Ionic
liquids (ILs) provide a new way for efficient separation
and recovery of NH3 because of low vapor pressure and adjustable
properties. However, high viscosity or solid state of functionalized
ILs at ambient temperature makes them impossible to use in traditional
scrubbing processes. Therefore, combining ILs with porous solid materials
to form novel IL-supported materials for NH3 adsorption
is an effective method to solve the above problem. In this work, three
protic ILs (PILs) including imidazolium bis(trifluoromethylsulfonyl)imide
([Im][NTf2]), 1-methylimidazolium bis(trifluoromethylsulfonyl)imide
([1-Mim][NTf2]), and 2-methylimidazolium bis(trifluoromethylsulfonyl)imide
([2-Mim][NTf2]) were supported onto activated carbon (AC)
to prepare PIL-supported materials. The effects of PILs and AC types,
PIL loadings, temperatures, and partial pressures on NH3 adsorption, as well as the recyclability of the PIL-supported materials,
were investigated in detail. Among the investigated PIL-supported
materials, 20 wt % [2-Mim][NTf2]-supported AC-980 exhibits
the higher capacity of 68.61 mg of NH3/g of adsorbent at
303.15 K and 0.10 MPa with good NH3 selectivity and fast
adsorption rate because of the synergistic interaction of hydrogen
bonding between the PIL and NH3 and hierarchical pores,
which is 30% higher than that of pure AC. Meanwhile, the PIL-supported
material shows good recyclability after five cycles, implying great
potentials for NH3 separation industrial processes.
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 mass-transfer 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.
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