Analogy between adsorption and sorption: An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation

doi:10.1016/j.cjche.2017.03.002

Chin.J.Chem.Eng. ›› 2017, Vol. 25 ›› Issue (12): 1740-1749.DOI: 10.1016/j.cjche.2017.03.002

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Analogy between adsorption and sorption: An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation

Pierre Schaetzel¹, Sébastien Thomas², Hasna Louahlia Gualous¹

1. Laboratoire Universitaire des Sciences Appliquées de Cherbourg, Université de Caen, IUT de Caen, Boulevard Maréchal Juin, 14032 Caen cedex, France;
2. Institut de chimie et procédés pour l'énergie, l'environnement et la santé, Université de Strasbourg, 25 rue Becquerel, 67087 Strasbourg cedex 2, France

Received:2016-12-06 Revised:2017-02-27 Online:2018-01-18 Published:2017-12-28
Contact: Pierre Schaetzel,E-mail address:pierre.schaetzel@unicaen.fr.

Analogy between adsorption and sorption: An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation

Pierre Schaetzel¹, Sébastien Thomas², Hasna Louahlia Gualous¹

1. Laboratoire Universitaire des Sciences Appliquées de Cherbourg, Université de Caen, IUT de Caen, Boulevard Maréchal Juin, 14032 Caen cedex, France;
2. Institut de chimie et procédés pour l'énergie, l'environnement et la santé, Université de Strasbourg, 25 rue Becquerel, 67087 Strasbourg cedex 2, France

通讯作者: Pierre Schaetzel,E-mail address:pierre.schaetzel@unicaen.fr.

Abstract

Abstract: The elementary mechanistic model of adsorption and sorption is based on a simple hypothesis: the adsorption sites are uniformly distributed on the surface of the pore walls in the adsorbent, the sorption sites are uniformly distributed in the volume of the polymer. In this first paperwewill analyze the simple casewhere one solute molecule is only allowed to occupy a single adsorption or sorption site. A common elementary occupation law of the free sites is assumed: the differential increase of the number of the adsorbed/sorbed molecules is proportional to the differential increase of the activity of the solute and the concentration of the free (non-occupied) sites in the solid. The proportionality coefficient is called affinity coefficient depending on the solid/solute couple and on the temperature and independent of the concentration of the solute. In adsorption the concentration of the free sites is a surface concentration on the porewalls and in sorption it is expressed by themolarity. The simple monolayer adsorption lawof Jovanovi? is obtained: n=n₀(1-e^-KP)where n is the number ofmoles adsorbed when the pressure is P. n₀ is the total number of adsorption sites and K the affinity coefficient for adsorption. The sorption law writes: a = 1/k [φ/(1-φ)] + (1-r)/k ln[1 + 1/r φ/(1-φ)] where φ, r and k hold respectively for the volume fraction of the solvent in the polymer, for the ratio of the molar volumes of the solvent to the elementary polymer chain containing one single adsorption site and for the sorption affinity coefficient. The confrontation of these equations to experimental isotherms is satisfactory in comparison with the classical Langmuir and Flory-Huggins equations: the best results are obtained for adsorption of vapors on a 5A zeolite and for all analyzed sorption results.

Key words: Adsorption isotherms, Sorption isotherms, Flory-Huggins theory, Langmuir equation

摘要： The elementary mechanistic model of adsorption and sorption is based on a simple hypothesis: the adsorption sites are uniformly distributed on the surface of the pore walls in the adsorbent, the sorption sites are uniformly distributed in the volume of the polymer. In this first paperwewill analyze the simple casewhere one solute molecule is only allowed to occupy a single adsorption or sorption site. A common elementary occupation law of the free sites is assumed: the differential increase of the number of the adsorbed/sorbed molecules is proportional to the differential increase of the activity of the solute and the concentration of the free (non-occupied) sites in the solid. The proportionality coefficient is called affinity coefficient depending on the solid/solute couple and on the temperature and independent of the concentration of the solute. In adsorption the concentration of the free sites is a surface concentration on the porewalls and in sorption it is expressed by themolarity. The simple monolayer adsorption lawof Jovanovi? is obtained: n=n₀(1-e^-KP)where n is the number ofmoles adsorbed when the pressure is P. n₀ is the total number of adsorption sites and K the affinity coefficient for adsorption. The sorption law writes: a = 1/k [φ/(1-φ)] + (1-r)/k ln[1 + 1/r φ/(1-φ)] where φ, r and k hold respectively for the volume fraction of the solvent in the polymer, for the ratio of the molar volumes of the solvent to the elementary polymer chain containing one single adsorption site and for the sorption affinity coefficient. The confrontation of these equations to experimental isotherms is satisfactory in comparison with the classical Langmuir and Flory-Huggins equations: the best results are obtained for adsorption of vapors on a 5A zeolite and for all analyzed sorption results.

关键词: Adsorption isotherms, Sorption isotherms, Flory-Huggins theory, Langmuir equation

Pierre Schaetzel, Sébastien Thomas, Hasna Louahlia Gualous. Analogy between adsorption and sorption: An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation[J]. Chin.J.Chem.Eng., 2017, 25(12): 1740-1749.

References

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Analogy between adsorption and sorption: An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation

Analogy between adsorption and sorption: An elementary mechanistic approach. I. Monolayer adsorption and sorption without solvent cluster formation

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