Morales et al. (2013) prepared GO/TiO 2 via simple mixing and sonication and
studied photodegradation ability against methyl orange dye. TiO 2 is the most
frequently used photocatalyst utilized for water purification due to its biocompatibility and high chemical stability (Leary and Westwood 2011). As graphene a
two-dimensional moiety with sp
2 carbon atom arranged in a honeycomb-like structure with high thermal and mechanical property (Singh et al. 2014, 2018, 2019a, b;
Dutta et al. 2019a, b; Shandilya et al. 2019). The unique property of graphene makes
graphene a promising material for practical application. A novel nano-graphene
oxide has been prepared using graphite as a precursor via modified Hummer’s
method (Shandilya et al. 2018a, b).
Recently, Mathew et al. (2019) synthesized nano-graphene oxide and ZnO
through sol–gel method using graphite and ZnCO 3 as precursor. The photocatalytic
activity was evaluated against rhodamine 6B, and nearly 96% of azo dye were
photodegraded in 3 h in the presence of nano-graphene oxide/ZnO, whereas only
66% was degraded through ZnO alone. The conversion of graphite into nanographene oxide was explained by powdered X-ray diffraction (Fig. 4.8). The presence of oxygen containing functionality in nano-graphene oxide was elucidated by
Fourier transform infrared spectroscopy.
Rosu et al. (2017) prepared TiO 2 -Pt/GO and TiO 2 -Pt/rGO for the degradation of
azo dyes in solar radiation. The degradation of various azo dyes with different
structures was examined through TiO 2 -Pt nanoparticles, TiO 2 -Pt/GO, and TiO 2 -Pt/
rGO nanocomposites under sunlight. The alteration in TiO 2 -Pt through graphene
oxide leads to more optical absorption in visible region, and thus, increase in its
photodegradation activity was observed. Results confirmed that nearly 99% of azo
dyes were photodegraded, and pseudo-first-order kinetic was obtained for the
reaction by using Langmuir–Hinshelwood reaction mechanism.
Other than graphene, activated carbon was also universally applied as adsorbent
due to its high porosity and large specific surface area. Mahmoodi (2014) prepared
activated carbon-supported TiO 2 nanoparticles for azo dye degradation. The activated carbon has been synthesized from the by-product of soya bean. The
photocatalytic study was performed for the degradation of reactive red 120 and
reactive red 198, respectively. The aliphatic acids like formate, acetate, and oxlate
were the major compounds detected during degradation, whereas nitrate, sulfate, and
chloride anions were the chief ions detected during mineralization through ultraviolet visible spectrometry and ion chromatography.
4.6 Others
Other than the above reported system, a zero-valent metal is also utilized for the
degradation of various azo dyes from the polluted water. A limitation of zero-valent
metal to undergo rapid corrosion can be minimized by coupling the metal atom with
highly stable noble metal (Cao et al. 1999; Shu et al. 2007). But still commercializing the system is the most important part of the research for which various factors
4 Photocatalytic Degradation of Azo Dyes in Water
137
studied photodegradation ability against methyl orange dye. TiO 2 is the most
frequently used photocatalyst utilized for water purification due to its biocompatibility and high chemical stability (Leary and Westwood 2011). As graphene a
two-dimensional moiety with sp
2 carbon atom arranged in a honeycomb-like structure with high thermal and mechanical property (Singh et al. 2014, 2018, 2019a, b;
Dutta et al. 2019a, b; Shandilya et al. 2019). The unique property of graphene makes
graphene a promising material for practical application. A novel nano-graphene
oxide has been prepared using graphite as a precursor via modified Hummer’s
method (Shandilya et al. 2018a, b).
Recently, Mathew et al. (2019) synthesized nano-graphene oxide and ZnO
through sol–gel method using graphite and ZnCO 3 as precursor. The photocatalytic
activity was evaluated against rhodamine 6B, and nearly 96% of azo dye were
photodegraded in 3 h in the presence of nano-graphene oxide/ZnO, whereas only
66% was degraded through ZnO alone. The conversion of graphite into nanographene oxide was explained by powdered X-ray diffraction (Fig. 4.8). The presence of oxygen containing functionality in nano-graphene oxide was elucidated by
Fourier transform infrared spectroscopy.
Rosu et al. (2017) prepared TiO 2 -Pt/GO and TiO 2 -Pt/rGO for the degradation of
azo dyes in solar radiation. The degradation of various azo dyes with different
structures was examined through TiO 2 -Pt nanoparticles, TiO 2 -Pt/GO, and TiO 2 -Pt/
rGO nanocomposites under sunlight. The alteration in TiO 2 -Pt through graphene
oxide leads to more optical absorption in visible region, and thus, increase in its
photodegradation activity was observed. Results confirmed that nearly 99% of azo
dyes were photodegraded, and pseudo-first-order kinetic was obtained for the
reaction by using Langmuir–Hinshelwood reaction mechanism.
Other than graphene, activated carbon was also universally applied as adsorbent
due to its high porosity and large specific surface area. Mahmoodi (2014) prepared
activated carbon-supported TiO 2 nanoparticles for azo dye degradation. The activated carbon has been synthesized from the by-product of soya bean. The
photocatalytic study was performed for the degradation of reactive red 120 and
reactive red 198, respectively. The aliphatic acids like formate, acetate, and oxlate
were the major compounds detected during degradation, whereas nitrate, sulfate, and
chloride anions were the chief ions detected during mineralization through ultraviolet visible spectrometry and ion chromatography.
4.6 Others
Other than the above reported system, a zero-valent metal is also utilized for the
degradation of various azo dyes from the polluted water. A limitation of zero-valent
metal to undergo rapid corrosion can be minimized by coupling the metal atom with
highly stable noble metal (Cao et al. 1999; Shu et al. 2007). But still commercializing the system is the most important part of the research for which various factors
4 Photocatalytic Degradation of Azo Dyes in Water
137