Measurement and Correlation of Liquid–Liquid Equilibrium Data for Ternary Systems Water + C1–C3 Alcohols + Diethyl Adipate at 298.15 K and Atmospheric Pressure

This paper investigates the feasibility of using diethyl adipate (DEA), a green organic solvent, as a separation agent for extracting various alcohols from aqueous solutions. In order to achieve this, liquid–liquid equilibria (LLE) experiments were carried out for four ternary systems: {water + methanol + DEA}, {water + ethanol + DEA}, {water + 1-propanol + DEA}, and {water + 2-propanol + DEA} at 298.15 K and atmospheric pressure. LLE experiments involve determination of certain thermodynamic data such as binodal curves and cloud-point data. Binodal curve data were determined by the cloud-point method using the titration technique, while the tie-line data were determined by optimizing the parameters based on the experimental measurements of the refractive index. Additionally, the distribution coefficients and the separation factors were calculated within the immiscibility region. Hand and Othmer–Tobias correlations were used to examine the reliability of the tie-line data. Also, the experimental ternary LLE data were correlated using the UNIversal QUAsiChemical (UNIQUAC) activity coefficient models. The results confirm that that DEA is a suitable choice for extracting methanol, ethanol, 1-propanol, and 2-propanol from water. The potential of DEA as a separation agent followed the sequence methanol < ethanol < 2-propanol < 1-propanol. UNIQUAC model proved to be effective in correlating the LLE data.