Composite Nanofiltration Research Articles

Enantiomeric Separation of Racemic Mixtures Using Chiral-Selective and Organic-Solvent-Resistant Thin-Film Composite Membranes.

Membrane-based chiral separation has emerged as a promising method for the efficient separation of chiral molecules. Ideally, the membranes should be able to achieve good enantioselectivity, while maintaining high stability in harsh solvents. However, engineering membranes for chiral molecular separation in harsh organic solvent environments is still a big challenge. In this study, we fabricated a novel thin-film composite nanofiltration membrane composed of (2-hydroxypropyl)-beta-cyclodextrin (HP-β-CD) as the chiral selector for the enantiomeric separation of racemic 1-phenylethanol chiral compounds in organic solvents. The fabricated membrane achieved 60-80% enantioselectivity of R-phenylethanol over S-phenylethanol in nonpolar n-hexane. It was found that HP-β-CD played a critical role in the enantioselective performance, as the membrane without HP-β-CD showed no chiral selectivity. Molecular docking calculations substantiate the experiments by showing that the average free binding energy of S-phenylethanol with HP-β-CD is stronger than that of R-phenylethanol, indicating that the complex of S-phenylethanol with HP-β-CD has a higher thermodynamic stability and greater interaction. Furthermore, the crosslinked network between HP-β-CD and the polyamide layer conferred the membrane with solvent stability in nonpolar solvents. Moreover, this new membrane exhibited good solvent permeance and a molecular weight cutoff of around 650 g mol-1.

Open and dense hollow fiber nanofiltration membranes through a streamlined polyelectrolyte-based spinning process

Polyelectrolyte composite hollow fiber membranes show a high potential to become applied in industrial nanofiltration applications such as water purification or downstream processing in several industries. This material platform allows multiple routes to achieve tailored selectivities and high permeances. Hollow fiber membranes promise a higher process efficiency due to higher packing densities and their backwash stability. However, the fabrication of composite polyelectrolyte hollow fiber nanofiltration membranes is more challenging compared to state of the art spiral wound modules. While the Layer-by-Layer deposition has proven versatile opportunities and is recently entering the commercial market, the multi-step post-treatment is elaborate. In this work, we streamline the fabrication of polyelectrolyte composite hollow fiber membranes. We extend our recently presented ”chemistry-in-a-spinneret” approach with a membrane modification in a subsequent coating bath. The additional modification can be incorporated in the composite hollow fiber membrane manufacturing process without additional process steps. Sulfonated polyethersulfone as a polyanionic additive is used in the polymer solution which complexates with the polycations polyethylenimine (PEI) or poly(diallyldimethylammonium chloride (PDADMAC) in the bore fluid during fiber spinning. The extruded fibers have a positively charged lumen surface which allows a subsequent modification with the polyanion poly(sodium 4-styrenesulfonate) (PSS) in the coating bath. The spun fibers reveal with 16-4 LMH/bar pure water permeance (PWP) and 2000-1100 Dalton (Da) molecular weight cut-off (MWCO) open nanofiltration characteristics, while the PEI+PSS modified fibers show dense nanofiltration characteristics (0.6 LMH/bar PWP and 360 Da MWCO). The fibers are backwash stable and the PDADMAC and PDADMAC+PSS fibers show a significantly higher sodium hypochlorite (NaOCl) stability compared to the PEI and PEI+PSS fibers. This new technique creates composite hollow fiber nanofiltration membranes with a polyelectrolyte bilayer without multi-step post-treatment. Therefore, it provides a promising alternative to the Layer-by-Layer post-modification, where two coating steps and one water washing post-treatment step are required to create a polyelectrolyte bilayer on a porous hollow fiber membrane support. • Composite hollow fiber nanofiltration membranes without multi-step post-treatment. • The chemistry in a spinneret technique is extended with a polyanion coating step. • Backwash stable hollow fibers feature open or dense NF characteristics. • PDADMAC and PDADMAC+PSS show higher NaOCl stability compared to PEI and PEI+PSS. • Fibers with open NF characteristics are competitive with commercial nanofiltration membranes.

