Characterization and properties of treated smectites

Two natural smectite clays named BC and AC were thermal and chemically treated. Apart from smectite, quartz and kaolinite, BC clay also contains calcite, whereas illite and higher quartz content is found in AC. Treatment at 823 K leads to a collapse of the smectite structure. Treating with H2SO4 or NaOH also leads to the elimination of calcite and Al and Si ions. The higher swelling capacity of BC clay is in accordance with its higher cation exchange capacity.γSd values for both smectites decreases with the applied treatments. The surface acid–base constants determined for BC clay are higher than those obtained for AC independently of the applied treatment. This result together with the higher nanorugosity index, has been attributed to the higher quartz of the AC clay. Moreover, it has been observed that the cationic exchange capacity increases in both clays with the acidity of the surface.