Aqueous two-phase system of poly(ethylene glycol) 4000 and sodium molybdate at different temperatures

•The ATPS Na2MoO4 + polyethylene glycol 4000 (PEG 4000) + H2O was studied at T = (288.15, 298.15 and 308.15) K.•Density, sound velocity, refractive index and viscosity of the top and bottom phases were measured.•The extended UNIQUAC model was used to correlate the experimental tie-line data.•A good agreement between experimental and correlated data was obtained.•An increase of the entropy is the driving force for biphasic formation.

Liquid–liquid equilibrium (LLE) data for the Na2MoO4 + polyethylene glycol 4000 (PEG 4000) + H2O system were determined experimentally at T = (288.15, 298.15 and 308.15) K. Additionally, experimental data of density, sound velocity, refractive index and viscosity are also reported 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 extended UNIQUAC model and the Othmer–Tobias and Bancroft equations were used to correlate the experimental tie-line data obtaining a good representation of the equilibrium. Moreover, the Merchuk equation was used to correlate the binodal curves. A good agreement between experimental and correlated values of the tie-lines was obtained.