BACKGROUND: Ionic liquids have become promising media for the treatment of tail gases containing ammonia (NH 3 ), which causes serious environmental problems and threatens human health.
RESULTS:In this work, four dual-functionalized protic ionic liquids (DPILs) [C n OHim]X (n = 1, 2; X = [NTf 2 ] − , [BF 4 ] − , [SCN] − ) with both weak acidity proton and hydroxyl group were designed and synthesized for enhanced NH 3 separation. Among them, the maximum NH 3 molar solubility of 3.11 mol NH 3 mol -1 IL was achieved in [EtOHim][NTf 2 ] at 40°C and atmospheric pressure, and the highest mass solubility of NH 3 could be 0.221 g NH 3 g -1 IL in [EtOHim][SCN]; this is the highest value of any absorbent ever reported under the same conditions. Not only superior NH 3 solubility, along with excellent selectivity of NH 3 /CO 2 (65) and NH 3 / N 2 (104), but also outstanding recyclability was exhibited in DPILs.
CONCLUSIONS:The highly efficient performance of NH 3 absorption by DPILs was ascribed to the synergistically physicochemical interaction between weak acidity proton, hydroxyl group and NH 3 , which was confirmed through both spectrum analysis and quantum chemical calculations. This work implied that DPILs have great potentials in NH 3 separation and recovery of NH 3 -containing tail gases.