Chromium (III) sorption on a weakly macroporous cation exchanger Amberlite IRC-50 (Na) is studied as a function of time and temperature. The rate constant values for chromium (III) sorption are calculated both for film and particle diffusion processes. The temperature is found to have a positive effect on both the diffusional processes. The high values of energy of activation confirm the particle diffusional nature of the process. The pH changes in the system show a competition between the Cr(OH)(2+) and H+ ions for the exchange sites of the adsorbent. Equilibrium data are explained with the help of Langmuir equation. Various thermodynamic parameters (Delta H degrees, Delta S degrees and Delta G degrees) from chromium (III) exchange on the resin are calculated. (c) 2008 Elsevier B.V. All rights reserved.