Page 77 - Gas Adsorption Equilibria

1. Basic Concepts 63

indicating thermodynamic instability which actually could not be
observed in any of the several experiments performed with this system.
Hence also proposition (P2) should not be used at high sorptive gas
pressures.

3) These data present absolute amounts of adsorbed masses calculated from
by using proposition (P3), i. e. optimization procedure (1.38) with
the Langmuirian isotherm (1.49). The data fit is reasonably well, cp. Table
1.7. Also data increase monotonously with increasing gas density, i. e. the
stability condition (1.47)

holds.

4) These data also present absolute masses of adsorbed on the AC Norit
R1 which have been calculated by proposition (P4) (1.43), i. e. taking the
(changing) volume of the adsorbate phase into account.
The volume of the AC impenetrable to the molecules has been
calculated by the optimization procedure (1.44) using the adsorption
isotherm (1.49). Data can easily be fitted by the Langmuir isotherm (1.49).
Also the thermodynamic stability condition (1.47) holds.

As one can recognize from the curves (1-4), all model assumption lead to
nearly the same results for low gas densities However, big
differences occur for high gas pressures Also, thermodynamics
inconsistencies occur for high gas pressures if the helium approximation for
the void volume is used as in propositions (P1,P2). No such
inconsistencies could be observed for propositions (P3, P4) using a value of
fitted to Eq. (1.49) and the experimental This can be more clearly
seen from the respective data of all the fits included in Table 1.7.