A MULTILAYER MODEL FOR ADSORPTION OF WATER ON ACTIVATED ALUMINA IN RELATION TO ADSORPTION POTENTIAL

Adsorption of water vapor on activated alumina was examined by a gravimetric method. The experimental results are described by a Freundlich-type polynomial with respect to the adsorption potential. In order to characterize the adsorption, a multilayer of water is assumed here on the alumina surface. Considering the hydrogen-bonding, several types of formation are modeled on structural hydroxyl groups supposed as the surface sites. In the modeling, two kinds of rules are observed in the relationship between the accumulating layers; structural ratios of molecules and allotment ratios of the potentials. In accordance with these rules, an attempt is made to derive an expression for the multilayer adsorption in a model by applying a Freundlich-type equation to the surface monolayer adsorption. The derivation gives a polynomial similar to the empirical expression. It is found from comparison of the parameters of both equations that the model multilayer is consistent in the examined adsorption system.