Cu2+/alginate nanofiltration membranes fabricated at the aqueous contra-diffusion “interface” for salt/dye rejection

Thin-film composite (TFC) membranes can find broad uses in desalination and wastewater treatment . However, industrialized interfacial polymerization involves many organic solvents and toxic monomers . An aqueous fabrication process can meet the standards of green and sustainable production, but fabricating defect-free thin films in a homogenous phase remains challenging. Herein, we fabricate a series of TFC nanofiltration membranes through a contra-diffusion process based on the cross-linking of metal ions and alginate . The film formation is confined at the ultrafiltration substrate surface due to the competition between reaction and restricted diffusion. Among a series of metal ion/alginate composites, the Cu 2+ /alginate composite membrane displays superior nanofiltration performance because of the strong affinity between Cu 2+ and alginate. The highly negatively charged membrane performs a high rejection to divalent anions and anionic dyes based on the Donnan effect . The effects of alginate concentration and diffusion time on membrane performance were investigated to achieve optimal fabrication conditions. The as-prepared membrane shows a rejection of 96.2% to Na 2 SO 4 with permeation flux around 50.2 L·m −2 ·h −1 under 0.6 MPa, and 99.5% to several dye molecules. Moreover, the membrane performs outstanding anti-fouling and anti-bacterial properties because of its excellent hydrophilicity and the existence of Cu 2+ .