| Parameter | Metal ion | Optimum Quantity Adsorbed at Equilibrium (mg/g) | |
| Iron oxide | Goethite | ||
| Contact Time | Co(II) | 95.1 | 100 |
| Ni(II) | 81.4 | 80.2 | |
| Adsorbent Dose | Co(II) | 96.2 | 105.6 |
| Ni(II) | 82.2 | 93.2 | |
| pH | Co(II) | 103.9 | 117.8 |
| Ni(II) | 85.2 | 100.6 | |