Electrokinetic study of dispersions of clay in hydrolyzed aluminium solutions

Abstract

Values are presented of the ζ-potential of dispersed clay particles, in the presence of hydrolyzed aluminium salts, that were obtained for a study of the water-treatment coagulation process. The values of ζ are determined by the concentration of polynuclear hydroxy-ions that appear to have a general affinity for aqueous interfaces. Their concentrations depend upon the solubility of the precipitated Al(oH)₃, which at low concentrations is present only as a relatively insoluble layer on the clay surface. As the iso-electric point falls from pH8 to 5, the rate of coagulation of the dispersed particles and the solubility of the hydroxide decrease and the strength of the aggregates formed by coagulation increases.