High-performance Nanofiltration Membranes Research Articles

Fabrication of Loose Nanofiltration Membrane by Crosslinking TEMPO-Oxidized Cellulose Nanofibers for Effective Dye/Salt Separation.

Dye/salt separation has gained increasing attention in recent years, prompting the quest to find cost-effective and environmentally friendly raw materials for synthesizing high performance nanofiltration (NF) membrane for effective dye/salt separation. Herein, a high-performance loose-structured NF membrane was fabricated via a simple vacuum filtration method using a green nanomaterial, 2,2,6,6-tetramethylpiperidine-1-oxide radical (TEMPO)-oxidized cellulose nanofiber (TOCNF), by sequentially filtrating larger-sized and finer-sized TOCNFs on a microporous substrate, followed by crosslinking with trimesoyl chloride. The resulting TCM membrane possessed a separating layer composed entirely of pure TOCNF, eliminating the need for other polymer or nanomaterial additives. TCM membranes exhibit high performance and effective dye/salt selectivity. Scanning Electron Microscope (SEM) analysis shows that the TCM membrane with the Fine-TOCNF layer has a tight layered structure. Further characterizations via Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) confirmed the presence of functional groups and chemical bonds of the crosslinked membrane. Notably, the optimized TCM-5 membrane exhibits a rejection rate of over 99% for various dyes (Congo red and orange yellow) and 14.2% for NaCl, showcasing a potential candidate for efficient dye wastewater treatment.

Two birds with one stone: By-product HCl consumption and in-situ template formation for high-performance nanofiltration membranes fabrication

Nanofiltration (NF) membrane with good permselectivity is highly desired. However, it often suffers from permeability-selectivity trade-off in practical applications. To overcome this challenge, a novel in-situ template strategy was proposed for the preparation of high-performance thin film nanocomposite (TFN) NF membrane by adding AgNO3 in the aqueous solution. The AgCl nanoparticles can be in-situ incorporated into the polyamide film due to the by-product of HCl from the interfacial polymerization and AgNO3 at the oil/water interface. Besides, water transportation channels can be further constructed in the polyamide film via removal the AgCl template using ammonia as post-treatment solution. The optimized NF-3 membrane with low water transportation resistance shows a two-fold permeance as well as equal salt rejection compared with the controlled NF-1 membrane, indicating that the “trade-off” effect is effectively inhibited. Consequently, the in-situ template strategy provides a new sight for the preparation of high-performance NF membrane.

Constructing high-performance nanofiltration membranes using nanofiber supports: Effects of structural stability and polyvinyl alcohol interlayers

Nanofiber supports are promising candidates for constructing high-performance nanofiltration (NF) membranes due to their unique interconnected pores and high porosity. Conventional nanofiber supports usually possess excessive surface roughness and low structural stabilities, influencing the formation of polyamide separation layers. However, research on the effects of nanofiber support properties on the NF membrane performances is relatively few. In this study, we systematically evaluated the effects of structural properties of the nanofiber supports on the performances of the fabricated thin-film nanofiber composite (TFNC) NF membranes. The polyimide (PI) support with heat-pressing post-treatments owns a smooth surface and high structural stability due to the welding and compaction of the PI nanofibers. This promoted the formation of a polyamide separation layer with high smoothness and low fouling tendencies. Consequently, the mechanical strength and long-term operation stability of the TFNC-PI NF membrane were much stronger than that of the membranes with polyacrylonitrile (PAN) and PVDF nanofiber supports. Membrane performance analyses illustrated that the TFNC NF membranes possess notable higher water permeance while slight lower salt rejection than the commercial NF membrane. Compared to TFNC-PAN NF membranes (18∼20 L m-2h−1 bar−1), the water permeance of the structurally stable TFNC-PI NF membrane was relatively low (15–16 L m-2h−1 bar−1) due to its smaller surface filtration area and membrane pore size. Further attempts illustrated that constructing interlayers with 2 wt% polyvinyl alcohol (PVA) coating solutions resulted in the formation of clear and regular Turing structures in the polyamide surface layer. It notably enhanced the water permeance of the membrane by ∼30 % without compromising the salt rejection capability of the membrane. This study provides fundamental insights into the effects of nanofiber support properties on NF performance and feasible pathways to construct high-performance TFNC NF membranes.

