HETEROGENEOUS ADSORPTION ON MICROPOROUS CARBONS.

The influence of heterogeneity in microporous carbons on adsorption of gases is studied by using the generalized adsorption isotherm (GAI) as a model. Adsorption of Ar at 77 K on two poly(vinylidene chloride) based carbons activated to 28 wt % and 80 wt % burn-off is measured by using a McBain spring-type balance. The GAI comprises three functions: the total isotherm (determined experimentally), the local isotherm (assumed), and the adsorption energy distribution (unkonwn). Problems of computing the energy distribution are considered. Two previously published analytic solutions of the GAI (Sircar's equation and the condensation approximation) and one numerical method (regularization, incorporating a new smoothing algorithm) are applied to the adsorption data. For all three methods the Langmuir equation is assumed for the local isotherm function. For both carbons the energy distributions obtained from the three methods are similar, but the dispersions of the distributions obtained from regularization are wider than those obtained from Sircar's equation. The distribution functions obtained from the condensation approximation are similar to those obtained from regularization, suggesting that it is a good approximation for adsorption of Ar at 77 K on these carbons.