THE INFLUENCE OF THE TEMPERATURE ON THE PARAMETERS OF EXTENDED FREUNDLICHS ISOTHERM

In this paper the expression for adsorption isotherm expressed by an a symptotic development, the extended Freundlich's isotherm, was applied to the study and interpretation of energetic heterogeneity. This expr ession presents the relative monolayer coverage of the entire surface as a dependence on adsorbate pressure (or concentration) and on parame ters m and b(0), which were identified with the Freundlich's parameter s. The value of m and b(0) were obtained by adjusting the cited expres sion to the experimental data for hydrogen adsorption on tungsten. The rn parameter shows a quadratic dependence on temperature. Our analysi s shows that N(Q) the exponential form for the continuous energy distr ibution, is very dependent on m. A representative parameter is the dis persion of N(Q), delta = RT/m. We interpret the dependence of N(Q) on m as an indication of the energetic heterogeneity of this system. The parameter b(0) was adjusted by a van't Hoff expression, indicating a t hermal process on the Langmuir adsorption sites. (C) 1998 Academic Pre ss.