Optimization study on continuous separation of equol enantiomers using enantioselective liquid–liquid extraction in centrifugal contactor separators

Abstract

Multistage enantioselective liquid–liquid extraction (MELLE) of equol (EQU) enantiomers using hydroxypropyl-β-cyclodextrin (HP-β-CD) as extractant was studied experimentally in a countercurrent cascade of centrifugal contactor separators (CCSs). A model was built on the base of single-stage model for chiral extraction of EQU enantiomers and the law of mass conservation. A series of experiments on the extract phase/washing phase ratio (W/O), extract phase/feed phase ratio (W/F), extractant concentration, pH value and temperature have been conducted to verify the multistage equilibrium model. It is found that the model predictions are in good agreement with the experimental results. High purity and yield of enantiomer can be obtained by changing W/O or extractant concentration, pH value or increasing number of stages. The model was further applied to predict the symmetrical separation of EQU enantiomers. By simulation, optimal process parameters for the symmetrical separation of EQU enantiomers can be obtained. Higher eeeq (equal enantiomeric excess) can be obtained at a higher W/F or a smaller W/O, and more stages.