Swelling and cation exchange capacity relationship for the samples obtained from a bentonite by acid activations and heat treatments

To investigate the effect of heating and acid activation on the cation exchange capacity (CEC) and swelling (SWE), a calcium bentonite (CaB) was used. The calcium bentonite (CaB) from the Kütahya (Turkey) region contains approximately 65% and 30% by mass calcium reach smectite (CaS) and opal-CT (OCT), respectively. The rest amount is illite (I) and other impurities. The 13 samples were heated at different temperatures between 100 and 1300 °C for 2 h. Furthermore, the sample was activated with H2SO4 having various dosages ranging between 0 and 70% by mass in the dry bentonite–acid mixture, by heating the aqueous suspensions at 97 °C for 6 h. The CEC and total SWE (crystalline and osmotic) were measured by the standard methylene blue (MB) method and as gel volume in definite amount water, respectively. The CEC and SWE decrease by the heating depending on the collapse of the 2:1 layers of the CaS. While the SWE decreases approximately linearly by increasing of the temperature, the CEC decreases faster after 600 °C and reaches to zero at 900 °C. While the CEC increases almost linearly with the H2SO4 dosage by the activation, the SWE decreases up to 20% and then does not change. In general, the SWE increases with CEC.