, the dependence of both νSi-O and ν2 on mw/mc was determined in the same samples. The absorption bands for Si-O stretching were resolved by using a curve-fitting technique to determine the frequency, area, and height of the component peaks. Two prominent peaks, labeled peak III and peak IV, were selected for analysis. It was found that ν Si-O for each peak and the ratio of the areas (or heights) of the two peaks were all exponential functions of mc/mw. Moreover, a linear relation was found between ln(νSi-O) and ln(ν2). These results were interpreted to mean that the Si-O stretching vibrations in the montmorillonite layers and the H-O-H bending vibrations in the interlayer water are coupled and that both change as the layers come closer together.

Adsorption Kinetics of Pentachloroethane by Iron-Bearing Smectites

“…The reduction of structural Fe also increases the surface-charge density of the clay (Stucki, 1988;Stucki and Tessier, 1991;Gates et al, 1993;Yan and Stucki, 1999), causing the Fe(II)-bearing smectites to acquire a strong nucleophilic character that facilitates the transformation of chlorinated alkanes. The high concentration of H20 relative to that of 5CA, and the fact that smectite surfaces hydrate (Yan et al, 10 ...... 1996b, 1996cYan and Stucki, 1999), suggest that H20 molecules mediate the hydrogen bridging and the long-range interactions between 5CA and the clay surface ("outer sphere complex"; Wilkins, 1991). The formation of tetrachloroethene (4CE) is explained by the dehydrochlorination of 5CA (Roberts and Gschwend, 1991;Cervini-Silva et al, unpubl.…”

Structural Perturbations in the Solid–Water Interface of Redox Transformed Nontronite

“…Recent research revealed that the structure of the layer lattice Si-O vibrations are modified by interaction with and are coupled to the structure of the interlayer water (3). These mutual structural modifications at the clay-water interface evidently are insensitive to the type or concentration of monovalent electrolyte surrounding the mont-morillonite layers (4).…”

Effects of Iron Oxidation State and Organic Cations on Dioctahedral Smectite Hydration

“…Infrared spectroscopic evidence indicates that interlayer water is strongly coupled to the clay-mineral surface (Yan et al, 1996a(Yan et al, , 1996b(Yan et al, , 1996c. The bond energy of Si-O in the tetrahedral sheet of the clay is modified by the interlayer H20 content, and is independent of the inorganic univalent cation in the interlayer.…”