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Liquid−liquid equilibria of water + formic acid + dimethyl carbonate have experimentally been specified at (298.2, 308.2, and 318.2) K. Each phase diagram was obtained by specifying binodal curves and tie-lines. The reliability of the experimental tie-lines was verified via the Othmer−Tobias correlation. The experimental tie-line data were correlated using the nonrandom two liquid and the universal quasichemical (UNIQUAC) models in order to obtain the binary interaction parameters. However, UNIQUAC functional-group activity coefficients (UNIFAC) and modified-UNIFAC methods were also used to predict the phase equilibrium in the system determined from experimental data using the interaction parameters between CH 3 , OCOO, HCOOH, and H 2 O functional groups. Distribution coefficients and separation factors were evaluated for the immiscibility region.

The layered double hydroxide (LDH) with high crystallinity was prepared via the coprecipitation method for studying the separation equilibria of lactic acid. It was characterized by FTIR, XRD, and molecular size analyses. The effects of the amount of LDH, temperature, and initial lactic acid concentration on the separation process have been investigated. Results show that the maximum removal of lactic acid was obtained as 66.49% in the case of 1 g of LDH at 298 K. The isothermal data were fitted to Langmuir, Freundlich, and Temkin adsorption isotherms. Elovich, Lagergren, and pseudo-second-order kinetic model equations were applied. The experimental data were fitted with the Langmuir isotherm according to R 2, which is 0.9894 at 298 K, 0.9972 at 308 K, and 0.9998 at 318 K respectively. Separation depended on initial lactic acid concentration at investigated different temperatures (298 K, 308 K, 318 K) significantly. Standard free energy (ΔG o), enthalpy (ΔH o), and entropy (ΔS o) are calculated. The variation of several thermodynamic parameters was calculated according to thermodynamic analysis.

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