The Influence of pH and the Concentration of Dispersants on the Coagulation and Dispersion of Fine Particles in Water

Abstract

The influence of pH and the concentration of dispersants on the coagulation and dispersion of fine particles in water is dealt with in this paper.
By using the Derlaguin-Landau-Verwey-Overbeek (DLVO) theory and the bulk zeta potentials at pH values, the coagulation values are obtained. The analytical results are compared with both the experimental ones obtained using roseki and talc as well as with data in the literature. As a result, the calculated and experimental values for quartz, feldspar, limestone and talc are found to be nearly coincident, but the calculated coagulation values for kaolin, bentonite and roseki representative of clays are recognized to differ somewhat from the experimental ones in the acidic region. It is considered that a cause for the discrepancy may be the oppositely charged potentials on the face and edge of the clays in the acidic region.
The influence of pH and the concentration of dispersants on the dispersion of some sorts of fine particles in water is shown to be explained semi-quantitatively by the DLVO theory. In particular, it is shown that the optimum concentration of a dispersant obtained experimentally is approximately in accordance with the concentration of the dispersant showing the maximum total potential energy calculated from the DLVO theory which is coincident with the one showing the maximum zeta potential or with the one showing a zeta potential a little lower than the maximum.