silicate nanoparticles have also shown extra ordinary removal properties. Silica
nanoparticles can be grouped with different ligands and non-specific moieties in
order to remove targeted pollutant (Wang et al. 2010).
6.6
Zero-Valent Metal-Based Nanomaterials
Zero-valent metal has an extraordinary potential in the wastewater treatments
because of their high reactivity, surface area, and specificity. For example, zerovalent zinc has marvelous degradation ability in case of heavy metals and other
hazardous substances as their negative standard reduction potential is way stronger
than any other metal nanoparticle. Some of the nanomaterials are discussed below
(Carroll et al. 2013; Rafiq et al. 2014; Ahmed and Yousef 2015).
6.6.1 Au Nanoparticles
Au nanoparticles chiefly used for the removal of mercury because of their high
electron affinity which leads to remarkable transformation into AuHg, AuHg 3 , and
Au 3 Hg (Ojea-Jimenez et al. 2012). They have high surface-to-volume ratio, biocompatible nature and less toxicity make them compatible for the removal of heavy
metals (Khlebtsov and Dykman 2011). Lisha et al. studied the properties of Au
nanoparticles for the removal of Hg (II)ions. Pradeep and co-workers also discovered gold nanoparticles which showed limited adsorption for Hg2+ ions due to the
poor electrostatic sorption. Lo et al. also prepared citrate-based gold
nanoparticles and immobilized them with the help of Al 2 O 3 and studied their
behavior for the removal of mercuric ions. Different other adsorbents like sodium
borohydride which is also used to strengthen Au nanoparticles to enhance its
removal capacity towards mercuric ions. Hence Gold nanoparticles shows greater
extermination towards mercury than any other adsorptive material. The amount used
for the adsorption is also very low so their recovery becomes very easy and efficient.
This implies that gold particles are successful and can be used for the treatment of
toxic heavy metals.
6.6.2 Iron Nanoparticles
Various zero-valent nanoparticles are used for the treatment of toxic metal
compounds like Fe, Al, Ni, and Zn. Because of their short life time and highly
reactive nature towards contaminants they can be used for the wide range of heavy
metal removal. Removal process in case of iron nanoparticles can take place either
by (1) Reduction, in which the outer shell of the nanoparticles participates. As it has
weak electrostatic forces which provides appropriate reactive site for the pollutants
to get attached to the surface and get reduced to form Zn
2+ , Ag
2+ , Cd
2+ ions shown in
Fig. 6.5, (2) Magnetic separation, in which external magnetic field applied for the
6 Nanotechnology for the Remediation of Heavy Metals
153
nanoparticles can be grouped with different ligands and non-specific moieties in
order to remove targeted pollutant (Wang et al. 2010).
6.6
Zero-Valent Metal-Based Nanomaterials
Zero-valent metal has an extraordinary potential in the wastewater treatments
because of their high reactivity, surface area, and specificity. For example, zerovalent zinc has marvelous degradation ability in case of heavy metals and other
hazardous substances as their negative standard reduction potential is way stronger
than any other metal nanoparticle. Some of the nanomaterials are discussed below
(Carroll et al. 2013; Rafiq et al. 2014; Ahmed and Yousef 2015).
6.6.1 Au Nanoparticles
Au nanoparticles chiefly used for the removal of mercury because of their high
electron affinity which leads to remarkable transformation into AuHg, AuHg 3 , and
Au 3 Hg (Ojea-Jimenez et al. 2012). They have high surface-to-volume ratio, biocompatible nature and less toxicity make them compatible for the removal of heavy
metals (Khlebtsov and Dykman 2011). Lisha et al. studied the properties of Au
nanoparticles for the removal of Hg (II)ions. Pradeep and co-workers also discovered gold nanoparticles which showed limited adsorption for Hg2+ ions due to the
poor electrostatic sorption. Lo et al. also prepared citrate-based gold
nanoparticles and immobilized them with the help of Al 2 O 3 and studied their
behavior for the removal of mercuric ions. Different other adsorbents like sodium
borohydride which is also used to strengthen Au nanoparticles to enhance its
removal capacity towards mercuric ions. Hence Gold nanoparticles shows greater
extermination towards mercury than any other adsorptive material. The amount used
for the adsorption is also very low so their recovery becomes very easy and efficient.
This implies that gold particles are successful and can be used for the treatment of
toxic heavy metals.
6.6.2 Iron Nanoparticles
Various zero-valent nanoparticles are used for the treatment of toxic metal
compounds like Fe, Al, Ni, and Zn. Because of their short life time and highly
reactive nature towards contaminants they can be used for the wide range of heavy
metal removal. Removal process in case of iron nanoparticles can take place either
by (1) Reduction, in which the outer shell of the nanoparticles participates. As it has
weak electrostatic forces which provides appropriate reactive site for the pollutants
to get attached to the surface and get reduced to form Zn
2+ , Ag
2+ , Cd
2+ ions shown in
Fig. 6.5, (2) Magnetic separation, in which external magnetic field applied for the
6 Nanotechnology for the Remediation of Heavy Metals
153