Adsorption isotherms Jovanovic isotherm

For both the Langmuir and Jovanovic isotherms several exact methods exist for the determination of the energy distribution function adsorption isotherm is precisely known. Rather than trying to modify these exact methods for desorption kinetics, this work will use two approximate methods which give simple analytical expressions for the distribution function in terms of derivatives of the overall isotherm, and which allow a better and more friendly analysis of results. 

The prediction of multicomponent equilibria based on the information derived from the analysis of single component adsorption data is an important issue particularly in the domain of liquid chromatography. To solve the general adsorption isotherm, Equation (27.2), Quinones et al. [156] have proposed an extension of the Jovanovic-Freundlich isotherm for each component of the mixture as local adsorption isotherms. They tested the model with experimental data on the system 2-phenylethanol and 3-phenylpropanol mixtures adsorbed on silica. The experimental data was published elsewhere [157]. The local isotherm employed to solve Equation (27.2) includes lateral interactions, which means a step forward with respect to, that is, Langmuir equation. The results obtained account better for competitive data. One drawback of the model concerns the computational time needed to invert Equation (27.2) nevertheless the authors proposed a method to minimize it. The success of this model compared to other resides in that it takes into account the two main sources of nonideal behavior surface heterogeneity and adsorbate-adsorbate interactions. The authors pointed out that there is some degree of thermodynamic inconsistency in this and other models based on similar -assumptions. These inconsistencies could arise from the simplihcations included in their derivation and the main one is related to the monolayer capacity of each component [156]. 

Quinones, I. Guiochon, G. Extension of a Jovanovic-Freundlich isotherm model to multicomponent adsorption on heterogeneous surfaces. J. Chromatogr. A 1998, 796, 15-40. 

Results of the Numerical Iterative Methods.—The application of more sophisticated local isotherms than the Langmuir or Jovanovic dictates the use of numerical iterative methods. The advantages of these methods are they do not require curve fitting of the experimental data to establish a total isotherm equation, nor assumptions regarding the general form of the adsorption energy distribution. However they generally necessitate extensive and reliable experimental data, the measurement of which has been made possible by the more... 

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