two types, single-walled nanotubes and multiwalled nanotubes (MWCNTs). They
have the property of high surface area and more adsorption sites. Also they have the
property of converting themselves into aggregates or bundles when they come in
contact with any aqueous medium. These bundles have more number of active sites
and large pores because of which the more number of organic contaminants get
adsorbed by them (Ji et al. 2009).
12.6.2 Metal-based Nano-adsorbents
Metal-based nano-adsorbents are basically used for the removal of the heavy metals
present in wastewater. The basic examples of metal-based nano-adsorbents are iron
oxide, titanium dioxide, zinc oxide, etc. As compared to other nano-adsorbents, they
are much cheaper and effective in their removal task. During the process of the
removal by these nano-adsorbents, the oxygen present in the metal oxide get coupled
with the heavy metals and form a complex like structure which easily gets dissolved
in the contaminated water. One unique feature of these nano-adsorbents is that, with
the decrease in size their adsorption power get increases (Grumezescu 2017). For
example—The adsorption power of the magnetite particle is same for As (III) at
300 and 20 nm, but as the size of the particle with range 20 nm get reduced the
adsorbing power get increased. This is called as the “nanoscale effect,” and with the
help of this effect magnetite nano rods are used to remove the heavy metal ions like
Fe
2+ , Pb
2+ , Zn
2+ , Ni
2+ , etc.
12.6.3 Polymeric Nano-adsorbents
The basic reason for the use of such nano-adsorbents is their good adsorption power
and thermal stability at wide range of pH. Also they are resistant to acid-base
hydrolysis, which makes it more advantageous. Such type of the nano-adsorbents
are used as the system into which the inorganic nano-sized particles can be inserted
and also used as the template for the preparation of the nanoparticles.
12.6.4 Zeolites
The Zeolites are the porous structures with the number of active sites with which the
large number of contaminants like heavy metals get attached for removal. This
feature of Zeolites makes them unique from the other nano-adsorbents. Zeolites
can be formed naturally or can be synthesized. The basic example of natural Zeolites
are analcime, chabazite, clinoptilolite, heulandite, etc. These are the three dimensional alumina silicate structures with which the cations like sodium, potassium,
calcium, etc. are attached very loosely. During the process of removal the cations
attached to these Zeolites get exchanged with the pollutants present in water and thus
the treatment of wastewater take place.
270
S. Vyas et al.
have the property of high surface area and more adsorption sites. Also they have the
property of converting themselves into aggregates or bundles when they come in
contact with any aqueous medium. These bundles have more number of active sites
and large pores because of which the more number of organic contaminants get
adsorbed by them (Ji et al. 2009).
12.6.2 Metal-based Nano-adsorbents
Metal-based nano-adsorbents are basically used for the removal of the heavy metals
present in wastewater. The basic examples of metal-based nano-adsorbents are iron
oxide, titanium dioxide, zinc oxide, etc. As compared to other nano-adsorbents, they
are much cheaper and effective in their removal task. During the process of the
removal by these nano-adsorbents, the oxygen present in the metal oxide get coupled
with the heavy metals and form a complex like structure which easily gets dissolved
in the contaminated water. One unique feature of these nano-adsorbents is that, with
the decrease in size their adsorption power get increases (Grumezescu 2017). For
example—The adsorption power of the magnetite particle is same for As (III) at
300 and 20 nm, but as the size of the particle with range 20 nm get reduced the
adsorbing power get increased. This is called as the “nanoscale effect,” and with the
help of this effect magnetite nano rods are used to remove the heavy metal ions like
Fe
2+ , Pb
2+ , Zn
2+ , Ni
2+ , etc.
12.6.3 Polymeric Nano-adsorbents
The basic reason for the use of such nano-adsorbents is their good adsorption power
and thermal stability at wide range of pH. Also they are resistant to acid-base
hydrolysis, which makes it more advantageous. Such type of the nano-adsorbents
are used as the system into which the inorganic nano-sized particles can be inserted
and also used as the template for the preparation of the nanoparticles.
12.6.4 Zeolites
The Zeolites are the porous structures with the number of active sites with which the
large number of contaminants like heavy metals get attached for removal. This
feature of Zeolites makes them unique from the other nano-adsorbents. Zeolites
can be formed naturally or can be synthesized. The basic example of natural Zeolites
are analcime, chabazite, clinoptilolite, heulandite, etc. These are the three dimensional alumina silicate structures with which the cations like sodium, potassium,
calcium, etc. are attached very loosely. During the process of removal the cations
attached to these Zeolites get exchanged with the pollutants present in water and thus
the treatment of wastewater take place.
270
S. Vyas et al.