Study of liquid-liquid and liquid-solid equilibria of the ternary aqueous system containing poly ethylene glycol dimethyl ether 2000 and tri-potassium phosphate at different temperatures: Experiment and correlation

The liquid-liquid and liquid-solid equilibrium for the poly ethylene glycol di-methyl ether 2000 (PEGDME2000)+K3PO4+H2O system has been determined experimentally at T=(298.15,303.15,308.15 and 318.15)K. The effect of temperature on the binodal curves and tie-lines for the investigated Aqueous Two-Phase System (ATPS) have also been studied. The reliability of some frequently used equations for fitting of obtained binodal data and a new empirical equation for this purpose was proposed which has better performance than these equations. In this work, the three fitting parameters of the Merchuk equation and new empirical equation were obtained with the temperature dependence expressed in the linear form with (T−T0) K as a variable. Furthermore, the Othmer-Tobias and Bancroft, Setschenow-type and also osmotic virial equations were used for the correlation and prediction of the liquid-liquid phase behaviour of the studied system. Furthermore, the effect of the type of salt on LLE and the salting-out effect is discussed. The complete phase diagram for the investigated system has also been determined at T=(298.15,308.15and318.15)K.