The adsorption behavior of Hg(II), Pb(II), and Cd(II) on Duolite C-433 synthetic resin has been determined at different temperatures by batch process. The various thermodynamic parameters, such as equilibrium constant (K-0), free energy (DeltaG(0)), entropy (DeltaS(0)), and enthalpy (DeltaH(0)), have been calculated in order to predict the nature of sorption. (C) 2004 Elsevier Inc. All rights reserved.