Efficient SO2 capture at ultra-low concentration using a hybrid absorbent of deep eutectic solvent and ethylene glycol

Deep eutectic solvents (DESs) are considered as the highly effective absorbents for sulfur dioxide (SO 2 ) capture. However, the high viscosity of DESs and the resulting slow absorption rate as well as low absorption capacity at low SO 2 concentration seriously hinder their industrial application. In this study, DES of N-methyldiethanolamine (MDEA) and imidazole (Im) is simply blended with ethylene glycol (EG) forming a hybrid absorbent, namely MDEA/Im-EG, which exhibits extremely high SO 2 capture capacity at low concentration. In particular, SO 2 capture capacity in MDEA/Im-EG (molar ratio = 1:1) reaches 0.446 g SO 2 /g absorbent at 293.2 K with SO 2 concentration of 2000 ppm. Moreover, the corresponding desorption enthalpy is only −40.67 kJ/mol. To well understand the results, thermodynamic analysis of SO 2 capture is performed and the SO 2 capture mechanism is speculated by nuclear magnetic resonance and Fourier transform infrared spectroscopy.