13.3.3 Manganese Oxides (MnO) Nanoparticles
A manganese oxide (MnOs) nanoparticle shows high adsorption ability due to their
high BET surface area and polymorphic structure (Luo et al. 2010). It has been
widely used for the removal of various heavy metals such as arsenic from wastewater
(Wang et al. 2011). Nano-porous/nano-tunnel manganese oxides and hydrous manganese oxide (HMO) are most frequently used modified MnOs (Gupta et al. 2015).
Zaman et al. (2009) and prepared HMO by adding MnSO 4 ÁH 2 O into NaClO
solution. Modified HMO has around 100.5 m
2 /g BET surface areas. Adsorption of
various heavy metals such as Pb (II), Cd (II), and Zn (II) on HMOs usually happens
due to the inner-sphere formation mechanism that can be defined by ion-exchange
process (Gupta et al. 2015). However, adsorption of divalent metals on the surface of
HMOs occurred in two steps. At first, metal ions adsorb on the external surface of
HMOs and then followed by intraparticle diffusion (Parida et al. 1981).
13.3.4 Zinc Oxide (ZnO) Nanoparticles
Zinc Oxide (ZnO) has a porous micro and nanostructure with high BET surface area
for the adsorption of heavy metals. Nano-assemblies, nano-plates, microspheres with
nano-sheets and hierarchical ZnO nano-rods are widely used as nano-adsorbent for
the removal of heavy metals from wastewater (Ge et al. 2012; Kumar et al. 2013).
The aforementioned modified forms of ZnO nano-adsorbent show high removal
efficiency of heavy metals as compared to commercial ZnO. Wang et al. (2010) used
ZnO nano-plates and porous nano-sheet for the removal of Cu (II) from wastewater.
These modified ZnO nano-adsorbent shows high removal efficiency of Cu (II) due to
their unique micro/nanostructure as compared to commercial ZnO. Moreover, nanoassemblies were used for the removal of different kinds of heavy metals which
include Co
2+ , Ni
2+ , Cu
2+ , Cd
2+ , Pb
2+ , Hg
2+ , and As
3+ (Singh et al. 2013). Microporous nano-assemblies show high affinity for the adsorption of Pb
2+ , Hg
2+ , and As
3+
due to their electropositive nature (Gupta et al. 2015). Kumar et al. (2013) reported
the high removal efficiency of Pb (II) and Cd (II) from wastewater by using
mesoporous hierarchical ZnO nano-rods.
13.3.5 Magnesium Oxide (MgO) Nanoparticles
Magnesium oxide (MgO) is used for the removal of different kinds of heavy metals
from contaminated water. MgO microspheres are of novel structure, which can
improve the adsorption affinity for the removal of heavy metals (Gupta et al.
2015). To increase the adsorption capacity of MgO, different types of modification
were carried out in nanoparticles morphology. These include nano-rods (Engates and
Shipley 2011), nano-belts (Zhu et al. 2001), fishbone fractal nanostructures induced
(Liang et al. 2004), by nanowires (Mo et al. 2005), nanotubes (Yin et al. 2002),
nano-cubes (Li et al. 2002), and three-dimensional entities (Klug and Dravid 2002).
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289
A manganese oxide (MnOs) nanoparticle shows high adsorption ability due to their
high BET surface area and polymorphic structure (Luo et al. 2010). It has been
widely used for the removal of various heavy metals such as arsenic from wastewater
(Wang et al. 2011). Nano-porous/nano-tunnel manganese oxides and hydrous manganese oxide (HMO) are most frequently used modified MnOs (Gupta et al. 2015).
Zaman et al. (2009) and prepared HMO by adding MnSO 4 ÁH 2 O into NaClO
solution. Modified HMO has around 100.5 m
2 /g BET surface areas. Adsorption of
various heavy metals such as Pb (II), Cd (II), and Zn (II) on HMOs usually happens
due to the inner-sphere formation mechanism that can be defined by ion-exchange
process (Gupta et al. 2015). However, adsorption of divalent metals on the surface of
HMOs occurred in two steps. At first, metal ions adsorb on the external surface of
HMOs and then followed by intraparticle diffusion (Parida et al. 1981).
13.3.4 Zinc Oxide (ZnO) Nanoparticles
Zinc Oxide (ZnO) has a porous micro and nanostructure with high BET surface area
for the adsorption of heavy metals. Nano-assemblies, nano-plates, microspheres with
nano-sheets and hierarchical ZnO nano-rods are widely used as nano-adsorbent for
the removal of heavy metals from wastewater (Ge et al. 2012; Kumar et al. 2013).
The aforementioned modified forms of ZnO nano-adsorbent show high removal
efficiency of heavy metals as compared to commercial ZnO. Wang et al. (2010) used
ZnO nano-plates and porous nano-sheet for the removal of Cu (II) from wastewater.
These modified ZnO nano-adsorbent shows high removal efficiency of Cu (II) due to
their unique micro/nanostructure as compared to commercial ZnO. Moreover, nanoassemblies were used for the removal of different kinds of heavy metals which
include Co
2+ , Ni
2+ , Cu
2+ , Cd
2+ , Pb
2+ , Hg
2+ , and As
3+ (Singh et al. 2013). Microporous nano-assemblies show high affinity for the adsorption of Pb
2+ , Hg
2+ , and As
3+
due to their electropositive nature (Gupta et al. 2015). Kumar et al. (2013) reported
the high removal efficiency of Pb (II) and Cd (II) from wastewater by using
mesoporous hierarchical ZnO nano-rods.
13.3.5 Magnesium Oxide (MgO) Nanoparticles
Magnesium oxide (MgO) is used for the removal of different kinds of heavy metals
from contaminated water. MgO microspheres are of novel structure, which can
improve the adsorption affinity for the removal of heavy metals (Gupta et al.
2015). To increase the adsorption capacity of MgO, different types of modification
were carried out in nanoparticles morphology. These include nano-rods (Engates and
Shipley 2011), nano-belts (Zhu et al. 2001), fishbone fractal nanostructures induced
(Liang et al. 2004), by nanowires (Mo et al. 2005), nanotubes (Yin et al. 2002),
nano-cubes (Li et al. 2002), and three-dimensional entities (Klug and Dravid 2002).
13 Phytoremediation and Nanoremediation
289