Mesoporous silica originating from a gaseous ammonia epoxide ring opening and the thermodynamic data on some divalent cation adsorptions

An organofunctionalized mesoporous HMS-like compound has been synthesized by reacting the silylating agent 3-glycidoxypropyltrimethoxysilane with gaseous ammonia. The reaction path leads to the opening of the three membered epoxide ring to incorporate ammonia to give the modified silylating agent. This new silylating agent was used to synthesize a mesostructure inorganic-organic hybrid through the neutral template directing agent, dodecylamine, using a co-condensation process, and exploring the ability of the silicon source tetraethoxysilane. The final solid named HMS-NH has been characterized through elemental analysis, X-ray powder diffraction, nitrogen gas adsorption, infrared spectroscopy and solid state NMR for the Si-29 nucleus. An amount of 1.06 +/- 0.10 mmol of pendant groups is covalently bonded to the inorganic backbone. The attached basic centers adsorbed divalent cations to give the maxima adsorption capacity of 0.74 +/- 0.03, 0.55 +/- 0.06, 0.53 +/- 0.05 and 0.51 +/- 0.06 mmolg(-1) for copper, nickel, zinc and cobalt, respectively. From calorimetric determinations the quantitative thermal effects for all these cation/basic center interactions gave exothermic enthalpy, negative Gibbs free energy and positive entropy. These thermodynamic data confirmed the energetically favorable condition of such interactions at the solid/liquid interface for all systems. (c) 2007 Elsevier Inc. All rights reserved.