Electrosprayed polyamide nanofiltration membrane with uniform and tunable pores for sub-nm precision molecule separation

• Electrosprayed polyamide nanofiltration membrane. • Polyamide membrane with uniform and tunable pores. • Sub-nm precision molecule separation. Interfacial polymerized polyamide composite nanofiltration membrane has been widely used in wastewater treatment. Despite its high selectivity towards water and solutes, differentiation of solutes with similar size is still a great challenge. Herein, we propose that polyamide nanofiltration membrane with uniform and tunable pores and sub-nm precision selectivity can be achieved through electrospraying strategy via controlling relative humidity (ratio of practical vapor pressure P 1 and its saturated vapor pressure P s ). The enhanced relative humidity facilitated the dispersion of piperazine (PIP) monomers on substrate and the reaction with trimesoyl chloride (TMC). The membrane (M78) fabricated at high humidity (70%-80%) exhibited more uniform pore size and narrower size region (0.26 nm-0.49 nm) at a designed rejection difference (e.g., 50%) compared with the membrane (0.26 nm-1.0 nm) obtained at low humidity (30%-40%). Membrane selectivity (e.g., Na 2 SO 4 and NaCl) was an order of magnitude high when humidity increased from 30%-40% to 70%-80%. The current study offered a facile and effective strategy for fabricating polyamide nanofiltration membrane with uniform pores and sub-nm selectivity.

Polyamine-based thin-film composite nanofiltration membrane embedded with catalytic chemical additive for enhanced separation performance and acid stability

Nanofiltration (NF) membranes with excellent acid stability and enhanced separation performance are of great benefit in treating acid wastewater and meeting freshwater demand. In this study, terephthalic acid (TPA) molecules with unique catalytic reactivity were directly incorporated as a chemical additive into the membrane selective layer via interfacial polymerization reaction to form a novel polyamine-based nanofiltration membrane. The resultant membrane morphology, chemical and functional composition, hydrophilicity, surface charge, separation performance, thermal stability and acid resistance were all investigated. The results showed improved hydrophilicity, electronegativity and cross-linking degree of the membranes. Compared with the bare membrane, the TPA incorporated membrane performance was best at 0.15% TPA concentration with improved water permeability of 14.1 LMH.bar −1 which was 1.6 times the control with an excellent salt rejection of 96.7% for MgCl 2 . Furthermore, after exposure to 5% (w/w) HCl and 20% (w/w) H 2 SO 4 acid solutions at 25 °C for 60-days, the membranes displayed excellent acid stability with appreciable increase and a corresponding decrease in water fluxes and salt rejections. No obvious change was observed in the membrane surface as revealed by the SEM, FTIR and XPS analysis after exposure period expiration. In addition, the membrane showed excellent pressure resistance and long-term stability after acid exposure for 30 days. Overall, incorporating TPA into the membrane provides a scalable system with great potential in water desalination and acid wastewater treatment. • Terephthalic acid (TPA) molecule act as additive/co-monomer for novel TFC membrane. • Incorporation of TPA enhances hydrophilicity, surface charge and thermal stability. • Optimal membrane has 14.1 LMHbar −1 water flux and 96.7% of MgCl 2 rejection. • Optimal membrane shows excellent acid stability after 60 days exposure period. • Membrane shows good prospect in water desalination and acid wastewater treatment.

Host-guest nanofiltration membranes having amino-complexed cucurbituril supramolecular channel for monovalent/divalent salts separation

Nanofiltration (NF) is widely used in separation of ions with different sizes and charges. However, thin-film composite NF membrane is hard to reach satisfied selectivity for monovalent/divalent salts separation. Herein, a novel host-guest NF membrane was designed and fabricated with cucurbituril-polyethyleneimine (CB-PEI) complex, which provided a “ring-like” supramolecular channel. The results indicated that CB-PEI/PSf membrane showed attractive separation performance for monovalent/divalent salts separation, purification and desalination of small molecule solutions. The as-prepared CB-PEI/PSf membrane exhibited superior pure water permeability up to 25.6 L·m−2·h−1·bar−1, and salt rejections of 97.4%, 90.6%, 41.9% and 12.4% to MgSO4, Na2SO4, MgCl2 and NaCl, respectively. The monovalent/divalent selectivelies for NaCl/MgSO4 and NaCl/Na2SO4 reached up to 30.0 and 8.9, respectively. Besides, the CB-PEI/PSf membrane exhibited very high separation factors for medicine/NaCl and dye/NaCl mixtures. Moreover, NF membrane processes were designed and operated for monovalent/divalent mixed salt separation by using CB-PEI/PSf membrane. The NaCl with mass fraction above 98% was successfully recovered after the single-stage membrane separation of NaCl/MgSO4 mixture and the two-stage membrane separation of NaCl/Na2SO4 mixture. Therefore, this novel host-guest NF membranes and process design provide a valuable basis for the industrial application of monovalent/divalent salts separation.

