Table 1 Empirical range and levels of independent parameters.
From: Separation of copper ions by nanocomposites using adsorption process
Independent versus code | Range and level | |||||
|---|---|---|---|---|---|---|
− 2 | − 1 | 0 | + 1 | + 2 | ||
pH | X1 | 1 | 2 | 3 | 4 | 5 |
The initial concentration of copper (mg L−1) | X2 | 60 | 170 | 280 | 390 | 500 |
Time (min) | X3 | 30 | 67.50 | 105 | 142.50 | 180 |
Temperature (°C) | X4 | 20 | 30 | 40 | 50 | 60 |
