recombination and makes the charge carrier separation more facile. Here, ferric
oxide with lower band gap acts as a photosensitizer for gallium oxide and assessed
photocatalytic activity against congo red dye under ultraviolet light.
To explore the role of various reactive oxidation species, the effect of various
scavengers has been investigated. Ammonium oxalate, AgNO 3 , tert-Butyl alcohol,
and benzoquinone were used as scavengers for holes, electron, hydroxyl radical, and
superoxide radical, respectively. The remarkable inhibition of congo red degradation
was reported which indicates that the electron and superoxide radical play an
important role in degradation. Gokul et al. (2017) reported the synthesize
CuO-TiO 2 /rGO photocatalyst and utilizes for the mineralization of methyl orange
underneath ultraviolet light. The film carrying 40 mg of nanoparticles was sufficient
to remove 3 parts per million solution of methyl orange within 13 h. Afterward five
consecutive cycles, these multilayer catalysts retained its catalytic activity and
stability. From photodegradation experiment, it can be concluded that the rate of
degradation was increased by improving migration of electrons from TiO 2 to CuO as
a function of catalyst loaded on reduced graphene oxide layer.
Fahimirad et al. (2017) synthesized La 2 O 3 /Al 2 O 3 binary metal oxide
nanocomposites by impregnation followed by precipitation method to degrade
basic green and basic red 46 azo dyes under exposure to ultraviolet radiation. The
photocatalytic efficiency of binary La 2 O 3 /Al 2 O 3 nanocomposites was high than pure
Al 2 O 3 bare nanoparticle under the ultraviolet. The favorable parameters, pH value of
5.88, irradiation time 56.3 min, and catalyst concentration for the mineralization
were 26.11 mg L
À1 for basic green and 1.4 mg L
À1 for basic red 46, respectively.
Nearly, 100% and 87% degradation were achieved for basic green and basic red
46, respectively. The increment in photo-efficiency was achieved by reduction in
energy gap of La 2 O 3 /Al 2 O 3 nanocomposites against bare Al 2 O 3 nanoparticle. The
obtained results demonstrated that after five consecutive photocatalytic cycles, the
catalytic activity of La 2 O 3 /Al 2 O 3 binary photocatalyst was nearly constant.
Patil et al. (2019) designed TiO 2 /WO 3 binary nanocomposites by sol–gel process
using chlorosulfonic acid. The nanocomposites showed 95% degradation of congo
red and methyl red dyes and azo dyes in 120 min in visible light. The degradation
experiment was repeated with the same procedure for five consecutive cycles and
found degradation efficiency of 90% in every repeat cycle. Thus, the synthesized
TiO 2 /WO 3 binary nanocomposites exhibited good reusability, stability, and recyclability during degradation process.
Further, hybrid binary metal oxide Cr 2 O 3 /Fe 2 O 3 nanocomposites prepared via
temperature-programmed oxidation method to produce high surface area
photocatalyst (Salari 2019). Acid blue 92 were completely degraded, and a clear
solution was obtained within 20 min of reaction. The magnetic separation and
reusability studied for five consecutive cycles for Cr 2 O 3 /Fe 2 O 3 nanocomposites
were demonstrated. High recyclability of Cr 2 O 3 /Fe 2 O 3 made them good contenders
for wastewater treatment. Chen et al. (2015) successfully demonstrated
photocatalytic ability of CuO/Co 3 O 4 composite photocatalyst by hydrothermal
process and cobalt containing solid precursor. The photostability experiment results
revealed that photodegradation efficiency of 56% of original organic methylene blue
134
P. Shandilya et al.
oxide with lower band gap acts as a photosensitizer for gallium oxide and assessed
photocatalytic activity against congo red dye under ultraviolet light.
To explore the role of various reactive oxidation species, the effect of various
scavengers has been investigated. Ammonium oxalate, AgNO 3 , tert-Butyl alcohol,
and benzoquinone were used as scavengers for holes, electron, hydroxyl radical, and
superoxide radical, respectively. The remarkable inhibition of congo red degradation
was reported which indicates that the electron and superoxide radical play an
important role in degradation. Gokul et al. (2017) reported the synthesize
CuO-TiO 2 /rGO photocatalyst and utilizes for the mineralization of methyl orange
underneath ultraviolet light. The film carrying 40 mg of nanoparticles was sufficient
to remove 3 parts per million solution of methyl orange within 13 h. Afterward five
consecutive cycles, these multilayer catalysts retained its catalytic activity and
stability. From photodegradation experiment, it can be concluded that the rate of
degradation was increased by improving migration of electrons from TiO 2 to CuO as
a function of catalyst loaded on reduced graphene oxide layer.
Fahimirad et al. (2017) synthesized La 2 O 3 /Al 2 O 3 binary metal oxide
nanocomposites by impregnation followed by precipitation method to degrade
basic green and basic red 46 azo dyes under exposure to ultraviolet radiation. The
photocatalytic efficiency of binary La 2 O 3 /Al 2 O 3 nanocomposites was high than pure
Al 2 O 3 bare nanoparticle under the ultraviolet. The favorable parameters, pH value of
5.88, irradiation time 56.3 min, and catalyst concentration for the mineralization
were 26.11 mg L
À1 for basic green and 1.4 mg L
À1 for basic red 46, respectively.
Nearly, 100% and 87% degradation were achieved for basic green and basic red
46, respectively. The increment in photo-efficiency was achieved by reduction in
energy gap of La 2 O 3 /Al 2 O 3 nanocomposites against bare Al 2 O 3 nanoparticle. The
obtained results demonstrated that after five consecutive photocatalytic cycles, the
catalytic activity of La 2 O 3 /Al 2 O 3 binary photocatalyst was nearly constant.
Patil et al. (2019) designed TiO 2 /WO 3 binary nanocomposites by sol–gel process
using chlorosulfonic acid. The nanocomposites showed 95% degradation of congo
red and methyl red dyes and azo dyes in 120 min in visible light. The degradation
experiment was repeated with the same procedure for five consecutive cycles and
found degradation efficiency of 90% in every repeat cycle. Thus, the synthesized
TiO 2 /WO 3 binary nanocomposites exhibited good reusability, stability, and recyclability during degradation process.
Further, hybrid binary metal oxide Cr 2 O 3 /Fe 2 O 3 nanocomposites prepared via
temperature-programmed oxidation method to produce high surface area
photocatalyst (Salari 2019). Acid blue 92 were completely degraded, and a clear
solution was obtained within 20 min of reaction. The magnetic separation and
reusability studied for five consecutive cycles for Cr 2 O 3 /Fe 2 O 3 nanocomposites
were demonstrated. High recyclability of Cr 2 O 3 /Fe 2 O 3 made them good contenders
for wastewater treatment. Chen et al. (2015) successfully demonstrated
photocatalytic ability of CuO/Co 3 O 4 composite photocatalyst by hydrothermal
process and cobalt containing solid precursor. The photostability experiment results
revealed that photodegradation efficiency of 56% of original organic methylene blue
134
P. Shandilya et al.