Table 2: Central composite rotatable quadratic polynomial model, experimental data, and actual and predicted values for five-level four-factor response surface analysis.

Run
Actual
(% Removal)
Predicted
(% Removal)

1102.50.083099.1399.22
283.50.064097.15102.21
3123.50.12098.3895.77
4102.50.083099.2399.22
583.50.062099.05106.87
6121.50.12095.1491.06
7102.50.083099.2399.22
8102.50.043073.1556.46
9102.50.083099.2399.22
10100.50.08303.47.40
11102.50.085091.890.49
12102.50.083099.2499.22
1362.50.083097.4895.01
14123.50.064099.23105.57
15102.50.123098.85111.33
16121.50.062024.6430.28
17104.50.083098.7790.56
1881.50.12095.1492.03
19121.50.14096.7192.12
2081.50.062030.2530.70
21102.50.083099.2399.22
22142.50.083099.1497.40
23102.50.081096.9894.08
2483.50.14098.7296.31
2581.50.064017.9423.77
2683.50.12097.9798.19
2781.50.14092.5887.88
28121.50.064027.8128.58
29123.50.14098.5799.11
30123.50.062099.32105.01

: time (h); : pH; : dosage (mg); : concentration (mg/L).