One-pot synthesis of polydopamine-Zn complex antifouling coatings on membranes for ultrafiltration under harsh conditions

In this work, dopamine is polymerized in a basic aqueous solution that contains zinc species to form a hybrid coating on polysulfone (PSf) ultrafiltration membranes. FTIR, UV-vis and X-ray absorption fine-structure spectroscopic studies confirm that the zinc species can form complex with polydopamine (PDA) oligomers, leading to uniform distribution of the Zn species in PDA thin coatings on the membranes. The smooth, hydrophilic complex coating surface endows the modified membranes with high water flux and good anti-fouling ability. More importantly, compared with neat PDA-coated PSf membrane, the complex-coated PSf membrane exhibits much enhanced stability in both highly acidic and alkaline solutions because the strong Zn-PDA coordination bonds act as cross-links to resist the electrostatic repulsion between charged PDA molecules and hence maintain the integrity of the thin coating under harsh conditions.