Covalent cross-linking mediated TA-APTES NPs to construct a high-efficiency GO composite membrane for dye/salt separation

The excellent water transport and molecular sieving properties of graphene oxide (GO)-based membranes have shown application prospects in solving the freshwater crisis. However, it is challenging to further increase water permeability while ensuring separation efficiency, and the destruction of the membrane structure caused by the electrostatic repulsion between the graphene oxide nanosheets also hinders its practical application. In this study, a simple vacuum-assisted method is proposed to prepare a chemical cross-linking mediated composite graphene oxide nanofiltration membrane (GO-TA-APTES-x) by adding tannic acid (TA)-aminopropyltriethoxysilane (APTES) nanoparticles (TA-APTES NPs). Thanks to the expansion of GO membrane interlayer spacing by TA-APTES NPs, the permeability of the GO-TA-APTES-10 membrane is 15 times higher than that of the original GO membrane, and the rejection rate of Congo red remains at 99.9%. In addition, TA-APTES NPs improves the application stability of composite membrane in water environment by means of chemical crosslinking agent, which is expected to promote the transformation of GO nanofiltration membrane from the laboratory environment to industrial application.

Fabrication of Poly(amide-co-ester) Solvent Resistant Nanofiltration Membrane from P-nitrophenol and Trimethyl Chloride via Interfacial Polymerization

P-nitrophenol (PNP), a refractory hazardous substance, has not been efficiently utilized so far. In this paper, PNP is used as a membrane modification material for preparing poly(amide-co-ester) composite nanofiltration membrane. An organic solvent nanofiltration (OSN) membrane was prepared via interfacial polymerization reactionby using PNP and trimethyl chloride (TMC) on a ethylenediamine (EDA) crosslinked polyetherimide substrate. The results of ATR-FTIR and XPS show that interfacial polymerization occurs among with PNP and TMC and the terminal amine groups on the ethylenediamine crosslinked -PEI support forming a poly(amide-co-ester) toplayer. The NF-1PNP membrane maintained stable DMF performance permeance of 2.2 L m−2 h−1 bar−1 and rejection of 98% for Rose Bengal red (RB 1017.64 g mol−1) in 36 h continuous separation process. Furthermore, the average pore diameter of the two membranes including NF-1PNP and NF-1.25PNP, which is 0.40 and 0.36nm, respectively. This study not only provides a good way for the preparation of OSN membrane, but also provides a good demonstration for the comprehensive utilization of PNP and other toxic and harmful pollutants.

Development of polyester filters with polymer nanocomposite active layer for effective dye filtration

Organic dyes such as methyl orange (MO) and methylene blue (MB) are widely used in different industries and have become one of the leading emerging water contaminants. The purpose of the current research is to develop new polymer nanocomposite filters for the effective elimination of the dyes, which are non-biodegradable and not efficiently removed by traditional treatment methods. New padded and covered filters were produced applying polystyrene-acrylic/ZnO nanocomposite on the polyester surface by blade coating and one-bath pad methods. Principal results determined by SEM analysis confirm that functionalised layer can create unprecedented function of filter textile material depending on the way of treatment. Due to the modification, the surface area increased from 5.9 for untreated polyester to 85.2 (padded), 44.6 (covered) m2/g. The measured pore size of produced filters is around 3.4 nm, which corresponds to the mesoporous structure. Our study reported effective filters with the rate of MB and MO removal efficiencies up to 60%. Moreover, a colourless reduced form of MB—leuco-methylene blue (LMB) could be created. The functionalised layer of the developed filters through hydrogen bonding between the –OH groups of styrene-acrylic molecules and the –N(CH3)2 groups on LMB can stabilise LMB.

