Variability in water sorption and in particle thickness of standard smectites

Influence of water density on the water-retention curve of expansive clays

“…These observations correlate with the results obtained on powder samples of montmorillonite (a kind of smectite) (Mooney et al, 1952a;Bihannic et al, 2001;Tournassat et al, 2003;Stepkowska et al, 2004), which suggest that the clay layers are ordered in stacks, forming particles that are grouped in larger particles (aggregates). The number of layers in the particles depends partly on the exchangeable cation type and on the water content of the sample.…”

Towards the establishment of a reliable proxy for the reactive surface area of smectite

“…The interlayer expansion, which affects the BET surface area, depends on both the exchangeable cation and the structural charge of the smectite (Olejnik, 1974;Slade, 1991). Analysis using transmission electron microscope and X-ray diffraction (XRD) showed that the size of the tactoids that are formed when dilute smectite suspensions are dried depends on the chemical identity of the interlayer cations: tactoids of Na-montmorillonitic smectites are composed almost entirely of single unit cell particles, Ca-montmorillonitic smectite tactoids, such as the SAz-1 sample used in the present study, consist of 7 to 11 unit layers, and tactoids of H-exchanged smectite consist of around 17 unit layers (Van Olphen, 1970;Vali and Bachmann, 1988;Blum, 1994;Schoonheydt, 1995;Stepkowska et al, 2004). Since smectite particles disperse to varying degrees ranging from fully dispersed TOT sheets, to faceto-face stacks of sheets, the rate law for smectite dissolution might be written as (Ganor et al, 1995a):…”

“…Since diluted smectite suspensions were used in the present study, and the sample was dispersed during the preparation for the AFM measurements, the vast majority of the particles were composed of a single unit layer. Stepkowska et al (2004) studied the particle thickness of SAz-1 and other standard smectites. According to Stepkowska et al (2004), a smectite particle is composed either of a single unit layer crystallite in a dilute suspension or of 3 to 9 unit layers.…”

“…Stepkowska et al (2004) studied the particle thickness of SAz-1 and other standard smectites. According to Stepkowska et al (2004), a smectite particle is composed either of a single unit layer crystallite in a dilute suspension or of 3 to 9 unit layers. The length of most of the axes of the particles was less than 200 nm (Fig.…”

Atomic-level studies of the depletion in reactive sites during clay mineral dissolution

“…Upon drying, smectite suspensions form aggregates that are significantly larger in size than individual clay layers (Stepkowska et al, 2004) whereas when the aggregates are placed in a dilute solution, the aggregates break apart into tactoids, or microaggregates, that vary widely in size based on properties of the smectites including exchangeable cations and the structural charge (Olejnik et al, 1974;Slade et al, 1991). These factors, in addition to the microporous nature of smectites, results in a wide range of A BET values.…”