Recovery of Propane-1,3-Diol from Aqueous Solutions Using Aqueous Two-Phase Systems with Inorganic Salts

The liquid–liquid equilibrium of potassium hydrogen phosphate (K2HPO4)/potassium carbonate (K2CO3)/sodium dihydrogen phosphate (NaH2PO4) + propane-1,3-diol (PDO) + water at 298.15 K was determined. Additionally, the temperature effect of systems containing K2HPO4 and K2CO3 at 308.15 and 318.15 K was evaluated. These ternary systems formed aqueous two-phase systems (ATPS). The electrolyte nonrandom two-liquid (ENRTL) thermodynamic model was used to correlate the experimental data of the ternary systems. The separation of PDO from aqueous solutions using the inorganic salts was evaluated, and it was found that the partition coefficient (Kp) and recovery yield (Y) are favored when the molality of the salts is close to saturation in the initial ATPS mixtures. The salts showed the following order according to PDO recovery from aqueous solutions: K2HPO4 > K2CO3. K2HPO4 presented the highest values of the ATPS parameters, achieving to concentrate a PDO aqueous solution from 13.5% mass to 83.07% mass with a Kp of 266.49 ± 0.05 and a Y of 93.86 ± 0.04%. Therefore, the aqueous two-phase system K2HPO4 + PDO + H2O is a promising technique for the recovery of PDO from aqueous solutions.