Table 1 Independent variables, their units and codes for the CCD design.
Parameters | Unit | Code | Levels | ||||
|---|---|---|---|---|---|---|---|
− α | − 1 | 0 | + 1 | + α | |||
pH of solution (pH) | – | A | 3 | 5.6 | 7.3 | 9 | 11.5 |
Adsorbent dosage (Dos) | g L−1 | B | 1.7 | 4 | 5.5 | 7 | 9.24 |
Time (t) | min | C | 5.28 | 15 | 21.5 | 28 | 37.71 |
Initial concentration (C) | mg L−1 | D | 1.78 | 10 | 15.5 | 21 | 29.21 |
Temperature (T) | °C | E | 17.27 | 24 | 28.5 | 33 | 39.72 |
Speed of stirring | rpm | F | 40 | 70 | 90 | 110 | 140 |
