In this study, the use of modified bentonites for the removal of phenol was investigated. Two alkylammonium derivatives, tetradecyl trimethyl bromide (TDTAB) and hexadecyl trimethylammonium bromide (HDTAB), were used in the modification in amounts equivalent to 100% of CEC. Crude and modified bentonites were subjected to XRD analyses to see the changes in basal spacing (d(L)) depending on modification. The increases observed in basal spacing are 8.93 angstrom and 8.55 angstrom for TDTAB- and HDTAB-bentonites, respectively. Batch adsorption studies were carried at pH of 5.5 and 20 degrees C. Adsorption isotherms of TDTAB- and HDTAB-bentonites have similar shape, and two regions are observed in isotherms. Adsorption behavior was modelled using Langmuir, Freundlich, BET, Bradley, Halsey, Henderson, Oswin, and Smith equations. The equations fitted better when the isotherm was divided into two concentration ranges. Adsorption efficiencies were defined in terms of relative increase in adsorbed amounts, and HDTAB-bentonite was found to be better.