nanoparticles are very much environment friendly and show a close relationship with
the microorganisms. They have some characteristics features such as wide band gap
in Near-UV spectral region, strong oxidation power, good photocatalytic property,
low cost, etc. Along with these, they have the capacity to absorb solar spectra and
other light quanta. They are used in obstructing the photo corrosion and easily get
coupled with the photo generated charges and results in low photocatalytic efficiency
(Lu et al. 2016). They are also used for the metal doping. The examples of metal
dopants which couple with ZnO nanoparticles are anionic dopants, cationic dopants,
co-dopants, etc.
12.5.2.3 Iron Oxides Nanoparticles
Iron oxide nanoparticles are the simplest and most easily available nanoparticles
among the all nanoparticles (Lu et al. 2016). The most common examples of the iron
oxide nanoparticles are the magnetic magnetite (Fe 3 O 4 ), magnetic magnemite
(γ-Fe 2 O 4 ), and the nonmagnetic hematite (α-Fe 2 O 3 ). The most common problem
which is faced in the process of the water treatment is the recovery of the
nanoparticles and their properties from the treated water and the contaminants. But
these iron oxide nanoparticles can be easily recovered by simply applying the
magnetic field. Therefore with the help of these nanoparticles the heavy metals can
be easily removed, as these heavy metals get attached to the nanoparticles and later
can be removed by using the magnetic field (Lu et al. 2016). The properties of these
nanoparticles are enhanced by coupling them with the ligands such as ethylene
diamine tetra acetic acid (EDTA), L-glutathione (GSH), mercaptobutyric acid
(MBA), α-thio-ω-(propionic acid) hepta (ethylene glycol) (PEG-SH), and meso2,3-dimercaptosuccinic acid (DMSA) or with the polymers (e.g., copolymers of
acrylic acid and crotonic acid). Among all the iron oxide nanoparticles, hematite
(α-Fe 2 O 3 ) is the most stable and cheap. It is used in various sensors, catalysis and in
many environmental applications. Most commonly it is used as nano-absorbents for
heavy metals present in tap water.
12.5.2.4 Carbon Nanotubes
Carbon nanotubes are the graphene sheet-like structure with diameter less than 1 nm.
They are unique type of structures having many wide applications, such as sorption
processes. They are used for the treatment of the water because of their features like
absorbing almost all types of the contaminants, fast kinetics, large specific surface
area, etc. Carbon nanotubes are the one which are used in various forms such as
carbon beads, carbon fibers, and nonporous carbons. Also they have the power to
absorb various types of absorbents such as dichlorobenzene, ethylbenzene, Zn
2+ ,
Pb
2+ , Cu
2+ , and Cd
2+ , and dyes because of their large surface area and porous mature
(Lu et al. 2016). These nanotubes structures are classified into two structures
(Chatterjee and Deopura 2002).
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S. Vyas et al.
the microorganisms. They have some characteristics features such as wide band gap
in Near-UV spectral region, strong oxidation power, good photocatalytic property,
low cost, etc. Along with these, they have the capacity to absorb solar spectra and
other light quanta. They are used in obstructing the photo corrosion and easily get
coupled with the photo generated charges and results in low photocatalytic efficiency
(Lu et al. 2016). They are also used for the metal doping. The examples of metal
dopants which couple with ZnO nanoparticles are anionic dopants, cationic dopants,
co-dopants, etc.
12.5.2.3 Iron Oxides Nanoparticles
Iron oxide nanoparticles are the simplest and most easily available nanoparticles
among the all nanoparticles (Lu et al. 2016). The most common examples of the iron
oxide nanoparticles are the magnetic magnetite (Fe 3 O 4 ), magnetic magnemite
(γ-Fe 2 O 4 ), and the nonmagnetic hematite (α-Fe 2 O 3 ). The most common problem
which is faced in the process of the water treatment is the recovery of the
nanoparticles and their properties from the treated water and the contaminants. But
these iron oxide nanoparticles can be easily recovered by simply applying the
magnetic field. Therefore with the help of these nanoparticles the heavy metals can
be easily removed, as these heavy metals get attached to the nanoparticles and later
can be removed by using the magnetic field (Lu et al. 2016). The properties of these
nanoparticles are enhanced by coupling them with the ligands such as ethylene
diamine tetra acetic acid (EDTA), L-glutathione (GSH), mercaptobutyric acid
(MBA), α-thio-ω-(propionic acid) hepta (ethylene glycol) (PEG-SH), and meso2,3-dimercaptosuccinic acid (DMSA) or with the polymers (e.g., copolymers of
acrylic acid and crotonic acid). Among all the iron oxide nanoparticles, hematite
(α-Fe 2 O 3 ) is the most stable and cheap. It is used in various sensors, catalysis and in
many environmental applications. Most commonly it is used as nano-absorbents for
heavy metals present in tap water.
12.5.2.4 Carbon Nanotubes
Carbon nanotubes are the graphene sheet-like structure with diameter less than 1 nm.
They are unique type of structures having many wide applications, such as sorption
processes. They are used for the treatment of the water because of their features like
absorbing almost all types of the contaminants, fast kinetics, large specific surface
area, etc. Carbon nanotubes are the one which are used in various forms such as
carbon beads, carbon fibers, and nonporous carbons. Also they have the power to
absorb various types of absorbents such as dichlorobenzene, ethylbenzene, Zn
2+ ,
Pb
2+ , Cu
2+ , and Cd
2+ , and dyes because of their large surface area and porous mature
(Lu et al. 2016). These nanotubes structures are classified into two structures
(Chatterjee and Deopura 2002).
266
S. Vyas et al.