FRACTAL DIMENSION OF MICROPOROUS CARBON ON THE BASIS OF THE POLANYI-DUBININ THEORY OF ADSORPTION - PART 3 - ADSORPTION AND ADSORPTION THERMODYNAMICS IN THE MICROPORES OF FRACTAL CARBONS
Ap. Terzyk et al., FRACTAL DIMENSION OF MICROPOROUS CARBON ON THE BASIS OF THE POLANYI-DUBININ THEORY OF ADSORPTION - PART 3 - ADSORPTION AND ADSORPTION THERMODYNAMICS IN THE MICROPORES OF FRACTAL CARBONS, Colloids and surfaces. A, Physicochemical and engineering aspects, 136(3), 1998, pp. 245-261
Fundamental thermodynamic relations are formulated based on the equati
on of physical adsorption on microporous fractal solids, proposed prev
iously and derived from the Polanyi-Dubinin theory of volume filling o
f micropores. A new adsorption isotherm and corresponding adsorption h
eat equations are verified using the experimental data published by Du
binin and Polstyanov of benzene and cyclohexane adsorption and adsorpt
ion heat on three microporous carbons. The obtained average correlatio
n coefficients are compared with those from the original Dubinin-Astak
hov (DA) equation. The correlation between the theoretical and experim
ental data is satisfactory, especially in the range of relative adsorp
tive pressures for which, following Stoeckli, the potential theory is
accepted as appropriate. It is shown that, for nearly all the cases, m
icropore volumes are similar to those obtained from the original DA eq
uation. Fractal dimensions calculated from adsorption data of both sor
bates on the same carbon are practically equal and can be treated as c
onstants that characterize the micropores of a solid. Average pore dia
meters, calculated from the obtained fractal dimensions, and also mini
mal and maximal pore widths are similar to those determined by the met
hods proposed by other authors, especially those obtained using the eq
uation of McEnaney, developed from the analysis of SAXS data. The expl
anation of why the approximate adsorption isotherm equation proposed b
y Avnir and Jaroniec cannot be applied for the correct determination o
f a micropore fractal dimension is given. (C) 1998 Elsevier Science B.
V.