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] |