A novel isopropanol salt aqueous two-phase system and its applications for 2, 3-butanediol extraction

At present, the hydrophilic alcohol and inorganic salt combined with the two-phase system have been widely used in the extraction of biological fermentation products. However, the residual salt in the extraction solution of the existing system caused the loss of salt and increased the energy consumption of subsequent product separation. Therefore, how to achieve organic phase without salt, water phase without extractant is particularly important. This paper studies the ternary liquid-liquid equilibrium of four highly soluble inorganic salts (K4P2O7, K2HPO4, K3PO4, K2CO3) + isopropanol + water at 298.15 K and their applications. By comparison, the extraction system with no salt and low water content in the organic phase and no extractant in the aqueous-rich phase was selected, with the K4P2O7/isopropanol aqueous phase system being the best system. Moreover, the screened system avoided the overuse of extraction solvent. The results showed that the isopropanol content had little effect on the water content in the extract phase. The salting-out extraction recovery rate of 2,3-butanediol is 100%, and the concentration coefficient is 5.74, which is much larger than other systems. More importantly, no salt was in the extract phase and no isopropanol was in the water-rich phase. Biofuel recovery from fermentation broth by K4P2O7/isopropanol aqueous two-phase system has the advantages of high selectivity and can effectively reduce energy demand.