Adsorption of Water Vapor by Homoionic Montmorillonites. Heats of Adsorption and Desorption

Cancela, G. Dios; Huertas, F. Javier; Romero, Esperanza; Sánchez-Rasero, F.; Laguna, Abilio

doi:10.1006/jcis.1996.4572

Cited by 72 publications

(104 citation statements)

References 8 publications

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“…A general feature, however, is that the amount of H20 sorbed at low-H20 contents (relative vapor pressure P/Po < 0.4) is influenced largely by the hydration energy of the exchangeable cation. In a combined sorption and microcalorimeter study, a similar relationship was observed by Cancela et al (1997) who showed that the amount of HeO sorbed by smectite was positively correlated with the hydration energy of the exchangeable cation. In addition, water-vapor adsorption isotherms for Na-, K-, Cs-, and Ca-exchanged SAz-1 were reported recently by Chiou and Rutherford (1997).…”

Section: Sorption Isothermssupporting

confidence: 75%

“…This work showed that water adsorption proceeds by initial solvation of the exchangeable cations followed by the occupancy of remaining interlayer space. Thus, the hydration characteristics of the clay mineral depend strongly on the exchangeable cation, This conclusion is also supported by recent computational studies of smectite-H20 complexes (Skipper et al, 199l, 1995a(Skipper et al, 199l, , 1995bKaraborni et al, 1996;Chang et al, 1997), and microcalorimeter data (Cancela et al, 1997), which are strongly dependent on tile type of interlayer cation.…”

Section: Introductionsupporting

confidence: 72%

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Infrared Study of Water Sorption on Na-, Li-, Ca-, and Mg-Exchanged (SWy-1 and SAz-1) Montmorillonite

2000

Clays and clay miner.

190

144

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Abstract--An environmental infrared microbalance (EIRM) cell was used to study H20 sorption on two montmorillonite samples as a function of water content and type of exchangeable cation. The vibrational spectra showed that H20 sorbed to the clay at low-water content was strongly influenced by the exchangeable" cation and by the close proximity to the clay surface. At water contents <6 H20 molecules per exchangeable cation, the H-O-H bending mode of H20 (v 2 mode) shifts to a lower frequency and is characterized by an increase in molar absorptivity. In contrast, the positions of the asymmetric and symmetric OH-stretching modes of sorbed water (vl and v3 modes) shift to higher energies. These observations indicate that H20 molecules sorbed to the clay surface at low-water content are less hydrogen bonded than in bulk H20. In addition, the vibrational-stretching and bending bands of the structural OH groups of the 2:1 layer are also strongly influenced by H20 content and type of exchangeable cation. By using the EIRM cell, the molar absorptivities of the structural OH-bending vibrations were measured as a function of H20 content. The position and molar absorptivity of the structural OH-bending bands at 920, 883, and 840 cm l are strongly influenced by H20 content and type of exchangeable cation. The molar absorptivity of the 920-cm ~ band, which is assigned to the A1A1OH group, decreased strongly at low-H20 content. This reduction in intensity is assigned to a dehydration-induced change in orientation of the structural OH groups resulting from the penetration of H20 molecules into siloxane ditrigonal cavities that are not associated with a net negative charge from isomorphous substitutions.

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Section: Sorption Isothermssupporting

confidence: 75%

Section: Introductionsupporting

confidence: 72%

Infrared Study of Water Sorption on Na-, Li-, Ca-, and Mg-Exchanged (SWy-1 and SAz-1) Montmorillonite

2000

Clays and clay miner.

190

144

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“…The equilibrium water density of such a hydrated clay depends on the type of clay mineral, the type of interlayer counterion, the applied pressure and temperature, and the water vapor pressure. [3][4][5][6] Although clay swelling is well understood on a qualitative level, the quantitative details are difficult to access experimentally, especially on the molecular level. Statisticalmechanical computer simulations are ideally suited to obtain such microscopic insight.…”

Section: Introductionmentioning

confidence: 99%

Adsorption isotherms of water in Li–, Na–, and K–montmorillonite by molecular simulation

Hensen

Tambach

Bliek

et al. 2001

The Journal of Chemical Physics

102

133

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A biased Monte Carlo method for the insertion of water in dense clay-water systems is presented. The use of this algorithm results in a considerable increase of the success rate of insertion attempts. It allows us to compute water adsorption isotherms up to high water densities, where the conventional Monte Carlo scheme fails. The isotherms were calculated by a combination of molecular dynamics and grand-canonical Monte Carlo simulation for Li-, Na-, and Kmontmorillonite at a fixed d(001) spacing of 12.0 Å. At low water pressure, the degree of clay hydration is governed by the type of counterion, Li-montmorillonite having the highest water content. Hydrogen bonding between water molecules is absent. Li ϩ and Na ϩ are small enough to be organized in two layers close to the clay mineral surfaces, whereas K ϩ is mainly located in the midplane. In both cases, the water molecules primarily reside in the midplane of the interlayer. Increasing the water pressure leads to water adsorption at higher energy sites closer to the surface, i.e., coordinating to the structural OH groups in the hexagonal cavities. A hydrogen bond network is formed in the clay interlayer. This points to water condensation and leads to a sharp increase in the clay water content.

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“…The hydration enthalpy is retrieved from data of [24] for montmorillonite -Na and -K and derived from differential heats of adsorption obtained from the measurements of the heat of immersion [18,20] The maximum number of moles of interlayer water was set to 5.5 moles. Figure 4A displays the comparison of integral enthalpy of hydration of a smectite-Na computed from the three models developed previously with different experimental values.…”

Section: Zeolite Mineralsmentioning

confidence: 99%

Thermodynamics of Hydration in Minerals: How to Predict These Entities

Vieillard¹

2012

Thermodynamics - Fundamentals and Its Application in Science

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Adsorption of Water Vapor by Homoionic Montmorillonites. Heats of Adsorption and Desorption

Cited by 72 publications

References 8 publications

Infrared Study of Water Sorption on Na-, Li-, Ca-, and Mg-Exchanged (SWy-1 and SAz-1) Montmorillonite

Infrared Study of Water Sorption on Na-, Li-, Ca-, and Mg-Exchanged (SWy-1 and SAz-1) Montmorillonite

Adsorption isotherms of water in Li–, Na–, and K–montmorillonite by molecular simulation

Thermodynamics of Hydration in Minerals: How to Predict These Entities

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