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[Display omitted] • Carboxylated starch nanoparticles (CSNPs) were synthesized and embedded in the separation layer of the nanofiltration membrane. • The aggregated or large CSNPs adsorb the aqueous phase to build an aqueous template during the interfacial polymerization transferring the reaction interface. • The compatibility problem of nanoparticles and separation layer was effectively solved. • The S NaCl/Na2SO4 of the modified nanofiltration membrane reached 180 with more than 2 times improvement in flux. The challenge of poor compatibility between nanoparticles and separation layers in thin film nanocomposite (TFN) nanofiltration (NF) membranes has always plagued the researchers. In this work, a carboxylated starch nanoparticles (CSNPs) were introduced into the polyamide (PA) separation layer of NF membrane by the IP reaction between trimesoyl chloride (TMC) and piperazine (PIP). The agglomerated or large size CSNPs could transfer the reaction interface above the particles through the formation of a water template by adsorption of aqueous phase monomers, which shaped the defect-free separation layer. Furthermore, the reduced thickness and increased density of the separation layer greatly enhanced the separation selectivity of the nanofiltration membrane thanks to the introduction of hydrophilic groups of nanoparticles. The modified membrane achieved a nearly 5-fold improvement in separation selectivity for NaCl and Na 2 SO 4 (S NaCl/Na2SO4 = 180) and a 2-fold increase in the water permeance. In addition, the modified NF membrane also possessed better chlorine-resistance property based on the formation of polyarylester between the reaction of hydroxyl groups in CSNPs and acyl chloride groups in TMC. Such novel aqueous-phase additives provide new insights to effectively solve the compatibility problem between the nanoparticles and separation layers, which is favorable for the commercial production of NF membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanofiltration membranes with strong negative charge were prepared by a new aqueous monomer 2,4,6-trimethyl-3,5-diaminobenzenesulfonamide (TMDBSA) through the traditional interfacial polymerization process without any post-treatment. • The membrane has high water permeability (19.6 L m−2 h−1 bar−1) and >98.3% methyl blue rejection. • It owns separation stability for the removal of MB in a harsh acid environment. • It has excellent antifouling performance and long-term stability during the filtration tests. • It demonstrates great practical application potential for treating acidic anionic dyes solutions. Nanofiltration (NF) membranes with negative surface charge are of critical significance for the efficient removal of anionic dyes from wastewater. In this work, a novel negatively charged NF membrane was prepared from a new sulfonamide monomer, 2,4,6-trimethyl-3,5-diaminobenzenesulfonamide (TMDBSA) and trimesoyl chloride (TMC) via interfacial polymerization. The unique diamino-sulfonamide structure of TMDBSA would be conducive to the formation of a poly (amide-sulfonamide) (PASA) layer with enhanced negative charge while maintaining the appropriate degree of crosslinking. The TMDBSA-TMC membrane prepared at optimized condition exhibits both high water permeability (19.6 L m−2h−1 bar−1) and superior rejections of anionic dyes with different molecular weights (e.g. 98.3% rejection for methyl blue), reveals that Donnan exclusion dominates the rejection mechanism. More importantly, benefiting from the strong negatively charged surface and PASA structure, the TMDBSA-TMC membrane shows separation stability for the removal of methyl blue in a broad pH range, even under a harsh acid environment. Meanwhile, the membrane has excellent antifouling performance and long-term stability during the filtration tests. The newly developed negatively charged NF membrane demonstrates great practical application potential for the removal of anionic dyes with small molecular weights. [ABSTRACT FROM AUTHOR]