Independent parameters | Range and level | ||||
2 | −1 | 0 | +1 | +2 | |
pH (X1) | 2 | 3 | 4 | 5 | 6 |
Initial Cr concentration (X2), mg/L | 10 | 15 | 20 | 25 | 30 |
Biosorbent dosage (X3), g/L | 10 | 15 | 20 | 25 | 30 |
Temperature (X4), K | 283 | 293 | 303 | 313 | 323 |