The available hydroxyl groups inside the lamellar cavity of barium phosphate (BaP) reacted with the silylating agents (RO)(3)Si(CH2)(3)L-x (L-1= NH2, L-2 = NH(CH2)(2)NH2, and L-3 = NH(CH2)(2) NH(CH2)(2)NH2), to yield organofunctionalized BaPSiL1, BaPSiL2 and BaPSiL3 nanomaterials. The amounts of organofunctional groups covalently attached to the inorganic layer were (1.24, 1.46, and 1.23) mmol . g(-1), respectively. The basic nitrogen atoms attached to the distinct pendant organic chains adsorb divalent nickel and cobalt from aqueous solutions, as represented by well-established isotherms. The energetic effects caused by metallic cation interactions were determined through calorimetric titration at the solid/liquid interface and gave a net thermal effect that enabled enthalpy and equilibrium constant calculations. Complete thermodynamic results composed of exothermic enthalpy, negative free Gibbs energy and positive entropy result in a set of favourable cation/basic centre interactions, to indicate that these nanomaterials could be useful tools to eliminate undesirable cations from aqueous systems. (C) 2008 Elsevier Ltd. All rights reserved.