Bioremediation: A Sustainable Approach for Environmental Cleanup 11

1.6 Phytoremediation

Phytoremediation is an effective biotechnology for dealing with metal and metalloid contamination

and has a distinct environmental application area (Gu 2018). Green technology for environmental

remediation plays a competitive role in transferring the soluble and bioavailable fractions

of hazardous metals and metalloids from the solution or adsorption phase into green plants for

accumulation, detoxification and stabilization (Yu and Gu 2007a,b, 2008a,b).

Phytoremediation is a non-conventional, cost-effective and eco-friendly technology that utilizes

plants to remove, transform or stabilize a variety of contaminants present in water, sediments

or soils (Prasad et al. 2001, Ladislas et al. 2012). Phytoremediation is the application of plants

for in-situ or ex-situ treatment/removal of heavy metals from contaminated soils, sediments and

water (Garbisu and Alkorta 2001, Shah and Daverey 2020) provides many benefits compared

to traditional approaches of contaminated land remediation such as lowered cost, maintenance,

exposure to workers, and is generally more aesthetically pleasing (Sharma and Yeh 2020). Plants

that have more metal-removal capacity through accumulation are known as hyperaccumulators.

These plants are used to remediate contaminants by the uptake or transpiration of contaminated

water (Cho-Ruk et al. 2006, Smolyakov 2012). Table 1.6 shows various types of aquatic plant

species capable of accumulating HMs. Plants absorb a significant number of toxic elements and

nutrients, but only a small portion of them are damaging, affecting plants at higher concentrations.

When the degree of pollution in plants rises, they are harmed or die. Various processes for treating

the water have been designed, for example, biological, physical and chemical, but they are costly

and only applicable to a small amount of wastewater (Rezania et al. 2015). As a result, an alternative

wastewater treatment procedure, phytoremediation has been proposed, in which diverse plants are

used to clean wastewater and eliminate hazardous contaminants.

Table 1.6. Various types of aquatic plant species capable of accumulating HMs.

Heavy Metals

Plant species

References

Cd, Zn, Pb, Cu

Sedum plumbizincicola

Li et al. 2018

Fe, Cu, Zn

Eichhornia crassipes

Typha latifolia

Abbas et al. 2021

Ni

Ricinus communis

Çelik and Akdaş 2019

Al, Fe

Ipomoea aquatica

Centella asiatica

Hanafiah et al. 2020

Pb, Cr, Cd

Trifolium repens L.

Lin et al. 2021

Cd, Zn, Cu

Rhazya stricta L.

Azab and Hegazy 2020

Zn, Cd, Cr, Ni

Jatropha curcas

Chang et al. 2014

Cd, Ni

Phragmites australis

Eid et al. 2020

Cu, Pb, Zn

Polygonum hydropiperoides

Rudin et al. 2017

1.6.1 Mechanisms of Phytoremediation

1.6.1.1 Phytoextraction

Phytoextraction or phytoaccumulation is the process in which metal contaminants are accumulated

and stabilized in the upper part of plants. During this process, the root uptake the metals and transfer

them to the upper portion. Selecting plants that absorb and concentrate harmful heavy metals in

various areas of the plant, this method aids in the removal of heavy metal pollution from the soil.

1.6.1.2 Phytovolatilization

In this process, contaminants are uptaken by roots, translocated in upper plant parts and released

through the leaves in the volatile form into the atmosphere (USEPA 2000). This process involves the