Exploring the potential of highly selective alkanolamine containing deep eutectic solvents based supported liquid membranes for CO2 capture

Amine based solvents are being used extensively for CO2 capture for the last several decades owing to their relatively high CO2 affinity. They are considered as standard solvents for CO2 separation but still, face limitations of high energy requirement, high volatility, high vapor pressure and toxicity. To overcome these limitations, for the first time in this study, amine based deep eutectic solvents (DES) are incorporated into membranes for CO2 capture. Three different alkanolamines; monoethanolamine, (MEA), diethanolamine (DEA), triethanolamine (TEA) were selected as HBDs and choline chloride as HBA. The synthesis of the DESs was confirmed by FTIR characterization as well as physicochemical properties of the resulting liquid mixture. Subsequently, the synthesized DESs were impregnated into the porous support to prepare supported liquid membranes (SLMs). The SLMs showed excellent selectivity of CO2 up to 70.47 and 78.86 for CO2/CH4 and CO2/N2 respectively. This high selectivity of CO2 over CH4 and N2 can be attributed to the chemisorption of CO2 with DES and high basicity of DES. The effect of operating temperature, the HBA: HBD mole ratio, and CO2 concentration on membrane performance was also investigated. The results of amine DESs were compared with the competing ionic liquids based membranes, and the significant high gas separation was attributed to the low viscosity and the high CO2 solubility in amines that makes them an appropriate alternative to the conventional ILs.