Adsorption of hexavalent chromium onto manganese nodule leached residues Was investigating as a possible alternative to the conventional methods of its removal from aqueous synthetic solutions. Adsorption behavior was studied as a function of time, pH, temperature, and coneentration of adsorbate and adsorbent in acetic acid-sodium acetate buffer medium. Cr (VI) removal was pH dependent and was found to be of a maximum at pH 3. The applicability of the Langmuir isotherm to the present system was tested. Increased adsorption capacity with increased temperature indicates that the adsorption reaction was endothermic in nature. Based on these studies, thermodynamic parameters such as Gibbs free energy change (Delta G(0)). standard enthalpy change (Delta H-0), and standard entropy change (Delta S-0) were calculated. (c) 2005 Elsevier Inc. All rights reserved.