Study of phase equilibrium butyric acid in aqueous solution using organic solvents (methyl ethyl ketone and diethyl ether)

In this study, the solubility results and tie-lines in ternary systems (water + butyric acid + organic solvent) were obtained at 298.2 K and 101.3 kPa. Methyl ethyl ketone and diethyl ether were selected as organic solvents. The binodal curves were determined experimentally using the cloud point method. The tie-line results were obtained using acid-base titration, Karl-Fisher method, and refractive index measurement. Both ternary systems show type one of liquid-liquid equilibrium. For investigation of the quality of both ternary systems, Othmer-Tobias and Hand equations were correlated with the empirical results. The distribution coefficients and selectivity factors were calculated in both ternary systems to evaluate the solvent's ability in extracting butyric acid from an aqueous solution. The average separation factor was calculated at 41.12 for methyl ethyl ketone and 296.71 for diethyl ether, respectively. Finally, for each system, the experimental tie-lines were correlated by a thermodynamic model including NRTL and UNIQUAC; also, the binary interaction parameters were estimated.