Influence of the exchangeable cations on stability and rheological properties of montmorillonite suspensions

The effects of NaCl and CaCl2 on the colloid stability and rheological properties of Na- and Ca-montmorillonite dispersions were studied. The distribution of cations between the surface and the bulk phase was determined. For both of monocationic montmorillonite, the critical coagulation concentration were 250 mmol NaCl/dm3 and 2 mmol CaCl2/dm3. The changes in the Bingham yield stresses of Na- and Ca-montmorillonite dispersions as functions of the NaCl and CaCl2 concentration could be explained in terms of the surface excess amount and equilibrium concentration of the cations, the second electroviscous effect and the formation of a gel structure.