Evaluation of surface energetics of zirconium-containing mesoporous silica using novel universal isotherm model

Abstract

A recently developed universal isotherm model was used in this work for the study of zirconium-added mesoporous silicas, focusing on the dehydration of low humidity gaseous streams. This modeling was chosen for its capability of calculating an energy distribution profile of the adsorption sites. This study was based on a systematic approach to evaluate three variables: the amount of zirconium substitution; the density of hydroxyl groups; and the volume of micropores. These variables were assessed using experimental techniques such as Fourier transform infrared spectroscopy, energy dispersive spectroscopy, thermogravimetry, nitrogen and water adsorption. The modeling was capable of identifying correctly the dynamics of the adsorption process and translated the physical phenomena governing the parameters investigated. Results showed that the amount of zirconium plays an important role on the adsorption site with highest energy (first group), while micropore volume has a stronger influence on the second group due to the pore size (0.8–2 nm). These conclusions were only possible using the proposed approach, since the direct observation of isotherms did not show any clear tendency. The methodology presented here has the potential to be applied to diverse adsorbent-adsorbate pairs, and opens a new field of exploration for the study and optimization of adsorption processes.