Environmental Engineering Reference
In-Depth Information
When
K
and
n
were known, a reverse fit was used to simulate multiadsorp-
tion processes for mixtures in batch experiments. Although six compounds
were used for comparison purposes, the number of compounds is only
restricted by the computation time and not by the number of components.
11.3.2.3.2 Comparison of Activated Carbons
A number of experiments are necessary to compare different activated car-
bons for a number of selected compounds. The time-consuming procedure
to measure adsorption isotherms was the main motivation for the develop-
ment of an applicable computer program to evaluate Freundlich parameters
from mixtures, discussed in the previous section. Hence, for a comparison of
six compounds on six activated carbons, a potential total of 36 experiments
was reduced to only six experiments using mixtures with six compounds.
However, suitable analytical methods for the evaluation of mixtures were
required for all of the components. Freundlich parameters were evaluated
for six mixtures using six activated carbons and the fit procedure described
in the
previous section was also implemented. The mea
n
Freundlich expo-
nent
n
for all 36 adsorption isothe
r
ms was found to be
n
±= ±
σ
0
.
34
0 0
.
7
with
n
max
=
0.
(benzene) respectively, for the
six activated carbons. The mean values
K
for the six compounds investigated
are presented in Figure 11.8.
min
= 0.
29
(benzofuran) and
n
45
250
Activated carbons used:
S
Hydraffin 30N
Epibon Y12×40
Norit ROW supra
Norit GAC 1240
Chemviron F400
Chemviron F200
200
±22%
150
CH
3
N
CH
3
O
±11%
100
OH
±23%
±23%
50
±14%
±23%
0
FIGURE 11.8
The mean Freundlich adsorption parameter
K
for six compounds obtained on six different
activated carbons with relative standard deviations. Data were obtained from adsorption iso-
therms of the corresponding mixtures at
T
= 20 ± 3°C.
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