Table 1.
Comparison of different preparation techniques and adsorption performances of various adsorbents for Cd(II) removal. The adsorbents are arranged according to the development sequence.
| Adsorbent | Preparation technique | Adsorption capacity (mmol/g) | Dose (g/L) | pH | Ref. |
|---|---|---|---|---|---|
| Oxidized carbon nanotubes (CNTs) | Oxidation of CNTs with HNO3 | 0.026 | 1.5 | 4.5 | [21] |
| Ethylenediamine-functionalized multi-walled carbon nanotubes (MWNTs) | Chemical modification of MWNTs with ethylenediamine | 0.199 | 0.1 | 8.0 | [50] |
| Nano zerovalent iron (nZVI) | Bottom-up’ method for reducing Fe3+ to Fe0 by NaBH4 | 6.843 | 0.5 | - | [51] |
| Fe3O4-orange peel powder (MNP-OPP) | Co-precipitation of orange peel with Fe3O4 nanoparticles | 0.635 | 0.1 | 7.0 | [52] |
| Graphene oxide (GO) | Oxidation of graphene with K2Cr2O7 | 4.715 | 0.1 | 5.0 | [34] |
| α-ketoglutaric acid-modified magnetic chitosan (α-KA-Fe3O4/CS) | Synthesis of Fe3O4/CS composite through co-casting method and modification with α-ketoglutaric acid | 1.789 | 1.3 | 6.0 | [53] |
| 3D sulfonated reduced graphene oxide (3D-SRGO) | Direct anchoring of sulfonic acid-containing aryl radicals to rGO | 2.089 | 0.1 | 6.0 | [12] |
| Nano zerovalent iron supported on reduced graphene oxides (NZVI/rGOs) | Synthesis of NZVI/rGOs using modified Hummers method followed by H2/Ar plasma technique | 3.787 | 0.1 | 5.0 | [54] |
| NaOH-impregnated biochar | Thermal treatment of torrefied loblolly pine chips at 300 °C for 15 min and activation with NaOH | 1.488 | 0.05 | 7.5 ± 0.1 | [9] |
| Potassium (K)-rich biochar | Slow pyrolysis of banana peels and cauliflower leaves at 600 °C for 2 h | 1.079 | 2.5 | - | [55] |
| rGO/magnetite/silver | Oxidation of graphene with KMnO4 and modification of GO with FeCl3·6H2O and AgNO3 | 3.441 | 0.2 | 4.0 ± 0.1 | This study |