One-step fabrication of recyclable polyimide nanofiltration membranes with high selectivity and performance stability by a phase inversion-based process

A novel one-step strategy is proposed for the recyclable polyimide nanofiltration (PI-NF) membranes. By designing the chain structure, the soluble polyimide polymer with coexisted imide rings and flexible pendant groups are fabricated. With the polyimide polymer as matrix, the NF membranes with integrally skinned asymmetric architecture were obtained by a phase inversion method. The structure evolution was demonstrated by scanning electron microscope and atomic force microscope analyses. The rejections of prepared PI-NF membrane for Rose Bengal, PEG 1000 and typical salts under optimized conditions were 92, 91.78, 98.68%, respectively. The rejections of NF membranes for different salts followed the order: Na₂SO₄ > MgSO₄ > NaCl > MgCl₂. Furthermore, the fabricated polyimide-based NF membranes show a stable performance during long-time filtration process and exhibit a confirmed excellent recyclable property.