21.3 Soil Remediation

337

surface, and groundwater, but they also accumulate in living organisms thereby

disrupting the food chain. Disposal of coating materials to prevent rust, dry cell bat-

teries, brass, bronze alloys, and certain other substances also contribute to the soil

pollution thus affecting the quality of soil.

These contaminants hide in saturated and unsaturated layer of the soil which is

underlying between the ground surface and groundwater level. Consequently, these

sites can have a high concentration of organic contaminants in soil layers in addition

to plausible groundwater contamination. They can even depict harmful effect on the

flora and fauna of affected habitats through uptake and accumulation in food chains,

and in some instances, serious health problems or genetic disorders in humans are

also observed.

Soil remediation is generally intended at removal of hydrocarbons (petroleum),

heavy metals, pesticides, cyanides, volatiles, creosotes (carbonaceous products

released during the distillation of several types of tars), and semi-volatiles. Con-

ventional methods that are chiefly being employed in remediation processes are

bioremediation, thermal soil remediation, air sparging, electrokinetic remediation,

phytoremediation, and soil washing [31]. However, these existing methods have

certain bottlenecks/disadvantages such as laborious and time consuming in such

cases, and immediate remediation is quite difficult.

21.3.1

Application of Nanotechnology for Soil Remediation

Application of nanotechnologies for environmental remediation has received

significant attention from the scientific community, specifically its use for reme-

diating heavy metal contaminated soil. Recently, nanoremediation is also being

used for the treatment of hazardous waste sites. It was Gillham, in 1996, who

for the first time investigated and presented the idea of utilizing zero-valent iron

nanoparticles (nZVIs) in the permeable barrier for the effective decontamination

of water-halogenated pollutants. Extensive studies have been carried out and lot of

literature is available pertaining to the application of nanotechnologies to remediate

the contaminated soils [32].

According to the literature, the nanoparticles have the ability to adsorb and facili-

tate degradation of pollutants through various mechanisms, such as redox reactions,

surface processes, adsorption, ion exchange, surface complexation, and electrostatic

interaction. Shi et al. [33] have analyzed nZVIs and zero-valence iron nanoparti-

cles impregnated on a matrix of bentonite (B-nZVI), in the effectual elimination of

chromium(VI) present in water and soil contaminated with heavy metals.

In a particular study, iron nanoparticles impregnated biocarbon depicted

a positive influence on the growth of cabbage and mustard plant grown in

chromium(VI)-contaminated soil compared to untreated plants.

Similarly, SiO2 nanoparticles coated with a lipid derivative of choline have been

extensively used in the bioremediation of PAHs. Other nanomaterials that have been

used are iron sulfide stabilized with carboxymethylcellulose for immobilizing mer-

cury in the polluted soils.