Effects of Layer Charge, Charge Location, and Energy Change on Expansion Properties of Dioctahedral Smectites

Abstract

Abstract--Expansion properties of ten homoionic smectites that differed in amount and location of layer charge were examined by X-ray powder diffraction analysis at various relative humidities, or after glycerol or ethylene glycol solvations. Except for K-samples with glycerol solvation, and Na-and Ca-samples with ethylene glycol, differences in the basal spacings are observed in samples having similar layer charge. These results show that the basal spacings are larger when the layer charge is located in octahedral sites than when it is in tetrahedral sites. This suggests that expansion is due to the combined effects of the charge location and amount.The effects of layer charge magnitude and location on expansion were represented by an energy change (expansion energy: AEr) during the hydration and solvation processes. Plots of basal spacings versus AEr show a reasonable relationship; the spacings generally decrease stepwise as the value of AEr increases. The basal spacings of K-samples with glycerol solvation, Na-saturated and K-saturated samples at 100% RH are apt to contract stepwise with increasing value of AEr. For these samples, the figures showing the relationship between each expanded phase and the charge characteristics are obtained from the isoquants of AEr, given the boundary of the expanded phases. A behavior test using these figures may be combined with the Greene-Kelly test to estimate the amount and the location of the layer charge of common smectites.

Chemical signature of two Permian volcanic ash deposits within a bentonite bed from Melo, Uruguay

“…Atomic coordinates for the different layer types were set as recommended by Moore and Reynolds (1989), and the structural formula determined from chemical analyses was used to define the layer composition. The d 00l of the different layer types was adjusted as needed within the limits given by Sato et al (1992) to improve the quality of the fit (Table I).…”

“…Three types of layers have been considered in the mixed layering depending on their respective layer charges (Sato et al 1992):…”

Porosities accessible to HTO and iodide on water-saturated compacted clay materials and relation with the forms of water: A low field proton NMR study

“…Sato et al, 1992) or modelled by molecular dynamic approaches (Tambach et al, 2004;Chavez-Paez et al, 2001). The number of water layers in the interlayer depends on the nature of the interlayer cations and on the compaction degree (Kozaki et al, 1998;Ferrage et al, 2005).…”

Experimental Determinations of the Coherent Scattering Domain Size Distribution of Natural Mica-Like Phases with the Warren-Averbach Technique

“…Both the assumptions of a constant strain broadening associated with interparticle swelling at 17 ~, (Eberl and Srodon, 1988) and of the absence of broadening induced by mixed-layering for even-order reflections of Ca-saturated (2 water-layer smectite) illitic I/S (Eberl and Blum, 1993) also seem unrealistic. Srodon (1980) and Sato et al (1992) indeed showed that the basal spacing ofa homoionic smectite (hydrated or ethylene-glycol solvated) varies significantly as a function of layer charge, charge location, relative humidity, and expansion energy.…”