Table 2.

Remediation approaches of HMs.

Remediation Type	Approach	HM	Advantages	Disadvantages	References
Physical	Replacement	Ni, Cd, Cr, Zn, Cu, Pb	Appropriate for smaller contaminated sites	Expensive	[114]
	Thermal desorption	Hg	Effective Safe Lack of secondary pollutants Short pretreatment period	Expensive devices Long desorption time	[115]
Chemical	Oxidation/reduction	Cu, As, Sb, Cr, Pb, Se	Suitable for soils that are heavily polluted with HMs	Expensive Need large quantity of chemicals	[116]
	Leaching	Cr, Zn, Cu, Pb, Ni, Cd	Suitable for soils that are heavily polluted with HMs	Formation of secondary pollutants	[117]
	Electrokinetic remediation-permeable reactive barrier	Cd, Pb, Cr, Ni	Suitable for soils that are heavily polluted with HMs	Time-consuming	[118]
	Stabilization	Pb, Cd, Cu, Mn, Zn, As, Fe, Ni	Effective Low cost Convenient	Pollutants cannot be removed thoroughly	[118]
Bioremediation	Microbial remediation	Cr, Pb, Ni, Zn, As,	Effective Low cost Lack of secondary pollutants	Concentration limit Time-consuming	[119]
	Phytoremediation	Se, Cd, Cu, Pb, Zn	Convenient Eco-friendly Low cost	Time-consuming Non-specific Low efficiency	[119]