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 (K_p) 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 K_p 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.