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

Table 4

Estimated regression coefficients for percentage recovery.

Term	Coefficient	Standard error of coefficient	𝑇	𝑃
Constant	89.8802	1.1292	79.597	0.000
pH	1.9683	0.7492	2.627	0.025*
NaCl	−3.0216	0.7492	−4.033	0.002*
Temperature	−0.7985	0.7492	−1.066	0.312
pH∗pH	−1.9375	0.7492	−2.657	0.024*
NaCl∗NaCl	−1.4779	0.7492	−2.026	0.070
Temperature∗Temperature	−2.6800	0.7492	−3.675	0.004*
pH∗NaCl	−0.5688	0.7492	−0.581	0.574
pH∗Temperature	−1.5687	0.7492	−1.603	0.140
NaCl∗Temperature	−2.7438	0.7492	−2.803	0.019*

𝑅² = 84.86%; 𝑅² (adj) = 71.22%.
*Significant at 95% confidence level.