dye was obtained in case of binary metal oxide nanocomposites higher than 40%
photodegradation efficiency of bare CuO nanoparticle. High photocatalytic activity
of binary CuO/Co 3 O 4 composite was achieved by the overlapping of band structure
that displays an important role in photo carrier charge separation and transformation.
CuO/Co 3 O 4 binary photocatalyst was favorable for practical wastewater management because of its catalytic stability and recyclability.
4.5 Carbon-Supported Photocatalyst for Azo Dye
Degradation
The carbon-supported photocatalyst had a wider range of application and can be
utilized in electrochemical sensing, hydrogen production, drug delivery, water
purification, and hydrogen storage and also as an antibacterial agent, as the combination of adsorption and photocatalyst offers a better alternative to decontaminate
water. Thus, the adsorption capacity of nanocomposites can be enhanced by using
carbonaceous material as a support which controls the size and shape of nanoparticle; it also helps to prevent the aggregation of nanoparticle (Singh et al. 2016).
Carbonaceous-based materials (carbon nanotubes, fullerenes, graphene oxide,
and graphitic carbon nitride) have been widely utilized for photodegradation of
azo dyes present in simulated water. Various research groups have been working
on the fabrication of Z-scheme-driven g-C 3 N 4 /CNT/Bi 2 Fe 4 O 9 prepared by hydrothermal technique for efficient degradation of acid orange 7 dye. The mechanism
follows a Z-scheme-driven process involving carbon nanotube as an electron mediator to reduce the electron–hole pair recombination (Di et al. 2018). Similarly, TiO 2
decorated with carbon nanotube has emerged as a potential candidate due to its
property of large surface area, immense electronic properties, and high mechanical
strength for photodegradation of acid orange 7 dye (Hsieh and Chen 2017). The
reports on fullerenes acting as support material on mesoporous silica have been
successful for photodegradation of orange G dye in the presence of ascorbic acid
(Kyriakopoulos et al. 2019). Other than carbon nanotube and fullerenes, graphene
oxide has also been utilized as a supporting material for MnO 2 (Saroyan et al. 2019).
The GO-MnO 2 nanocomposites showed improved photoactivity against reactive
black 5 azo dye. The enhanced photoactivity of the sample was ascribed by the
superior contact formed between MnO 2 and graphene oxide.
Moreover, the GO-MnO 2 nanocomposites were efficient to cleave azo bonds to
form NH 2 groups, and as a result, the dye gets discolored, and new products like
amino naphthalene sulfonate and aromatic amines were formed. The aforementioned
nanocomposites successfully discolored 98% of reactive black 5 with 20% concentration of MnO 2 in the nanohybrid. In another report, the ternary GO-TiO 2 -ZnO
nanocomposites were tested for its photocatalytic efficacy to remove methyl
orange (Raliya et al. 2017). Besides, the photocatalytic performances of individual
4 Photocatalytic Degradation of Azo Dyes in Water
135
photodegradation efficiency of bare CuO nanoparticle. High photocatalytic activity
of binary CuO/Co 3 O 4 composite was achieved by the overlapping of band structure
that displays an important role in photo carrier charge separation and transformation.
CuO/Co 3 O 4 binary photocatalyst was favorable for practical wastewater management because of its catalytic stability and recyclability.
4.5 Carbon-Supported Photocatalyst for Azo Dye
Degradation
The carbon-supported photocatalyst had a wider range of application and can be
utilized in electrochemical sensing, hydrogen production, drug delivery, water
purification, and hydrogen storage and also as an antibacterial agent, as the combination of adsorption and photocatalyst offers a better alternative to decontaminate
water. Thus, the adsorption capacity of nanocomposites can be enhanced by using
carbonaceous material as a support which controls the size and shape of nanoparticle; it also helps to prevent the aggregation of nanoparticle (Singh et al. 2016).
Carbonaceous-based materials (carbon nanotubes, fullerenes, graphene oxide,
and graphitic carbon nitride) have been widely utilized for photodegradation of
azo dyes present in simulated water. Various research groups have been working
on the fabrication of Z-scheme-driven g-C 3 N 4 /CNT/Bi 2 Fe 4 O 9 prepared by hydrothermal technique for efficient degradation of acid orange 7 dye. The mechanism
follows a Z-scheme-driven process involving carbon nanotube as an electron mediator to reduce the electron–hole pair recombination (Di et al. 2018). Similarly, TiO 2
decorated with carbon nanotube has emerged as a potential candidate due to its
property of large surface area, immense electronic properties, and high mechanical
strength for photodegradation of acid orange 7 dye (Hsieh and Chen 2017). The
reports on fullerenes acting as support material on mesoporous silica have been
successful for photodegradation of orange G dye in the presence of ascorbic acid
(Kyriakopoulos et al. 2019). Other than carbon nanotube and fullerenes, graphene
oxide has also been utilized as a supporting material for MnO 2 (Saroyan et al. 2019).
The GO-MnO 2 nanocomposites showed improved photoactivity against reactive
black 5 azo dye. The enhanced photoactivity of the sample was ascribed by the
superior contact formed between MnO 2 and graphene oxide.
Moreover, the GO-MnO 2 nanocomposites were efficient to cleave azo bonds to
form NH 2 groups, and as a result, the dye gets discolored, and new products like
amino naphthalene sulfonate and aromatic amines were formed. The aforementioned
nanocomposites successfully discolored 98% of reactive black 5 with 20% concentration of MnO 2 in the nanohybrid. In another report, the ternary GO-TiO 2 -ZnO
nanocomposites were tested for its photocatalytic efficacy to remove methyl
orange (Raliya et al. 2017). Besides, the photocatalytic performances of individual
4 Photocatalytic Degradation of Azo Dyes in Water
135