Table 2. Effects of acid concentration and solid–liquid ratio on metal leaching efficiency from limonite ore, and concentration of residual H+ and Fe3+ in the leach liquors.
| I | II | III | IV | V | ||
|---|---|---|---|---|---|---|
| Leaching conditions | Acid concentration (mol L−1) | 3 | 4 | 4.8 | 6 | 8 |
| Solid to liquid ratio (g mL−1) | 1 : 8 | 1 : 6 | 1 : 5 | 1 : 4 | 1 : 3 | |
| Leaching temperature (°C) | 100 | 100 | 100 | 100 | 100 | |
| Leaching time (min) | 60 | 60 | 60 | 60 | 60 | |
| Leaching efficiency (%) | Ni | 97.3 | 97.2 | 97.5 | 97.0 | 97.0 |
| Co | 95.3 | 95.2 | 95.3 | 95.2 | 95.0 | |
| Mn | 97.7 | 97.5 | 97.3 | 97.0 | 97.2 | |
| Mg | 90.3 | 92.5 | 93.6 | 94.8 | 95.6 | |
| Fe | 97.5 | 96.5 | 95.6 | 95.0 | 94.5 | |
| Concentration | Residual H+ ions (mol L−1) | 0.51 | 0.65 | 0.78 | 0.86 | 1.02 |
| Fe3+ ions (g L−1) | 62.0 | 80.2 | 94.3 | 120.7 | 157.0 |