Repulsive effect of salt on solvent extraction of 2,3-butanediol from aqueous fermentation solution.

BACKGROUND Solvent extraction of 2,3-butanediol from dilute fermented systems is a challenging downstream unit operation. Addition of certain kosmotropic salts to the aqueous fermentation broth during the solvent extraction process can have considerable influence on the distribution of 2,3-butanediol. This work evaluates the usefulness of solvent extraction and the salting-out effect on the extraction characteristic of 2,3-butanediol in aqueous synthetic and fermented solutions. RESULTS Addition of 10 wt% dipotassium phosphate (K₂HPO₄) to the fermented 2,3-butanediol broth during solvent extraction results in 1.5-3-fold increase in distribution coefficient (K_d) and 7-14-fold increase in separation factor (α) for 2,3-butanediol using 2-sec butyl phenol and 1-butanol as extractants. Of various solvent-salt combinations studied; 2-sec butyl phenol + 10 wt% K₂HPO₄ provided K_d and α of 3.04 and 59.17 whereas 1-butanol + 10 wt% K₂HPO₄ provided K_d and α of 2.41 and 15.68, respectively, in fermented 2,3-butanediol broth solution. CONCLUSION This study demonstrated the prospects of repulsive salts addition to the fermented broth during the solvent extraction process. The results showed that this study may be used as a model to choose an appropriate combination of water-immiscible (hydrophobic) organic solvent and inorganic salt type and concentration for the economical recovery of 2,3-butanediol from fermentation broth. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]