Chemistry Reference
In-Depth Information
5
SS mesh #2, 0.0216”
SS mesh #4, 0.028”
SS mesh #6, 0.028”
4
O
2
40 mL/min
O
2
200 mL/min
O
2
500 mL/min
4
3
3
2
2
1
1
0
0
0
30
60
90
0
30
60
90
(a)
Time (min)
(b)
Time (min)
FIGURE 8.62
H
2
O
2
concentration for various mesh electrode sizes at a fixed O
2
flow rate
and fixed operating conditions (a) and various O
2
gas flow rates at a fixed mesh size and
fixed operating conditions (b). H
2
O
2
concentration increases with growing mesh width and O
2
flow rate. (From Anpilov, A.M. et al.,
J. Phys. D: Appl. Phys.
, 34, 993, 2001.)
Experiments using the water treatment reactor (Figure 8.60) were carried out
with the objective to
1. Ascertain the potential of pulsed electric discharges in water to generate
reactive oxidants such as OH, O
3
, O, and H
2
O
2
2. Quantify the potential to decompose organic contaminants in the water such
as phenol and rhodamine as well as energetic compounds (i.e., explosives)
such as TNT, HMX, and CL20 [420]
An excellent discussion of the mechanisms for the formation of some of the
oxidants can be found in the paper of Anpilov et al. [408]. Figure 8.62 shows
the production of hydrogen peroxide, H
2
O
2
, as a function of the size of the mesh
electrodes and the O
2
gas flow rate under otherwise constant operating conditions.
Since the discharge produces a significant amount of hydrogen peroxide, the Fenton
reaction, i.e., the reaction of H
2
O
2
with Fe
2
+
to form Fe
3
+
along with OH
−
and OH can
be used to increase the decomposition rate of organic materials. Experiments were
performed with the objective to assess the potential of pulsed electrical discharges
in bubbled water to decompose the energetic compound HMX. This was done at a
reduced pH
3, which increases the reaction rate [421]. The reaction was initiated
by adding FeSO
4
to the water to yield an Fe
2
+
concentration of 0.3 mmol/L. Roughly
50% of the energetic compound HMX is decomposed in about one hour when O
2
bubble are used. The decomposition efficiency is significantly lower when Ar bubbles
are used (Figure 8.63).
=
8.3.4 Summary
This brief review touched on some aspects of the physical and chemical processes
that are initiated by pulsed electrical discharges in bubbled water. As an example of
