Abstract
Zeta (ζ) potential of clay minerals, which affects the dispersion and the flocculation in their water suspension, is generally determined by an electrophoresis method. This method is, however, required the diluted suspension system which is thoroughly dispersed, and needs considerably long times for the measurement. An electrokinetic sonic amplitude (ESA) method for the ζ-potentials was applied to four kinds of Na+-saturated clay minerals, kaolinite, halloysite, montmorillonite and allophane. The pH-dependence of ζ-potential was discussed comparing with the changes of their mean particle or aggregate sizes determined by a laser scattering method. The ζ-potential of kaolinite, halloysite, montmorillonite and allophane was 22, -15, -25 and -50 mV in the clay samples saturated with Na+ at about pH 7.0, respectively. These approximated to the values reported in the previous studies. The ζ-potential of clay minerals estimated with the ESA method was clearly related with the dispersibility of their suspension at various pHs. The ESA method was effective for the estimation of ζ-potential of clay minerals, in conclusion.
