431
The nanostructured bimetals were found to exhibit remarkable catalytic activity
in reduction of dyes. Bokare et al. (2008) found that the Fe–Ni bimetallic nanoparticles could efficiently degrade azo dye orange G in aqueous environment. The
results showed that the catalytic reduction of the azo dye leads to the formation of
intermediate compounds of aniline and naphthol amine. Cai et al. (2014, 2015)
synthesized two kinds of bimetal-supported catalysts of Fe–Co/GAC and Fe–Co/
SBA-15 and then utilized them in degrading acid orange 7 and orange II.
Mixed Oxides
The mixed metal oxides play a key role in wide applications like photocatalysis and
manufacture of absorbents (Ansari and Salavati-Niasari 2016; Mahdiani et al. 2017;
Miller and Ko 1997). In recent years, the development of new metallic oxide-based
hybrid materials has been rapidly attracting attention for use in several fields,
including environmental applications. Hybrid materials have the advantages of their
parent oxides, but they clearly exhibit the synergistic effect of all other oxides, leading to enhanced electronic (Guo et al. 2016) and physicochemical characteristics
(Thanh et al. 2016). Metal-doped iron oxides for the synthesis of bimetal oxides
have also been of interest to scientists. Bimetal oxides have been studied as adsorbents or catalysts to eliminate a wide range of pollutants (Wen et al. 2015a, b).
Recently, researchers have increased their endeavors in probing the utilization of
metal oxide-based adsorbents to remove pollutants from wastewater. In this regard,
mixed metal oxides, such as Sn–Fe oxide in removing fluoride (Biswas et al. 2009),
Zn–Ni oxide in removing tartrazine and methyl orange (Klett et al. 2014), and Mn–
Fe oxide in removing selenium (Szlachta and Chubar 2013), have been examined.
The mixed oxides have favorable features such as small crystalline size and high
surface area which will have a considerable effect on the adsorption process.
Therefore, more attention has been paid to the development of new adsorbents with
different properties. Phatai and Futalan (2016) studied the adsorption behavior of
mesoporous Ce–Al oxides toward methyl violet dye. Banu and Santhi (2013) investigated Zn–Mn–Fe triple oxides to adsorb reactive yellow 15 from aqueous medium.
Dan Li et al. (2016) used ultrasonic spray pyrolysis process to prepare hierarchical core–shell ZnO/NiO. Yudin et al. (2016) synthesized NiO hollow nanostructure
powder by ultrasonic spray pyrolysis technique. NiO/Ag 3 VO 4 nanocomposite was
prepared by sonication-assisted synthesis route to investigate the photocatalytic
activity (Raja et al. 2018). Kara et al. prepared magnetite/nickel oxide mixed metal
oxide nanoparticles and applied as a novel adsorbent to dispose of dye wastewater.
Among metal oxides, nanoparticles of Fe 2 O 3 , MnO 2 , ZrO 2 , CeO 2 , and Al 2 O 3 have
widely been assessed for adsorption of dye from polluted water (Debnath et al.
2016; Asfaram et al. 2015). Sahoo et al. (2015) used Fe 3 O 4 –MnO 2 nanohybrid for
the efficient removal of methylene blue and crystal violet dyes from contaminated
water. Singh et al. (2018) prepared Fe–Mn–Zr triple metal oxide and used it for the
adsorption of methyl orange and eosin yellow dyes from mixed dye solution. The
16 Hybrid Adsorbents for Dye Removal from Wastewater
The nanostructured bimetals were found to exhibit remarkable catalytic activity
in reduction of dyes. Bokare et al. (2008) found that the Fe–Ni bimetallic nanoparticles could efficiently degrade azo dye orange G in aqueous environment. The
results showed that the catalytic reduction of the azo dye leads to the formation of
intermediate compounds of aniline and naphthol amine. Cai et al. (2014, 2015)
synthesized two kinds of bimetal-supported catalysts of Fe–Co/GAC and Fe–Co/
SBA-15 and then utilized them in degrading acid orange 7 and orange II.
Mixed Oxides
The mixed metal oxides play a key role in wide applications like photocatalysis and
manufacture of absorbents (Ansari and Salavati-Niasari 2016; Mahdiani et al. 2017;
Miller and Ko 1997). In recent years, the development of new metallic oxide-based
hybrid materials has been rapidly attracting attention for use in several fields,
including environmental applications. Hybrid materials have the advantages of their
parent oxides, but they clearly exhibit the synergistic effect of all other oxides, leading to enhanced electronic (Guo et al. 2016) and physicochemical characteristics
(Thanh et al. 2016). Metal-doped iron oxides for the synthesis of bimetal oxides
have also been of interest to scientists. Bimetal oxides have been studied as adsorbents or catalysts to eliminate a wide range of pollutants (Wen et al. 2015a, b).
Recently, researchers have increased their endeavors in probing the utilization of
metal oxide-based adsorbents to remove pollutants from wastewater. In this regard,
mixed metal oxides, such as Sn–Fe oxide in removing fluoride (Biswas et al. 2009),
Zn–Ni oxide in removing tartrazine and methyl orange (Klett et al. 2014), and Mn–
Fe oxide in removing selenium (Szlachta and Chubar 2013), have been examined.
The mixed oxides have favorable features such as small crystalline size and high
surface area which will have a considerable effect on the adsorption process.
Therefore, more attention has been paid to the development of new adsorbents with
different properties. Phatai and Futalan (2016) studied the adsorption behavior of
mesoporous Ce–Al oxides toward methyl violet dye. Banu and Santhi (2013) investigated Zn–Mn–Fe triple oxides to adsorb reactive yellow 15 from aqueous medium.
Dan Li et al. (2016) used ultrasonic spray pyrolysis process to prepare hierarchical core–shell ZnO/NiO. Yudin et al. (2016) synthesized NiO hollow nanostructure
powder by ultrasonic spray pyrolysis technique. NiO/Ag 3 VO 4 nanocomposite was
prepared by sonication-assisted synthesis route to investigate the photocatalytic
activity (Raja et al. 2018). Kara et al. prepared magnetite/nickel oxide mixed metal
oxide nanoparticles and applied as a novel adsorbent to dispose of dye wastewater.
Among metal oxides, nanoparticles of Fe 2 O 3 , MnO 2 , ZrO 2 , CeO 2 , and Al 2 O 3 have
widely been assessed for adsorption of dye from polluted water (Debnath et al.
2016; Asfaram et al. 2015). Sahoo et al. (2015) used Fe 3 O 4 –MnO 2 nanohybrid for
the efficient removal of methylene blue and crystal violet dyes from contaminated
water. Singh et al. (2018) prepared Fe–Mn–Zr triple metal oxide and used it for the
adsorption of methyl orange and eosin yellow dyes from mixed dye solution. The
16 Hybrid Adsorbents for Dye Removal from Wastewater