Chemistry Reference
In-Depth Information
SA4-bioregeneration
SA4-abiotic desorption
(a)
180
160
140
120
100
80
60
40
20
0
0
20
40
60
80
Time (h)
CA1-bioregeneration
CA1- abiotic desorption
(b)
100
90
80
70
60
50
40
30
20
10
0
0
20
40
60
80
Time (h)
Figure 7.3 Profiles of phenol loadings on powdered activated carbons (a) Norit SA4
(thermally activated) and (b) Norit CA1 (chemically activated) in bioregeneration reactors
integrated with activated sludge and during desorption in the absence of activated sludge
(redrawn after [16]).
On the other hand, it is also suggested that enzyme molecules are larger than
micropores, so that bioregeneration cannot occur due to enzymatic reactions [22].
According to this view, for an enzyme to actively act as a catalyst in a pore, the pore
diameter should be at least three times greater than the enzyme size to allow the
enzyme to approach and induce a fit [22]. Considering that the average molecular
diameter of a monomeric enzyme (molecular weight between 13 000 and 35 000)
is above 31-44
˚
, the diameter of the pore in which the exoenzyme can catalyze
should be larger than 10 nm (100
˚
).Thus,thisexcludesmicropores(
f
o
2nm)and
some of mesopores (
2-50 nm) [22]. Since low-molecular-weight aromatic com-
pounds (e.g. phenol) are mainly adsorbed in pores with a diameter under 0.7 nm
[23], the effect of hypothetical exoenzymatic reactions is expected to be limited in
f¼
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