drawback of the Fenton process is about the need for low pH (around 3) and the
formation of iron precipitates at higher pH. In this context, De la Cruz et al. (2012)
evaluated the removal of 32 micropollutants by the Photo-Fenton process using
ultraviolet 254 at near neutral pH. The authors observed that wastewater from wastewater treatment plant contain low amounts of iron, sufficient to perform the PhotoFenton process. In another study, De la Cruz et al. (2013) applied neutral PhotoFenton process for removal of 22 micropollutants on a pilot scale. The results
indicated that the maximum hydrogen peroxide dose was of 50 mg L
À1 and that
the excess iron in the reactor did not improve the process. Klamerth et al. (2011)
focused on a modified solar Photo-Fenton, using 5 mg L
À1 of iron, at initial pH of
7 and 50 mg L
À1 of hydrogen peroxide for the degradation of 15 micropollutants
spiked in wastewatereffluents using a solar compound parabolic collector pilot plant.
Additionally, the authors also tested the influence of oxalic acid, humic acid, and the
mixing of influents and effluents. The results indicated that oxalate and humic acid
(10 mg L
À1 ) enhanced the process, whereas the wastewater treatment plant spiked
with a mixture of emergent contaminants was unsuccessful. In another study,
Klamerth et al. (2013) compared the conventional and modified Photo-Fenton
processes at neutral pH with low iron concentration for the degradation of pharmaceuticals and personal care products in wastewater treatment plant effluents using a
solar compound parabolic collector pilot plant. In summary, several mechanism
involved in Photo-Fenton pharmaceuticals and personal care products degradation
can occur, namely, (i) direct photolysis; (ii) excited dissolved organic matter reacting
with pollutant or oxygen to form a singlet molecular oxygen (
1 O 2 ); (iii) direct
cleavage of hydrogen peroxide (ultraviolet 254 nm) to produce
●
OH; (iv) traditional
Fenton reaction in the dark, promoting hydroxyl formation; (v) formed organic
radicals can react to oxygen, forming the superoxide and hydroperoxide radicals;
and (vi) production of hydrogen peroxide through the reaction of superoxide/hydroperoxide radicals with subsequent
●
OH formation (De la Cruz et al. 2012, 2013).
The schematic mechanism is displayed in Fig. 10.10.
Another possibility regarding the drawback of low pH is the development the
Fenton-like reactions using others metals that show effectiveness for pharmaceuticals and personal care products degradation. Copper, via Fenton-like reactions, for
example, shows higher activity in alkaline conversion of hydrogen peroxide into
reactive oxidants species. In this regard, Lee et al. (2014) evaluated the operating
parameters such as pH, amount of copper, and adding radical scavengers that affect
carbamazepine and diclofenac degradation employing the combination of Cu(II)/
hydrogen peroxide in the dark and under ultraviolet radiation. The results indicated
that pH 8 was more efficient for compound degradation, since the Cu(II) reduction
rate increased with accelerated hydrogen peroxide decomposition and promoted the
formation of oxidant radicals than
● OH.
As an alternative to conventional oxidant agents, Fenton reactions can be
performed by the decomposition of the sulfate radical (SO 4
•- ), which has a strong
redox potential (2.5–3.1 V). Using this approach, Ahmed et al. (2014) compared the
photo-Fenton mediated peroxymonosulfate as an oxidant for six contaminants
including carbamazepine and diclofenac. Except for carbamazepine, k app values
338
E. M. Saggioro
formation of iron precipitates at higher pH. In this context, De la Cruz et al. (2012)
evaluated the removal of 32 micropollutants by the Photo-Fenton process using
ultraviolet 254 at near neutral pH. The authors observed that wastewater from wastewater treatment plant contain low amounts of iron, sufficient to perform the PhotoFenton process. In another study, De la Cruz et al. (2013) applied neutral PhotoFenton process for removal of 22 micropollutants on a pilot scale. The results
indicated that the maximum hydrogen peroxide dose was of 50 mg L
À1 and that
the excess iron in the reactor did not improve the process. Klamerth et al. (2011)
focused on a modified solar Photo-Fenton, using 5 mg L
À1 of iron, at initial pH of
7 and 50 mg L
À1 of hydrogen peroxide for the degradation of 15 micropollutants
spiked in wastewatereffluents using a solar compound parabolic collector pilot plant.
Additionally, the authors also tested the influence of oxalic acid, humic acid, and the
mixing of influents and effluents. The results indicated that oxalate and humic acid
(10 mg L
À1 ) enhanced the process, whereas the wastewater treatment plant spiked
with a mixture of emergent contaminants was unsuccessful. In another study,
Klamerth et al. (2013) compared the conventional and modified Photo-Fenton
processes at neutral pH with low iron concentration for the degradation of pharmaceuticals and personal care products in wastewater treatment plant effluents using a
solar compound parabolic collector pilot plant. In summary, several mechanism
involved in Photo-Fenton pharmaceuticals and personal care products degradation
can occur, namely, (i) direct photolysis; (ii) excited dissolved organic matter reacting
with pollutant or oxygen to form a singlet molecular oxygen (
1 O 2 ); (iii) direct
cleavage of hydrogen peroxide (ultraviolet 254 nm) to produce
●
OH; (iv) traditional
Fenton reaction in the dark, promoting hydroxyl formation; (v) formed organic
radicals can react to oxygen, forming the superoxide and hydroperoxide radicals;
and (vi) production of hydrogen peroxide through the reaction of superoxide/hydroperoxide radicals with subsequent
●
OH formation (De la Cruz et al. 2012, 2013).
The schematic mechanism is displayed in Fig. 10.10.
Another possibility regarding the drawback of low pH is the development the
Fenton-like reactions using others metals that show effectiveness for pharmaceuticals and personal care products degradation. Copper, via Fenton-like reactions, for
example, shows higher activity in alkaline conversion of hydrogen peroxide into
reactive oxidants species. In this regard, Lee et al. (2014) evaluated the operating
parameters such as pH, amount of copper, and adding radical scavengers that affect
carbamazepine and diclofenac degradation employing the combination of Cu(II)/
hydrogen peroxide in the dark and under ultraviolet radiation. The results indicated
that pH 8 was more efficient for compound degradation, since the Cu(II) reduction
rate increased with accelerated hydrogen peroxide decomposition and promoted the
formation of oxidant radicals than
● OH.
As an alternative to conventional oxidant agents, Fenton reactions can be
performed by the decomposition of the sulfate radical (SO 4
•- ), which has a strong
redox potential (2.5–3.1 V). Using this approach, Ahmed et al. (2014) compared the
photo-Fenton mediated peroxymonosulfate as an oxidant for six contaminants
including carbamazepine and diclofenac. Except for carbamazepine, k app values
338
E. M. Saggioro