Phase Diagrams of Aqueous Two-Phase Systems with Organic Salts and F68 Triblock Copolymer at Different Temperatures

Phase diagrams of aqueous two-phase systems (ATPS) composed of F68 triblock copolymer + salt + water were constructed at different temperatures. The ATPS composed of F68 + (NH4)3C6H5O7 + H2O was investigated at (278.15, 288.15, and 298.15) K, and the F68 + Na3C6H5O7 + H2O, F68 + Na2C4H4O6 + H2O, F68 + Na2CO3 + H2O, and F68 + Na2C4H4O4 + H2O systems were examined at (283.15, 298.15, and 313.15) K. For all ATPS, the position of the binodal curve was affected by temperature, evidence of the enthalpic contribution to the formation of the biphasic system. As temperature increased, both the extent of the two-phase region in the diagrams and the slope of the tie line increased. The salt Na3C6H5O7 was more effective in promoting phase separation than (NH4)3C6H5O7. The capacity of the different anions tested for inducing ATPS formation with F68 followed the order: CO3 2− > C6H5O7 3− > C4H4O6 2− > C4H4O4 2−. The consistencies of the tie-line experimental compositions were improved by applying the Othmer−Tobias correlation. The experimental equilibrium data of ternary systems were correlated to find new interaction energy parameters through the NRTL model for the activity coefficient. The results were considered excellent with global root-mean-square deviations as low as 0.93 %.