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.