Hydration and Mobility of Interlayer Ions of (Nax, Cay)-Montmorillonite: A Molecular Dynamics Study

Zhang, Lihu; Lu, Xiancai; Liu, Xiandong; Zhou, Jinhong; Zhou, Huiqun

doi:10.1021/jp508427c

Cited by 97 publications

(129 citation statements)

References 93 publications

(159 reference statements)

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“…As shown by the plots of interlayer water density profiles ( Fig. 2c ), well-defined 1, 2 and 3-layer hydration states develop at layer distances that agree with experimental observations of low-charge smectite 6 9 11 12 13 . Although these stable hydration states exhibit the most structured water perpendicular to the layers, the plot of the mean lateral diffusion rates for each configuration ( Fig.…”

supporting

confidence: 86%

“…Although there have been many studies showing the preference for the fully developed hydration layers 4 5 6 7 10 11 13 19 20 , this is believed to be the first study showing that the formation of stable and transition states affects the mobility of water confined between uncharged smectite layers. Moreover, our simulations predict that external aqueous solutions can restrict the mobility of water confined within thin layers.…”

mentioning

confidence: 87%

“…The dynamics of water molecules confined between smectite layers differ from bulk water. Both simulations and experiments 6 9 11 12 13 report a lower self-diffusion coefficient of trapped water as compared to the bulk water, which approaches the macroscopic value as clay hydration (swelling) progresses. It has been shown that interlayer water mobility is determined by several short-range interactions including intermolecular hydrogen bonding 14 15 and water-mineral interactions that are significant for highly confined fluids 16 17 .…”

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confidence: 93%

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Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers

Zarzycki

Gilbert

2016

Sci Rep

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Water diffusion within smectite clay interlayers is reduced by confinement and hence is highly determined by the interlayer spacings that are adopted during swelling. However, a molecular understanding of the short- and long-range forces governing interlayer water structure and dynamics is lacking. Using molecular dynamics simulations of water intercalated between pyrophyllite (smectite prototype) layers we provide a detailed picture of the variation of interlayered water mobility accompanying smectite expansion. Subtle changes in hydrogen bond network structure cause significant changes in water mobility that is greater for stable hydration states and reduced for intermediate separations. By studying pyrophyllite with and without external water we reveal that long-range electrostatic forces apply a restraining effect upon interlayer water mobility. Our findings are relevant for broad range of confining nanostructures with walls thin enough to permit long-range interactions that could affect the mobility of confined solvent molecules and solute species.

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confidence: 86%

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confidence: 87%

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confidence: 93%

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Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers

Zarzycki

Gilbert

2016

Sci Rep

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“…This fact suggests a higher mobility of water associated with the monovalent ions than with the divalent ions. 28,30 However, there are exceptions, e.g., water is less mobile in the 1W hydration state of Li-montmorillonite possibly due to the presence of inner-sphere surface complexes. Interestingly, in the presence of CO 2 , the water diffusion is more restricted in Cs-montmorillonite when compared to K-montmorillonite.…”

Section: Diffusion Of Hmentioning

confidence: 99%

Layer Charge Effects on Adsorption and Diffusion of Water and Ions in Interlayers and on External Surfaces of Montmorillonite

Yang

Nair

Sun

2019

ACS Earth Space Chem.

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Molecular simulations using classical force fields were performed to study the adsorption and diffusion properties of water and ions in the high-charge (Arizonatype) montmorillonite clays with varying relative humidity (RH) at 298.15 K. The simulation results of basal distances derived from swelling free energy curves and of water uptake are in good agreement with experiments. Overall, the simulated self-diffusion coefficients of the interlayer species are in reasonable agreement with experiments and lower than those estimated for the external surfaces. Influence of the magnitude of the layer charge was studied by comparing these simulation results with those obtained for the low-charge (Wyoming-type) montmorillonite clays. Most importantly, these comparisons confirm the experimental finding that the high-charge clay generally shifts swelling transitions toward lower RH values. Therefore, the adsorption and dynamics of water and ions are significantly different in the low-and high-charge clays near the transition RH values. We find that the amount of water in an interlayer hydration state is mostly independent of the layer charge, probably due to steric reasons. In contrast, the externally adsorbed water content increases with increasing layer charge. Furthermore, the mobility of water and ions is generally lower in the high-charge montmorillonite than in the corresponding low-charge system. However, mobility of cations in the mesopores of high-charge montmorillonite is typically higher than that of the corresponding low-charge system which might be attributed to the presence of the tetrahedral substitutions in the later case.

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“…[2][3][4]34,[37][38][39][40][41][42][43][44][45][46] The swelling process typically exhibits two regimes: crystalline swelling at basal d-spacings < ∼ 19Å and osmotic swelling corresponding to basal d-spacings > ∼ 30Å. 47,48 The stable basal dspacing is about 10Å for dry clays (no water molecules in the interlayer) and increases upon contact with water to the range 11.5-12.5Å yielding a fully saturated monolayer (1W) water arrangement.…”

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confidence: 99%

Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

2016

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Molecular dynamics simulations were carried out to study the structural and transport properties of carbon dioxide, methane, and their mixture at 298.15 K in Na-montmorillonite clay in the presence of water. The simulations show that, the self-diffusion coefficients of pure CO 2 and CH 4 molecules in the interlayers of Na-montmorillonite decrease as their loading increases, possibly because of steric hindrance. The diffusion of CO 2 in the interlayers of Na-montmorillonite, at constant loading of CO 2 , is not significantly affected by CH 4 for the investigated CO 2 /CH 4 mixture compositions. We attribute this to the preferential adsorption of CO 2 over CH 4 in Na-montmorillonite. While the presence of adsorbed CO 2 molecules, at constant loading of CH 4 , very significantly reduces the self-diffusion coefficients of CH 4 , and relatively larger decrease in those diffusion coefficients are obtained at higher loadings. The preferential adsorption of CO 2 molecules to the clay surface screens those possible attractive surface sites for CH 4 . The competition between screening and steric effects leads to a very slight decrease in the diffusion coefficients of CH 4 molecules at low CO 2 loadings. The steric hindrance effect, however, becomes much more significant at higher CO 2 loadings and the diffusion coefficients of methane molecules significantly decrease. Our simulations also indicate that, similar effects of water on both carbon dioxide and methane, increase with increasing water concentration, at constant loadings of CO 2 and CH 4 in the interlayers of Na-montmorillonite. Our results could be useful, because of the significance of shale gas exploitation and carbon dioxide storage.

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Hydration and Mobility of Interlayer Ions of (Na_x, Ca_y)-Montmorillonite: A Molecular Dynamics Study

Cited by 97 publications

References 93 publications

Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers

Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers

Layer Charge Effects on Adsorption and Diffusion of Water and Ions in Interlayers and on External Surfaces of Montmorillonite

Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

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