Table 3 Four-factor five-level central composite design for RSM
Run Experimental conditions TC degradation rate (%)
pH (A) Tetracycline (mg/L) (B) Persulfate (mM) (C) Time (min) (D) Observed (%) Predicted (%)
1 7.5 (0) 50 (0) 3 (0) 90 (0) 51.06 49.82
2 2.5 (−2) 50 (0) 3 (0) 90 (0) 55.64 55.74
3 7.5 (0) 50 (0) 3 (0) 90 (0) 48.45 49.82
4 5 (−1) 70 (+1) 4 (+1) 60 (−1) 45.16 44.64
5 5 (−1) 30 (−1) 4 (+1) 120 (+1) 86.62 86.33
6 10 (+1) 70 (+1) 2 (−1) 120 (+1) 61.02 61.32
7 7.5 (0) 50 (0) 3 (0) 150 (+2) 81.85 81.17
8 5 (−1) 30 (−1) 2 (−1) 60 (−1) 34.55 35.25
9 10 (+1) 30 (−1) 2 (−1) 60 (−1) 47.25 46.91
10 10 (+1) 30 (−1) 4 (+1) 60 (−1) 70.44 69.95
11 5 (−1) 30 (−1) 2 (−1) 120 (+1) 61.85 61.79
12 7.5 (0) 50 (0) 1 (−2) 90 (0) 28.72 28.18
13 10 (+1) 70 (+1) 4 (+1) 120 (+1) 85.05 84.34
14 7.5 (0) 50 (0) 3 (0) 90 (0) 49.75 49.82
15 10 (+1) 30 (−1) 2 (−1) 120 (+1) 75.56 76.07
16 10 (+1) 30 (−1) 4 (+1) 120 (+1) 94.25 95.04
17 5 (−1) 70 (+1) 2 (−1) 60 (−1) 12.65 11.98
18 5 (−1) 30 (−1) 4 (+1) 60 (−1) 64.04 63.86
19 7.5 (0) 90 (+2) 3 (0) 90 (0) 41.15 41.31
20 10 (+1) 70 (+1) 4 (+1) 60 (−1) 54.88 55.05
21 7.5 (0) 50 (0) 3 (0) 90 (0) 50.55 49.82
22 7.5 (0) 50 (0) 3 (0) 90 (0) 49.75 49.82
23 7.5 (0) 50 (0) 5 (+2) 90 (0) 79.38 79.82
24 12.5 (+2) 50 (0) 3 (0) 90 (0) 80.62 80.42
25 7.5 (0) 10 (−2) 3 (0) 90 (0) 75.55 75.28
26 7.5 (0) 50 (0) 3 (0) 90 (0) 49.35 49.82
27 7.5 (0) 50 (0) 3 (0) 30 (−2) 24.75 25.33
28 5 (−1) 70 (+1) 2 (−1) 120 (+1) 42.25 42.72
29 10 (+1) 70 (+1) 2 (−1) 60 (−1) 27.68 27.96
30 5 (−1) 70 (+1) 4 (+1) 120 (+1) 70.85 71.31