Design and fabrication of polyamine nanofiltration membrane by constituting multifunctional aliphatic linear amine and trifunctional cyanuric chloride for selective organic solvent nanofiltration

BackgroundThin film composite nanofiltration (TFC-NF) membranes have been developed for organic solvent nanofiltration. Most of the polyamide TFC-NF membranes are vulnerable to nucleophilic hydrolysis. MethodsA multifucntional amine was crosslinked with a trifucntional non-aqueous monomer namely cyanuric chloride (CC) on surface of self-fabricated polysulfone/polyester terephthalate (PS/PET) membarne support leading to a new polyamine active layer containing TFC-NF membrane named as PA@PS/PET. The fabricated PA@PS/PET membrane was thoroughly characterized by several characterization techniques such as ATR-FTIR, XPS, FE-SEM, Water Contact Angle (WCA), and EDX analysis. Significant FindingsPA@PS/PET TFC-NF membrane showed remakable perfomance in terms of solvent flux for all tested solvents including water, methanol, ethanol and isopropanol. The highest flux was found to be 29.58 L m−2h−1 at 8 bar for methanol. The flux of solvents was found to be inversly related to the viscosity of the solvents. The PA@PS/PET membrane showed remarkably high rejection of solute (Congo Red) reaching to a value of ∼98%. Moreover, the PA@PS/PET membrane showed permanant flux of 8.45 L m−2 h−1 at 2 bar during solute separation (CR dye rejection) tests which hinted the stability of the membrane under the applied operating conditions.

High flux and high selectivity thin-film composite membranes based on ultrathin polyethylene porous substrates for continuous removal of anionic dyes

Thin-film composite (TFC) nanofiltration (NF) membranes efficiently remove dyes from wastewater. However, most of the membranes often sacrifice water flux for high rejection because of the trade-off between them. The demand for TFC membranes with high rejection and high water flux is increasing. Here, polyethylene (PE) membrane with a thickness of 7 µm was covered by polydopamine and polyethyleneimine (PDA/PEI), and then directly initiated interfacial polymerization (IP) with trimesoyl chloride (TMC), forming the dense and negatively charged polyamide-polyester selective layer. As the amount of PDA/PEI increases, the selective layer becomes denser, leading to the efficient removal of anionic dyes at high water flux. The water flux of the optimal membrane is 61.0 ± 18.3 L m−2 h−1 bar−1, and the removal efficiency is 91.4 ± 0.8% for an anionic dye eosin Y (EY, Mw = 691.9 Da), but poor decolorization for natural VB12 (Mw = 1355.4 Da). Moreover, the TFC membrane shows excellent selectivity for filtrating dye/NaCl mixture solution. The synergistic effect of adsorption-filtration control the removal of anionic dyes from wastewater in large flux. This work utilizes commercial PE porous substrate to fabricate TFC membrane having outstanding separation performance and a low thickness of about 7 µm.

Intrinsic Dependence of Groundwater Cation Hydraulic and Concentration Features on Negatively Charged Thin Composite Nanofiltration Membrane Rejection and Permeation Behavior.

Commercial nanofiltration membranes of different molecular weight cut-offs were tested on a pilot plant for the exploration of permeation nature of Ca, Mg, Mn, Fe, Na and ammonium ions. Correlation of transmembrane pressure and rejection quotient versus volumetric flux efficiency on nanofiltration membrane rejection and permeability behavior toward hydrated divalent and monovalent ions separation from the natural groundwater was observed. Membrane ion rejection affinity (MIRA) dimension was established as normalized TMP with regard to permeate solute moiety representing pressure value necessary for solute rejection change of 1%. Ion rejection coefficient (IRC) was introduced to evaluate the membrane rejection capability, and to indicate the prevailed nanofiltration partitioning mechanism near the membrane surface. Positive values of the IRC indicated satisfactory rejection efficiency of the membrane process and its negative values ensigned very low rejection affinity and high permeability of the membranes for the individual solutes. The TMP quotient and the efficiency of rejection for individual cations showed upward and downward trends along with flux utilization increase. Nanofiltration process was observed as an equilibrium. The higher the Gibbs free energy was, cation rejection was more exothermic and valuably enlarged. Low Gibbs free energy values circumferentially closer to endothermic zone indicated expressed ions permeation.

Mechanistic Insights of a Thermoresponsive Interface for Fouling Control of Thin-Film Composite Nanofiltration Membranes.

