Page 109 - Gas Adsorption Equilibria

2. Volumetry / Manometry 95

Here with is the mol number of the gas in the

storage vessel prior to adsorption, likewise with is

the mol number of the sorptive gas after equilibration. The dispersions
refer to concentrations in the gas prior and after adsorption

Approximate values of the dispersions referring to the total masses
of the sorptive gas prior and after adsorptionare given by Eqs.
(2.16*) and (2.16f) respectively. Formulae (2.33, 2.34 a, b) clearly show the
profound influence of the dispersions of sorptive’s gas molar
concentrations respectively. Measurements of these should be
performed with meticulous care in order to get useful values of the masses
of the adsorbate components. In practice, concentration measurements
(by GC or MS) should maintain uncertainties of Provided
uncertainties of all the other measured quantities are of the orders of
magnitude given at the end of Sect. 2.3, one may expect relative uncertainties
for binary (N = 2) mixture measurements of about and for

ternary (N = 3) mixture measurements of

4.4 Example

In this section we present data for the coadsorption equilibria of
gas mixtures on activated carbon (AC) Norit R 1 Extra taken at T = 298 K and
total gas pressure p = 0.3 MPa. Measurements were performed using the
volumetric – gas chromatographic method described above (N = 2). Standard
activation procedures of the AC were applied, namely vacuum (10 Pa) at
400 K for 4 hours, then cooling down to ambient temperature under vacuum
within 12 hours. First the system was investigated by M. Tomalla at the
author’s institution in 1993, [2.20]. Measurements were repeated using the
same method by St. Dohrmann in the labs of O. Talu, Cleveland State
University, Cleveland, USA in 1997. Results of both measurements are shown
in Figures 2.7 and 2.8 below. Figure 2.7 shows the partial molar Gibbs surface