Advances in High-Performance Nanofiltration Membranes Facilitated by Two-Dimensional Materials

Nanofiltration membranes (NF) have been widely used in the field of water treatment because of their advantages of high separation precision, easy operation, and no phase change. Conventional NF membranes, ensnared by the “trade-off” effect, grapple with the challenge of achieving breakthroughs in both separation efficacy and stability. Recent advancements in research have unveiled the potential of nanoscale porous two-dimensional (2D) materials, characterized by their atomic thinness and superlative mechanical strength. These materials, crafted into nanofiltration membranes as thin as a single atom, boast minimal transport resistance and maximal permeation flux, thereby facilitating the highly discerning transport of water, and are heralded as the quintessential materials for fabricating ultra-thin membranes. This comprehensive review delves into the latest advancements in the research on 2D material NF membranes. A range of performance aspects related to 2D-material-modified NF membranes, including water flux, permeability, pollutant retention rates, and anti-pollution performance, were evaluated, and this review covers the impact of and major approaches to optimizing membrane performance in recent years, providing valuable insights into potential future developments in NF membranes.

The improvement of nanofiltration membrane performance with lignin Cu complex as interlayer

Nanofiltration (NF) membranes are instrumental in separating small molecular organics and salts, finding widespread application in industrials such as food, pharmaceuticals, and dye printing for product purification and wastewater treatment. However, the performance of these membranes is often restricted by the inherent “trade-off” effect between selectivity and permeability. In this study, a copper- demethylated lignin (Cu-DL) interlayer between the substrate and the selective layer was fabricated, aimed at augmenting the NF membrane's efficiency. This enhancement primarily results from Cu2+ coordination adsorption with piperazine (PIP), serving to regulate the diffusion and optimize the structure of the selective layer. Concurrently, the interlayer prevents the infiltration of the selective layer to reduce the mass transfer resistance. Compared to conventional NF membranes, the NF membrane based on the Cu-DL interlayer, exhibited a marked increase in permeability from 6.2 L m-2h-1bar-1 to 12.9 L m-2h-1bar-1, while essentially maintaining its retention capabilities for Na2SO4 solutions. Additionally, this membrane exhibits the excellent separation of salts and dyes under various concentrations. This work can provide a solution for the fabrication of high-performance NF membranes and new ideas for the utilization of biomass.

Nanofiltration membrane functionalized with CuxP nanoparticles: A promising approach for enhanced pesticide removal and long-term stability

The present study focuses on developing a high-performance nanofiltration (NF) membrane based on polyethersulfone (PES), incorporating green furosemide functionalized CuxP nanoparticles (NPs). This research aims to improve the membrane properties and enhance its ability to reject diazinon pesticide. The PES NF membrane underwent activation with CuxP, followed by varying concentrations (0, 0.1, 0.5, and 1.0 wt%) of the aforementioned NPs. Characterization of the NF membranes was achieved by using atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), zeta potential measurements, Brunauer-Emmett-Teller (BET) analydsis and tensile strength evaluation. Additionally, the membranes were subjected to investigations pertaining to mean pore radius, porosity, surface hydrophilicity, antifouling properties, chemical oxygen demand (COD), NO3−, and turbidity removal. Also, membrane rejection with and without chlorine treatment over 10 days in different pH levels (1–13), pure water flux (PWF), and flux recovery ratio (FRR) in long-term performance in dead-end and cross-flow setup were investigated.Among the fabricated membranes, the 0.1 wt% CuxP membrane exhibited noteworthy performance. It demonstrated a PWF of 29.86 kg/m2h, approximately 2.58 times higher than the bare membrane. Furthermore, the optimal membrane achieved FRR of 93.27%, representing a 1.60-fold improvement over the bare membrane. Importantly, the optimally modified membrane displayed the highest permeability and surface hydrophilicity, effectively reducing irreversible fouling while maintaining a high pesticide rejection rate of 98.72%. The efficiency of the CuxP membranes in agricultural wastewater filtration was also evaluated. The results demonstrated that these membranes yielded a high normalized flux and exhibited impressive removal rates, including 98.56% for COD, 97% for turbidity, and 86.02% for nitrate ions (NO3−). Overall, the developed CuxP membranes showcased outstanding separation performance, remarkable antifouling properties, and significant potential for application in agricultural wastewater treatment facilities.

Bioinspired cell membrane-based nanofiltration membranes with hierarchical pore channels for fast molecular separation

Owing to intrinsic perm-selectivity, cell membranes have attracted considerable attention in the field of biomimetic membranes. Herein, largest possible cell membranes of E.coli were prepared and then used as two-dimensional (2D) materials to fabricate high-performance nanofiltration (NF) membranes. The structure parameters of the selective layer of the E.coli-NF membrane could be finely tailored through the loading mass of cell membranes and the applied pressure during vacuum filtration. The E.coli-NF membrane exhibited a high rejection towards dyes (98.5%, brilliant blue R), antibiotics (91.1%, erythromycin), and divalent ions (64.8%, sodium sulfate). The membrane effective pore size was found to be significantly smaller than the interlayer spacing because of the small intrinsic nanochannels inside the E.coli cell membranes, which is distinct from GO and MXene-based 2D membranes. Moreover, the membrane water permeance was 52.6 L m−2 h−1 bar−1, higher than that of most of the reported 2D materials-based NF membranes. The E.coli-NF membrane exhibited the typical separation behavior of the negatively charged NF membranes governed by Donnan effect and size exclusion. This work gives some insights into the fabrication of the selective membranes using cell membranes as 2D materials with intrinsic nanochannels and fruitful choices in nature.

