The sorption of chlorobenzenes (CBs) by cetyltrimethylammonium bromide (CTMAB) modified bentonite and kaolinite was investigated. The sorption isotherms for CBs were nearly linear, suggesting that sorption could be described by a distribution process. The distribution coefficient (K-d) was primarily affected by the amount of sorbed surfactant. The organic carbon normalized sorption coefficient (K-oc), however, was particularly dependent on arrangement of the surfactant cations. The K-d of CBs was larger for CTMAB-bentonites than that for CTMAB-kaolinites, while the case for K-oc was opposite. Thus, the clay mineral structure and morphology had a considerable influence on the surfactant arrangement, which was responsible for the partitioning of CBs. The sorption of CBs onto both CTMAB-bentonites and CTMAB-kaolinites followed pseudo-second-order kinetics. The intra-particle diffusion model for sorption was also investigated and compared to identify sorption mechanism. The sorption of CBs both on CTMAB-bentonites and CTMAB-kaolinites was exothermic in nature and accompanied by an increase in entropy and a decrease in Gibbs energy in the temperature range of 15-35 degrees C. The results indicated that CBs strongly interacted with CTMAB modified bentonite and kaolinite. (C) 2009 Elsevier B.V. All rights reserved.