Chemistry Reference
In-Depth Information
delivered two electrons, one at a time, at different points to result in iron(III)-
peroxo and iron(V)-oxo species (Fig. 6.23).
In the last few years, efforts have been made to understand the role of
Fe
V
=O in enzymatic reactions by carrying out oxidation of organic substrates
by the mixture of iron complexes and H
2
O
2
[284-287]. The generation of an
Fe(V)=O species in nonheme Fe(II) complex/H
2
O
2
has been demonstrated
using variable-temperature mass spectrometry (VT-MS) [288]. This system
catalyzed the oxidation of olefins, which are otherwise difficult to achieve
conventionally. Oxygen atoms from both H
2
O
2
and H
2
O were shown involved
in the
cis
-dihydroxylation reaction of olefins using isotopic labeling experi-
ments. The Fe(V)-nitrido complex has also been synthesized and characterized
spectroscopically [289]. under reducing conditions, the reaction of this complex
with water produced ammonia with a final iron product as Fe(II). These results
may have implications in the chemistry of nitrogenase.
Trace amounts of the iron-tetraamidomacrocyclic ligand (Fe-TAML) cata-
lysts were able to activate hydrogen peroxide to generate intermediates,
Fe
IV
=O and Fe
V
=O [290-296]. This Fe-TAML-H
2
O
2
system demonstrates
peroxidase-like activities and longevities. The Fe
III
-TAML activation has also
been applied to demonstrate degradation of various pollutants [297-299].
Examples include degradation of estrogens, bisphenols, pharmaceuticals, and
Orange II dye and inactivation of bacterial spores [297, 298, 300-302]. Products
of the oxidation reaction were found to be nontoxic [297, 298]. Other examples
are the desulfurization of heavy oil and the remediation of pulp and paper
industry effluent [300, 303].
High-valent iron-based compounds (ferrates) are emerging disinfectants
and oxidants in treating water [18, 19, 224, 304-311]. Ferrates are environmen-
tally friendly and can address the concerns associated with the common treat-
ment approaches. For example, ferrate(VI) (
Fe O
VI 2−
, Fe(VI)) does not produce
bromate ion because of its nonreactivity with bromide ion [19]. Comparatively,
ozone, a commonly used treatment oxidant, forms carcinogenic bromate ion.
Disinfection tests of sodium ferrate(VI) on spore-forming bacteria showed
that aerobic spore formers are reduced up to 3-log units while sulfite-reducing
clostridia are effectively killed by ferrate(VI) [308]. Both aerobic spore formers
and sulfite-reducing clostridia resist chlorine treatment. The multifunctional
properties of ferrate(VI) can thus be utilized in a single dose for recycling and
reuse of water and wastewater. Ferrate(VI) is a “green chemistry” chemical
for coagulation and disinfection, and an oxidant for the multipurpose treat-
ment of water and wastewater. A use of ferrate(VI) in developing a high
charge-storage rechargeable battery, a “super iron battery” has also been
demonstrated [312-318]. The rust generated from the discharge of the super
iron battery is preferable to toxic manganese compounds currently used in
commercial batteries.
The importance of ferrate species in the chemistry of natural water
and atmospheric water droplets has also been demonstrated [259]. For
example, the Fenton reaction plays an important role in atmospheric chemistry
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