RESUMO
SBA-16 silica samples with cubic Im3 m symmetry were synthesized according to methods reported in literature and characterized by nitrogen adsorption and X-ray diffraction. The adsorption behavior of the n-octane(1)/octanol(2), n-octane(1)/ethanol(3), and octanol(2)/ethanol(3) binary liquid mixtures on SBA-16 was studied over the whole concentration range at 25 degrees C. Inverted U-shape isotherms were found and described by mathematical functions. The experimental binary data were verified by using a consistency test for the specific free wetting energies on the liquid/solid interface. The ternary adsorption excess isotherms of n-octane(1)/octanol(2)/ethanol(3) at 25 degrees C were predicted from the binary data. The work presents the first complete and consistent tabular set of binary liquid adsorption data for creating ternary data on ordered mesoporous silica.
RESUMO
Physical adsorption from binary or higher-order liquid mixtures on solids is often accompanied by adsorption phenomena at the liquid/gas interface. As long as the adsorption effects are comparable, both interfaces have to be included in the respective thermodynamic equations. A purely phenomenological thermodynamic description in terms of excess quantities is given of the simultaneous adsorption from multicomponent liquid mixtures at the liquid/solid and liquid/gas interfaces. In order to illustrate the thermodynamic procedure, the individual and simultaneous adsorption excess isotherms of three binary liquid mixtures at the liquid/Teflon and liquid/vapor interfaces are calculated from experimental surface-tension and contact-angle data taken from the literature. Special attention is focused on the estimation of error in calculated adsorption isotherms. A line of approach is given to find the confidence limits of adsorption isotherms that cover the entire mole fraction scale. The isotherms as well as their confidence limits are presented and discussed.
RESUMO
The thermodynamic equations for the calculation of binary and ternary immersion data in excess formalism are presented. Immersion enthalpies and entropies of the n-hexane/n-octane, n-octane/n-tetradecane and n-hexane/n-tetradecane binary mixtures as well as the n-hexane/n-octane/n-tetradecane ternary mixture on activated carbon are calculated from the temperature dependence of adsorption isotherms. In order to evaluate the quality of the calculations, the calculated immersion enthalpies of the binary mixtures on activated carbon are compared with those that were measured calorimetrically. It is shown that phenomenological thermodynamics can be used successfully to predict calorimetric data on the basis of adsorption excess isotherms.
