Adsorptive performance of un-calcined sodium exchanged and acid modified montmorillonite for Ni2+ removal: Equilibrium, kinetics, thermodynamics and regeneration studies

Abstract

The efficacy of un-calcined sodium exchanged (Na-MMT) and acid modified montmorillonite (A-MMT) has been investigated for adsorptive removal of Ni2+ from aqueous solution. Physico-chemical parameters such as pH, initial Ni2+ concentration, and equilibrium contact time were studied in a series of batch adsorption experiments. The equilibrium time of contact for both adsorbents was about 230 min. The Redlich-Peterson model best described the equilibrium sorption of Ni2+ onto Na-MMT and the Dubinin-Radushkevich model was the best model in predicting the equilibrium sorption of Ni2+ onto A-MMT. The kinetics of Ni2+ uptake by Na-MMT and A-MMT followed the pseudo second-order chemisorption mechanism. Sorptions of Ni2+ onto Na-MMT and A-MMT were spontaneous and endothermic. Regeneration was tried for several cycles with a view to recover the adsorbed Ni2+ and also to restore Na-MMT and A-MMT to their original states. The un-calcined Na-MMT and A-MMT have adsorptive potentials for removal of Ni2+ from aqueous bodies. © 2009 Elsevier B.V. All rights reserved.