Derivation and Application of a Jovanovic–Freundlich Isotherm Model for Single-Component Adsorption on Heterogeneous Surfaces

✍ Scribed by Igor Quiñones; Georges Guiochon

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 196 KB
• Volume: 183
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.0518

✦ Synopsis

ponents are required, there are methods to derive reason-A new Jovanovic-Freundlich isotherm model is derived for deable approximations of these competitive isotherms from scribing single-component adsorption equilibria on heterogeneous single-component isotherms. These methods allow consurfaces. The equation is obtained by assuming that the rate of siderable reduction in the time and cost required by the decrease of the fraction of the surface unoccupied by the adsorbate data acquisition. Their accuracy depends greatly on the molecules is proportional to a certain power of the partial pressure availability of accurate correlation for the single-compoof the adsorbate. The equation reduces to the Jovanovic equation nent isotherm data ( 1, 2 ) . However, except in rare cases when the surface becomes homogeneous. At low pressures, the involving homogeneous surfaces ( e.g., graphitized carbon equation reduces to the Freundlich isotherm but at high pressures, black, zeolites ) , the single-component isotherms cannot a monolayer coverage is achieved. This model has been applied successfully to the description of the adsorption behavior of a be calculated from first principles but must be measured. series of chlorinated hydrocarbons on a microporous silicagel, at Then arises the problem of selecting a proper isotherm different temperatures. The monolayer capacity and the heterogemodel for correlating these data ( 2 ) .

neity parameter exhibit a weak temperature dependence. The third Theoretical models of single-component adsorption isoparameter of the model decreases exponentially with increasing therms have been derived using a variety of kinetic, statistitemperature. The fit of the experimental data to the new model cal mechanical, or thermodynamic approaches (2, 3). These described is shown to be better than the comparable fits to classical fundamental studies assume the solid surface to be homogeisotherms used for heterogeneous surfaces. The energy distribution neous. Most of the adsorbents used in current practice, such function corresponding to the model for Langmuir local adsorption

as activated carbons, silica gels, alumina, and even zeolites behavior was derived using the Sips procedure and evaluated nuexhibit surface and structural heterogeneities (3). For such merically in a few selected cases. This distribution is an exponential decay.