Critical Flocculation Concentration of Montmorillonite, Beidelite, Illite and their Mixed Suspensions

Abstract

Little is known about colloidal properties of beidelite, a member of smectite group. Also, colloidal behavior of mixed-clay suspension is not wholly clear. In this study, critical flocculation concentration (CFC) of Na-saturated montmorillonite, beidellite and illite suspension, and of mixtures between of them was measured. Na-saturated clay minerals having diameter smaller than 2//m were mixed with NaCl solution to prepare different electrolyte concentration. Flocculation of these suspensions was detected by transmission of 700 nm wave length light. CFCs of montmorillonite, beidellite and illite were 0.02, 0.005-0.01, and 0.0125-0.025 mol L_1, respectively, depending on clay concentration of 0.3 to 0.1 kgm-3. CFCs of the mixed clay suspension were smaller than the greater CFC of the either single clay suspension. Observation of flocs and x-ray diffraction pattern suggested that binding between different clay minerals occurred in the process of flocculation.