Exploring NH₃ Transport Properties by Tailoring Ionic Liquids in Pebax-Based Hybrid Membranes

Ammonia (NH₃) separation and recovery from NH₃-containing gases favor resource utilization and ecological protection. Ionic liquids (ILs) are promising alternatives to fabricate polymer-based hybrid membranes with excellent and tunable properties. Herein, [Eim]­[NTf₂] and [Emim]­[NTf₂], with different hydrogen bond donating abilities and viscosities, were used to tailor NH₃ transport properties in the membranes for enhancing NH₃ separation performance. Poly­(ether-block-amide) (Pebax)/[Eim]­[NTf₂] membranes exhibit superior NH₃ permeability of 2118.7 Barrer with NH₃/N₂ and NH₃/H₂ selectivities of 467.0 and 127.2, respectively. NH₃ solubility in Pebax/[Eim]­[NTf₂] membranes increases significantly when increasing the IL content, while the solubility in Pebax/[Emim]­[NTf₂] membranes is almost unchanged, mainly because the hydrogen bond interaction between NH₃ and [Eim]­[NTf₂] is stronger. NH₃ diffusion in Pebax/[Eim]­[NTf₂] membranes decreases when increasing the IL content, while the diffusion in Pebax/[Emim]­[NTf₂] membranes exhibits the reverse trend, corresponding to NH₃ diffusion properties in pure ILs. Therefore, NH₃ solubility is the more dominant factor in improving NH₃ permeability in the membranes.