Textural Characterization by Using an Alternative Langmuir Isotherm and a New Thickness Function

Abstract

Samples with micropores can not be adequately described by using the Langmuir isotherm. The Langmuir expression is obtained by using the monolayer assumption, which is not valid in samples with micropores. Then, we propose to include in the isotherm a corrective parameter related to the sample porosity. We show that the modified isotherm enables us to describe the experimental values for different samples (aluminas, clays, silicas, zeolites, and zirconias) in low and full relative pressure ranges. Indeed, a new thickness function for the adsorbate layer in terms of the relative pressure is proposed. Then, a better description of the external surface areas, mesopores, and micropores of the samples can be obtained with the new thickness function. The VBS model with this new thickness shows a better pore distribution description.

Study of hygroscopic properties of the mixture of porous and non-porous materials by using optical techniques

“…The specific surface area is a crucial textural characteristic of the samples, and it is usually determined using the BET isotherm to describe the experimental data of nitrogen sorption. However, by Ref Mojica et al Mojica-Sepúlveda et al (2022) showed that the BET isotherm underestimates the value of the specific surface area of the samples. In this work, an alternative isotherm is proposed that provides an accurate description of nitrogen sorption in the samples.…”