Polyamide nanofiltration membranes mediated by mesoporous silica nanosheet interlayers display substantial desalination performance enhancement

Recently, thin-film nanocomposite membranes with interlayered structures (TFNi) have demonstrated great promise for breaking the permeance-selectivity trade-off in nanofiltration (NF). Here, we first report the polyamide (PA) nanofiltration membranes mediated by mesoporous silica nanosheet (MSNS) interlayers. According to the characterizations and chemical analysis, it suggested that the inclusion of MSNS greatly affected the PA membrane surface topography and chemical structure, leading to an enhancement in surface roughness, hydrophilicity, and negative charge and a reduction in crosslinking degree and thickness of the PA layer. Ultimately, the fabricated optimal membrane displayed a favorable combination of high water permeance of 22.5 L m−2 h−1 bar−1 (2.5 times higher than pristine PA) and satisfactory Na2SO4 rejection of 97.8 %, superior to most of the TFNi membranes reported so far when compared by NaCl/Na2SO4 permeation selectivity versus water permeance. Additionally, the MSNS aided design endowed the TFNi membranes with drastically improved antifouling property and high operational stability. Also, the structural advantages of MSNS were highlighted by conducting a control experiment with zero-dimensional (0D) silica nanoparticles. This work is expected to stimulate the use of silica-based nanomaterials for preparing high-performance NF membranes for efficient desalination.

Enhanced performance polyamide membrane by introducing high-porosity SOD/GO composite interlayer to tailor the interfacial polymerization process

Controllable preparation of high-performance polyamide nanofiltration (NF) membranes that can be used in various applications such as seawater desalination and wastewater treatment is very promising. In this work, a high-performance polyamide NF membrane was designed using high-porosity hydroxy sodalite/graphene oxide (SOD/GO) composite interlayer to slow down the diffusion of amine monomer and control the interfacial polymerization (IP) process. The unique tortuous effect and hydrogen bonds with amine monomers caused by the dense interlayer significantly inhibit the diffusion of amine monomers (reduction of 50 % in diffusion rate), thereby resulting in the controllable slow IP process. The slowing IP process facilitates the formation of thinner dense polyamide (PA) layer with stripe morphology and narrow pore size. Consequently, the optimal polyamide membrane with composite interlayer possesses a superior water permeability of 22.05 L m-2h−1⋅bar−1, nearly 2.5 fold that of the controlled one, while retaining an excellent rejection of Na2SO4 (97.25 ± 0.81 %). Moreover, the polyamide membrane depicts outstanding antifouling propensity (flux-recovery ratio (FRR) = 82 %), long-term stability (80 h) and pressure resistance (9 bar). This work provides a novel strategy for controllable construction of high-performance NF membrane and deepens the slights into the interlayer influences IP process.

Low temperature regulated reverse interfacial polymerization for fabricating thin film composite membranes based on nanofibrous substrates

In this study, a novel thin film nanofibrous composite (TFNC) nanofiltration (NF) membranes comprised of polyacrylonitrile (PAN) nanofibrous supporting layer and polyamide (PA) compact separating layer was constructed by low-temperature-controlled reverse interfacial polymerization (LTIP-R) at − 5 °C. The strategy for lowering the temperature of organic phase solution played a crucial role in forming a dense and thin PA layer on the PAN nanofibrous substrate with submicron pores. The results revealed that the reduced evaporation rate of organic phase at low temperature was contributed to maintaining a complete and uniform interface for the following reverse IP process, effectively overcoming shortcomings of surface incompleteness and easy infiltration of PA barrier layer. Owing to the reduced thickness and the enhanced wholeness of the PA separating layer via LTIP-R, the optimized TFNC membranes exhibited NF performance with great rejection of divalent salt ions (98.2%) and an improved permeation (13.3 L‧m−2‧h−1‧bar−1). This work would provide an efficient and facile method to fabricate high performance NF membranes for practical applications.

