Scientific Achievement

3D imaging of hydrated clay structure reveals new structures, importance of curvature

Significance and Impact

  • All clay swelling is osmotic swelling
  • ‘Crystalline’ swelling is due to osmotic pressure of mineral, contrasting ‘osmotic’ swelling due to electrolyte solution

Research Details

  • New cryo electron tomography observations show montmorillonite layers interacting in aqua
  • Layers separate into distinct colloidal phases
  • Phases have different surface charge despite identical structural charge
  • Surface charge is regulated by ion (de)hydration at interface
  • Layer curvature modulates hydration state by altering relative proportions of hydration, electrostatic, and dispersion forces
  • Dynamic equilibrium between colloidal phases controls properties such as swelling pressure

Publication Details

M. L. Whittaker, M. Shoaib, L. N. Lammers, Y. Zhang, C. Tournassat, B. Gilbert. “Smectite phase separation is driven by hydration-mediated interfacial charge.” Journal of Colloid and Interface Science (2023).
DOI: 10.1016/j.jcis.2023.05.085