structure. Contamination of drinking water sources with micropollutants, contamination of surface water with runoffs, and contamination of wastewaters with effluents from industry or less efficient wastewater treatment plants represent rather
varied occurrence of pollutants, which can be potentially treated by ferrates.
One of the most discussed groups of pollutants occurring in surface- and wastewater is estrogens. The reactivity of ferrates with estrogens was tested and, except for
ferrate(IV), an efficient removal/degradation of estrogens was observed (Machalová
Šišková et al. 2016). The intermediates confirmed oxidation steps in the degradation.
The hydroxyl groups of the parent molecule were attacked by the ferrate, which led
to quinone-like structures, and subsequently the opening of an aromatic ring was
observed. The product of degradation was malonic acid, finally mineralized to water
and carbon dioxide (Fig. 8.6).
Another abundantly occurring pollutants are pesticides and herbicides. Most of
them constitute a threat to the environment due to endocrine disrupting properties
and bioaccumulation. As an example of this pollutant family, total atrazine and
iodosulfuron degradation can be mentioned. Although the kinetics of the reaction
was fast, some of the intermediates were determined (Zajíček et al. 2015). The
oxidation of alkyl chain by ferrate(VI) generated a carbonyl group in structure of
the intermediate phase. Ferrate predominantly attacks the ethyl group rather than the
isopropyl group in the pollutant structure (Fig. 8.7). Generally, the formation of
molecules with higher molar mass (oxygen insertion into the structure) is relatively
common. This was, for instance, observed also during carbamazepine oxidation
(Hu et al. 2009). For iodosulfuron degradation, products formed from the fission of
the parent molecule (the both S-N and C-N bond cleavage) were confirmed.
In addition to carbamazepine or estrogens, lots of different pharmaceutical
compounds constitute a threat to the purity of water and for the environment.
Long-term exposition can cause toxic effects; and in the case of antibiotics, related
increasing bacterial resistance was observed. The commonly discussed point is that
these compounds are not fully removed from water in wastewater treatment plants.
Ferrate(VI) exhibited effective oxidation properties to pharmaceuticals such as
ciprofloxacin, enrofloxacin, sulfamethoxazole, ibuprofen, trimethoprim, propranolol, flurbiprofen. For most of them, optimal pH range was at neutral or slightly basic,
which is acceptable for water treatment and does not increase operational costs. As
another example of pharmaceuticals degradation, breaking of isoxazole ring was
observed for sulfamethoxazole and conversion of amino group to nitro group or
nitroso group. The determined final products were thus less toxic than the parent
compound (Sharma et al. 2006).
Fe(VI) was also identified as an efficient oxidant to remediate several antibiotics
such as β-lactam (cloxacillin, ampicillin, amoxicillin, penicillin G, cephalosporin)
with the attack on the thioether moiety, tetracycline, and fluoroquinolone (Feng et al.
2016, 2017; Sharma et al. 2013, 2016a). Penicillin G and cephalosporin were
converted initially to sulfoxide derivatives and finally to sulfones. Moreover, in
the case of cephalosporin, also C-N bond can be attacked by a ferrate(VI) ion to form
ammonia (Sharma 2010; Sharma et al. 2013). During the degradation of aliphatic
amines by Fe(VI), dealkylation products or respective hydroxylamines are formed,
8 Ferrates as Powerful Oxidants in Water Treatment Technologies
189
varied occurrence of pollutants, which can be potentially treated by ferrates.
One of the most discussed groups of pollutants occurring in surface- and wastewater is estrogens. The reactivity of ferrates with estrogens was tested and, except for
ferrate(IV), an efficient removal/degradation of estrogens was observed (Machalová
Šišková et al. 2016). The intermediates confirmed oxidation steps in the degradation.
The hydroxyl groups of the parent molecule were attacked by the ferrate, which led
to quinone-like structures, and subsequently the opening of an aromatic ring was
observed. The product of degradation was malonic acid, finally mineralized to water
and carbon dioxide (Fig. 8.6).
Another abundantly occurring pollutants are pesticides and herbicides. Most of
them constitute a threat to the environment due to endocrine disrupting properties
and bioaccumulation. As an example of this pollutant family, total atrazine and
iodosulfuron degradation can be mentioned. Although the kinetics of the reaction
was fast, some of the intermediates were determined (Zajíček et al. 2015). The
oxidation of alkyl chain by ferrate(VI) generated a carbonyl group in structure of
the intermediate phase. Ferrate predominantly attacks the ethyl group rather than the
isopropyl group in the pollutant structure (Fig. 8.7). Generally, the formation of
molecules with higher molar mass (oxygen insertion into the structure) is relatively
common. This was, for instance, observed also during carbamazepine oxidation
(Hu et al. 2009). For iodosulfuron degradation, products formed from the fission of
the parent molecule (the both S-N and C-N bond cleavage) were confirmed.
In addition to carbamazepine or estrogens, lots of different pharmaceutical
compounds constitute a threat to the purity of water and for the environment.
Long-term exposition can cause toxic effects; and in the case of antibiotics, related
increasing bacterial resistance was observed. The commonly discussed point is that
these compounds are not fully removed from water in wastewater treatment plants.
Ferrate(VI) exhibited effective oxidation properties to pharmaceuticals such as
ciprofloxacin, enrofloxacin, sulfamethoxazole, ibuprofen, trimethoprim, propranolol, flurbiprofen. For most of them, optimal pH range was at neutral or slightly basic,
which is acceptable for water treatment and does not increase operational costs. As
another example of pharmaceuticals degradation, breaking of isoxazole ring was
observed for sulfamethoxazole and conversion of amino group to nitro group or
nitroso group. The determined final products were thus less toxic than the parent
compound (Sharma et al. 2006).
Fe(VI) was also identified as an efficient oxidant to remediate several antibiotics
such as β-lactam (cloxacillin, ampicillin, amoxicillin, penicillin G, cephalosporin)
with the attack on the thioether moiety, tetracycline, and fluoroquinolone (Feng et al.
2016, 2017; Sharma et al. 2013, 2016a). Penicillin G and cephalosporin were
converted initially to sulfoxide derivatives and finally to sulfones. Moreover, in
the case of cephalosporin, also C-N bond can be attacked by a ferrate(VI) ion to form
ammonia (Sharma 2010; Sharma et al. 2013). During the degradation of aliphatic
amines by Fe(VI), dealkylation products or respective hydroxylamines are formed,
8 Ferrates as Powerful Oxidants in Water Treatment Technologies
189