Imidazolium ionic liquids-based salting-out extraction of 2,3-butanediol from fermentation broths

Salting-out extraction is an efficient technique for the separation of bio-based chemicals from fermentation broths. So far, salting-out extraction of 2,3-butanediol has mainly focused on systems composed of organic solvents and salts, while less attention has been given to the green solvent ― ionic liquids. In this research, imidazolium ionic liquids were used to examine the recovery of 2,3-butanediol from fermentation broths. The influences of the temperature and concentration of 2,3-butanediol on phase formation were determined using two systems of 1-butyl-3-methylimidazolium chloride ([C4mim][Cl])-K2HPO4 and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2mim][CF3SO3])-K2HPO4. The partition behaviors of 2,3-butandiol and ionic liquids, and the selectivity of 2,3-butanediol over glucose and organic acids were investigated and compared at different concentrations of ionic liquids and K2HPO4. Most of 2,3-butanediol and ionic liquids were distributed to the top phase, whereas different trends of partition coefficient variation were observed. Under the condition of 25% [C2mim][CF3SO3]-30% K2HPO4 (w/w), the recovery of 2,3-butanediol and [C2mim][CF3SO3] was 95.7% and 99.5%, respectively, and selectivity for glucose, succinic acid and lactic acid was 2.59, 115 and 20.8, respectively.