The structure and dynamics of 2-dimensional fluids in swelling clays

Neal T. Skipper, Peter A. Lock, James O. Titiloye, Jan Swenson, Zakaria A. Mirza, W. Spencer Howells, Felix Fernandez-Alonso

Research output: Contribution to journalArticle

Abstract

The interlayer pores of swelling 2:1 clays provide an ideal 2-dimensional environment in which to study confined fluids. In this paper we discuss our understanding of the structure and dynamics of interlayer fluid species in expanded clays, based primarily on the outcome of recent molecular modelling and neutron scattering studies. Counterion solvation is compared with that measured in bulk solutions, and at a local level the cation-oxygen coordination is found to be remarkably similar in these two environments. However, for the monovalent ions the contribution to the first coordination shell from the clay surfaces increases with counterion radius. This gives rise to inner-sphere (surface) complexes in the case of potassium and caesium. In this context, the location of the negative clay surface charge (i.e. arising from octahedral or tetrahedral substitution) is also found to be of major importance. Divalent cations, such as calcium, eagerly solvate to form outer-sphere complexes. These complexes are able to pin adjacent clay layers together, and thereby prevent colloidal swelling. Confined water molecules form hydrogen bonds to each other and to the clays' surfaces. In this way their local environment relaxes to close to the bulk water structure within two molecular layers of the clay surface. Finally, we discuss the way in which the simple organic molecules methane, methanol and ethylene glycol behave in the interlayer region of hydrated clays. Quasi-elastic neutron scattering of isotopically labelled interlayer CH 3OD and (CH2OD)2 in deuterated clay allows us to measure the diffusion of the CH3- and CH2-groups in both clay and liquid environments. We find that in both the one-layer methanol solvates and the two-layer glycol solvates the diffusion of the most mobile organic molecules is close to that in the bulk solution.
Original languageEnglish
Pages (from-to)182-196
Number of pages15
JournalChemical Geology
Volume230
Issue number3-4
DOIs
Publication statusPublished - 22 Jun 2006

Fingerprint

swelling
Swelling
clay
Fluids
fluid
neutron scattering
Neutron scattering
Molecules
Methanol
methanol
cation
Cesium
Glycols
Molecular modeling
Elastic scattering
Ethylene Glycol
Water
cesium
Divalent Cations
Methane

Keywords

  • swelling clay
  • confined fluid
  • fluid diffusion

Cite this

Skipper, N. T., Lock, P. A., Titiloye, J. O., Swenson, J., Mirza, Z. A., Howells, W. S., & Fernandez-Alonso, F. (2006). The structure and dynamics of 2-dimensional fluids in swelling clays. Chemical Geology, 230(3-4), 182-196. https://doi.org/10.1016/j.chemgeo.2006.02.023
Skipper, Neal T. ; Lock, Peter A. ; Titiloye, James O. ; Swenson, Jan ; Mirza, Zakaria A. ; Howells, W. Spencer ; Fernandez-Alonso, Felix. / The structure and dynamics of 2-dimensional fluids in swelling clays. In: Chemical Geology. 2006 ; Vol. 230, No. 3-4. pp. 182-196.
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Skipper, NT, Lock, PA, Titiloye, JO, Swenson, J, Mirza, ZA, Howells, WS & Fernandez-Alonso, F 2006, 'The structure and dynamics of 2-dimensional fluids in swelling clays', Chemical Geology, vol. 230, no. 3-4, pp. 182-196. https://doi.org/10.1016/j.chemgeo.2006.02.023

The structure and dynamics of 2-dimensional fluids in swelling clays. / Skipper, Neal T.; Lock, Peter A.; Titiloye, James O.; Swenson, Jan; Mirza, Zakaria A.; Howells, W. Spencer; Fernandez-Alonso, Felix.

In: Chemical Geology, Vol. 230, No. 3-4, 22.06.2006, p. 182-196.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The structure and dynamics of 2-dimensional fluids in swelling clays

AU - Skipper, Neal T.

