Montmorillonite clay-water interactions

K.S. Kattia, and D.R. Katti, Effect of Clay-Water Interactions on Swelling in Montmorillonite Clay, Proc. ASCE Engineering Mechanics Conference,... 

Key words montmorillonite — clay — water — clay/water interface — clay/water interaction-pollution... 

Johnston, C.T., G. Sposito, and G. Erickson (1992). Vibrational probe studies of water interactions with montmorillonite. Clays Clay Min., 40 722-730. 

D Or, L., M. Haccuria, and R. Machiroux, 1955. Infrared absorption spectra of silica in its different forms and of the hexagonal variety of germanium dioxide. Industr. Chim. Beige 20 (Spec. No.) 150. Dowdy, R. H., and M. M. Mortland, 1967. Alcohol-water interactions on montmorillonite surfaces. I. Ethanol. Clays Clay Min. 15 259. 

The severe interaction of the zinc bromide fluid, 19.2 ppg (2.32 g/cc), was unexpected. Severe plugging of the core occurred, caused by precipitation of zinc hydroxide, as the injected solution mixed with and was neutralized by formation brine. Tests in which the zinc bromide fluid was simply titrated with distilled water also produced a precipitate, 0.0036 g/cc. Titration in the presence of the common reservoir clay, montmorillonite, increased both the rate of precipitation, and total quantity to 0.03 g/cc. 

Clays are aluminosilicates with a two-dimensional or layered structure including the common sheet 2 1 alumino- and magnesium- silicates (montmorillonite, hectorite, micas, vermiculites) (figure 7.4) and 1 1 minerals (kaolinites, chlorites). These materials swell in water and polar solvents, up to the point where there remains no mutual interaction between the clay sheets. After dehydration below 393 K, the clay can be restored in its original state, however dehydration at higher temperatures causes irreversible collapse of the structure in the sense that the clay platelets are electrostatically bonded by dehydrated cations and exhibit no adsorption. 

Montmorillonite is a 2 1 clay with isomorphic substitutions mainly in the octahedral sheet and some substitutions in the tetrahedral sheets. When the clay is exchanged with monovalent ions, water and electrolyte ions can enter the interlayer spacing and delaminate the system. With Li+ or Na+ as the exchanging cations the delamination is almost complete, whereas with K+ or Cs+ the delamination is less effective.4849 At low pH, edge-to-face interactions can lead to the formation of aggregates. 

Clays of the montmorillonite family are lamellar aluminosificates [46] used in many industrial processes and in products such as paints, softeners, and composite materials [47]. They swell when brought into contact with water, which is due to the insertion of water molecules between the sheets. Complete exfoliation can be induced leading to dispersions of disk-like particles of 10 A thickness and 300-3000 A in diameter, depending on the variety of clay used. These clay platelets bear a rather large surface electrical charge so that electrostatic interactions between them must be considered and are actually responsible for the colloidal stability of these dispersions. These suspensions have been widely studied as model colloids and also because they form physical thixotropic gels. 

To further analyze dependency on the ion type. Figure 2.3 is plotted where the normalized K t of different soil types with similar molar concentrations of the different ions are shown. The values are normalized by the measured K t values of respective blank clays, those mixed and consolidated only with distilled water. At low soil concentrations of Cs, Cd, and Sr, (<0.01 M), the concentration and the type of ion appear to control the K t factor as all soil types (except montmorillonite for Sr) show very close to constant normalized values of K t for the three ions involved. Subsequently, as the concentrations of the contributing ions increase beyond 0.01 M, fewer soil types comply with the categorization, as the mineralogy of the soil, hence its unique chemical interaction with the dominant ion comes into effect. Because of the uniqueness of this interaction, the normalized values show greater variation for each ion involved at high concentration (Cr, Pb, Zn), then the low concentration (Cs, Cd, Sr), group. 

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