Measurements and Modeling of Liquid-Liquid Equilibrium of Polyethylene Glycol 400, Sodium Phosphate, or Sodium Citrate Aqueous Two-Phase Systems at (298.2, 308.2, and 318.2) K

Experimental equilibrium data were obtained for aqueous,two-phase systems composed. of polyethylene glycol 400 g.mol(-1) + sodium phosphate, and polyethylene glycol 400 g.mol(-1) + sodium Citrate, at T = (298.2, 308.2, and 318.2) K. For the system formed by sodium phosphate, at the studied range, the temperature effect on the position of the binodal curves was not relevant. For the system composed of sodium citrate, the temperature increase caused an expansion of the biphasic region. The efficacy of the salts in inducing phase segregation follows the order sodium phosphate > sodium citrate at temperatures of (298.2 and 308.2) K. Energy interaction parameters for the NRTL and UNIQUAC models were estimated, and the mean deviations between experimental and calculated compositions were 0.46 %, and 0.32 %, respectively. These results show that both models, NRTL and UNIQUAC, are able to represent the phase behavior of polymer-salt aqueous two-phase systems evaluated.