AU - Lock, Peter A.

AU - Titiloye, James O.

AU - Swenson, Jan

AU - Mirza, Zakaria A.

AU - Howells, W. Spencer

AU - Fernandez-Alonso, Felix

N1 - Copyright 2011 Elsevier B.V., All rights reserved.

PY - 2006/6/22

Y1 - 2006/6/22

N2 - The interlayer pores of swelling 2:1 clays provide an ideal 2-dimensional environment in which to study confined fluids. In this paper we discuss our understanding of the structure and dynamics of interlayer fluid species in expanded clays, based primarily on the outcome of recent molecular modelling and neutron scattering studies. Counterion solvation is compared with that measured in bulk solutions, and at a local level the cation-oxygen coordination is found to be remarkably similar in these two environments. However, for the monovalent ions the contribution to the first coordination shell from the clay surfaces increases with counterion radius. This gives rise to inner-sphere (surface) complexes in the case of potassium and caesium. In this context, the location of the negative clay surface charge (i.e. arising from octahedral or tetrahedral substitution) is also found to be of major importance. Divalent cations, such as calcium, eagerly solvate to form outer-sphere complexes. These complexes are able to pin adjacent clay layers together, and thereby prevent colloidal swelling. Confined water molecules form hydrogen bonds to each other and to the clays' surfaces. In this way their local environment relaxes to close to the bulk water structure within two molecular layers of the clay surface. Finally, we discuss the way in which the simple organic molecules methane, methanol and ethylene glycol behave in the interlayer region of hydrated clays. Quasi-elastic neutron scattering of isotopically labelled interlayer CH 3OD and (CH2OD)2 in deuterated clay allows us to measure the diffusion of the CH3- and CH2-groups in both clay and liquid environments. We find that in both the one-layer methanol solvates and the two-layer glycol solvates the diffusion of the most mobile organic molecules is close to that in the bulk solution.

AB - The interlayer pores of swelling 2:1 clays provide an ideal 2-dimensional environment in which to study confined fluids. In this paper we discuss our understanding of the structure and dynamics of interlayer fluid species in expanded clays, based primarily on the outcome of recent molecular modelling and neutron scattering studies. Counterion solvation is compared with that measured in bulk solutions, and at a local level the cation-oxygen coordination is found to be remarkably similar in these two environments. However, for the monovalent ions the contribution to the first coordination shell from the clay surfaces increases with counterion radius. This gives rise to inner-sphere (surface) complexes in the case of potassium and caesium. In this context, the location of the negative clay surface charge (i.e. arising from octahedral or tetrahedral substitution) is also found to be of major importance. Divalent cations, such as calcium, eagerly solvate to form outer-sphere complexes. These complexes are able to pin adjacent clay layers together, and thereby prevent colloidal swelling. Confined water molecules form hydrogen bonds to each other and to the clays' surfaces. In this way their local environment relaxes to close to the bulk water structure within two molecular layers of the clay surface. Finally, we discuss the way in which the simple organic molecules methane, methanol and ethylene glycol behave in the interlayer region of hydrated clays. Quasi-elastic neutron scattering of isotopically labelled interlayer CH 3OD and (CH2OD)2 in deuterated clay allows us to measure the diffusion of the CH3- and CH2-groups in both clay and liquid environments. We find that in both the one-layer methanol solvates and the two-layer glycol solvates the diffusion of the most mobile organic molecules is close to that in the bulk solution.

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KW - confined fluid

KW - fluid diffusion

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Skipper NT, Lock PA, Titiloye JO, Swenson J, Mirza ZA, Howells WS et al. The structure and dynamics of 2-dimensional fluids in swelling clays. Chemical Geology. 2006 Jun 22;230(3-4):182-196. https://doi.org/10.1016/j.chemgeo.2006.02.023