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Description of the experimental conditions according to the Box-Behnken design
| Experiment | pH | Dose of sorbent (mg/L) | Initial concentration of REEs (µmol/L) |
|---|---|---|---|
| 1 | 8 | 20 | 3 |
| 2 | 6 | 100 | 3 |
| 3 | 4 | 100 | 5 |
| 4 | 6 | 20 | 1 |
| 5 | 8 | 100 | 5 |
| 6 | 8 | 100 | 1 |
| 7 | 6 | 100 | 3 |
| 8 | 6 | 100 | 3 |
| 9 | 6 | 180 | 5 |
| 10 | 6 | 180 | 1 |
| 11 | 4 | 20 | 3 |
| 12 | 6 | 20 | 5 |
| 13 | 4 | 100 | 1 |
| 14 | 4 | 180 | 3 |
| 15 | 8 | 180 | 3 |
