Efficient Absorption of Low Partial Pressure SO2by 1-Ethyl-3-methylimidazolium Chloride Plus N-Formylmorpholine Deep Eutectic Solvents

The removal of SO2from 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 SO2absorption. The absorption performance of SO2in 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 SO2absorption capacity as high as 0.220 g SO2/g of DES of EmimCl-NFM (1:1) at 293.15 K and SO2partial 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 SO2due to their easy preparation, high absorption capacity, and good reversibility.