Table 4.
Statistical parameters of the experiments using CCD/RSM—evaluation of the effects.
| Parameter | Evaluation of the Effects, ∑Cu,Cd,Zn, mg/L, R2 = 0.9119, R2adj = 0.8532, 3 Parameters, 1 Block, 16 Experiments, MS = 0.1219 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Effect | Standard Error | p-Value * | −95% Confidence Interval | +95% Confidence Interval | Factor | Standard Error of Factor | Lower Confidence Interval | Upper Confidence Interval | |
| Constant Value | 0.7197 | 0.2461 | 0.01693 | 0.1628 | 1.2765 | 0.7197 | 0.2461 | 0.1628 | 1.2765 |
| pH (L) | −1.5049 | 0.1889 | 0.00002 | −1.9324 | −1.0775 | −0.7525 | 0.0945 | −0.9662 | −0.5388 |
| pH (Q) | 1.0509 | 0.2294 | 0.00133 | 0.5320 | 1.5699 | 0.5255 | 0.1147 | 0.2660 | 0.7850 |
| Na2CS3 (L) | −0.4548 | 0.1889 | 0.03942 | −0.8823 | −0.0274 | −0.2274 | 0.0945 | −0.4411 | −0.0137 |
| Na2CS3 (Q) | 0.1706 | 0.2294 | 0.47608 | −0.3484 | 0.6896 | 0.0853 | 0.1147 | −0.1742 | 0.3448 |
| Time (L) | −0.0781 | 0.1889 | 0.68885 | −0.5056 | 0.3493 | −0.0391 | 0.0945 | −0.2528 | 0.1746 |
| Time (Q) | 0.1529 | 0.2294 | 0.52178 | −0.3660 | 0.6719 | 0.0765 | 0.1147 | −0.1830 | 0.3359 |
L—linear effect; Q—quadratic effect; * statistically significant if p < 0.05. The analysis showed a significant (p < 0.05) influence of pH (L), pH (Q) and Na2CS2 (L) on the value of ∑Cu,Cd,Zn. Other parameters turned out to be statistically insignificant (p > 0.05), including Time (L) and Time (Q). The calculated values of R2 = 0.9119 and R2adj = 0.8532 (91.19% and 85.32%, respectively) indicated that 91.19% of the variability of the dependent variable was explained by the model.