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.