Sorption properties of XC-72 carbon and multi-walled carbon nanotubes (MWCNTs) for Pb(II) removal from aqueous solution as a function of pH, ionic strength, solid content and initial Pb(II) concentration were investigated to evaluate their availability performance in wastewater treatment. The results indicate that Pb(II) sorption on XC-72 carbon and on MWCNTs are dependent on pH. The maximum sorption capacities of Pb(II) calculated by the Langmuir model are similar to 125.0 mg/g for XC-72 carbon and similar to 17.5 mg/g for MWCNTs at pH = 6.0. The results reveal that XC-72 carbon possesses better performance of Pb(II) sorption than MWCNTs in Pb(II) removal from large volumes of aqueous solutions. The sorption isotherms of Pb(II) on XC-72 carbon and MWCNTs are simulated by constant capacitance model with the aid of FITEQL 3.1 code. At low pH, the major species of Pb(II) sorbed on XC-72 carbon is equivalent to XOHPb2+, and the low Pb(II) sorption can be partly attributed to the competition between H+ and Pb2+ ions on the surface sites. At pH 5.9-7.0, the removal of Pb(II) is accomplished by simultaneous sorption of Pb2+ and Pb(OH)(+), and the species of Pb(II) sorbed on XC-72 carbon are equivalent to XOHPb2+ and equivalent to XOPbOH. At pH >7.0, the removal of Pb(II) is accomplished by simultaneous precipitation of Pb(OH)2 and the sorption of Pb(OH)(+). As for MWCNTs, the species of sorbed Pb(II) are equivalent to XOHPb2+ at pH <5.7, equivalent to XOHPb2+ and equivalent to XOPbOH+ at pH 5.7-8.5, and equivalent to XOPbOH at pH > 8.5. (C) 2011 Elsevier B.V. All rights reserved.