THE DYNAMIC MOBILITY AND DIELECTRIC RESPONSE OF KAOLINITE PARTICLES

A new electroacoustic instrument (AcoustoSizer, Matec Applied Sciences ) has been used to measure the dynamic mobility of Nakaolinite and gam ma-aluminium hydroxide (gibbsite) suspensions at MHz frequencies. In b oth suspensions the particles consist of thin, approximately hexagonal plates. Information about the particle size and the electrokinetic ch arge or zeta potential can be obtained from the dynamic mobility spect rum, For kaolinite particles, the interpretation of the dynamic mobili ty spectrum is complicated by the presence of anomalously high surface conductance. This profoundly affects the shape of the dynamic mobilit y spectrum at low (<5 x 10(-3) M) electrolyte concentrations, An appro ximate formula which takes surface conductance and particle shape into account has recently been derived by Loewenberg (1), Our measured dyn amic mobility spectra are in good agreement with this theory. The surf ace conductance of the particles can be determined directly by dielect ric response measurements on a high-frequency conductance bridge. The surface conductances determined in this way compare qualitatively with those needed to fit the dynamic mobility data using the theory descri bed above. (C) 1995 Academic Press Inc.