Table 1.
Box–Behnken design factors with coded and un-coded factors and data of the experimental response.
| Run | Factor 1 A: biosorbent dose (g/L) | Factor 2 B: pH | Factor 3 C: initial Cu2+ conc. (mg/L) | Response: Cu2+ removal (%) | Predicted values |
|---|---|---|---|---|---|
| 1 | 1 (− 1) | 2 (− 1) | 60 (0) | 44.25 | 47.28 |
| 2 | 5 (+ 1) | 2 (− 1) | 60 (0) | 64.03 | 68.36 |
| 3 | 1 (− 1) | 6 (+ 1) | 60 (0) | 51.67 | 57.53 |
| 4 | 5 (+ 1) | 6 (+ 1) | 60 (0) | 87.68 | 78.62 |
| 5 | 1 (− 1) | 4 (0) | 30 (− 1) | 56.80 | 57.22 |
| 6 | 5 (+ 1) | 4 (0) | 30 (− 1) | 77.90 | 78.31 |
| 7 | 1 (− 1) | 4 (0) | 90 (+ 1) | 56.90 | 47.58 |
| 8 | 5 (+ 1) | 4 (0) | 90 (+ 1) | 64.34 | 68.67 |
| 9 | 3 (0) | 2 (− 1) | 30 (− 1) | 62.97 | 56.93 |
| 10 | 3 (0) | 6 (+ 1) | 30 (− 1) | 68.43 | 67.18 |
| 11 | 3 (0) | 2 (− 1) | 90 (+ 1) | 50.91 | 47.29 |
| 12 | 3 (0) | 6 (+ 1) | 90 (+ 1) | 55.39 | 57.54 |
| 13–17* | 3 (0) | 4 (0) | 60 (0) | 60.20 | 57.24 |
*Mean value of five center point assays.