Optimization of Aqueous Two-Phase Systems for the Recovery of Soluble Proteins from Tannery Wastewater Using Response Surface Methodology

Table 6

Estimated regression coefficients for recovery (%) without outlier.

Term	Coefficient	Standard Error of coefficient	𝑇	𝑃
Constant	89.8078	0.5011	179.231	0.000*
pH	1.9683	0.3324	5.922	0.000*
NaCl	−3.0216	0.3324	−9.091	0.000*
Temperature	0.7622	0.4108	1.855	0.097
pH∗pH	−1.4647	0.3317	−4.416	0.002*
NaCl∗NaCl	−1.0051	0.3317	−3.030	0.014*
Temperature∗Temperature	−4.4476	0.4236	−10.500	0.000*
pH∗NaCl	−0.5688	0.4343	−1.310	0.223
pH∗Temperature	−1.5687	0.4343	−3.612	0.006*
NaCl∗Temperature	−2.7438	0.4343	−6.318	0.000*

𝑅² = 97.27%; 𝑅² (adj) = 94.54%.
*Significant at 95% confidence level.