STUDY OF MECHANISM OF STRUCTURE FORMATION IN AQUEOUS DISPERSIONS OF Na+-SMECTITES

Present paper contains the results of an experimental study of the colloidal structures and rheology of aqueous dispersions of Na+-montmorillonite, which were obtained by capillary and rotational viscometry methods. Aqueous dispersions of clay colloids undergo significant structural changes, accompanied by great change in the type of the flow. All these changes are managed by alteration in indifferent electrolyte concentration within a narrow concentration range. Certain critical concentration was found to appear near about 3 mM NaCl concentration for the series of dispersions with 0.25-3.0 wt% solid content. This concentration point is significantly lower than the coagulation thresholds known from the experimental and theoretical works in this field. Existence of such a critical region may reflects both processes of formation/disruption of aggregates and change in the mechanism of either aggregation or structure formation. The obtained rheological data were compared with theoretical calculations and the results of dispersion analysis (by DLS method) of aqueous dispersions which might make a bit development in the field of colloid structure investigation of smectite dispersions.