Abstract

The thermodynamic behavior of aqueous solutions containing the solutes ferric sulfate and poly( ethylene glycol) with an average molecular weight of 4000 (PEG 4000) was studied. These three compounds are vital components for forming the aqueous two-phase system. Consequently, the water activity of the ternary system at 303.15, 313.15, 323.15 and 333.15 K were determined, using vapor pressure osmometry. The concentration of PEG was fixed to 0.050, 0.100, 0.150 and 0.200 mass fraction whereas the salt concentration was fixed to 0.050, 0.075, 0.100, 0.125, 0.150, 0.175 and 0.200 mass fraction. Additionally, the water activities of the constituent binary system (Fe-2(SO4)(3) + H2O) were measured in the same temperature range for different salt concentrations. The results show that ferric sulfate has a significant effect on the water activity in the salt-PEG-water system. From these measurements, values of the vapor pressure of solutions were determined. Finally, the experimental data were correlated with the UNIQUAC model, obtaining a good agreement between experimental and correlated data. (C) 2019 Elsevier B.V. All rights reserved.