On the Lo/σ Range of the TVFM

Adsorption isotherms of nitrogen, carbon dioxide, methanol, dichloromethane, benzene and neopentane were determined on a range of molecular sieve and super-activated carbons with the objective of establishing the range of validity of the Theory of Volume Filling of Micropores (TVFM) in terms of the ratio of pore width to molecular diameter, Lo/σ. It is shown that, in the absence of molecular-sieving effects, both the characteristic curve concept and the DR equation are valid over the whole of the micropore range, corresponding to values of Lo/σ less than or equal to 5 and to at least a slight enhancement in the characteristic energy, E0, of the adsorbent when compared with the corresponding value obtained with non-porous carbon blacks. On the other hand, estimation of the mean micropore width was only possible for values of Lo/σ up to ca. 2.3, corresponding to at least a two-fold enhancement in E0. Results obtained using N2 at 77 K showed some significant differences to those obtained with organic adsorptives at higher temperature.

Binary Adsorption of Vapours in Active Carbons Described by the Combined Theories of Myers—Prausnitz and Dubinin (II)

The new MPD method, described recently, has been applied to the adsorption of benzene +1,2-dichloroethane vapours by a typical active carbon at 293 K. A total of 102 experiments have been carried out for adsorbed mole fractions between 0.06 and 0.94. Good agreement was found between the experimental and calculated values of the selectivity of the carbon for benzene, which decreased as the mole fraction of benzene increased. This variation reflects the heterogeneity of the carbon, which is taken into account by the DR equation. Although the liquid mixture is ideal, deviations from Raoult's law are observed in the adsorbed state, indicating a clear preference for benzene. The values of the activity coefficients obtained from the liquid/solid equilibrium improve the fit of the MPD method.

An Attempt to Apply Analogs of the Dubinin-Radushkevich and Freundlich Equations for Describing Isotherms of Adsorption from Binary Liquid Solutions of Non-Electrolytes with Unlimited Miscibility

An extention of the Dabrowski and Jaroniec concept of describing adsorption from binary liquid solutions of non-electrolytes on solids in terms of the Dubinin-Radushkevich (DR) and Freundlich (F) equations is presented. A new solution has been advanced based on the definition of the chemical affinity of the process of generation of equilibrium bulk phase from the pure components of the solution. The real adsorption isotherm equation has been formulated in which particular cases are the quasi-DR equation and the quasi-F equation. Some adsorption systems are described.