Ether-Linked Diamine Carboxylate Ionic Liquid Aqueous Solution for Efficient Absorption of SO₂

Ionic liquids (ILs) as promising absorbents for SO₂ capture in flue gas desulfurization have been extensively studied. In this work, a multisite absorption strategy was used to synthesize ether-linked diamine protic ionic liquids (EDPILs) for efficient SO₂ capture. The prepared EDPILs containing ether-linkage chain exhibited superior SO₂ absorption relative to conventional protic ionic liquids (PILs). Density functional theory calculations demonstrated that the ether-linkage chain intensified the physical interaction between EDPILs and SO₂. In a subsequent experiment, bis­(2-dimethylaminoethyl) ether dilactate [BDMAEE]­[L]₂, which possessed outstanding SO₂ capture capacities, was used to prepare aqueous solutions (aq), which reduced viscosity of PILs and improved their applicability. An in-depth assessment of the desulfurization performance of [BDMAEE]­[L]₂ aq revealed that effective SO₂ absorption can be achieved even at relatively low concentrations. Specifically, 50 wt % [BDMAEE]­[L]₂ aq exhibited a high absorption capacity (1.04 mol_SO2/mol_ILs, 0.097 g_SO2/g_absorbents) as well as a high SO₂/CO₂ selectivity at 0.2 vol % SO₂ and 40 °C. Overall, ether-linked absorbents with improved desulfurization performance (high SO₂ absorption capacity, satisfactory SO₂ removal efficiency, and excellent reusability) possess good application prospects in flue gas desulfurization.