applied in the large scale compared with other treatment methods in homogeneous
photocatalysis, because of its high-energy requirement for both ozone generator and
UV lamps (Kim and Tanaka 2011), resulting in higher operating costs. The removal
efficiencies of pharmaceuticals and personal care products by different conditions of
photo-Fenton systems have been reviewed (Wang and Wang 2016). Tetracycline
with the initial concentration as high as 24 mg/L can be completely removed by
photo-Fenton process. Moreover, bezafibrate, ibuprofen, and diclofenac with the
trace initial concentration of millimolar level can also be completely removed by this
process (Wang and Wang 2016).
Treatments of Persistent Organic Pollutants
Persistent organic pollutants, a group of hazardous pollutants, such as pesticides that
are often found in agricultural wastewater, also continuously increased the environmental risks, so it is a challenge to solve this problem. A number of physical and
chemical methods have been developed to treat persistent organic pollutants.
Degradation of persistent organic pollutants can be carried out by ozonation
process. Atrazine has been reported to be degraded by catalytic ozonation with
iron scraps (Li and Zhou 2019). Pesticide wastewater (Solís et al. 2019) and
organophosphorus pesticide in water (Aimer et al. 2019) can be treated by ozonation.
Fenton or photo-Fenton is one of the alternative ways for remediation of persistent organic pollutants. Fe
III
(OH)
2+ under UV irradiation has been revealed to
generate OH radicals which can further degrade 4-cholorophenol and other Cr
(VI) phenolic compounds (e.g., 4-bromophenol, 4-nitrophenol, and phenol) (Kim
et al. 2019). Among the typical iron salts, iron (III) nitrate can generate iron aquo
complexes in aqueous and organic solutions, which are highly efficient and selective
homogenous photocatalyst for degradation of cyclohexane into cyclohexanol and
cyclohexanone up to 80 and nearly 100%, respectively (Iqbal et al. 2018). Fipronil, a
pesticide, can be degraded via photo-Fenton catalysis (Singh et al. 2019). It has been
found that the catalysis exhibited the highest degradation efficiency of 88.71% at
pH 3 with an H 2 O 2 concentration of 10 mM and the amount of catalyst of 1.5 g/L for
120 min reaction time (Singh et al. 2019). These show photo-Fenton is a promising
technique due to the fast regeneration of Fe
2+ and the less formation of iron sludge
compared with the conventional Fenton process. Carbendazim can be degraded
with a degradation efficiency of 96% within 15 min by Fenton process (da Costa
et al. 2019). Moreover, modified Fenton processes (e.g., electro-Fenton) have been
introduced (Méndez-Torres et al. 2019) with potential uses for degradations or
removals of pesticide mixtures (Rosa Barbosa et al. 2018), organochlorine pesticide
lindane (Dominguez et al. 2018), chlordimeform insecticide (Rezgui et al. 2018),
and methoxychlor (Huang et al. 2018). It should be noted that the modified Fenton
processes that use solid-state materials as the ferrous sources may also be considered
as heterogeneous photocatalysis.
Normally, heterogeneous photocatalytic degradation of pesticides is a promising
method because of the short time of treatment. However, it also needs more technical
24
P. Kemacheevakul and S. Chuangchote
photocatalysis, because of its high-energy requirement for both ozone generator and
UV lamps (Kim and Tanaka 2011), resulting in higher operating costs. The removal
efficiencies of pharmaceuticals and personal care products by different conditions of
photo-Fenton systems have been reviewed (Wang and Wang 2016). Tetracycline
with the initial concentration as high as 24 mg/L can be completely removed by
photo-Fenton process. Moreover, bezafibrate, ibuprofen, and diclofenac with the
trace initial concentration of millimolar level can also be completely removed by this
process (Wang and Wang 2016).
Treatments of Persistent Organic Pollutants
Persistent organic pollutants, a group of hazardous pollutants, such as pesticides that
are often found in agricultural wastewater, also continuously increased the environmental risks, so it is a challenge to solve this problem. A number of physical and
chemical methods have been developed to treat persistent organic pollutants.
Degradation of persistent organic pollutants can be carried out by ozonation
process. Atrazine has been reported to be degraded by catalytic ozonation with
iron scraps (Li and Zhou 2019). Pesticide wastewater (Solís et al. 2019) and
organophosphorus pesticide in water (Aimer et al. 2019) can be treated by ozonation.
Fenton or photo-Fenton is one of the alternative ways for remediation of persistent organic pollutants. Fe
III
(OH)
2+ under UV irradiation has been revealed to
generate OH radicals which can further degrade 4-cholorophenol and other Cr
(VI) phenolic compounds (e.g., 4-bromophenol, 4-nitrophenol, and phenol) (Kim
et al. 2019). Among the typical iron salts, iron (III) nitrate can generate iron aquo
complexes in aqueous and organic solutions, which are highly efficient and selective
homogenous photocatalyst for degradation of cyclohexane into cyclohexanol and
cyclohexanone up to 80 and nearly 100%, respectively (Iqbal et al. 2018). Fipronil, a
pesticide, can be degraded via photo-Fenton catalysis (Singh et al. 2019). It has been
found that the catalysis exhibited the highest degradation efficiency of 88.71% at
pH 3 with an H 2 O 2 concentration of 10 mM and the amount of catalyst of 1.5 g/L for
120 min reaction time (Singh et al. 2019). These show photo-Fenton is a promising
technique due to the fast regeneration of Fe
2+ and the less formation of iron sludge
compared with the conventional Fenton process. Carbendazim can be degraded
with a degradation efficiency of 96% within 15 min by Fenton process (da Costa
et al. 2019). Moreover, modified Fenton processes (e.g., electro-Fenton) have been
introduced (Méndez-Torres et al. 2019) with potential uses for degradations or
removals of pesticide mixtures (Rosa Barbosa et al. 2018), organochlorine pesticide
lindane (Dominguez et al. 2018), chlordimeform insecticide (Rezgui et al. 2018),
and methoxychlor (Huang et al. 2018). It should be noted that the modified Fenton
processes that use solid-state materials as the ferrous sources may also be considered
as heterogeneous photocatalysis.
Normally, heterogeneous photocatalytic degradation of pesticides is a promising
method because of the short time of treatment. However, it also needs more technical
24
P. Kemacheevakul and S. Chuangchote