Hydration of a Synthetic Clay with Tetrahedral Charges:  A Multidisciplinary Experimental and Numerical Study

Abstract

The interaction of water with a synthetic saponite clay sample, with a layer charge of 1 per unit cell (0.165 C m(-2)), was investigated by following along water adsorption and desorption in the relative pressure range from 10(-6) to 0.99 (i) the adsorbed amount by gravimetric and near-infrared techniques, (ii) the basal distance and arrangement of water molecules in the interlayer by X-ray and neutron diffraction under controlled water pressure, and (iii) the molecular structure and interaction of adsorbed water molecules by near-infrared (NIR) and Raman spectroscopy under controlled water pressure. The results thus obtained were confronted with Grand Canonical Monte Carlo (GC/MC) simulations. Using such an approach, various well-distinct hydration ranges can be distinguished. In the two first ranges, at low water relative pressure, adsorption occurs on external surfaces only, with no swelling associated. The next range corresponds to the adsorption of water molecules around the interlayer cation without removing it from its position on top of the ditrigonal cavity of the tetrahedral layer and is associated with limited swelling. In the following range, the cation is displaced toward the mid-interlayer region. The interlamellar spacing thus reached, around 12.3 A, corresponds to what is classically referred to as a "one-layer hydrate," whereas no water layer is present in the interlayer region. The next hydration range corresponds to the filling of the interlayer at nearly constant spacing. This leads to the formation of a well-organized network of interlayer water molecules with significant interactions with the clay layer. The structure thus formed leads to a complete extinction of the d001 line in D2O neutron diffraction patterns that are correctly simulated by directly using the molecular configurations derived by GC/MC. The next range (0.50 < P/P0 < 0.80) corresponds to the final swelling of the structure to reach d spacing values of 15.2 A (usually referred to the "two-layer hydrate"). It is associated with the development of a network of liquidlike water molecules more structured than in bulk water. The final hydration range at high relative pressure mainly corresponds to the filling of pores between clay particles.

Hydration Properties and Interlayer Organization of Water and Ions in Synthetic Na-Smectite with Tetrahedral Layer Charge. Part 1. Results from X-ray Diffraction Profile Modeling

“…That on layer abundance was considered to vary linearly from (2% when the relative proportion of a given layer is 100% or 0% to (5% when this layer represents 50% of the total layers. corresponds to ∼5 and ∼3H 2 O molecules per cation for the low-and high-charge saponite, respectively, in agreement with results obtained by Rinnert et al 40 on similar samples. These values are also consistent with the three-dimensional (3D) structure determination obtained for Ca-, Sr-, Li-, Ba-, or Nasaturated vermiculite minerals in which the cation hydration shell was found to not exceed 4 H 2 O molecules per cation with a coordination similar to a flat tetrahedron.…”

“…The investigated saponites were prepared at ISTO (Orléans, France) by hydrothermal treatment as described in detail elsewhere, 40 before being sodium saturated. 20 Their structural formulas are the following: Na x (Si 8-x ,Al x )(Mg 6 )O 20 (OH) 4 , with x ) 0.8 and 1.4.…”

“…20 Positional disorder of interlayer H 2 O molecules is, however, suggested by the 3D structure refinement of vermiculites, [45][46][47] and by computational studies. 36,37,40,42,44,[48][49][50][51] The present XRD modeling study thus integrates this positional disorder in the determination of the fine interlayer structure of smectite and of its evolution upon dehydration using low-and high-charge synthetic saponites. The water content determined from the modeling procedure is compared to results obtained from water vapor adsorption/desorption isotherms experiments.…”

Hydration properties of synthetic high-charge micas saturated with different cations: An experimental approach

“…The swelling properties of clays have been studied extensively, both experimentally (Weiss et al, 1990;Cases et al, 1992;Bérend et al, 1995;Michot et al, 2002;Rinnert et al, 2005;Trausch et al, 2006;Salles et al, 2008) and theoretically (Boek et al, 1995a,b;de Siqueira et al, 1997;Young and Smith, 2000;Hensen et al, 2001;Hensen and Smit, 2002;Whitley and Smith, 2004;Tambach et al, 2004;Liu and Lu, 2006;Smith et al, 2006;Tambach et al, 2006) and are now relatively well understood. Mooney et al 3 (1952a,b) were among the first authors to show that smectites are able to sorb up to half their mass in water and that the water sorption behavior is strongly dependent on the nature of the exchangeable cation.…”

On the Thermodynamic and Dynamic Aspects of Immersion Ice Nucleation

“…The interaction between the particle and the vicinal water becomes more significant as the temperature decreases and the viscosity increases (Wolfe et al, 2002). Recent studies have shown the presence of ordered 10 water near interfaces in biological (Cooke and Kuntz, 1974;Snyder et al, 2014), metallic (Michot et al, 2002) and clay (Yu et al, 2001;Rinnert et al, 2005) particles, a notion that is also supported by molecular dynamics simulations (Lupi et al, 2014;Cox et al, 2015). In a groundbreaking work, Anderson (1967) found strong evidence of ice formation several molecular diameters away from the clay-water interface.…”