Anomalous temperature behavior in clay swelling due to ion-ion correlations

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Abstract

We show, experimentally and theoretically, that swelling of both natural and refined clays has an anomalous temperature behavior depending on counterion valency. In an aqueous clay dispersion dominated by monovalent counterions the swelling pressure increases with temperature as expected from entropic arguments. In a clay with predominantly divalent counterions, the opposite behavior is found. The explanation is due to the fact that ion-ion correlations increase with temperature. Ion-ion correlations are important at strong electrostatic coupling and in an aqueous solution the dielectric permittivity, ϵr, drops with increased temperature, T, in such a way that the product ϵrT also decreases. Thus, the net effect is an increased coupling.

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Authors
Organisations
External organisations
  • Clay Technology AB
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Materials Chemistry
Original languageEnglish
Article number38002
JournalEurophysics Letters
Volume114
Issue number3
Publication statusPublished - 2016 May 1
Publication categoryResearch
Peer-reviewedYes