Liquid–liquid equilibrium of potassium/sodium carbonate + 2-propanol/ethanol + water aqueous two-phase systems and correlation at 298.15 K

Abstract

Binodal data for 2-propanol + potassium/sodium carbonate + water systems and ethanol + sodium carbonate + water system were experimentally determined at 298.15 K, and the phase diagram was plotted. Three empirical equations were used to correlate binodal data. Base on the proposed equation with highest accuracy and lever rule, the phase equilibrium compositions for 2-propanol + potassium/sodium carbonate + water system were directly calculated by MATLAB. The Othmer–Tobias equation and the Bancroft equation were used to correlate tie-line data. The results indicate that the calculation method and corresponding tie-line data are reliable. The effect of salts on phase-separation was discussed. Salting-out coefficient and effective excluded volume of potassium carbonate and sodium carbonate in 2-propanol–water component solvent were calculated to evaluate the salting-out ability of salts. An effective excluded volume of sodium carbonate in ethanol/2-propanol–water component solvents was used to evaluate the phase-separation ability of investigated alcohols. Based on the experimental and calculated results, it can be concluded that sodium carbonate shows a higher salting-out ability than potassium carbonate and 2-propanol is easier to be excluded to the alcohol-rich phase than ethanol.