Calcined tetrabutylammonium kaolinite and montmorillonite and adsorption of Fe(II), Co(II) and Ni(II) from solution

Kaolinite and montmorillonite were modified with tetrabutylammonium (TBA) bromide, followed by calcination. The structural changes were monitored with XRD, FTIR, surface area and cation exchange capacity measurements. The modified clay minerals were used for adsorption of Fe(III), Co(II) and Ni(II) ions from aqueous solution under different conditions of pH, time and temperature. The uptake of the metal ions took place by a second order kinetics. The modified montmorillonite had a higher adsorption capacity than the corresponding kaolinite. The Langmuir monolayer capacities for the modified kaolinite and montmorillonite were Fe(III): 93 mg g(-1) and 22.6 mg g(-1): Co(II): 9.0 mg g(-1) and 22 3 mg g-(1); and Ni(II): 8.4 mg g(-1) and 19.7 mg g(-1). The modified kaolinite interacted with Co(II) in an endothermic manner. but all the other interactions were exothermic. The decrease of the Gibbs energy in all the cases indicated spontaneous adsorption. (C) 2009 Elsevier B.V. All rights reserved.