Swelling Pressure of Montmorillonite Layers Versus H-O-H Bending Frequency of the Interlayer Water

Abstract

Abstract--The in-depth perturbation of vicinal water by the surfaces of montmorillonite layers was investigated by relating the swelling pressure, II, of the montmorillonite layers to the H-O-H bending frequency, v 2, of the interlayer water. For this purpose, an oriented montmorillonite gel was deposited on a porous filter in an environmental chamber. On its underside the filter was in contact with a solution maintained at atmospheric pressure. By admitting nitrogen gas at a known pressure to the environmental chamber, water was squeezed from the gel into the solution until equilibrium was reached and H equalled the applied pressure. Then the gel was divided into 2 parts. One part was used for the gravimetric determination of the water content, mJm C. It was possible, therefore, to determine mJm C as a function of II. The other part of the sample was transferred to an FTIR spectrometer where the v 2 of the water within it was measured by attenuated total reflectance. Thus, the same samples were used to determine the dependence of both 11 and v2 on mJm C. It was found that H and v2 were both exponential functions of mJm w and so a linear relation was found between ln(H + 1) and ln(v2/v2~ where v2 ~ is the H-O-H bending frequency of bulk water. These results strongly support the conclusion that the in-depth perturbation of the water by the surfaces of the montmorillonite layers is primarily responsible for both the development of H and the departure of vz from v2 ~

Infrared Study of Water Sorption on Na-, Li-, Ca-, and Mg-Exchanged (SWy-1 and SAz-1) Montmorillonite

“…Experimentally, they reported that the position of the v2 mode of H20 decreased upon lowering the H20 content for Na-and Li-exchanged montmorillonite, which is in agreement with the data reported here and Russell and Farmer (1964), Poinsignon et al (1978), and Johnston et al (1992. Yan et al (1996aYan et al ( , 1996b interpreted the decrease in frequency of the v2 band to a coupling between H20 molecules and the Si-O stretching vibrations of the 2:1 layer through the formation of hydrogen bonds. The shift of the v 2 mode to lower frequency, however, is not consistent with this interpretation or with the observed blue-shift of the v(OH) modes of sorbed H20 reported here.…”

“…These coordinated H20 molecules are restricted in their ability to form hydrogen bonds with adjacent H20 molecules. Yan et al (1996aYan et al ( , 1996b suggested that the structure of interlayer H20 is affected mainly by the formation of hydrogen bonds between H20 molecules and the siloxane surface. Experimentally, they reported that the position of the v2 mode of H20 decreased upon lowering the H20 content for Na-and Li-exchanged montmorillonite, which is in agreement with the data reported here and Russell and Farmer (1964), Poinsignon et al (1978), and Johnston et al (1992.…”

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.…”

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.…”