Liquid–liquid equilibrium of the CuSO4 + PEG 4000 + H2O system at different temperatures

• LLE of the CuSO4 + PEG 4000 + H2O system at T = 288.15, 298.15 and 308.15 K was measured.
• Density, refractive index and viscosity of the bottom and top phases were measured.
• The Chen-NRTL and modified Wilson models were used to correlate the experimental tie-line data.
• The quality of fitting is better with the modified Wilson model.
• The thermodynamic properties calculated show that the entropy increase is the driving force for biphasic formation.

Phase diagram and liquid–liquid equilibrium (LLE) data for the CuSO4 + polyethylene glycol 4000 (PEG 4000) + H2O system were determined experimentally at T = 288.15, 298.15 and 308.15 K. The effect of temperature on the binodal curves and tie-lines was studied and it was found that an increasing in temperature caused the expansion of two-phase region. The Chen-NRTL and modified Wilson models were used to correlate the experimental tie-line data. The results show that the quality of fitting is better with the modified Wilson model.