Chapter 7. The Colloidal Nature of Kaolinite

  1. William M. Carty
  1. William M. Carty

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294673.ch7

Materials & Equipment/Whitewares: Ceramic Engineering and Science Proceedings, Volume 22, Issue 2

Materials & Equipment/Whitewares: Ceramic Engineering and Science Proceedings, Volume 22, Issue 2

How to Cite

Carty, W. M. (2001) The Colloidal Nature of Kaolinite, in Materials & Equipment/Whitewares: Ceramic Engineering and Science Proceedings, Volume 22, Issue 2 (ed W. M. Carty), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294673.ch7

Author Information

  1. Whiteware Research Center, Alfred University, Alfred, New York

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2001

ISBN Information

Print ISBN: 9780470375723

Online ISBN: 9780470294673

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Keywords:

  • kaolinite;
  • mineralogy;
  • sheet silicate;
  • colloidal theory;
  • colloidal alumina

Summary

The commonly held view of kaolinite particles in water — that of negatively-charged basal plane surfaces with positive edges — is inconsistent with the mineralogy and dispersion behavior. Kaolinite is a 1:1 sheet silicate, one side silica-like and other aluminum hydroxide-like, with a variable edge nature. Therefore, based on the colloidal theory and the generation of surface potential in an aqueous environment, it is proposed that the silica-like surface will be negatively charged and the aluminum hydroxide-like surface will be positively charged over a broad pH range. The edges of the particle will adopt a net charge (either negative or positive) as a function of the suspension pH. The dispersant demand for kaolinite particles is consistent with roughly one-half as much dispersant necessary to reach the minimum in the viscosity curve, compared to the dispersant demand for colloidal alumina, further supporting the dual basal plane surface model. In aqueous suspension, the silica-like basal plane surface charge should be negative and the alumina-like basal plane surface charge should be positive over a broad pH range. The charge on the edge is dependent on pH.