Chemistry Reference
In-Depth Information
Figure 3.14.
Proposed mechanisms for chlorite decomposition and O
2
evolution cata-
lyzed by
Dechloromonas aromatica
(DA-Cld) (adapted from goblirsch et al. [148] with
the permission of Elsevier Inc.). See color insert.
ClO
2
+ OH
-
(HOCl(O)O)
-
(OClOOH)
-
ClO
2
+
OH
-
ClO
2
+
ClO
2
Cl
2
O
4
ClO
2
ClO
2
ClO
2
-
Fast
OH
-
Pathway 1
Pathway 2
Pathway 3
ClO
2
-
OH
-
OH
-
H
2
O
+ ClO
3
-
ClO
3
-
H
2
O
HOCl(O)O
O
2
+
H
2
O + 2ClO
2
-
HOCl(O)O + ClO
2
-
OClOOH
Fast
Fast
2OH
-
Fast
H
2
O
2ClO
2
HOO
-
+ ClO
2
-
OH
-
Figure 3.15.
Decomposition pathways of ClO
2
in alkaline solution (adapted from Odeh
et al. [151] with the permission of the American Chemical Society).
.
(3.16)
2
ClO
+
2
OH
−
→
ClO ClO H O
−
+
−
+
2
2
3
2
Significantly, equal amounts of
ClO
−
and
ClO
−
were formed at millimolar
or higher concentrations of ClO
2
, but the yield of
ClO
−
was greater than the
yield of
ClO
−
at micromolar levels of ClO
2
. The additional reaction (Eq. 3.17)
could account for the change in the molar stoichiometry of
ClO
−
to
ClO
−
(Eq.
3.17):
−
−
4
ClO
+
4
OH
→
ClO O
+
+
2
H O
.
(3.17)
2
2
2
2
Both first-order and second-order dependence on the concentration of
ClO
2
have been suggested for the disproportionation of ClO
2
[151]. The rate
expression (Eq. 3.18) for the second-order dependence is given as
2
−
(3.18)
−
d
[
ClO /
]
dt k
=
[
ClO OH
] [
].
2
2
Three mechanisms, shown in Figure 3.15, were given to explain the kinetics
and stoichiometry of the decomposition of ClO
2
in alkaline solution [151]. All
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