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Clays as Colloids

Clays as Colloids. R. F. Giese Geology glgclay@acsu.buffalo.edu. Meaning of “clay”. Engineering small particles of any material Geological small particles of layer silicate minerals. Outline. Uses. Structure. Chemistry. Surface properties. Stability of clay-water systems Landslide.

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Clays as Colloids

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  1. Clays as Colloids R. F. Giese Geology glgclay@acsu.buffalo.edu

  2. Meaning of “clay” • Engineering • small particles of any material • Geological • small particles of layer silicate minerals

  3. Outline • Uses. • Structure. • Chemistry. • Surface properties. • Stability of clay-water systems • Landslide

  4. Importance of clays • Industrial • thickeners (paints, drilling muds) • catalysts (cracking of hydrocarbons) • fillers (rubber, plastics) • adsorbents • Geological • alteration products of rock • formation of hydrocarbons

  5. Importance of clays • Scientific • large surface area • known surface structure • nano-composites • insulators • designer surfaces

  6. Clay Minerals • Layer silicates • Silicates are oxides of silicon and other elements: • Aluminum, magnesium, iron, calcium, sodium • Oxygen (anion) is larger than the other elements (cations)

  7. Origin and calculation of the layer charge for 2:1 clay minerals.

  8. Kaolinite: TEM replica

  9. Kaolinite: TEM

  10. Halloysite: TEM

  11. Micas

  12. Smectites Vermiculites

  13. Organo-clays

  14. Montmorillonite: TEM replica

  15. Montmorillonite: TEM

  16. Allophane TEM replica

  17. Allophane TEM replica

  18. Surface tension measurements • Single crystals (micas) • oriented films (smectites) • thin layer wicking (kaolinite)

  19. Generalities for clays

  20. For all natural clays: difference between hydrophobic and hydrophilic

  21. Natural and modified clay materials

  22. Coverage of talc by a long chain amine (in wt%)

  23. Coverage of smectite by organic matter

  24. Interactions in water • Flocculation • Adsorption • DLVO versus XDLVO

  25. Montmorillonite: XDLVO

  26. Stability of montmorillonite

  27. Quick clays • Clays deposited in marine environment • sea level drops • rain leaches out the salty pore water • attraction between particles is weakened • soil becomes unstable • Canada, Scandinavia

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