Highly permeable acid-resistant nanofiltration membrane based on a novel sulfonamide aqueous monomer for efficient acidic wastewater treatment

Thin-film composite (TFC) membrane with high permeability and selectivity is appealing in the field of industrial wastewater treatment. However, polyamide (PA) TFC membranes, the premier choice for water treatment, undergo structure deterioration when continually exposed to acidic environment. Here, we apply surface activation assisted multi-step interfacial polymerization (IP) of 3-aminobenzenesulfonamide (ABSA) and trimesoyl chloride (TMC) to prepare a poly(amide-sulfonamide) (PASA) nanofiltration (NF) membrane with strong acid resistance. Thereinto, stable sulfonamide structure of ABSA effectively prevents the direct attack of acid to the PASA layer. Importantly, the nascent PASA layer acting as a hydrophilic interlayer can promote the subsequent IP reactions to form a less defective separation layer. When the surface activation (water soaking) is carried out during the multi-step IP process, the surface smoothness and hydrophilicity as well as the water permeability of the membrane are improved. Compared to the control, the resultant NF membrane exhibits similar to 200% increase in water permeability (12.4 Lm(-2)h(-1)bar(-1)) and >95.0% Na2SO4 rejection. Benefiting from the strong steric exclusion, it also has high color removal when treating model acidic dye solutions (>99.3%) or real resin elution wastewater, showing great potential in the acid reuse for decolorization resin regeneration. Moreover, such membrane owns impressive long-term stability after exposure to strong acid (20 wt% of H2SO4 for 30 days), and its hydrophilic surface contributes to excellent anti-fouling performance. This acid-resistant NF membrane with high permeability and stability provides a new perspective in acidic wastewater treatment.