Simultaneous determination of cation exchange capacity and surface area of acid activated bentonite powders by methylene blue sorption

To distinguish the ion exchanged and physically adsorbed methylene blue cations (MB+) on ionic surfaces, acid activated bentonite samples were used as porous adsorbents. A natural calcium bentonite (CaB) sample from Enez/Edirne, Turkey, was acid activated at 90 degrees C for 16 h with various HCl/CaB ratios. The irreversible exchange and physical adsorption of MB+ cations on the ionic solids have simultaneously occurred. The ion exchanged (m(ex)) and physically adsorbed (m(ad)) MB+ contents were obtained as the values of sorption capacity at c = 0 and the increase to a plateaus of adsorption isotherms, respectively. The m(ad) value was taken to be monolayer adsorption capacity. Cation exchange capacity (CEC) and specific surface area (S-MB) for each sample were calculated from the mex and m(ad) values, respectively. Also, the BET specific surface areas (S-BET) and pore size distribution were determined from low temperature nitrogen adsorption/desorption data. A linear correlation between the SMB and SBET values was found. (C) 2011 Elsevier B.V. All rights reserved.