Table 1 Twelve-trials Plackett–Burman experimental design for evaluation of independent variables with coded and actual levels along with the observed and predicted values of lead (Pb2+) removal by Gelidium amansii biomass.
Run no. | Coded and actual levels of independent variables | Pb2+ removal (%) | Residuals | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Contact time (minutes) | Pb2+ concentration (mg/L) | pH | Temperature (°C) | Biomass (g/L) | Agitation -Static | Actual value | Predicted value | ||||||||
1 | −1 | 60 | −1 | 25 | −1 | 4 | 1 | 50 | 1 | 4 | 1 | Agitation | 97.34 | 97.14 | 0.20 |
2 | −1 | 60 | −1 | 25 | 1 | 7 | 1 | 50 | 1 | 4 | −1 | Static | 93.98 | 93.62 | 0.36 |
3 | −1 | 60 | 1 | 200 | 1 | 7 | 1 | 50 | −1 | 1 | 1 | Agitation | 94.32 | 94.90 | −0.58 |
4 | 1 | 180 | −1 | 25 | 1 | 7 | 1 | 50 | −1 | 1 | 1 | Agitation | 93.45 | 93.43 | 0.02 |
5 | 1 | 180 | −1 | 25 | −1 | 4 | −1 | 25 | 1 | 4 | 1 | Agitation | 94.95 | 95.27 | −0.32 |
6 | −1 | 60 | 1 | 200 | −1 | 4 | −1 | 25 | −1 | 1 | 1 | Agitation | 97.93 | 97.30 | 0.63 |
7 | 1 | 180 | 1 | 200 | −1 | 4 | 1 | 50 | −1 | 1 | −1 | Static | 99.69 | 99.49 | 0.20 |
8 | 1 | 180 | 1 | 200 | 1 | 7 | −1 | 25 | 1 | 4 | 1 | Agitation | 92.52 | 92.47 | 0.05 |
9 | −1 | 60 | −1 | 25 | −1 | 4 | −1 | 25 | −1 | 1 | −1 | Static | 96.06 | 96.57 | −0.51 |
10 | 1 | 180 | −1 | 25 | 1 | 7 | −1 | 25 | −1 | 1 | −1 | Static | 92.55 | 92.30 | 0.25 |
11 | 1 | 180 | 1 | 200 | −1 | 4 | 1 | 50 | 1 | 4 | −1 | Static | 98.73 | 98.93 | −0.20 |
12 | −1 | 60 | 1 | 200 | 1 | 7 | −1 | 25 | 1 | 4 | −1 | Static | 93.13 | 93.22 | −0.09 |
