Liquid–liquid equilibrium of aqueous two-phase systems containing thermo-sensitive copolymer L31 and salts

Liquid–liquid equilibrium data of aqueous two-phase systems (ATPSs) composed of the thermo-sensitive copolymer L31 and (NH4)2SO4 at 288.15 K, L31 and (NH4)2SO4/Na2SO4/Li2SO4/Na2C4H4O6 at 293.15 K were determined, respectively. The Othmer–Tobias and Bancroft equations were successfully used to correlate the tie-line data of the investigated systems. In the L31–(NH4)2SO4 ATPS, it was found that the size of the two-phase region of phase diagrams increased with an increase in temperature. Meanwhile, the salting out ability of cations followed the order: Na+ > NH4+ > Li+, and the salting out ability of SO42− is stronger than C4H4O62−. It was found that evaluating the salting outing ability of ions by using the Gibbs energy of hydration or Hofmeister series is not available for all of ATPSs.