Naturally occurring bentonite is able to adsorb phenol from aqueous solutions. Sodium-treated bentonite underwent several activation methods before its exposure to the phenol solution. It was treated with cetyltrimethyl ammonium bromide (CTAB) as a cationic surfactant, with aluminum-hydroxypolycation as a pillaring agent and a combination of the two (CATB/Al-Bentonite). The Na-bentonite was also physically treated in an oven operated at 850 degreesC. Batch adsorption tests were carried out to remove phenol from aqueous solution using the above-mentioned bentonites. It was found that the amount of phenol removal was seriated in the following order: CTAB/Al-Bentonite > Al-Belntonite > CTAB bentonite > thermal-treated bentonite > cyclohexane-treated bentonite > natural bentonite. X-ray diffraction analysis showed that an increase in the microscopic platelets of bentonite when treated with CTAB was the reason behind the highest uptake of phenol. The increase in sorbent concentration or initial pH values of the solutions resulted in more phenol removal from the solution. The increase in temperature decreased phenol uptake by the bentonites used in this work. The Freundlich isotherm model was employed and well represented the experimental data. (C) 2002 Elsevier Science B.V. All rights reserved.