Liquid-liquid extraction of n-butanol and n-butyl acetate with ionic liquid and thermodynamic modeling with COSMO-RS and NRTL

Ionic liquids (ILs) have attracted interest in liquid-liquid extraction due to their high polarity, offering a sustainable and safer alternative to traditional organic solvents in separation processes. Imidazolium-based ILs are notable for their high thermal stability, low volatility, and broad solubility, which enable effective separations under various conditions. Their ability to form biphasic systems, thanks to their affinity for both organic and inorganic substances, makes them especially suitable for industrial applications. This study focused on examining the liquid-liquid equilibrium of ternary mixtures made up of n-butyl acetate, n-butanol, and synthesized 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). After synthesizing and characterizing the [BMIM][Cl] using magnetic resonance and infrared methods, the compound’s molecular structure and functional groups were determined. Its physicochemical properties were examined. Liquid-liquid equilibrium (LLE) experiments were carried out to determine the best conditions for [BMIM][Cl] to act as an extracting agent, with butanol as the solute and butyl acetate as the diluent, at 298.15 and 308.15 K, and 101.3 kPa. The sigma profile and sigma potential were obtained using the COSMO-RS model, and the tangency of the tie-lines with the Gibbs energy surface was evaluated. The present research contributed to the application of green solvents in liquid-liquid extraction through azeotropic separation.