Table 2.

Comparison of adsorption capacities of natural adsorbents for removal of toxic metal ions.

S. No.	Adsorbent	Metal Ion/Adsorption Capacity	Reference
1	Lignin	Pb2+ = 1865 mg/g, Zn2+ = 95 mg/g	[107]
2	Chitosan (powder)	Cd2+ = 420 mg/g	[108]
3	Chitosan (beads)	Cd2+ = 518 mg/g	[108]
4	Seaweed brown algae	Cd2+ = 67 mg/g	[109]
5	A. nodosum seaweed	Cd2+ = 215 mg/g	[109]
6	Formaldehyde cross-linked A. nodosum seaweed	Cd2+ = 149 mg/g	[110]
7	Starch xanthate	Cd2+ = 33.3 mg/g Cr2+ = 17.6 mg/g Hg2+ = 1.15 mg/g	[111,112]
8	Cellulose xanthate	Cd2+ = 19.9 mg/g Cr2+ = 19.7 mg/g Hg2+ = 0.64 mg/g	[111]
9	Xanthated sawdust	Cd2+ = 21.4 mg/g Hg2+ = 30.1 ± 40.1	[112]
10	Zeolites	Pb2+ = 155.4 mg/g Cd2+ = 84.3 mg/g Cr3+ = 26.0 mg/g Hg2+ = 150.4 mg/g	[113]