Terpene-Derived Low-Viscosity Deep Eutectic Solvent for Energy-Efficient CO₂ Absorption

Deep eutectic solvent (DES) is considered an attractive solution for mass transfer operations due to its favorable vapor pressure and physicochemical properties. This study investigated the CO₂ absorption capacity of a type V hydrophobic natural DES (HNDES) having camphor (CAM) and menthol (MEN) as HBAs and HBDs, respectively. The HNDES was prepared at a 4:7 molar ratio and obtained from the Conductor-like Screening Model for Real Solvents. The properties, namely, viscosity, vapor pressure, boiling point, and flash point, were measured. The solvent's viscosity was found to be 23 mPa.s at 298.15 K. The CO₂ solubility was investigated at a temperature range of 298.15-323.15 K. The operating pressure was varied from 0.2 to 0.6 MPa. The highest mole fraction of CO₂ in the solvent was observed to be 0.044 at 303.15 K and 0.6 MPa. The enthalpy of absorption (-14.7 kJ.mol^-1) indicates a decrease in solubility at elevated temperature. Moreover, the CO₂ physisorption was also validated by FTIR, Raman, and NMR analysis.