Protic Ionic-Liquid-Supported Activated Carbon with Hierarchical Pores for Efficient NH3 Adsorption

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.