Compression study on hydrophobic layered silicates dispersed in organic liquid mixtures

E. Tombácz, István Deér, I. Dékány

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7 Citations (Scopus)

Abstract

The behaviour of n-octadecylammonium montmorillonite particles dispersed in pure methanol and pure benzene or their mixtures was studied under compressive and decompressive conditions by using an analytical ultracentrifuge. Series of pressure and volume fraction data relating to the same state of dispersion were calculated. On the supposition of a flat-to-flat ordered structure of the silicate layers in the sediment, both the distance between lamellae and the basal spacing values could be calculated from the volume fraction data of the solid component. Conclusions were drawn from comparisons of determined basal spacings with experimental basal spacings obtained from X-ray diffraction measurements for the same systems and with the calculated values of the most probable arrangement of the alkyl chains between the silicate layers. As the compression is increased, the pendent long alkyl chains on the opposing layers can interpenetrate. At the highest compression, the chains lie flat on the silicate layers, similarly to their structure in the dried state. On decrease of the deformation force, the alkyl chains rise and reach the tilt angle of 55° calculated from the molecular geometry of the organocomplex. The silicate layers with pendent alkyl chains can move further away as liquid transport from the supernatant leads to a solid/liquid (S/L) adsorption equilibrium at lower compression. Reversible changes in basal spacing during a compressive-decompressive cycle can take place at the azeotropic composition of liquid mixture adsorption, when the decrease in the excess free energy function of the adsorption exchange process calculated from the excess isotherm of methanol-benzene adsorption is a maximum.

Original languageEnglish
Pages (from-to)269-276
Number of pages8
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume71
Issue number3
DOIs
Publication statusPublished - Jun 9 1993

Fingerprint

Silicates
organic liquids
silicates
Adsorption
spacing
Liquids
Benzene
adsorption
Methanol
Volume fraction
Bentonite
methyl alcohol
liquids
benzene
Clay minerals
Free energy
Isotherms
lamella
montmorillonite
Sediments

Keywords

  • Compression
  • layers
  • silicates.

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry

Cite this

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abstract = "The behaviour of n-octadecylammonium montmorillonite particles dispersed in pure methanol and pure benzene or their mixtures was studied under compressive and decompressive conditions by using an analytical ultracentrifuge. Series of pressure and volume fraction data relating to the same state of dispersion were calculated. On the supposition of a flat-to-flat ordered structure of the silicate layers in the sediment, both the distance between lamellae and the basal spacing values could be calculated from the volume fraction data of the solid component. Conclusions were drawn from comparisons of determined basal spacings with experimental basal spacings obtained from X-ray diffraction measurements for the same systems and with the calculated values of the most probable arrangement of the alkyl chains between the silicate layers. As the compression is increased, the pendent long alkyl chains on the opposing layers can interpenetrate. At the highest compression, the chains lie flat on the silicate layers, similarly to their structure in the dried state. On decrease of the deformation force, the alkyl chains rise and reach the tilt angle of 55° calculated from the molecular geometry of the organocomplex. The silicate layers with pendent alkyl chains can move further away as liquid transport from the supernatant leads to a solid/liquid (S/L) adsorption equilibrium at lower compression. Reversible changes in basal spacing during a compressive-decompressive cycle can take place at the azeotropic composition of liquid mixture adsorption, when the decrease in the excess free energy function of the adsorption exchange process calculated from the excess isotherm of methanol-benzene adsorption is a maximum.",
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N2 - The behaviour of n-octadecylammonium montmorillonite particles dispersed in pure methanol and pure benzene or their mixtures was studied under compressive and decompressive conditions by using an analytical ultracentrifuge. Series of pressure and volume fraction data relating to the same state of dispersion were calculated. On the supposition of a flat-to-flat ordered structure of the silicate layers in the sediment, both the distance between lamellae and the basal spacing values could be calculated from the volume fraction data of the solid component. Conclusions were drawn from comparisons of determined basal spacings with experimental basal spacings obtained from X-ray diffraction measurements for the same systems and with the calculated values of the most probable arrangement of the alkyl chains between the silicate layers. As the compression is increased, the pendent long alkyl chains on the opposing layers can interpenetrate. At the highest compression, the chains lie flat on the silicate layers, similarly to their structure in the dried state. On decrease of the deformation force, the alkyl chains rise and reach the tilt angle of 55° calculated from the molecular geometry of the organocomplex. The silicate layers with pendent alkyl chains can move further away as liquid transport from the supernatant leads to a solid/liquid (S/L) adsorption equilibrium at lower compression. Reversible changes in basal spacing during a compressive-decompressive cycle can take place at the azeotropic composition of liquid mixture adsorption, when the decrease in the excess free energy function of the adsorption exchange process calculated from the excess isotherm of methanol-benzene adsorption is a maximum.

AB - The behaviour of n-octadecylammonium montmorillonite particles dispersed in pure methanol and pure benzene or their mixtures was studied under compressive and decompressive conditions by using an analytical ultracentrifuge. Series of pressure and volume fraction data relating to the same state of dispersion were calculated. On the supposition of a flat-to-flat ordered structure of the silicate layers in the sediment, both the distance between lamellae and the basal spacing values could be calculated from the volume fraction data of the solid component. Conclusions were drawn from comparisons of determined basal spacings with experimental basal spacings obtained from X-ray diffraction measurements for the same systems and with the calculated values of the most probable arrangement of the alkyl chains between the silicate layers. As the compression is increased, the pendent long alkyl chains on the opposing layers can interpenetrate. At the highest compression, the chains lie flat on the silicate layers, similarly to their structure in the dried state. On decrease of the deformation force, the alkyl chains rise and reach the tilt angle of 55° calculated from the molecular geometry of the organocomplex. The silicate layers with pendent alkyl chains can move further away as liquid transport from the supernatant leads to a solid/liquid (S/L) adsorption equilibrium at lower compression. Reversible changes in basal spacing during a compressive-decompressive cycle can take place at the azeotropic composition of liquid mixture adsorption, when the decrease in the excess free energy function of the adsorption exchange process calculated from the excess isotherm of methanol-benzene adsorption is a maximum.

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