The effect of lead (Pb) on the sorption of phenol onto montmorillonite-based sorbents was studied using a batch equilibration method when phenol and Pb were sorbed simultaneously and either Pb or phenol was previously sorbed. The sorbents were Na+-, Ca2+-, hexadecyl trimethylammonium (HDTMA)-Na+-, and HDTMA-Ca2+-montmorillonites. Pb diminished the sorption of phenol largely onto Na+- or Ca2+-montmorillonites, while phenol had little effect on the sorption of Pb onto all sorbents. Pb had no effect on the sorption of phenol onto HDTMA-Na+- or HDTMA-Ca2+-montmorillonites either. The sorption capacity of phenol followed the order HDTMA-Na+- > HDTMA-Ca2+- > Na+- > Ca2+-montmorillonites. The pseudo-second-order equation described the kinetics of phenol sorption well. Sorption isotherms of phenol followed the Freundlich equation. Phenol sorption on HDTMA-Na+- and HDTMA-Ca2+-montmorillonites was linear, while that on Na+- and Ca2+-montmorillonites was nonlinear. (c) 2007 Elsevier Inc. All rights reserved.