432
results showed a removal efficiency of 99.26% and 99.55% for methyl orange and
eosin yellow dyes, respectively, at optimal experimental conditions.
The application of Co and Ni binary oxide in removing methylene blue and
Procion red has been reported (Khosravi and Eftekhar 2014). Also, Fe 2 O 3 –Al 2 O 3
exhibited an appropriate adsorption capacity toward Congo red (Mahapatra et al.
2013). Wawrzkiewicz et al. (2017) proposed a novel mesoporous aluminosilicate
adsorbent for the removal of acid orange 7, reactive black 5, and direct blue 71 dyes
from the wastewaters.
The highly efficient adsorption of azo and nitro dyes has also been reported by
using bimetal oxides. Hua et al. (2013) studied the catalytic performance of CuO/γ- -
Al 2 O 3 for degradation of two dyes. Results revealed complete transformation of dye
to H 2 O and CO 2 .
Chiou et al. (2013) prepared Ag–Fe oxide nanohybrid and used it for removing
4-nitrophenol. Safavi and Momeni (2012) assessed the catalytic activity of Pd/
hydroxyapatite/Fe 3 O 4 nanocatalyst in degrading the selected azo dyes.
Layered Double Hydroxides
It has been reported that layered double hydroxides are efficient adsorbents for the
removal of anionic pollutants from wastewater (Extremera et al. 2012; Abdellaoui
et al. 2017). The layered double hydroxides are popular adsorbents because of their
high chemical stability, low cost, reusability, less toxicity, and easy preparation
(Almoisheer et al. 2019). The layered double hydroxides are anionic clay with 2D
nanostructures. The layered double hydroxides have a general chemical composition as [M
2+ (1 − X) M
3+ (X) (OH) 2 ]
X+
(A
n−
) X/n .mH 2 O, where M
2+
, M
3+
, and A
n−
stand for
bi- and trivalent cations, respectively (Fig. 16.15) (Scarpellini et al. 2014; Ai
et al. 2011).
The layered double hydroxides have a hydrophilic nature due to the presence of
the intercalated inorganic anions, but their surface may be hydrophobic by incorporating large organic anions into the interlayer space (Abdellaoui et al. 2019). The
layered double hydroxide-based hybrids have found to be the promising materials
in wastewater treatment (Daud et al. 2019). The facile modification of layered double hydroxides has made them efficient adsorbents for removing anionic dyes
(Zubair et al. 2017a). Table 16.7 presents the recent findings on utilizing layered
double hydroxide-based hybrids for removing a wide variety of dyes. As can clearly
be seen from the data in Table 16.7, the layered double hydroxide-based hybrids
exhibited excellent dye adsorption/removal performance. However, the adsorption
process can be influenced by operating conditions (Stawiński et al. 2017; Zhang
et al. 2017).
Anionic dyes can be adsorbed based on the strong electrostatic attraction due to
the positively charged surface of layered double hydroxides and anionic dyes. The
hybridization of layered double hydroxide by integrating nanomaterials such as
nanoparticles (carbon nanotubes, iron), polymers, surfactants, and anions can
remarkably enhance the adsorption efficiency. Despite good dye adsorption
R. M. Moattari and T. Mohammadi
results showed a removal efficiency of 99.26% and 99.55% for methyl orange and
eosin yellow dyes, respectively, at optimal experimental conditions.
The application of Co and Ni binary oxide in removing methylene blue and
Procion red has been reported (Khosravi and Eftekhar 2014). Also, Fe 2 O 3 –Al 2 O 3
exhibited an appropriate adsorption capacity toward Congo red (Mahapatra et al.
2013). Wawrzkiewicz et al. (2017) proposed a novel mesoporous aluminosilicate
adsorbent for the removal of acid orange 7, reactive black 5, and direct blue 71 dyes
from the wastewaters.
The highly efficient adsorption of azo and nitro dyes has also been reported by
using bimetal oxides. Hua et al. (2013) studied the catalytic performance of CuO/γ- -
Al 2 O 3 for degradation of two dyes. Results revealed complete transformation of dye
to H 2 O and CO 2 .
Chiou et al. (2013) prepared Ag–Fe oxide nanohybrid and used it for removing
4-nitrophenol. Safavi and Momeni (2012) assessed the catalytic activity of Pd/
hydroxyapatite/Fe 3 O 4 nanocatalyst in degrading the selected azo dyes.
Layered Double Hydroxides
It has been reported that layered double hydroxides are efficient adsorbents for the
removal of anionic pollutants from wastewater (Extremera et al. 2012; Abdellaoui
et al. 2017). The layered double hydroxides are popular adsorbents because of their
high chemical stability, low cost, reusability, less toxicity, and easy preparation
(Almoisheer et al. 2019). The layered double hydroxides are anionic clay with 2D
nanostructures. The layered double hydroxides have a general chemical composition as [M
2+ (1 − X) M
3+ (X) (OH) 2 ]
X+
(A
n−
) X/n .mH 2 O, where M
2+
, M
3+
, and A
n−
stand for
bi- and trivalent cations, respectively (Fig. 16.15) (Scarpellini et al. 2014; Ai
et al. 2011).
The layered double hydroxides have a hydrophilic nature due to the presence of
the intercalated inorganic anions, but their surface may be hydrophobic by incorporating large organic anions into the interlayer space (Abdellaoui et al. 2019). The
layered double hydroxide-based hybrids have found to be the promising materials
in wastewater treatment (Daud et al. 2019). The facile modification of layered double hydroxides has made them efficient adsorbents for removing anionic dyes
(Zubair et al. 2017a). Table 16.7 presents the recent findings on utilizing layered
double hydroxide-based hybrids for removing a wide variety of dyes. As can clearly
be seen from the data in Table 16.7, the layered double hydroxide-based hybrids
exhibited excellent dye adsorption/removal performance. However, the adsorption
process can be influenced by operating conditions (Stawiński et al. 2017; Zhang
et al. 2017).
Anionic dyes can be adsorbed based on the strong electrostatic attraction due to
the positively charged surface of layered double hydroxides and anionic dyes. The
hybridization of layered double hydroxide by integrating nanomaterials such as
nanoparticles (carbon nanotubes, iron), polymers, surfactants, and anions can
remarkably enhance the adsorption efficiency. Despite good dye adsorption
R. M. Moattari and T. Mohammadi