In spite of extensive research, fouling is still the main challenge for nanofiltration membranes, generating an extra transport resistance and requiring a larger operational pressure in practical applications. We fabricated a highly antifouling nanofiltration membrane by grafting poly(N-isopropylacrylamide) (PNIPAM) chains on a bromine-containing polyamide layer. The resulting membrane was found to have a double permeance compared to the pristine membrane, while the rejection of multivalent ions remained the same. In addition, PNIPAM chains yielded a better deposition resistance and adhesion resistance, thereby mitigating the increase of fouling and promoting the recovery of flux during the filtration and traditional cleaning stages, respectively. Moreover, PNIPAM chains shrank when the water temperature was above the lower critical solution temperature (LCST), indicating the formation of a buffer layer between the membrane and pollutants. The buffer layer would eliminate the membrane-foulant interaction energy, thus further enhancing the detachment of pollutants. This simple and efficient cleaning method could act as an enhanced cleaning procedure to remove irreversible fouling. This provides new insights into the fabrication of enhanced antifouling membranes using smart responsive polymer chains.

Extra-thin composite nanofiltration membranes tuned by γ-cyclodextrins containing amphipathic cavities for efficient separation of magnesium/lithium ions

Although nanofiltration (NF) membrane as a new frontier technique had made significant progress in the field of lithium extraction from salt lakes, they still suffered from the conventional permeability–selectivity trade-off effect. In this study, γ-cyclodextrins(CDs) containing amphipathic cavities and polyethyleneimine (PEI) acted as the aqueous phase monomer, which was carried out interfacial polymerization with the trimesoyl chloride (TMC) as the organic phase monomer to fabricate thin film composite (TFC) NF membranes with the extra-thin active layer. The hydrophilic surface and hydrophobic cavity of γ-CDs enhanced the hydrophilicity of the membrane surface and the water flux of the nanofiltration membrane. Moreover, the cavity size of γ-CDs also effectively screened magnesium and lithium ions to a certain extent. Under the best preparation conditions, the permeation flux of the PEI/γ-CDs-TMC nanofiltration membrane was 4.86 L⋅m−2⋅h−1⋅bar−1, SLi, Mg was 10.8. It was noteworthy that we used the molecular dynamics simulation method to confirm that the participation of γ-CDs led to the diffusion rate of the water phase monomers during the interfacial polymerization reaction slowed down. Thus, the thickness of the active layer of the nanofiltration membrane formed was also significantly reduced from 110.16 nm to 52.84 nm. This PEI/γ-CDs-TMC membrane provided a new strategy for preparing nanofiltration membranes with excellent overall magnesium-lithium separation performance.

Engineering novel high-flux thin-film composite (TFC) hollow fiber nanofiltration membranes via a facile and scalable coating procedure

A novel defect-free polyamide/(polyether sulfone/poly(vinylidene fluoride)) PA/(PES/PVDF) thin-film composite (TFC) hollow fiber membrane (HFM) with desirable separation characteristics were developed through a facile and scalable coating procedure. By the introduction of piperazine (PIP) monomers into the PES coating solutions, the functional monomer-enriched PES coating layer was formed on the shell side of porous matrix-reinforced hollow fiber (HF) support through phase inversion process. Subsequently, PIP and TMC was interfacial polymerized during the fiber coating line to form a thin and defect-free polyamide (PA) functional layer for TFC HFM with high water permeability. Furthermore, the introduction of aqueous monomers only into the PES layer allowed economizing the cost of membrane manufacturing compared with bulk modification of the membrane substrate. Interestingly, the formation of bowl-like structures endowed the separation layer with higher permeation surface area and thus favored high water permeability. On combining these separation features, the optimized TFC membranes presented a high pure water permeability (PWP) of 13.8 L·m−2·h−1·bar−1, approximately twice than that of conventional TFC membrane, with a satisfying Na2SO4 rejection of 98.2%. Moreover, the PA/(PES/PVDF) TFC HFM exhibited excellent stability, backwash ability and anti-fouling ability, suggesting its huge potential for the water purification. Compared with the conventional two-step IP process on flat sheet membrane, the in-situ IP procedure performed on HF greatly simplifies the manufacturing process, shortens the production period and reduces monomer usage while the high packing density and great surface area per unit volume are obtained. This work may provide a simple and economical strategy for engineering high-performance TFC HFM.

