Sodium hypochlorite activated dual-layer hollow fiber nanofiltration membranes for mono/divalent ions separation

• Published in: Chemical engineering research & design 2023-05, Vol.193, p.565-575
• Main Authors: Tao, Sheng-Nan, Wang, Yue, Fu, Zheng-Jun, Wang, Yi-Meng, Lu, Qing-Lin, Tang, Ming-Jian, Wang, Wei-Jian, Mamba, Bhekie B., Sun, Shi-Peng, Wang, Zhen-Yuan
• Format: Article
• Language: English
• Subjects: Dual-layer hollow fiber membranes; Mono/divalent ions separation; NaClO activation; Nanofiltration
• ISSN: 0263-8762
• DOI: 10.1016/j.cherd.2023.04.013

The tailoring of nanofiltration membranes for the precise separation of mono/divalent ions often involves complicated procedures to modify the surface chemistry and structure. Herein, an efficient sodium hypochlorite (NaClO) activation method is developed to tune the selective layer of cross-linked polyimide (PI)/polyethersulfone (PES) dual-layer hollow fiber membranes. By oxidizing the hydroxyl and imine groups while hydrolyzing the amide groups in the cross-linked structure, the membranes are effectively tailored with the negatively charged surface and a more open pore structure with 0.47 nm mean effective pore size. The NaClO-activated membranes show over 97.85% rejection of Na2SO4 while the NaCl rejection decreases from 93.83% to − 19.85% during treating the mixed ions solutions. The fabricated membranes with high separation efficiency and long-term stability exhibit vast potential for the separation of mono/divalent ions in industries. Moreover, the elaborated NaClO activation mechanism potentially gives fundamentals for the modification of the PI membranes with cross-linked structures for other applications. [Display omitted] •NaClO activated dual-layer hollow fiber NF membranes were fabricated.•NaClO activation oxidizes the imine groups and hydrolyzes the amide groups.•The membranes are tailored negatively charged with loose structure by activation.•The activated membranes show a high SO42-/Cl- selectivity over 117.