Abstract
This research investigates the use of Choline Chloride and Lactic Acid-based (ChCl:LA) Deep Eutectic Solvents (DES) to overcome thermodynamic limitations in water-ethanol mixtures separation using a rotary evaporator under reduced pressure. It addresses batch single-stage extractive distillation on a laboratory scale and explores operational parameters, including molar ratio (1:2, 1:1.5), bath temperature (60-65 °C), vacuum pressure (100-150 mbar), and chiller temperature (15-20 °C). Separation efficiency was quantified by Karl Fischer titration, density, pH, and Ford Cup viscosity measurements. The DES ChCl:LA(1:1.5) showed improved performance, reducing distillate water content from 66 % (feed) to 26.33 % at 60 °C and 150 mbar, in a single stage, representing an ethanol enrichment of ~115 %. Lowering the bath temperature was associated with higher ethanol purity by maximizing the vapor pressure difference between ethanol and the DES-water complex. Conversely, excessive vacuum (100 mbar) or higher chiller temperatures (20 °C) negatively impacted efficiency due to water carryover or incomplete condensation. The residue high density (> 1.07 g/cm³), increased viscosity, greenish coloration, and low pH (0.5-1.5) suggested partial water sequestration by DES. Meanwhile, the distillate appeared colorless, with lower viscosity and pH closer to that of pure ethanol. These results suggest that the DES ChCl:LA (1:1.5) may act as a non-volatile solvent for bioethanol purification after optimizing process parameters, providing a biodegradable and sustainable pathway for breaking the water-ethanol binary system.
