Chemistry Reference
In-Depth Information
•Washing processes involving enzymes that attack specific impurities in
the fabric and simultaneously produce small amounts of hydrogen
peroxide up to concentrations of about 1 g l
-1
. Such concentrations are
not high enough for bleaching, but have disinfecting properties.
As an example of these possible applications, a semi-industrial test was per-
formed, simulating a washing process with the involvement of enzymes that
produce hydrogen peroxide
in situ
by reduction of dissolved oxygen. The
experiment was performed at room temperature in a tank through which
cotton fabric was pulled. The tank was filled with an aqueous solution con-
taining 1% of enzyme at near-neutral pH (pH of about 7). The convection
obtained in the solution owing to the movement of the cotton fabric allowed
the establishment of a steady state in the uptake rate of dissolved oxygen,
and a sensor determined this uptake rate. The result is shown in Fig. 3.10,
curve 1. Initially, the concentration of hydrogen peroxide increases as a
function of time over a period of about 2 min because a large amount of
oxygen is present in solution. After these 2 min, the oxygen uptake starts to
determine the overall rate of hydrogen peroxide formation, and at the same
time hydrogen peroxide is consumed in the disinfection reaction. It can be
seen that after about 3 min a steady state is obtained, which means that,
1.2
1.0
2
0.8
1
0.6
0.4
0.2.
0
0
100
200
300
400
500
600
700
Time (s)
3.10
Variation of hydrogen peroxide concentration during a disinfec-
tion process in a semi-industrial setup at
T
=
298.0 K and pH
=
7
using (1) cotton fabric and (2) prior-disinfected cotton fabric.
(From Sensor system for simultaneous measurement of oxygen
and hydrogen peroxide concentration during glucose oxidase
activity in
Electroanalysis Journal
, 1999. Reprinted by permission
of Wiley-VCH)
