Direct Measurement of the Relation Between Swelling Pressure and Interlayer Distance in Li-Vermiculite

Abstract

Abstract--To test the double-layer theory of swelling as applied to layer silicates, the interlayer separation, X, in a Li-saturated vermiculite from Grouse Creek, Utah, was measured as a function of the swelling pressure, II. An oriented sample of the vermiculite (46-105 izm) was placed in an environmental chamber mounted on an X-ray diffractometer and compressed between N2 gas and a porous membrane in contact with a solution draining to the outside atmosphere. After equilibration at each of several successively higher gas pressures, the c-axis spacing was measured by X-ray diffraction, and the corresponding k was calculated by subtracting the thickness of an elementary silicate layer. The results of these measurements showed that: (1) the relation between II and ~ for vermiculite is the same as that previously observed for Na-montmorillonite, i.e., 131 is an exponential function of 1/),; (2) the values of II predicted by doublelayer theory are much smaller than those observed if the surface potential is assigned the appropriate value; and (3) the observed relation between II and ~, does not have the form predicted by this theory. On the basis of these results, a repulsive force not ascribable to double-layer overlap must be primarily responsible for swelling; this force must result from the in-depth perturbation of the water by the surfaces of the vermiculite layers.

Effects of Octahedral-Iron Reduction and Swelling Pressure on Interlayer Distances in Na-Nontronite

“…The work of Viani et al (1983Viani et al ( , 1985 also supports the concept that changes in the chemistry of clay layers affect only the short-range forces between them, namely, the forces that do not extend beyond the energy barrier in Figure 9. They studied the relation between X and 1/for several expanding phyllosilicates (eight Nasmectites and Li-vermiculite) having a wide range of layer charge and found that the value of II at which partially expanded layers became evident and that the value of X for these layers decreased as the layer charge increased (e.g., X was ~ 10 ,~ for the Na-smectites and ~ 6/~ for the Li-vermiculite).…”

“…As reduction of octahedral Fe proceeded, the particles tended to become less dispersed. Therefore, the distance between the fully expanded layers must have depended on Yl but not on Fe2+/Fe 3+, the distance between the partially expanded layers must have depended on Fe2+/Fe 3+ but not on II, and the Relation between interlayer distance and swelling pressure for fully expanded layers of Na-nontronite at two different stages of reduction (dashed line represents lower limit of relations between interlayer distance and swelling pressure for Na-smectites and Li-vermiculite studied by Viani et al, 1983Viani et al, , 1985.…”

“…They found that the swelling of these clays decreased as the reduction of octahedral Fe increased. Inasmuch as unexpanded, partially expanded and fully expanded clay layers can coexist in the same system (Foster et al, 1955;Rhoades et al, 1969;Viani et al, 1983Viani et al, , 1985, this decrease in swelling on reduction could have been caused by the conversion of fully expanded layers to unexpanded or partially expanded layers or by a decrease in the distance between fully expanded layers. Stucki et al (1984c), however, postulated that the decrease in swelling was due to the conversion of fully expanded to unexpanded or partially expanded layers.…”

Effects of Iron Oxidation State on the Specific Surface Area of Nontronite

“…With regard to phenomenon (1), several studies have reported the coexistence of collapsed, partially expanded, and fully expanded layers in clay-water systems (Foster et al, 1955;Rhoades et al, 1969;Viani et al, 1983Viani et al, , 1985. If during Fe reduction some layers collapse completely, a portion of the exchangeable cation should become non-exchangeable or fixed between the layers.…”

Determination of Surface Free Energy of Kaolinite

“…In addition to adsorption properties, wetting processes (Dekany et al, 1983;Szfint6 et al, 1986;, swelling properties (Low, 1987;Viani et al, 1983Viani et al, , 1985Lagaly et al, 1983;Oliphant and Low, 1982), and electrokinetic properties are also of considerable interest (Delgado et al, 1986a(Delgado et al, , 1986b. At least four different, nonspecific mechanisms of water adsorption can be distinguished; i.e., hydrogen bond formation, hydration of surface cations, permanent dipoles of the surface-water dipoles interaction, and London dispersion forces interactions are present in all systems (Low, 1961;Jackson et al, 1971;SwartzenAllen and Matijevi6, 1974).…”