Equilibrium of liquid-liquid extraction of 2-phenylbutyric acid enantiomers: Experiment and model

The utilization of liquid–liquid extraction for the separation of 2-phenylbutyric acid (2-PBA) enantiomers was proposed. Factors affecting the extract process were investigated, including organic solvents, β-cyclodextrin derivatives, cyclodextrin concentration, pH and temperature. A model was proposed to describe the separation process based on the homogeneous phase reaction mechanism. Important parameters of this model were determined experimentally. The physical distribution coefficients for molecular and ionic 2-PBA were 0.129 and 7.455, respectively. The equilibrium constants of the complexation reactions were 89.36 and 36.78   L·mol −   1 for (+)− and (−)-2-PBA, respectively. The model was verified by experiments and proved to be an excellent means to optimize the separation system. Through modeling prediction and experiment, the best conditions ( e.g. , pH value of 3.00, extractant concentration of 0.1   mol·L −   1 , temperature of 5.0   °C) were acquired. Under this condition, the maximum enantioselectivity (2.096) was obtained.