An Overview of Ammonia Separation by Ionic Liquids

Ammonia (NH3) is an important chemical in several fields, such as agriculture, pharmaceutical, material, and chemicals manufacturing. However, NH3 is a toxic gaseous pollutant and NH3 release results in environment pollution. Minimizing NH3 emission is of great significance for solving NH3-related environmental issues and promoting the reuse of NH3 resources. Ionic liquids (ILs) are energy-saving gas absorbents, because of their low vapor pressure, good chemical stability, and high NH3 solubility. The recent research progress of conventional, functionalized ILs and novel IL-based materials and solvents for NH3 separation was summarized. The effects of anions and cations on NH3 absorption capacity, as well as the absorption mechanism of ILs, were discussed in detail in this Review. The simulated dynamic parameters of NH3-IL systems including mass diffusivity, heat-and masstransfer coefficient were also discussed. In addition, this Review summarized the industrial application achievement of ILs in NH3 separation and recovery from NH3-containing tail gas, which spans from simulation, pilot plant to industrial applications. Finally, the research trends in NH3 separation by IL-based systems were proposed based on existing research.