Natural deep eutectic solvent-based gels with multi-site interaction mechanism for selective membrane separation of SO2 from N2 and CO2

Abstract

The researches on capture of SO2 from flue gas using deep eutectic solvents (DESs) are rapidly emerging due to their unique natures, such as high efficiency and simple synthesis. However, to the best of our knowledge, DESs have not been applied to membrane separation of SO2 yet. Herein, we firstly reported novel natural deep eutectic solvent (NDES)-based gels consisting of betaine/glycerol DES (1:2) and 12-hydroxystearic acid (HSA) for selective membrane separation of SO2. Characterization of the prepared gels involving chemical structures, thermal stability and sol–gel transition temperatures were conducted. The corresponding gel membranes were facbricated and their morphology and pressure resisitance were characterized. Gas permeation test shows that the permeability of SO2 reaches 1809 barrers (0.025 bar, 40 °C) in DES + HSA 4% gel, with SO2/N2 and SO2/CO2 selectivities of 624 and 67.8, respectively. FTIR and NMR spectroscopy were used for characterize the facilitated transport of SO2, and the multisite-interaction mechanism was proposed. Surprisingly, the SO2 permeability is found to be significantly enhanced to 15,200 barrers without compromise on selectivity under humidified condition. Moreover, the effects of HSA content, SO2 partial pressure and temperature on separation performance were also investigated. Overall, this work offers an illustration of SO2 separation using DES-based gels, offering an alternative strategy for designing novel DES-based membrane materials for flue gas desulfuration.