Acid-resistant polyamide-sulphonamide nanofiltration membrane with positive charge for efficient removal of dyes/metal ions in acidic wastewater

The selection of separability and surface positive charge is of significant importance for treating acidic industrial wastewater with acid-resistant nanofiltration (NF) membranes. In this work, polyvinylidenefluoride (PVDF) flat membrane was used as the base membrane material, with polyethyleneimine (PEI) as the aqueous monomer and trimesoyl chloride (TMC)/benzene-1,3-disulfonyl chloride (BDSC) as the organic phase monomers, to prepare PEI-polyamide-sulphonamide (PASA) NF membrane through interfacial polymerization (IP). The influence of reaction conditions on membrane separation performance and corrosion resistance were studied, and the performance differences of the membrane under different ratios of TMC and BDSC were explored. PEI-PASA NF membrane was characterized by FTIR, XPS, SEM, contact angle tester, and mechanical strength tester. The results showed that the PEI-PASA NF membrane prepared under optimal conditions had a strong positive charge on the surface, with a water flux of 17.54 L·m−2·h−1 at 5 bar, and after static assessments in 10 % H2SO4 solution at 55 °C for 24 h, the methyl orange rejection remained kept over 95 %; after dynamic filtration in 1 % HCl for 120 h, the rejection performance of the membrane remained stable (FeCl3 96.88 %, CuCl2 93.72 %), indicating the potential application inharsh conditions, especially acid wastewater treatment.