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Independent variables and the coded and actual values used for optimization.
| Independent Variable | Units | Symbol | Coded Levels | ||
|---|---|---|---|---|---|
| −1 | 0 | 1 | |||
| Sonication time | min | X1 | 20 | 30 | 40 |
| Liquid-solid ratio | mL/g | X2 | 16:1 | 20:1 | 24:1 |
| Ethanol concentration | % | X3 | 90 | 95 | 100 |
