Equilibrium study on chromium (III) ion removal by adsorption onto rice hull ash

The adsorption of chromium (III) ion from aqueous solution by rice hull ash at equilibrium was investigated. The adsorption data was found to follow both the Freundlich and Langmuir models. Thermodynamic parameters for the adsorption process, that is, K-C, Delta G, Delta H and Delta S have also been calculated. The positive value of Delta S and negative values of Delta G displayed the spontaneous nature of this adsorption system, while the positive value of Delta H pointed out this is an endothermic process. (c) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.