Modified Langmuir Isotherm For Description Of Gas Adsorption Isotherms On Active Carbon
MODIFIED LANGMUIR ISOTHERM FOR DESCRIPTION OF GAS ADSORPTION ISOTHERMS ON ACTIVE CARBON
L. Czepirski1, M.R. Balys1, V.V. Kutarov2
1University of Mining and Metallurgy, Faculty of Fuels and Energy,
al. Mickiewicza 30, 30-059 Cracow, Poland
2Physical Research Institute, Odessa Mechnikov National University,
Pastera st. 27, Odessa 270026, Ukraine
High – pressure adsorption under equilibrium conditions when both pressure and temperature are higher than the critical, is sometimes referred to as supercritical adsorption. Research interest in this field has been promoted both by theory and engineering practice. The physical picture for supercritical adsorption has not been clearly depicted and, hence, certain theoretical difficulties have not been overcome in the interpretation of equilibrium data. Practically, the pertinent theory for the supercritical adsorption has not been established.
The derivation of a scientifically based adsorption isotherm was first achieved by Langmuir (1918). The Langmuir isotherm model assumes monolayer adsorption on a homogeneous surface. Originally based on the kinetic basis, the model is thermodynamically consistent as it reduces to Henry’s law at low pressures. The model was also derived based on statistical thermodynamics.
Although the Langmuir isotherm was introduced more than 80 years ago, it still remains the most commonly used adsorption isotherm equation. Its success undoubtedly reflects its ability to fit a wide variety of adsorption data quite well, but it may also partly reflect the appealing simplicity of the isotherm equation and the ease with which its adjustable parameters can be estimated.
By using more realistic assumptions, many modifications have been made to the Langmuir isotherm, which are well summarized in monographs for instance of Ruthven, Yang, Adamson, Rudzinski and Everett.
The purpose of this study is to propose some generalization of Langmuir isotherm, which will give the possibility to describe adsorption data in supercritical region.
Related articles::