Dehydration of Ca-montmorillonite at the crystal scale. Part I: Structure evolution

Ferrage, Eric; Kirk, Caroline A.; Cressey, G.; Cuadros, Javier

doi:10.2138/am.2007.2396

Cited by 81 publications

(77 citation statements)

References 49 publications

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“…Indeed for smectite saturated with divalent cations (Ca 2+ ,S r 2+ ,M g 2+ ) an increase of σ z values is systematically observed for bihydrated states. 20,25,26 In the case of saponite, an increase of layer charge appears to slightly lower the value of σ z when 1W layers prevail (0.28 and 0.21 Å for S-Na 0.8 and S-Na 1.4 samples, respectively; Tables 1 and 2). This may tentatively be assigned to stronger cation-layer interactions but additional studies are required to confirm such an assumption.…”

Section: Discussionmentioning

confidence: 96%

“…Using a systematic fitting procedure the evolution of layer type abundance and of crystal parameters can be followed accurately along the water vapor desorption isotherm, which allows assessing the specificity of the studied saponite by comparison with previous studies performed on natural smectites. 20,25,26 Structure Models and Crystal Parameters EWolution. The CSDSs along the c* axis (N parameter, Tables 1 and 2) are higher for saponites than for natural smectites.…”

Section: Discussionmentioning

confidence: 99%

“…A similar CSDS increase with decreasing hydration was already observed as a result of either RH decrease or temperature increase. 20,25,26 It was interpreted as a disruption of some 2W layer stacks owing to weaker electrostatic interactions between layers resulting from increasing interlayer distances upon hydration. Although consistent with this interpretation, the CSDS increase during the 2W-1W transition is less significant than that for Na-saturated low-charge montmorillonite (increase of ∼25% and ∼50%, respectively).…”

Section: Discussionmentioning

confidence: 99%

“…[21][22][23][24] By fitting positions and profiles of the 00l reflections over a large angular range, the relative proportions of the different layer types can be determined together with the thickness and water content of the different layer types. 20,25,26 These studies showed systematic hydration heterogeneity whatever the interlayer cation, relative humidity (RH), amount, and location of layer charge and temperature.…”

Section: Introduction and Background Informationmentioning

confidence: 99%

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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

Ferrage¹,

Lanson²,

Michot³

et al. 2010

J. Phys. Chem. C

205

246

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The dehydration of two Na-saturated synthetic saponites with contrasting layer charge was studied by modeling the X-ray diffraction (XRD) patterns recorded along a water vapor desorption isotherm. The interlayer configurations used to reproduce the XRD data over a large angular range include Na + cations located in the interlayer midplane and H 2 O molecules normally distributed about one or two main positions for mono-and bihydrated layers, respectively. Although strongly reduced in comparison to natural smectites, hydration heterogeneity was systematically observed for these synthetic saponites, especially along the transition between two hydration states. Using improved models for the description of the interlayer organization, the influence of layer charge on the structure of interlayer water can be precisely assessed. In addition, the comparison with water contents obtained from water vapor gravimetry experiments allows discriminating the relative contributions of H 2 O molecules from 1W and 2W interlayers (crystalline water) and from the pore space network.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introduction and Background Informationmentioning

confidence: 99%

See 2 more Smart Citations

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

Ferrage¹,

Lanson²,

Michot³

et al. 2010

J. Phys. Chem. C

205

246

View full text Add to dashboard Cite

show abstract

“…Three and two layers associated with the interlayer ions Na + ,Ca 2+ and Mg 2+ , respectively for SM and MX-80 (Kozaki et al, 1998;Van Loon et al, 2007;Cases et al, 1997, Ferrage et al, 2007Melkior et al, 2009). Since Na/Ca-smectites tend to segregate into a mixture of Na-smectite and Ca-smectite (Iwasaki and Takashi, 1988), the mean coverage in the interlayers was calculated according to the following relation:…”

Section: Characteristics Of the Water-saturated Compacted Clay Mediamentioning

confidence: 98%

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

Montavon

Guo

Tournassat

et al. 2009

Geochimica et Cosmochimica Acta

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. 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. Geochimica et Cosmochimica Acta, Elsevier, 2009, 73 (24) AbstractThe aim of the present work was to quantify accessible porosities for iodide and for a water tracer (HTO) on water-saturated compacted clay samples (illite, montmorillonite and MX-80 bentonite) and to relate these macroscopic values to the forms of water in these porosities (surface/bulk water, external/internal water). Low field proton NMR was used to characterize and quantify the forms of water. This enabled the three different populations (structural OH, external surface and internal surface water) to be differentiated on hydrated clays by considering the difference in proton mobility. An accurate description of the water forms within the different populations did not appear possible when water molecules of these populations were in contact because of the occurrence of rapid exchange reactions. For this 2 reason, it was not possible to use the low resolution NMR method to quantify external surface and bulk water in fully water-saturated compacted clay media at room temperature. This latter information could however be estimated when analyzing the samples at -25°C. At this temperature, a distinction based on the difference in mobility could be made since surface water remained in a semi-liquid state whereas bulk water froze. In parallel, accessible porosities for anions and HTO were determined by an isotopic dilution method using capillaries to confine the materials. HTO was shown to probe the whole pore volume (i.e. the space made of surface and bulk water). When the surface water volume was mainly composed of interlayer water (case of montmorillonite and bentonite), iodide was shown to be located in the pore space made of bulk water. When the interlayer water was not present (case of illite), the results showed that iodide could access a small fraction of the surface water volume localized at the external surface of the clay particles.

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Constraining clay hydration state and its role in active fault systems

Schleicher

Hofmann

Pluijm

2013

Geochem Geophys Geosyst

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[1] To understand the role of hydrated clay minerals in active fault systems, a humidity chamber connected to an X-ray diffractometer was used to determine the adsorption of water onto and/or into the crystal structure of smectite. This new type of analysis was carried out under specific temperature and humidity conditions, using powdered clay size fractions (< 2 mm) of rock samples from the San Andreas Fault (USA) and the Nankai Trough (Japan). Pressure cannot be controlled, but does not significantly affect clay swelling at shallow conditions. Air-dried samples show a discrete smectite phase that swells after traditional ethylene glycolation to an interlayer distance of 1.5 and 1.7 nm. Using the humidity chamber, however, the samples show a shorter interlayer distance, between 1.09 and 1.54 nm. Based on our analysis, we show that (i) ethylene glycol overestimates the size of the interlayer space, and therefore water content, so is a crude maximum only; (ii) interlayer swelling occurs in smectite clay minerals at all temperatures between 25 and 95 C; and (iii) particle orientation increases with increasing humidity, indicating a higher mobility of smectite from interlayer hydration. Detailed characterization of the hydration state of smectite under original conditions is critical for understanding of clay-fluid interaction, the mechanical behavior during fault displacements, and fluid budgets at depth. We propose that humidity chamber experiments should be the new standard procedure to constrain swelling characteristics of natural and synthetic clay minerals.

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Dehydration of Ca-montmorillonite at the crystal scale. Part I: Structure evolution

Cited by 81 publications

References 49 publications

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

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

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

Constraining clay hydration state and its role in active fault systems

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