The zeta potential of kaolin

Clay minerals serve as filler materials in a variety of applications. The complex structure of these aluminium phyllosilicates raises debates about their charging behaviour in an aqueous environment. Hence, we have systematically assessed the zeta potential in kaolin dispersions.

In a recent application report we have demonstrated the capability of the instrument Litesizer 500 for the size and zeta potential analyses of latex particles for the production of latex gloves [1]. In this report we focus on the zeta potential as a representative indicator for the dispersion stability of a potential filler material: kaolin.
Kaolin is a clay mineral, which belongs to the group of layered silicates. The main component is kaolinite with the chemical composition Al2Si2O5(OH)4. The structure of kaolinite may be represented by hexagonal platelets [2, 3] with predominantly negatively charged faces (SiO2) and positively charged edges (Al2O3). The platelet structure and the non-uniform charge distribution enhance the probability of particle aggregation.
The method of a potentiometric titration is available for the direct analysis of the particle charge. On the other hand, for the application of kaolin, e.g., as a filler material, the preparation of a homogeneous particle dispersion with a predictable stability requires information about the average charge density, which is represented by the zeta potential. We report on the measurement of the electrophoretic mobility of particle dispersions of kaolin in aqueous solutions of monovalent KCl at different ionic strength and pH.

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