Comparative study of liquid–liquid equilibria for aqueous mixtures of lactic acid with structurally similar cyclic and non-cyclic ketones

Abstract

Liquid-liquid equilibria (LLE) were studied and compared for the aqueous mixtures of lactic acid (L(+) enantiomer) with the two structurally similar α,β-unsaturated ketones (mesityl oxide or isophorone)} at 298.2, 308.2, and 318.2 K and 101.3 kPa. Due to the close structural similarity of the chosen solvents, an experimental and correlational study was systematically carried out on performance of mesityl oxide and isophorone to extract l-lactic acid from water. The ternary systems exhibit type-1 behavior of LLE. The thermodynamic models of NRTL and UNIQUAC were successfully applied to fit the experimental tie-lines and the model binary interaction parameters were determined. The consistency of the calculated NRTL parameters was validated and qualified through topological analysis connected to the Gibbs tangent principle and stability test. Evaluation of the capacity of each solvent was performed using the calculation of distribution coefficients and separation factors. The influence of extraction temperature and the chemical structure of the solvent on the immiscibility region were found to be small. As a result, the selectivities specify that both the cyclic and non-cyclic ketones were found to be promising extractants for the separation of lactic acid from its dilute aqueous solutions.