Liquid–liquid equilibrium of aqueous two-phase systems containing poly(ethylene glycol) of different molecular weights and several ammonium salts at 298.15 K

Liquid–liquid equilibrium data of aqueous two-phase systems (ATPSs) formed by poly(ethylene glycol) (PEG) of different molecular weights (1000, 2000, 6000) + ammonium carbonate ((NH4)2CO3), ammonium tartrate ((NH4)2C4H4O6), diammonium hydrogen phosphate ((NH4)2HPO4), ammonium sulfate ((NH4)2SO4) + water were determined at 298.15 K, respectively. The binodal data were correlated by using a four-parameter equation. The effect of PEG molecular weight on binodal curves was investigated, and it was found that the biphasic region expanded with an increase in PEG molecular weight. Meanwhile, it was also observed that the ability of the investigated salts for phase separation follows the order: (NH4)2HPO4 > (NH4)2SO4 > (NH4)2C4H4O6 > (NH4)2CO3. Furthermore, a relatively simply two parameter equation, Othmer–Tobias and Bancroft equations was successfully used to correlate the tie-line data.