Liquid-liquid equilibrium data of aqueous two-phase systems (ATPS) formed by mixture of aqueous solutions of triblock copolymer poly(ethylene oxide-b-propylene oxide-b-ethylene oxide), L64, and sulfate salts were obtained. L64 + lithium sulfate + water, L64 + magnesium sulfate + water, L64 + sodium sulfate + water, and L64 + zinc sulfate + water were formed at (278.15, 288.15, and 298.15) K. The influence of temperature in the binodal position was pronounced. The phase separation process was endothermic for the L64 + Li 2 SO 4 system and exothermic for the L64 + MgSO 4 , L64 + Na 2 SO 4 and L64 + ZnSO 4 systems. Also, the slope of the tie line tended to increase with an increase in temperature. Also, the capability of the salts to induce the formation of the biphasic system followed the order ZnSO 4 ) MgSO 4 > Na 2 SO 4 > Li 2 SO 4 .

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In extraction procedures, the more commonly used aqueous two-phase systems (ATPS) comprise mainly water, salt, and macromolecule, particularly the macromolecule poly­(ethylene oxide) (PEO). However, one limitation of such ATPS is their capacity to separate compounds that are more hydrophobic. One possible solution to overcome this restriction is the use of ATPS formed with triblock copolymers, which are more hydrophobic and therefore enable the extraction of hydrophobic solutes. In addition, the range of applications of ATPS formed with thiocyanate salts can be broader, mainly to extract metal ions. In view of this, equilibrium data were acquired in this work by constructing phase diagrams for ATPS comprising macromolecules [poly­(ethylene oxide), PEO, or (poly­(ethylene oxide))-(poly­(propylene oxide))-(poly­(ethylene oxide)) triblock copolymers, F68 or L64] + thiocyanate salts (ammonium, sodium, or potassium) + water at 25.0 °C. The influence of the nature of the cation on the formation of the ATPS was investigated and followed the order K+ > Na+ > NH4 +. The capacity of different macromolecules to enable ATPS formation was also examined and followed the order L64 > F68 > PEO1500. Phase inversion occurred with the (L64 or F68) + NH4SCN + water ATPS, in that the top phase is rich in salt and the bottom phase is rich in macromolecule. This aspect is different in most ATPS that are typically described in the literature.