literature. All of the pesticides were completely removed, when the TiO 2 coated
glass plates were used as a baffle wall of the reactor under solar light irradiation
(Senthilnathan and Philip 2012).
Treatments of Organic Dyes
Photocatalyst-coated substrates can also be applied for degradation the organic dyes
in water, which can form reactive oxygen species to individual or combination
treatments. These coated substrates can be prepared by traditional coating techniques, such as pulsed laser deposition, spin coating, electron beam evaporation,
spray pyrolysis, chemical bath deposition, sol–gel, dip-coating, and doctor blade.
For instance, titanium dioxide-coated glass, ceramic tile, and stainless steel sheets
can decolorize methylene blue and industrial dye wastewater up to 93% and can
reuse up to 20 times with the same efficiencies (Sirirerkratana et al. 2019). TiO 2
layers immobilized on glass substrates by dip-coating technique for degradation of
methyl orange were reported (Bouarioua and Zerdaoui 2017). It was found that three
layers of TiO 2 are the best condition for the test with good adhesion and reproducibility. Besides, they claimed that immobilized TiO 2 can replace the suspension
mode and eliminate the costly separation process of the catalysts (Bouarioua and
Zerdaoui 2017). Other examples of photocatalyst-coated substrates for organic dye
degradation are carbon-coated tungsten oxide (Tong et al. 2019), nebulizer spraycoated BiVO 4 thin films (Dhas et al. 2019), Fe ion-doped polyaniline film on
tin-doped indium oxide (ITO)-coated glass substrate (Haspulat et al. 2013), and
P-doped TiO 2 nanoparticles film coated on a ground glass substrate (Lv et al. 2011).
1.5 Modifications of Heterogeneous Photocatalysts
It has been proven that heterogeneous photocatalysis is one of the most potential
methods for the treatment of organic pollutants in water. Relatively large band gap
energy is a limitation of metal oxide-based heterogeneous photocatalysts, causing
the requirement of UV light for activation. In addition, electron–hole recombination
can also occur after the charge separation and migration of photogenerated carriers,
resulting in the unsatisfactory photocatalytic activity to treat the target pollutants.
The electronic band structure modifications and charge separation improvements of
metal oxide-based photocatalysts have attracted significant attentions in the field of
environmental treatments. Modifications of electronic band can be achieved by
doping and composites of semiconductors. These enhance the photocatalytic activity
of photocatalysts and shift the light absorption range toward visible region.
Another modification technique in heterogeneous photocatalysts is the utilization
of electrical potential in photocatalysis. The coated semiconductor photocatalysts are
used as the photoelectrodes in photo-electrocatalytic applications.
1 Photocatalytic Remediation of Organic Pollutants in Water
29
glass plates were used as a baffle wall of the reactor under solar light irradiation
(Senthilnathan and Philip 2012).
Treatments of Organic Dyes
Photocatalyst-coated substrates can also be applied for degradation the organic dyes
in water, which can form reactive oxygen species to individual or combination
treatments. These coated substrates can be prepared by traditional coating techniques, such as pulsed laser deposition, spin coating, electron beam evaporation,
spray pyrolysis, chemical bath deposition, sol–gel, dip-coating, and doctor blade.
For instance, titanium dioxide-coated glass, ceramic tile, and stainless steel sheets
can decolorize methylene blue and industrial dye wastewater up to 93% and can
reuse up to 20 times with the same efficiencies (Sirirerkratana et al. 2019). TiO 2
layers immobilized on glass substrates by dip-coating technique for degradation of
methyl orange were reported (Bouarioua and Zerdaoui 2017). It was found that three
layers of TiO 2 are the best condition for the test with good adhesion and reproducibility. Besides, they claimed that immobilized TiO 2 can replace the suspension
mode and eliminate the costly separation process of the catalysts (Bouarioua and
Zerdaoui 2017). Other examples of photocatalyst-coated substrates for organic dye
degradation are carbon-coated tungsten oxide (Tong et al. 2019), nebulizer spraycoated BiVO 4 thin films (Dhas et al. 2019), Fe ion-doped polyaniline film on
tin-doped indium oxide (ITO)-coated glass substrate (Haspulat et al. 2013), and
P-doped TiO 2 nanoparticles film coated on a ground glass substrate (Lv et al. 2011).
1.5 Modifications of Heterogeneous Photocatalysts
It has been proven that heterogeneous photocatalysis is one of the most potential
methods for the treatment of organic pollutants in water. Relatively large band gap
energy is a limitation of metal oxide-based heterogeneous photocatalysts, causing
the requirement of UV light for activation. In addition, electron–hole recombination
can also occur after the charge separation and migration of photogenerated carriers,
resulting in the unsatisfactory photocatalytic activity to treat the target pollutants.
The electronic band structure modifications and charge separation improvements of
metal oxide-based photocatalysts have attracted significant attentions in the field of
environmental treatments. Modifications of electronic band can be achieved by
doping and composites of semiconductors. These enhance the photocatalytic activity
of photocatalysts and shift the light absorption range toward visible region.
Another modification technique in heterogeneous photocatalysts is the utilization
of electrical potential in photocatalysis. The coated semiconductor photocatalysts are
used as the photoelectrodes in photo-electrocatalytic applications.
1 Photocatalytic Remediation of Organic Pollutants in Water
29