Removal of Heavy Metals in Contaminated Soil by Phytoremediation Mechanism: a Review

The rapid development of industrial sector has increased the heavy metal pollution issue recently, as the need of various metals is increasing for manufacturing purpose. These metals are the natural components that can be found in soil, but contamination happens when the concentration of these metals are high in soil due to anthropogenic activities. Several remediation techniques such as physical method, thermal desorption, chemical, and electrokinetic remediation are used to remediate the soil contaminated by heavy metals recently. As these remediation technologies have limitation on cost, effectiveness, and environmental friendly remediation issue, phytoremediation is then attracting the attention from various researchers due to its advantages of efficient, cost-effective, and eco-friendly remediation method. The mechanisms of phytoremediation are phytoextraction, phytostabilization, phytovolatilization, phytodegradation, phytodesalination, rhizofiltration, rhizodegradation, and phytoevaporation. However, these mechanisms were affected by several factors such as the plant species, properties of medium, bioavailability of metal, and the addition of chelating agent. The type of plant utilized for phytoremediation (metallophytes) is categorized as metal indicators, metal excluders, and metal hyperaccumulators. This review article comprehensively discusses the source and effect of heavy metal on human health as well as phytoremediation techniques and mechanism during the heavy metal removal.