Study of phase equilibria of aqueous two phase system containing poly ethylene glycol di-methyl ether 2000 and sodium nitrate at different temperatures and application of this system in separation of iodine

In this work, the liquid-liquid equilibrium of {polyethylene glycol di-methyl ether 2000 (PEGDME2000) + NaNO3 + H2O} system has been determined experimentally at T = (298.15, 308.15 and 318.15) K and atmospheric pressure (≈ 85 kPa). The Merchuk equation and an empirical equation were used for reproducing the experimental binodal results, and their fitting parameters were obtained with the temperature dependence expressed in the linear form with (1/(T − T0)) K as a variable. The tie-line data were correlated by using Othmer-Tobias and Bancroft equations, Setschenow type equation, and osmotic virial model. Moreover, the effect of temperature on the binodal curves and the tie-lines for the investigated aqueous two-phase system have been studied. Also, the free energies, enthalpies and entropies of cloud points for this system was calculated from which it was concluded that the increase of the entropy is the driving force for formation of this aqueous two-phase system. In addition the partitioning behaviour of the iodine molecule on the investigated aqueous two-phase system was studied.