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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]

The thin-film composite (TFC) nanofiltration (NF) membrane is an excellent choice to solve water shortage based on the advantages of high flux and selective separation. However, the current NF membrane still causes a tremendous amount of energy consumption in the practical applications due to the limitation of flux. In this work, dextran nanoparticles (DNPs) with the cross-linked organic components, numerous hydrophilic groups and internal cavities were added into the aqueous phase solution, and novel NF membranes were fabricated by adjusting the concentration and particle size of DNPs to control the interfacial polymerization (IP) reaction. After modification, the decrease of membrane thickness and the increase of surface hydrophilicity improved the separation performance of NF membrane. The water flux of NF membrane with 0.5 wt% DNPs doping was up to 211.2 Lm−2h−1MPa−1, which was more than twice as high as the unmodified membrane with Na 2 SO 4 retention up to above 98%. It was also worth mentioning that the modified membrane indicated excellent monovalent/divalent ion selectivity and anti-fouling performance. This strategy of improving membrane performance by controlling the concentration and particle size of the aqueous phase additives with the advantages of simplicity and universality provides a certain impetus for the development of TFC membrane. • Dextran nanoparticles were successfully incorporated into the separation layer of NF membrane. • The water flux of the DNPs-modified NF membrane increased 2–3 times without sacrificing the Na 2 SO 4 retention. • The influence of the particle size and concentration of DNPs was discussed detailedly. • The anti-fouling performance and monovalent/divalent ion selectivity of the membrane improved. [ABSTRACT FROM AUTHOR]