The detailed electrokinetic and coagulation behavior of TiO2 and Al2O3 hydrous oxide colloids, is reported as a function of pH and indifferent electrolyte concentration. The isoelectric point values for TiO2 (pH 5.9) and Al2O3 (pH 8.9) were obtained by both techniques.
Comparison of the observed coagulation rates with those calculated on the basis of observed ζ-potentials using the Derjaguin—Landau—Verwey—Overbeek theory supports the general validity of the theory for oxide colloids. Specifically rapid coagulation, whether induced by pH or KNO3 concentration changes, occurs at |ζ| ⩽ 14 ± 4 mV in all systems.
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