A novel PPTA/PPy composite organic solvent nanofiltration (OSN) membrane prepared by chemical vapor deposition for organic dye wastewater treatment

In this study, a stable and controllable poly(p-phenylene terephthamide)/polypyrrole (PPTA/PPy) composite organic solvent nanofiltration (OSN) hollow fiber membrane was successfully prepared based on the robust chemical vapor deposition (CVD) method. The structure and properties of the prepared PPTA/PPy OSN membranes were studied in detail. Interestingly, after modifying by PPy, SEM showed that the surface of the membrane formed a layer of “Turing-like” structure and evenly covered the surface of the membrane. It was evident that the prepared PPTA/PPy OSN membranes achieved good dye-removal ability with a molecular weight cut-off range from 200 to1000 Da, and the rejection of negative dyes was higher than 93.4%. Especially at high temperature (80 °C) and organic solvent (N,N-dimethylacetamide, DMAc), the PPTA/PPy OSN membranes still exhibited excellent permeation and separation performance. Furthermore, at room temperature, the immersion experiment of the fabricated PPTA/PPy OSN membranes in both ethanol and DMAc for one month also proved the stability of long-term organic solvents. Based on the above results, this work offered a novel PPTA based hollow fiber nanofiltration membrane, which was expected to be applied in thermal and organic dye wastewater treatment.

Preparation and characterization of a novel emphatically charged strengthened chitosan composite nanofiltration membrane

In this paper, chitosan was grafted with acrylic acid and positively charged elements, and a series of reinforced nanofiltration membranes were prepared by coating modified chitosan polymer with polysulfone ultrafiltration membrane as support. The structure of chitosan derivatives and polymers was characterized by infrared spectrum, and the membrane structure was characterized by scanning electron microscope and atomic force microscope. The performance of composite nanofiltration membrane was closely related to the structure of polymer and the electrical properties of positively charged elements. The rejection rate of 50% molar ratio composite nanofiltration membrane to CaCl2 reached 97.4%. The corresponding flux is 430.7 Lm-2h-1. The retention order was: CaCl2 > NaCl > Na2SO4. The tensile strength increased by 27.3%. Acid resistance (5%HCl)) was improved by 50.5%. Alkali resistance (5%NaOH) increased by 42.2%. The results showed that the positive charge enhanced chitosan composite nanofiltration membrane had excellent performance. The charge effect had no effect on NaCl and Na2SO4, but had significant effect on CaCl2. The membrane is a typical positive charged nanofiltration membrane suitable for separating high-valent cations from weak acids or weak bases.

Trimethylamine N-Oxide-Derived Zwitterionic Polyamide Thin-Film Composite Nanofiltration Membranes with Enhanced Anti-Dye Deposition Ability for Efficient Dye Separation and Recovery

Trimethylamine N-Oxide-Derived Zwitterionic Polyamide Thin-Film Composite Nanofiltration Membranes with Enhanced Anti-Dye Deposition Ability for Efficient Dye Separation and Recovery

A novel multilayer thin-film membrane with high durability: preparation, characterization, performance investigation

The main aim of this research is the improvement of the performance in desalination of polyamide (PA) thin film composite nanofiltration membranes by modification of nanofibrous polyvinylidene fluoride as a support layer.

Fabrication of a graphene oxide-embedded separation bilayer composite nanofiltration membrane using a combination of layer-by-layer self-assembly and interfacial polymerization

Layer-by-layer (LbL) self-assembly combined with interfacial polymerization (IP) was utilized to prepare a separation bilayer composite nanofiltration (NF) membrane containing a polyelectrolyte (PE) sub-layer and a polyamide (PA) top-layer.

Novel Poly(piperazinamide)/poly(m-phenylene isophthalamide) composite nanofiltration membrane with polydopamine coated silica as an interlayer for the splendid performance

Nanofiltration (NF) is a potential separation technology in the field of water treatment. However, NF membrane generally has the bottleneck problems of low permeability and poor selective separation. Therefore, this study proposed to use polydopamine coated silica microspheres as the intermediate layer to modify the poly(m-phenylene isophthalamide) (PMIA) substrate, then to prepare poly(piperazinamide) composite NF membrane via interfacial polymerization technique. Because both dopamine and silica contain a large number of hydroxyl groups, which can limit the diffusion of aqueous monomers to the water/oil boundary due to the hydrogen bonding force. The obtained NF membrane presented a nano-tubular Turing structure. As a result, the membrane exhibited extremely high permeability with the pure water flux of 31.37 ± 1.06 LMH/bar, and the corresponding rejection to Na2SO4 could reach to 97.0%, which was three times that of traditional polyamide NF membrane. Moreover, the performance of one-valent/bivalent salt was excellent. The composite nanofiltration membrane made of polydopamine coated silica as the intermediate layer provides a potential strategy to construct polyamide membrane with improved permeation and selectivity, which will be beneficial to save energy consumption during the actual application.