RECOVERY OF GREEN TERPENE-BASED EUTECTIC SOLVENTS IN LIPID PROCESSING: PHASE EQUILIBRIUM AND THERMODYNAMIC INSIGHTS

Terpene-Based Eutectic Solvents (TES) are bio-based mixtures that exhibit significant melting point depression through intermolecular interactions, serving as sustainable alternatives to n-hexane in lipid recovery. Despite their potential, industrial implementation has been hindered by a lack of fundamental vapor-liquid equilibrium (VLE) data, which is essential for designing energy-efficient solvent regeneration units. This study addressed these gaps by evaluating the experimental boiling temperatures of TES composed of L-carvone or DL-menthol and acetic acid (1:1 molar ratio) under ambient and reduced pressures. The ebulliometric apparatus was validated using anhydrous ethanol, demonstrating high accuracy against literature values and ensuring methodological robustness. From the experimental data, the molar enthalpy of vaporization was determined via Clausius-Clapeyron linearization. Furthermore, the results were integrated with the UNIFAC group-contribution model to construct VLE diagrams, which provided the necessary parameters for optimized industrial separation. To ensure chemical stability post-recovery, the integrity of the hydrogen bond network was verified using Fourier-Transform Infrared Spectroscopy (FTIR). At ambient pressure, the boiling temperature of the eutectic mixture was found to be intermediate between those of the pure components: acetic acid (117.9 °C) and L-carvone (230.0 °C). This behavior aligned with literature reports, highlighting the complexity of thermophysical properties in eutectic solvents resulting from strong intermolecular interactions. By establishing precise boiling point curves as a function of pressure, this work facilitated the recovery of eutectic solvents within a circular economy framework, minimizing waste and enhancing the sustainability of industrial lipid processing.