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|Type:||Artigo de periódico|
|Title:||Silica-gel-immobilized Acetylacetone-some Thermodynamic Data In Non-aqueous Solvents|
|Abstract:||Acetylacetone was covalently immobilized on silica gel to produce a new surface (Sil-ac), having 0.62 mmol of ligand attached per gram of silica, which was characterized by means of elemental analysis and physical measurements, before being submitted to calorimetric measurements. Thus, a suspension of this anchored surface in ethanol or acetone was calorimetrically titrated with divalent cations (Co, Ni, Cu, Zn, Cd, Hg). The resulting isotherms conformed to a modified Langmuir equation. After linearization of these isotherms, the enthalpies of cation/surface adsorption and the interfacial equilibrium constant, as well as the variation of free energies and entropies, were calculated. In acetone, adsorption of copper gives rise to an exothermic ΔH of - 93.38 ± 0.94 kJ mol-1, while cobalt, 41.80 ± 0.42 kJ mol-1, and zinc, 2.38 ± 0.02 kJ mol-1, give an endothermic adsorption. In ethanol, the endothermic ΔH of 52.64 ± 0.53 kJ mol-1 for zinc contrasts with the exothermic enthalpies of adsorption observed for other cations, especially for mercury, - 102.20 ± 1.02 kJ mol-1 and nickel, -137.70 ± 1.38 kJ mol-1. © 1995.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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