Liquid−Liquid Equilibrium of Potassium Phosphate/Potassium Citrate/Sodium Citrate + Ethanol Aqueous Two-Phase Systems at (298.15 and 313.15) K and Correlation

Binodal data for the ethanol + K3PO4/K3C6H5O7/Na3C6H5O7 + water systems were experimentally determined at (298.15 and 313.13) K. On the basis of the binodal data fitting equation with the highest accuracy and the Lever rule, the liquid−liquid equilibrium data for the investigated systems at 298.15 K were directly calculated by MATLAB. The Othmer−Tobias equation and Bancroft equation were used to correlate tie-line data and evaluate the reliability of the calculation method and the corresponding tie-line data. The salting-out strength of salt ions was compared by the parameter of effective excluded volume and the binodal curves plotted in molality, while the salting-out strength of salts was compared by the parameter of salting-out coefficient and the binodal curves plotted in mass fraction. The salting-out strength of the investigated salts is in the order K3PO4 > Na3C6H5O7 > K3C6H5O7. As for salt ions, the salting-out strength of anions is in the order PO43− < C6H5O73−, while the salting-out strength of Na+ is similar to K+. The effects of salt, hydrophilic alcohol, and temperature on liquid−liquid equilibria were also discussed. The shapes and locations of binodal curves are not sensitive to the investigated temperature range. The additions of salt and ethanol both increase the tie-line length and the absolute value of the tie-line slope.