Thin-Film Composite Nanofiltration Membrane Modified by Fulvic Acid to Enhance Permeability and Antifouling Performance

A novel thin-film composite (TFC) nanofiltration (NF) membrane was manufactured by interfacial polymerization (IP) with addition of the additive fulvic acid (FA) into the piperazine (PIP) aqueous solution onto a poly(m-phenylene isophthalamide) (PMIA) substrate. The aqueous phase additive FA can effectively modify the PA layer structure by slowing down the diffusion of the PIP monomer and reacting with trimesoyl chloride (TMC) to generate ester groups. The pure water permeability (PWP) of the optimized NF membrane enhanced from 10.4 to 22.3 L m–2 h–1 bar–1, and the Na2SO4 rejection remained above 97.8%. The outstanding performance benefited from superior hydrophilicity, enlarged pores, and a relatively thin separation layer. Furthermore, the obtained NF membrane presented ascendant thermal stability, long-term stability, and fouling resistance. Therefore, this work offers novel insight into regulation of the PA layer structure and promotion of NF membrane performance.