The effect of pH, ionic strength, solid/liquid ratio, contact time and temperature on sorption of Pb(II) to NKF-6 zeolite is investigated using batch technique under ambient conditions. The NKF-6 zeolite is characterized using XRD and FTIR. The sorption results indicate that the sorption of Pb(II) on NKF-6 zeolite is strongly dependent on pH. The sorption of Pb(II) is affected by ionic strength at pH < 6, while it is independent of ionic strength at pH > 6. The sorption of Pb(II) is dominated by ion exchange or outer-sphere surface complexation at low pH values, and by inner-sphere surface complexation at high pH values. The thermodynamic parameters (Delta H-0, Delta S-0 and Delta G(0)) calculated from the temperature dependent sorption isotherms suggest that the sorption of Pb(II) on NKF-6 zeolite is endothermic and spontaneous process. The results are quite important to understand the interaction of Pb(II) with zeolite in aqueous solutions. This investigation shows that the NKF-6 zeolite can be used as a suitable adsorbent for the preconcentration and solidification of Pb(II) from large volumes of aqueous solutions. (C) 2010 Elsevier B.V. All rights reserved.