The interaction mechanism of Al-Mg MMH sols with Na-montmorillonite suspensions

The effects of inorganic salts (NaCl, KCl and CaCl2) and pH values on the interaction between Al-Mg MMH soi(aluminum magnesium mixed metal hydroxides) and Na-montmorillonite (Na-Mt) suspensions have been studied Ly the measurments of rheology, electrophoretic mobility and pH. The results show that the increase of MMH in Na-Mt suspensions produced an increase in YP(yield point) at first and then a decrease after a maximum but a gradual decrease in pH, The results are interpreted as meaning that the MMH sols can interact with Na-Mt suspensions through an ion exchange mechanism. In the presence of saturated NaCl, a much less change of YP and no YP maximum under the experimental concentrations of MMH can be explained by DLVO theory. Due to the effects of pH on ion exchange reaction the change of YP with pH of MMH/Na-Mt systems is in terms of parabolic curve. Inorganic salts lower YP and pH in the order of CaCl2 > KCl similar to NaCl, and the order is found to be consistent with that for experimental estimates of the number of unit layers in face-to-face association. This would imply that the metallic ions must. function as the exchangeable cations.