Abstract: The effects of inorganic salts(NaCl,KCl and CaCl₂)and pHvalues on the interaction between Al-Mg MMHsol(aluminum magnesium mixed metal hydroxides)and Na-montmorillonite(Na-Mt)suspensions have been studied by the measurments of rheology,electrophoretic mobility and pH.The results show that the increase of MMHin 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 MMHsols can interact with Na-Mt suspensions through an ion exchange mechanism.In the presence of saturated NaCl,a much less change of YPand no YPmaximum under the experimental concentrations of MMH can be explained by DLVOtheory.Due to the effects of pHon ion exchange reaction the change of YPwith pHof MMH/Na-Mt systems is in terms of parabolic curve.Inorganic salts lower YPand pHin the order of CaCl₂>KCl～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.

Key words: Aluminum magnesium mixed metal hydroxides, Na-montomorillonite suspensions, Rheology