Table 2.

Comparison of maximum adsorption capacities for heavy metals on some adsorbents.

Biomass/waste name	Activated agent	Created as adsorbent	Adsorbate	Max.adsorption capacity (mg g−1)	References
Green waste tea residue	No any activating agent	Without activation	Cu2+ and Ni2+	15.6 and 15.9	Present work
Sewage sludge	ZnCl2	Activated	Cu, Zn, and Al	15.58, 24.09 and 27.70	68
Bamboo SM1 SM2	No any activating agent	Activated	Cu(II), Cd(II) and Pb(II)	0.4, 0.17 and 0.40 0.4, 0.25 and 0.39	69
Pistachio shell	Fe3O4 NPs@AC@SO3H	Activated	Pb(II), As(III) and Cd(III)	147.05, 151.51 and 119.04	70
Sugarcane	ZnCl2	activated	Cu2+, Ni2+ and Pb2+	2.99, 13.24 and 19.3	71
Coconut shell	H3PO4	Activated	Cd(II)	33.71	72
Vegetable wastes	H2SO4, H3PO4 and NH4NO3	Activated	Cd2+, Ni2+ and Zn2+	4.97, 3.29 and 3.07	73
Sand	α-Fe2O3	Coated	Cu(II)	3.93	35
Sugarcane Bagasse	H3PO4	Activated	Hg	107.7	74