Zwitterionic Polyamide Thin-Film Composite Membranes with Tunable Architecture for n -Butanol Dehydration

The efficient dehydration of n-butanol is critical for biofuel purification and solvent recovery; however, conventional distillation remains highly energy-intensive due to azeotrope formation. In this work, thin-film composite (TFC) membranes were fabricated via interfacial polymerization by systematically tuning the ratio of triethylenetetramine (TETA) and zwitterionic 2-aminoethyl piperazine (zAEP) in the aqueous phase. The controlled incorporation of sulfonate functionalities enabled precise modulation of the polyamide network structure, surface morphology, hydrophilicity, and cross-linking degree. ATR-FTIR analysis confirmed the successful incorporation of −SO3– groups, while FESEM and AFM revealed a composition-dependent transition from nodular to smoother surface morphologies. Water contact angle measurements indicated enhanced surface hydrophilicity with increasing zAEP content. The optimized membrane exhibited a permeation flux of 2397 g m–2 h–1, a separation factor of 142.6, and a pervaporation separation index (PSI) exceeding 3.3 × 105 g m–2 h–1 for n-butanol dehydration. Systematic evaluation of operating parameters demonstrated thermally activated transport behavior, accompanied by stable selectivity across a range of feed compositions. Long-term operation over 168 h further confirmed the membrane’s structural stability and consistent separation performance. These results demonstrate that precise control of amine composition during interfacial polymerization is an effective strategy to balance hydrophilicity and cross-linking density, thereby enabling high-performance polyamide TFC membranes for energy-efficient n-butanol dehydration.