Study on a novel nanofiltration membrane prepared by interfacial polymerization with zwitterionic amine monomers

A novel zwitterionic amide monomer (N-aminoethyl piperazine propane sulfonate, AEPPS) was synthesized and utilized in conjunction with piperazine (PIP) to perform the interfacial polymerization with trimesoyl chloride (TMC), producing thin-film composite (TFC) nanofiltration membranes (NFMs) with improved separation performance and antifouling property. Chemical structures and compositions of the zwitterionic monomers AEPPS and NFMs were characterized by (attenuated total reflectance) fourier transform infrared spectroscopy, nuclear magnetic resonance spectrometer and X-ray photoelectron spectroscopy. The surface morphology and hydrophilicity of NFMs were examined by field emission scanning electron microscopy, atomic force microscopy, dynamic water contact angle. The water permeability and antifouling property of NFMs are improved via introducing AEPPS into membranes. When tested with 1 g L−1 K2SO4 aqueous solution at 25 °C and 0.6 MPa, the water flux of NFMs increases from 23.4 L m−2 h−1 to 43.1 L m−2 h−1 with increasing AEPPS content from 0 mol% to 3.2 mol%, while K2SO4 rejection maintains around 97%. The NFMs containing zwitterionic moieties can resist bacterial adsorption and protein fouling efficiently, and show a stable and good separation performance during a long-time filtration process of 288 h.