The Dynamic Mobility and Dielectric Response of Kaolinite Particles

✍ Scribed by William Neil Rowlands; Richard Wyndham O'Brien

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 738 KB
• Volume: 175
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1995.1445

✦ Synopsis

(\Lambda) new electroacoustic instrument ( AcoustoSizer, Matec Applicd Sciences) has been used to measure the dynamic mobility of (\mathrm{Na}) kaolinite and (\gamma)-aluminium hydroxide (gibbsite) suspensions at (\mathrm{MHz}) frequencies. In both suspensions the particles consist of thin, approximately hexagonal plates. Information about the particle size and the electrokinetic charge or (\zeta) potential can be obtained from the dynamic mobility spectrum. For kaolinite particles, the interpretation of the dynamic mobility spectrum is complicated by the presence of anomalously high surface conductance. This profoundly affects the shape of the dynamic mobility spectrum at low (\left(<5 \times 10^{-3} M\right.) ) electrolyte concentrations. An approximate formula which takes surface conductance and particle shape into account has recently been derived by Loewenberg (1). Our measured dynamic mobility spectra are in good agreement with this theory. The surface conductance of the particles can be determined directly by dielectric 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 described above. 1995 Acadenic Press, Inc.

Key Words: electroacoustics; dynamic mobility; dielectric response; kaolinite; gibbsite; oblate spheroids; surface conductance; zeta potential; particle size.