Highly Efficient and Reversible Absorption of SO ₂ Using Deep Eutectic Solvents Consisting of Tetraethylammonium Chloride and Acetamide

Deep eutectic solvents (DESs) have emerged as promising green solvents for gas capture due to their low cost, tunable chemical structures, and environmental friendliness. This study focuses on designing and evaluating DESs based on tetraethylammonium chloride (TEAC) and acetamide (AA) for efficient and selective SO 2 absorption. In this experiment, DESs with different molar ratios were synthesized, and their physicochemical properties and SO 2 absorption performance under different conditions were systematically investigated. The TEAC-AA (1:2) DES exhibited the highest SO 2 absorption capacity of 1.07 g SO 2 /g DES at 20 °C, along with excellent regenerability (97% desorption efficiency after five consecutive absorption–desorption cycles) and remarkable selectivity (SO 2 /CO 2 selectivity = 40). Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance ( 1 H NMR) analyses indicated that SO 2 absorption by the DESs was a physical process. Quantum chemical calculations revealed that the Cl – anion in TEAC plays a dominant role in interacting with SO 2 . This work highlights the potential of the TEAC-AA DES as a sustainable and cost-effective absorbent for industrial flue gas desulfurization.