No.

Synthesis Method

Coating agents

Surface functionalized group

Removal efficiency (%)

Metal removed

Ref.

1

Thermolysis of precursors

Dimercaptosuccinic acid

Thiol group

-

Hg(II), Ag(I), Pb(II),

Cd(II), Tl(I)

[58]

2

Co-precipitation

Succinic acid

Carboxylic group

91As, but 100 for others. pH = 8

Cr(III), Co(II), Ni(II),

Cu(II), Cd(II), Pb(II),

As(III)

[64]

3

Thermolysis of precursors

Ethylenediamine

Amine group

95 As but 100 for others pH = 8

4

Thermolysis of precursors followed by ligand exchange process

Dimercaptosuccinic acid

Thiol group

97 As but 100 for others pH = 8

5

Co-precipitation

Humic acid

Carboxylic and phenolic group

99, pH = 6.5 - 8.1

Hg(II), Pb(II),

[33] [43] [44] [45] [65]

95, pH = 6.5 - 8.1

Cd(II), Cu(II)

98.5, pH = 2.53

Rhodamine B

>90, pH = 6.6

Phosphate

6

Co-precipitation

Carboxymethyl-β-

cyclodextrin

Carboxylic group

96.2

Cu(II)

[66]

7

Crystallization from ferrous

hydroxide gels

Polyethylenimine

Amine group

-

Cu(II)

[67]