Continuous countercurrent liquid–liquid extraction method for the separation of 2,3-butanediol from fermentation broth using n-butanol and phosphate salt

Abstract

In this study, we examined continuous countercurrent liquid–liquid extraction (CC-LLE) of 2,3-butanediol (BDO) from synthetic (BDO+water) and fermented broth solutions in a bubble column using n-butanol as an extractant solvent. To elucidate salting-out effect on the extraction feasibility of BDO, CC-LLE experiments were also conducted for synthetic and fermented BDO solutions by adding 10wt% K2HPO4 salt to the aqueous feed. Distribution coefficients, volumetric mass transfer coefficients, number of equilibrium stages, minimum solvent requirement, and extraction efficiencies were determined from the CC-LLE experiments for three different concentrations of BDO in feed. The results showed that addition of phosphate salt to the aqueous feed increased the BDO extraction efficiency by 81.8% for synthetic BDO solution and by 30% for fermented BDO solution at 2.5wt% BDO in feed. Furthermore, modeling of CC-LLE for synthetic BDO solution using a newly parameterized UNIFAC-LL (Universal Functional Group Activity Coefficient – Liquid–Liquid) method within the Aspen Plus simulation program predicted that 99% BDO extraction efficiency can be achieved with 6 theoretical equilibrium stages.