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Adsorption deformation of Na-montmorillonite during interaction with methanol vapours

A.V. Tvardovskiy

Tver State Technical University

DOI: 10.26456/pcascnn/2025.17.XXX

Original article

Abstract: Classical ideas about the adsorption process have always been based on the fact that the adsorbent remains inert and does not change its size when interacting with gases or vapors. Its role is limited to creating an adsorption field where the adsorbate molecules fall. It is on the basis of this principle that the well-known adsorption equations of Henry, Langmuir, Fowler-Guggenheim, Brunauer-Emmett-Teller and others were derived. However, modern experimental studies show that adsorbents are deformed in the adsorption process. This fact significantly changes the entire picture of the consideration of this phenomenon. For example, when the geometric dimensions of the pores of the adsorbent change during deformation of the latter, the adsorption field into which the adsorbate molecules fall changes significantly. And this affects the value of the calorimetric heat of adsorption removed during the studies. Thus, the adsorbent is an equal participant in the adsorption process along with the adsorptive, and the adsorption system should be considered as a two-component one. In this regard, when conducting adsorption studies, a comprehensive approach is needed, including taking isotherms, measuring calorimetric heats of adsorption, and conducting dilatometric experiments to study the adsorption deformation of adsorbents. Such a comprehensive approach was used for the Na-montmorillonite – methanol vapor system. The differential heat and adsorption isotherm at T = 293 K were obtained using a Calvet-type microcalorimeter and a McBain-Bakr microbalance. The adsorbent deformations were measured using a highly sensitive dilatometer. The main part of this dilatometer was a linear differential transformer, the core of which was connected to the adsorbent by means of a rod. Any changes in the geometric dimensions of the adsorbent changed the position of the core in the transformer, which affected the signal taken from the secondary winding of the transformer. Having calibrated the dilatometer, the adsorption deformation of the adsorbent was determined. Such a comprehensive approach allowed us to significantly detail the description of the adsorption process for this studied system.

Keywords: adsorption, adsorbent, adsorption isotherm, calorimetric heat of adsorption, adsorption deformation of the adsorbent, dilatometric method

  • Andrey V. Tvardovskiy – Dr. Sc., Professor, Acting Rector, Tver State Technical University

Reference:

Tvardovskiy A.V. Adsorbtsionnaya deformatsiya Na-montmorillonita pri vzaimodejstvii s parami metanola [Adsorption deformation of Na-montmorillonite during interaction with methanol vapours], Fiziko-khimicheskie aspekty izucheniya klasterov, nanostruktur i nanomaterialov [Physical and chemical aspects of the study of clusters, nanostructures and nanomaterials], 2025, issue 17, pp. __-__. DOI: 10.26456/pcascnn/2025.17.XXX. ⎘

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