Liquid–Liquid Equilibrium of Dipotassium Hydrogen Phosphate/Sodium Dihydrogen Phosphate + Butane-1,4-diol + Water Systems: Experimental Measurement and Correlation

Abstract

The liquid−liquid equilibrium of the ternary systems dipotassium hydrogen phosphate (K 2 HPO 4 )/sodium dihydrogen phosphate (NaH 2 PO 4 ) + butane-1,4-diol (BDO) + water was determined at T = (298.15, 308.15, and 318.15) K. The salting-out effect of the tie lines of the aqueous two-phase systems (ATPS) was evaluated, and it was found that K 2 HPO 4 had a larger salting-out coefficient, indicating that it has greater ability in phase separation because it presented a larger biphasic area in the ternary diagram. The electrolyte nonrandom two-liquid thermodynamic model was used to correlate the experimental data of both systems at different temperatures. It was found that the partition coefficients and BDO recovery are favored for both systems when the molality of the salts in the initial ATPS mixture increases. K 2 HPO 4 presented the highest values of the ATPS, a partition coefficient of 1219.83, a recovery of 95.78%, and a purity of 87.60% mass, under conditions close to salt saturation; therefore, a process can be designed to recover BDO that is produced by the biotechnological route because BDO can be concentrated from dilute aqueous solutions.