Phenol-Based Ternary Deep Eutectic Solvents for Highly Efficient and Reversible Absorption of NH3

In this work, a class of deep eutectic solvents (DESs) formulated by choline chloride (ChCl), phenol (PhOH), and ethylene glycol (EG) were designed and synthesized for NH 3 capture. The effects of temperature, pressure, and DES composition on NH 3 capacities were investigated systematically. By utilizing the weak acidity of PhOH, highly efficient and reversible absorption of NH 3 was realized in PhOH-based ternary DESs. The absorption capacities of NH 3 in prepared DESs can reach as high as 9.619 mol/kg (0.162 g/g) at 298.2 K and 101.3 kPa, ranking one of the best reported to date. The captured NH 3 could be easily stripped out at elevated temperature and reduced pressure, with negligible loss in NH 3 capacities after 10 adsorption–desorption cycles. The thermodynamic properties of the NH 3 absorption process, such as reaction equilibrium constants, Henry’s constants, and absorption enthalpies, were also calculated with the assistance of thermodynamic modeling. It is found that the NH 3 absorption process exhibits a moderate enthalpy change of −36.91 kJ/mol, indicating the potentially energy-efficient feature of a subsequent desorption process. The results obtained herein suggest that PhOH-based ternary DESs are promising media for the capture of NH 3 from industrial gases.