Liquid–liquid equilibrium (LLE) data were obtained for aqueous two-phase systems composed of polyethylene glycol (PEG) 400 g mol^–1 + organic salt (Na₂SO₄) + water at different temperatures (293.15, 298.15, 303.15 and 308.15)/K, and pH values of 3.0, 4.0, and 5.0. The effect of temperature and pH on the binodal curves were evaluated, and it was verified that the increase of the variables resulted in a larger biphasic region. The salting-out effect was studied using the values of parameters of the effective excluded volume (EEV) model. The experimental results of LLE have been correlated using the UNIFAC model. The root-mean-square deviations between the experimental and predicted LLE compositions for the PEG 400 + Na₂SO₄ systems were very low. The UNIFAC model was able to represent satisfactorily the aqueous two-phase systems studied.

中文翻译：

---

PEG 400，Na ₂ SO ₄和水在不同温度和pH值下组成的两相水体系的液-液相平衡：相关性和热力学模型

在不同温度（293.15、298.15、303.15和308.15 ）下，获得了由400 g mol ^–1的聚乙二醇（PEG）+有机盐（Na ₂ SO ₄）+水组成的水两相系统的液-液平衡（LLE）数据。）/ K，pH值分别为3.0、4.0和5.0。评估了温度和pH对双曲线曲线的影响，并证实了变量的增加导致更大的双相区域。使用有效排除体积（EEV）模型的参数值研究了盐析效果。使用UNIFAC模型将LLE的实验结果进行了关联。PEG 400 + Na ₂ SO ₄的实验和预测的LLE组成之间的均方根偏差系统非常低。UNIFAC模型能够令人满意地表示所研究的水相两相系统。