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Bioremediation for Sustainable Environmental Cleanup

16.4.2.2 Metal based Nano-adsorbents

Metal oxides, such as Fe, Cu, Ti, Mn, Mg, Zn, Si and Al, can be used to synthesize nanoparticles

(Table 16.5). Due to metal-ligand precipitation or the generation of ternary ligands, metal oxide

nanoparticles have a greater degree of adsorption than regular sized oxide (Stietiya and Wang 2014).

Metal oxide-based nanomaterials with very well structural, crystalline and surface properties act as

semiconductors with large band gaps. They also have advantageous properties such as non-toxicity

and excellent water stability. Metal oxides include ferric oxides, Ti, Ce, and Zn, provide low-cost

adsorbents. The adsorption capacity of metal-based nanoparticles is pH deepened. Heavy metals

adsorption from the media enhanced with pH due to an increase in electrostatic interactions and

formation of ionic or covalent bonds. In addition, improvement in pH favors the release of protons

of nanosorbent, enhancing the negatively charged sites. Nassar (2012) showed 36 mg g^–1 absorption

capacity of Fe3O4 nanoadsorbents for the removal of Pb (II) ions. Moreover, ultrafine magnesium

ferrite (MgO.27Fe2.5O4) nanoadsorbent synthesized by Tang et al. (2013) functioned as a good

adsorbent for As from contaminated water. Alumina nanoadsorbent produced through the solution

combination synthesis method was reported to be highly efficient in removing Zn (II) from wastewaters.

It is notable that nanosized iron oxide particles have superparamagnetism, which distinguishes them

from other oxide nanoparticles. Super paramagnetic nanoparticles have a higher surface area, are

biocompatible, less hazardous, chemically inert, have a low diffusion resistance and their surface may

be changed with organic molecules, inorganic ions or functional groups, making them ideal surfaces

for absorbing heavy metals. Fe3O4 superparamagnetic nanoadsorbents with a diameter less than

Table 16.5. Removal efficiency of different metal based nano absorbents and carbon nanotube-based adsorbents.

Metal based nano-adsorbent

Metal removal

Efficiency (mg g^–1)

References

Fe3O4 nanoadsorbents

Pb (II)

36

Nassar 2012

Anatase oxide nanoadsorbent

Pb, Cu, As

31.25, 23.74, 16.98

Kocabas-Atkali and Yurum

2013

Magnesium ferrite nanoadsorbent

As

127.4 (As⁺³) and 83.2 (As⁺⁵)

Tang et al. 2013

Manganese feroxyhyte

nanoadsorbent

As

11.7 μg mg^-1 (As⁺³), 6.7 μg/mg

(As⁺⁵)

Tresintsi et al. 2013

Fe-La composite oxide

As

58.2

Zhang et al. 2012

Alumina nanoadsorbent

Zn

1047.83

Bhargavi et al. 2015

Fe3O4 magnetic nanoparticles

Hg

-

Nassar 2012

Mercapto-functionalized nano­

Fe3O4 magnetic nanoadsorbent

(SH-Fe3O4-NMPs)

Hg

-

Chalasani and Vasudevan

2012

Fe3O4 superparamagnetic

nanoadsorbent coated with

ascorbic acid

As

16.56 (As⁺³) and 46.06 (As⁺⁵)

Nassar 2012

MnFe2O4 nanoadsorbent

Pb, Cu and Cd

481.2 for Pb⁺², 386.2 for Cu⁺² and

345.5 for Cd⁺²

Ma et al. 2015

SWCNTs

Hg

41.66

Alijani and Shariatinia

2018

SWCNTs-Fe3O4-CoS

Hg

1666

Alijani and Shariatinia

2018

MWCNTs

Cr

1.26

Dehghani et al. 2015

Al2O3-MWCNTs

Pb

-

Gupta 2017

Porous graphene

As

-

Tabish et al. 2018

Activated carbon

Pb, Cd, Cu,

Ni

238.1, 96.2, 87.7, 52.4

Li et al. 2018