and economic developments, because the main source of the system (UV irradiation)
often requires a large amount of the electrical energy and the use of UV with ozone
or hydrogen peroxide causes relatively high costs of the processes.
Treatments of Organic Dyes
Homogeneous photocatalysis has proved to be sufficiently effective alternatives for
remediation of organic dyes in water, even though it has some limitations.
A few works have recently focused on the degradation of organic dyes by
ozonation. For example, degradation of reactive red 24 from aqueous solution
(Van et al. 2019), removal of methylene blue in wastewater (Ikhlaq et al. 2019),
organic dye removals with acid-treated clay catalysts (Boudissa et al. 2019), and
degradation of azo dyes (El Hassani et al. 2019; Pérez et al. 2019; Pandian et al.
2018) have been reported with ozonation relations.
Azo dyes (Wang et al. 2019b; Innocenzi et al. 2019), acid orange 7 (AO7) (Wang
et al. 2019b), reactive black 5 (RB5) (Wang et al. 2019b), reactive red 24 (Van et al.
2019), rhodamine B (Wang et al. 2019a), and methylene blue (Anantharaman et al.
2019; Ikhlaq et al. 2019) have been studied to be decolorized by Fenton or photoFenton processes.
UV/H 2 O 2 is an alternative way that is often found for photocatalytic remediation
of organic dyes (e.g., methylene blue (Malvestiti et al. 2019), brilliant green
(Rehman et al. 2018), and rhodamine B (Changchao et al. 2018)) in water.
In a comparison of Fenton and UV/H 2 O 2 for dye degradation, increasing concentration of ferrous ions (that catalyze the Fenton reaction) can increase the generation of OH radicals from hydrogen peroxide up to an optimum level, while in
UV/H 2 O 2 , the hydroxyl radicals generated are less due to the presence of photostable organic UV absorbers (ultimately, it reduces the efficiency of UV/H 2 O 2
oxidation).
1.4.2 Heterogeneous Photocatalysis
Photocatalysts used in heterogeneous photocatalysis can be used as (1) powder and
suspension forms and (2) coated forms on supporters or substrates.
Powder and Suspension Forms of Photocatalysts
Suspension of the small size photocatalysts, such as microparticles, nanoparticles,
and other nanomaterials in other forms, in wastewater, is the traditional way to
remove the organic contaminants via heterogeneous photocatalysis.
1 Photocatalytic Remediation of Organic Pollutants in Water
25
often requires a large amount of the electrical energy and the use of UV with ozone
or hydrogen peroxide causes relatively high costs of the processes.
Treatments of Organic Dyes
Homogeneous photocatalysis has proved to be sufficiently effective alternatives for
remediation of organic dyes in water, even though it has some limitations.
A few works have recently focused on the degradation of organic dyes by
ozonation. For example, degradation of reactive red 24 from aqueous solution
(Van et al. 2019), removal of methylene blue in wastewater (Ikhlaq et al. 2019),
organic dye removals with acid-treated clay catalysts (Boudissa et al. 2019), and
degradation of azo dyes (El Hassani et al. 2019; Pérez et al. 2019; Pandian et al.
2018) have been reported with ozonation relations.
Azo dyes (Wang et al. 2019b; Innocenzi et al. 2019), acid orange 7 (AO7) (Wang
et al. 2019b), reactive black 5 (RB5) (Wang et al. 2019b), reactive red 24 (Van et al.
2019), rhodamine B (Wang et al. 2019a), and methylene blue (Anantharaman et al.
2019; Ikhlaq et al. 2019) have been studied to be decolorized by Fenton or photoFenton processes.
UV/H 2 O 2 is an alternative way that is often found for photocatalytic remediation
of organic dyes (e.g., methylene blue (Malvestiti et al. 2019), brilliant green
(Rehman et al. 2018), and rhodamine B (Changchao et al. 2018)) in water.
In a comparison of Fenton and UV/H 2 O 2 for dye degradation, increasing concentration of ferrous ions (that catalyze the Fenton reaction) can increase the generation of OH radicals from hydrogen peroxide up to an optimum level, while in
UV/H 2 O 2 , the hydroxyl radicals generated are less due to the presence of photostable organic UV absorbers (ultimately, it reduces the efficiency of UV/H 2 O 2
oxidation).
1.4.2 Heterogeneous Photocatalysis
Photocatalysts used in heterogeneous photocatalysis can be used as (1) powder and
suspension forms and (2) coated forms on supporters or substrates.
Powder and Suspension Forms of Photocatalysts
Suspension of the small size photocatalysts, such as microparticles, nanoparticles,
and other nanomaterials in other forms, in wastewater, is the traditional way to
remove the organic contaminants via heterogeneous photocatalysis.
1 Photocatalytic Remediation of Organic Pollutants in Water
25