Effects of pH on dielectric relaxation of montmorillonite, allophane, and imogolite suspensions

Tomoyuki Ishida, Tomoyuki Makino

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


Dielectric measurements were performed on montmorillonite, allophane, and imogolite suspensions under various pH conditions, using time domain reflectometry over the frequency range 10 kHz-20 GHz. A dielectric relaxation peak due to bound water could be observed for all the clays. Allophane has two peaks, indicating that its peaks are very similar to those of silica- alumina gels. Although imogolite has a similar chemical composition, only one peak was found. The relaxation strength of montmorillonite is greater than that of the other two clays. For all the clays, the relaxation strength depended on the pH. A change in the relaxation strength according to a change in pH is explained in terms of the different network structures of the clay particles. It is suggested that bound water influences the network structure formation. In montmorillonite, a great relaxation process detected at low frequency is caused by surface polarization of counterions. The change in measure of the structural unit with the pH, identified from Schwartz's theory, has a tendency similar to that postulated by other experimental techniques, and surface charge densities identified are close to those estimated from CEC.

Original languageEnglish
Pages (from-to)152-161
Number of pages10
JournalJournal of Colloid And Interface Science
Issue number1
Publication statusPublished - 1999 Apr 1
Externally publishedYes


  • Bound water
  • Clay minerals
  • Complex permittivity
  • Dielectric relaxation
  • Interfacial polarization

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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