Table 1 Box-Behnken experimental design with coded and un-coded operational variables and the obtained results for the removal of Fe(II) and Fe(III) from aqueous solutions.
Std. order | pH | Iron concentration | Adsorbent concentration | Responses (% removal) | |
|---|---|---|---|---|---|
Fe(II) | Fe(III) | ||||
1 | 3 (− 1) | 5 (− 1) | 5 (0) | 15.87 | 30.56 |
2 | 7 (1) | 5 (− 1) | 5 (0) | 55 | 65.85 |
3 | 3 (− 1) | 15 (1) | 5 (0) | 2.5 | 10.67 |
4 | 7 (1) | 15 (1) | 3 (0) | 39.36 | 9.32 |
5 | 3 (− 1) | 10 (0) | 5 (− 1) | 10.05 | 13.60 |
6 | 7 (1) | 10 (0) | 2 (− 1) | 49.32 | 29.95 |
7 | 3 (− 1) | 10 (0) | 2 (1) | 11.54 | 7.73 |
8 | 7 (1) | 10 (0) | 8(1) | 62.49 | 37.37 |
9 | 5 (0) | 5 (− 1) | 8 (− 1) | 48.19 | 69.06 |
10 | 5 (0) | 15 (1) | 2 (− 1) | 47.03 | 26.01 |
11 | 5 (0) | 10 (− 1) | 8 (1) | 64.82 | 65.66 |
12 | 5 (0) | 10 (1) | 8 (1) | 25.95 | 35.05 |
13a | 5 (0) | 10 (0) | 5 (0) | 20.39 | 27.25 |
