Salt effect on liquid–liquid equilibria of tetrahydrofuran/water/5-hydroxymethylfurfural systems

Salts strongly affect the phase equilibria of aqueous systems in biotechnological processes. In this work, the influence of salt on the performance of extracting 5-hydroxymethylfurfural (HMF) from aqueous media using tetrahydrofuran (THF) was investigated. The liquid–liquid equilibria (LLE) of ternary (THF/water/MCl, M = Li, Na or K) and quaternary (THF/water/HMF/MCl) systems were determined at 303.15 K and atmospheric pressure. The salting-out effects of LiCl, NaCl , and KCl were studied at different concentrations within their solubility limits. From the experimental LLE of the THF/water/MCl, it was found that THF was salted out from the aqueous phase upon addition of salt. Based on the LLE of THF/water/HMF/MCl, the partition coefficient of HMF and selectivity were determined. Finally, the experimental equilibrium data of the quaternary systems were correlated via the nonrandom two-liquid (NRTL) model, and the calculation results showed good agreement with the experimental data.