99
affinity to adsorb inorganic species of As(III) and As(V) (Bhowmick et al. 2014).
It was mentioned by Bhowmick et al. that montmorillonite-supported nanoscale
zero-valent iron retained As(III) and As(V) inorganic species via ligand-like
adsorption with fast kinetic, and the adsorption capacity decreased above pH 8
(Bhowmick et al. 2014).
In a study, montmorillonite–iron oxide composite was used to remove Cs
+
from
aqueous solution. It was observed that prepared nanoadsorbent had high affinity to
Cs
+
and that the removal efficiency decreased in the presence of Sr
2+
(Ararem et al.
2013). When montmorillonite was modified with iron oxide, the zeta potential was
changed to positive from the negative below pH 6.5, which is point of zero charge
of iron oxide–montmorillonite composite (Cottet et al. 2014). The change in zeta
potential can be explained by the fact that the maximum adsorption of heavy metals
onto Iron oxide–montmorillonite composite is achieved above pH 6.5 via interacting to negatively charged surface of composite..
Kalantari et al. used Fe 3 O 4 –montmorillonite nanocomposite for the Cu(II),
Ni(II), and Pb(II) removal from aqueous system. The diameter of composite was
8.4 nm, and the adsorption efficiencies were yielded between approximately 76%
and 90% depending on the solid to liquid ratio used in the experiments. The magnetic nanocomposite was found to be an efficient adsorbent for removing heavy
metals from aqueous solutions by the authors (Kalantari et al. 2015).
Pb(II), Cu(II), Zn(II), and Cd(II) removal from highly acidic solution was performed by adsorption process using montmorillonite–kaolinite–TiO 2 composite as
an adsorbent. The optimal amount of TiO 2 as an additive was determined 20% to
achieve improved adsorption ability. The results showed that fabricated composite
had high affinity at whole pH range from pH 2 to 6. Especially, 96% removal was
obtained for Pb(II) ions at pH 2, while the maximum removal for other ions was
41%. The dramatic enhancement of heavy metal adsorption at low pHs was explained
by the changes in microstructural and morphological characteristics of composite in
the presence of TiO 2 with different crystalline forms and by well dispersion of TiO 2
on the surface of the clay matrix (Đukić et al. 2015).
Zheng et al. fabricated ammonium-pillared montmorillonite–CoFe 2 O 4 composite caged in calcium alginate beads which has magnetic character and investigated
Cs
+
adsorption in terms of adsorption properties, mechanism, and capacity. As a
result, Zheng et al. expressed that fabricated composite showed high Cs
+
adsorption
efficiency with the high selectivity, and this composite might be used to removal of
Cs
+
from Cs-contaminated environments (Zheng et al. 2017).
Pb(II) and Cu(II) adsorptions on zinc oxide–montmorillonite nanocomposite
were investigated by Sani et al. It was determined that the composite showed high
adsorption efficiency in a wide pH range. As a result of regeneration experiments, it
was decided the composite could be used for three adsorption–desorption cycles.
The kinetics of adsorptions was well explained by pseudo-second-order model,
while the equilibria of adsorptions were described by Langmuir isotherm (Sani
et al. 2017).
4 Montmorillonite Clay Composite for Heavy Metal Removal from Water
affinity to adsorb inorganic species of As(III) and As(V) (Bhowmick et al. 2014).
It was mentioned by Bhowmick et al. that montmorillonite-supported nanoscale
zero-valent iron retained As(III) and As(V) inorganic species via ligand-like
adsorption with fast kinetic, and the adsorption capacity decreased above pH 8
(Bhowmick et al. 2014).
In a study, montmorillonite–iron oxide composite was used to remove Cs
+
from
aqueous solution. It was observed that prepared nanoadsorbent had high affinity to
Cs
+
and that the removal efficiency decreased in the presence of Sr
2+
(Ararem et al.
2013). When montmorillonite was modified with iron oxide, the zeta potential was
changed to positive from the negative below pH 6.5, which is point of zero charge
of iron oxide–montmorillonite composite (Cottet et al. 2014). The change in zeta
potential can be explained by the fact that the maximum adsorption of heavy metals
onto Iron oxide–montmorillonite composite is achieved above pH 6.5 via interacting to negatively charged surface of composite..
Kalantari et al. used Fe 3 O 4 –montmorillonite nanocomposite for the Cu(II),
Ni(II), and Pb(II) removal from aqueous system. The diameter of composite was
8.4 nm, and the adsorption efficiencies were yielded between approximately 76%
and 90% depending on the solid to liquid ratio used in the experiments. The magnetic nanocomposite was found to be an efficient adsorbent for removing heavy
metals from aqueous solutions by the authors (Kalantari et al. 2015).
Pb(II), Cu(II), Zn(II), and Cd(II) removal from highly acidic solution was performed by adsorption process using montmorillonite–kaolinite–TiO 2 composite as
an adsorbent. The optimal amount of TiO 2 as an additive was determined 20% to
achieve improved adsorption ability. The results showed that fabricated composite
had high affinity at whole pH range from pH 2 to 6. Especially, 96% removal was
obtained for Pb(II) ions at pH 2, while the maximum removal for other ions was
41%. The dramatic enhancement of heavy metal adsorption at low pHs was explained
by the changes in microstructural and morphological characteristics of composite in
the presence of TiO 2 with different crystalline forms and by well dispersion of TiO 2
on the surface of the clay matrix (Đukić et al. 2015).
Zheng et al. fabricated ammonium-pillared montmorillonite–CoFe 2 O 4 composite caged in calcium alginate beads which has magnetic character and investigated
Cs
+
adsorption in terms of adsorption properties, mechanism, and capacity. As a
result, Zheng et al. expressed that fabricated composite showed high Cs
+
adsorption
efficiency with the high selectivity, and this composite might be used to removal of
Cs
+
from Cs-contaminated environments (Zheng et al. 2017).
Pb(II) and Cu(II) adsorptions on zinc oxide–montmorillonite nanocomposite
were investigated by Sani et al. It was determined that the composite showed high
adsorption efficiency in a wide pH range. As a result of regeneration experiments, it
was decided the composite could be used for three adsorption–desorption cycles.
The kinetics of adsorptions was well explained by pseudo-second-order model,
while the equilibria of adsorptions were described by Langmuir isotherm (Sani
et al. 2017).
4 Montmorillonite Clay Composite for Heavy Metal Removal from Water