The sorption of Cr(III) and Cu(II) ions from aqueous solutions with the Diphonix resin in the sodium form have been investigated. Irreversible ion-exchange equilibrium isotherms were obtained for each pair metal/resin and well described by the Langmuir and Langmuir-Freundlich models. The maximum exchange capacities, which are temperature dependent, were estimated to be 2.73 and 3.74 meq/g(dryresin) for Cr(III) at 25 and 50 degrees C, respectively. For Cu(II), those values were 2.45 and 3.17 meq/g(dryresin). The effects of resin dosage, initial chromium concentration and initial pH on the uptake rate of Cr(III) were studied. The pseudo-second-order rate, pore diffusion and shrinking core models were applied for describing the kinetic data. The shrinking core model, based on non-steady state intraparticle diffusion, enabled a more realistic prediction of the evolution of concentrations of chromium and sodium in solution with time. By fitting the model equations to experimental data, the effective pore diffusivities of Cr(III), D-pef = 2.66 x 10(-11) m(2)/s for initial metal concentrations of 250 and 500 mg/L and, D-pef = 5.31 x 10(-11) m(2)/s for initial concentration of 750 mg/L were evaluated. (C) 2011 Elsevier B.V. All rights reserved.