The removal of SO2 from flue gas for the improvement of atmospheric quality and human health has attracted sustainable attention. In this work, 1-ethyl-3-methylimidazolium chloride (EmimCl) was paired with N-formylmorpholine (NFM) to form deep eutectic solvents (DESs) as the media for SO2 absorption. The absorption performance of SO2 in EmimCl-NFM DESs with various molar ratios was experimentally measured. Results showed that all the DESs exhibited efficient and reversible absorption behavior for low concentration SO2, with SO2 absorption capacity as high as 0.220 g SO2/g of DES of EmimCl-NFM (1:1) at 293.15 K and SO2 partial pressure of 1.0 kPa, surpassing that of most absorbents/adsorbents previously reported. The DES could retain satisfactory absorption performance and thermal stability after five consecutive cycles. The viscosity, density, thermogravimetric analysis, Fourier transform infrared spectroscopy, and NMR spectroscopy were utilized to characterize systematically the changes between fresh and SO2-loaded DESs. The present DESs showed potential application in the purification of gas containing SO2 due to their easy preparation, high absorption capacity, and good reversibility.

The hydrogen bond donor (HBD) of glycerol and hydrogen bond acceptor (HBA) selected from azole compounds were paired to construct functional deep eutectic solvents (DESs) as NH3 absorbents.

In the present work, dihydric alcohols (including 1,4-butanediol, 2,3-butanediol, and 1,3-propanediol) were paired with choline chloride (ChCl) to form deep eutectic solvents (DESs) with the molar ratio of ChCl to dihydric alcohol fixed at 1:3 and 1:4. The solubility of NH3 in these DESs was systematically determined at 303.15, 313.15, 323.15, and 333.15 K under pressures up to 420.0 kPa using the isochoric saturation method and was correlated using the Krichevsky–Kasarnovsky (K–K) equation. The dissolution Gibbs free energy, enthalpy, and entropy changes of NH3 solvation were further calculated according to the temperature dependence of Henry’s constants. Based on the reported CO2 solubility data, the selectivities of NH3/CO2 in DESs used herein were calculated. The density and viscosity data of the DESs were also measured and fitted at a temperature range of 303.15–343.15 K. Overall, the dihydric alcohol-based DESs present quite promising NH3 absorption and separation performance, with a value of 3.0 mol NH3 per kg DES and an NH3/CO2 selectivity of 98 at 303.15 K and 100.0 kPa.

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