Table 2 Experimental range and levels of input process variables assessed
Variables | Code | Levels | ||
|---|---|---|---|---|
 − 1 | 0 | 1 | ||
pH | A | 5 | 7 | 9 |
Dye concentration (mg/L) | B | 5 | 50 | 100 |
Temperature (°C) | C | 30 | 35 | 40 |
Dosage (g/L) | D | 2.0 | 4.0 | 6.0 |
Variables | Code | Levels | ||
|---|---|---|---|---|
 − 1 | 0 | 1 | ||
pH | A | 5 | 7 | 9 |
Dye concentration (mg/L) | B | 5 | 50 | 100 |
Temperature (°C) | C | 30 | 35 | 40 |
Dosage (g/L) | D | 2.0 | 4.0 | 6.0 |