Thermodynamic Studies of the Aqueous Two-Phase System Containing Polyethylene Glycol Dimethyl Ether 2000 and Sodium Nitrite at (298.15, 308.15, and 318.15) K

Liquid–liquid equilibrium data including binodals and tie-line compositions have been measured for aqueous ternary biphasic system containing polyethylene glycol dimethyl ether 2000 (PEGDME2000) and sodium nitrite at three temperatures (298.15–318.15) K and atmospheric pressure (≈ 85 kPa). The salting-out of the polymer by the salt was studied at different temperatures. Furthermore, the ΔG c, ΔH c, and ΔS c of the cloud points were computed at working temperatures from which it was found that the entropy is the driving force for phase separation. For representing the experimental binodal data two empirical equations with the temperature dependency were used. The Setschenow equation was utilized for correlating the measured tie-lines. Different versions of nonrandom two-liquid models were also selected in generating the obtained tie-lines. The plait point, and the characteristics of tie-lines (slope and the length) have been determined at working temperatures. The partitioning behavior of the iodine molecule in the above system was also studied.