The coagulation of Ca3Al2(OH)12 in aqueous electrolyte solutions

Abstract

Coagulation rate measurements of Ca3Al2(OH)12 in different aqueous electrolyte solutions (NaOH, NaNO3, Ca(OH)2) show that, at concentrations lower than 0.1 M NaNO3 and 0.3 M NaOH respectively, the stability increases with increasing ionic strength. This fact cannot be explained as either primary or secondary coagulation according to the DLVO theory. However, polymeric ions such as poly-aluminate ions, present in the liquid phase can cause the observed coagulation behaviour at these concentrations. At NaNO3 concentrations higher than 0.1 M NaNO3 the coagulation behaviour can be explained as primary coagulation according to the DLVO theory assuming ψσ =ζ with A1(2) = 0.03 X 10-20J. Assuming a distance between the plane with average potential ψgs and ζ of 0.3 to 0.4 nm, A1(2) =0.28 -0.30 x 10-20J depending on the conditions between these two layers. © 1979 Dr. Dietrich Steinkopff Verlag.