Polyamide nanofiltration membrane fabricated via a metal-chelate strategy for high-flux desalination

Nanofiltration (NF) technology, utilizing polyamide (PA) membranes fabricated through interfacial polymerization (IP), has found extensive application in desalination processes . The pursuit of enhancing water permeance while maintaining high rejection rates of NF membranes has garnered substantial research attention. This study proposed a metal-chelate strategy by incorporating calcium chloride (CaCl 2 ) as an aqueous additive during the IP process and employing EDTA-4Na for post-treatment. In the presence of Ca 2+ , the EDTA-4Na-soaked membrane achieved suitable swelling to better regulate membrane pores, which benefited water flux enhancement and avoided severe structural defects . Meanwhile, the modified membrane also showed a more hydrophilic and negatively charged surface , leading to a significant performance in removing Na 2 SO 4 . As a result, the optimized membrane exhibited a water flux of 24.6 L m −2  h −1  bar −1 , nearly 3 folds that of the initial PA membrane, while maintaining a satisfactory Na 2 SO 4 rejection (97.2 %). Moreover, the obtained membrane showed good operation stability and anti-fouling properties during long-term use. This work proves that the metal-chelate strategy can be an efficient modification method and inspires the fabrication of high-performance NF membranes with coupling processing.