화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.105, No.44, 10857-10866, 2001
A fractal approach to adsorption on heterogeneous solids surfaces. 2. Thermodynamic analysis of experimental adsorption data
The isotherm equations developed in part I of this publication have been further generalized to account for the effects of multilayer adsorption. This was done employing the fractal BET isotherm developed by Fripiat et al. Their BET equation takes into account the geometric effects of fractality on the formation of second and subsequent layers, but ignores the energetic effects of fractality on adsorption in the first layer, closest to the surface. To correct this, their expression was integrated with the generalized adsorption energy distribution developed in part I (Rudzinski, W.; Lee, S.-L.; Panczyk, T.; Yan, C.-C. S. J. Phys. Chem. B 2001, 105, 10847). Using the generalized fractal BET equation obtained in this way, we are able to correlate the experimental data from the lowest pressures investigated up to the surface loadings approaching coverage by two layers. Two adsorption systems have been subjected to this analysis. One was nitrogen adsorbed on a commercially available silica, and the second nitrogen adsorbed by a commercially available activated carbon. As a result of these fittings, there have been obtained the parameters characterizing both the geometric and energetic heterogeneities of these two gas/solid systems.