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In-Depth Information
(a)
800
IDA
400
0
-400
-800
-1200
350
400
450
500
550
600
650
Wavelength (nm)
(b)
800
EDTA
400
0
-400
-800
-1200
350
400
450
500
550
600
Wavelength (nm)
Figure 6.40.
Δ Extinction coefficient versus wavelength measured at 0.01 ms (open
circles: −Fe(VI) + Fe(V)) and 500 ms (filled circles: −Fe(VI)] (adapted from Noorhasan
et al. [385] with the permission of Elsevier Inc.).
The characteristic spectrum of Fe(IV) (see Fig. 6.24) was not observed in these
experiments, demonstrating the reaction of Fe(V) with APC proceeded via a
concerted two-electron oxidation, which converted ferrate(V) to Fe(III) (Eq.
6.144):
Fe V APC
(
)
+
→
Fe III APC oxidized
(
)
+
(
).
(6.144)
The reactions of ferrate(VI) and ferrate(V) with EDTA as a function of
pH have been studied (Figs. 6.35 and 6.41) [384, 385]. The dissociation con-
stants of the EDTA species suggest there are five different species of EDTA
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