Amino acid-bonded Ti3C2Tx MXene nanofiltration membranes with superior antifouling property for enhanced water purification

MXene nanosheets have been identified as promising building blocks for high-performance nanofiltration (NF) membranes in water purification. Herein, we report a series of amino acid-bonded Ti3C2Tx MXene membranes with enhanced NF performance and antifouling properties via glycine (Gly), l-glutamic acid (L-Glu), l-lysine (L-Lys) or l-cysteine (L-Cys) modification. The physicochemical properties, separation performances and anti-fouling behaviors of the pure Ti3C2Tx MXene membrane, Gly-, L-Glu-, L-Lys- and L-Cys-bonded Ti3C2Tx MXene membranes were comparatively investigated. The stable Ti–N bonds were found between the amino acids and the MXene nanosheets and different amino acids lead to different properties of the corresponding membranes. While maintaining ultra-high rejections to various organic dyes, all the amino acid functionalized membranes exhibited enhanced water permeability (7.17–13.11 L·m−2·h−1·bar−1) compared with that of the pure MXene membrane. Importantly, the Gly-bonded membrane showed the optimal separation performance with high salt rejections of 86.28%, 81.36%, 72.88% and 66.82% to MgSO4, MgCl2, Na2SO4 and NaCl, respectively, and the membrane also exhibited superior anti-fouling property with a flux recovery rate of 80.59% to bovine serum albumin (BSA). The separation mechanism was further revealed which may offer a simple yet efficient way for enhancing 2D MXene-based NF membranes.

Phytic acid and ferric chloride compound additives-regulated interfacial polymerization for high-performance nanofiltration membrane

To balance the permeability-selectivity trade-off effect of the polyamide nanofiltration membrane, interfacial polymerization regulation strategy is widely used to optimize the physicochemical structure of the polyamide film. In the present work, the compound additives of phytic acid and ferric chloride were added into the aqueous phase to regulate the interfacial polymerization process. On the one hand, a lot of piperazine monomers will be adsorbed around the phytic acid molecules due to the electrostatic interaction between phosphoric acid groups and amino groups. Meanwhile, the phytic acid molecules and ferric ions can form a complex in the piperazine solution, which results in a low diffusion rate of the other piperazine monomers without adsorbed on the phytic acid and ferric chloride complex due to steric hindrance. The synergistic effect of electrostatic interaction and steric hindrance leads to the optimized nanofiltration membrane with a thinner and looser polyamide structure. The best-performing nanofiltration membrane exhibits an approximately four-fold water permeance (28.4 L m−2 h−1 bar−1) compared with the controlled M0 nanofiltration membrane (6.5 L m−2 h−1 bar−1) without obviously sacrificing the Na2SO4 rejection (96.9 %). This simple interfacial polymerization regulation strategy provides a novel insight for the preparation of high-performance NF membrane.

Polyurea nanofiltration membranes with extreme-pH stability and high separation performance

Development of high-performance nanofiltration membranes with extreme-pH stability is an urgent need for treatment of wastewater from metallurgical and paper industries. In this study, we design a kind of oil phase monomer toluene diisocyanate (TDI) and the aqueous phase monomer polyethyleneimine (PEI) to prepare polyurea nanofiltration membranes. The special bonding type and dense crosslinking structure of polyurea were used to resist the attack of extreme pH conditions. The support-free interface polymerization was employed to minimize the membrane thickness. The TDI-PEI10000 composite membranes achieved rejection of 97.5% for MgCl2, with a corresponding pure water permeance of 20.0 L m-2 h-1 bar-1. After exposure to H2SO4 solution with pH=1 for 440 h or NaOH solution with pH=13 for 200 h, the MgCl2 rejection remained above 90%. Our study provides a facile approach to constructing extreme pH-stable separation membranes.

UiO-66-(OH)2-mediated transition layer for ultra-thin homogeneous defect-free polyamide membrane

The synthesis of ultra-thin, uniform and continuous polyamide (PA) membranes is a crucial prerequisite for enhancing their desalination performance. Research has indicated that effectively slowing down the interfacial polymerization (IP) reaction and promoting the interface stability are key strategies for achieving ultra-thin, uniformly nano-structured membranes with excellent performance. Herein, we have demonstrated the successful design of a continuous and uniform PA membrane, ranging from 10 to 20 nm, by utilizing the UiO-66-(OH)2 n-hexane dispersion as a transition layer to regulate IP reaction and enable efficient water-salt separation. The results showed that the presence of the transition layer facilitated a bidirectional diffusion-contact reaction between the two monomers, resulting in improved interface stability and alleviating the occurrence of severe IP that may lead to heterogeneous membrane structures. As a result, the PA active layers formed through this approach exhibited superior thinness and uniformity compared to those produced via traditional IP methods. Moreover, the transition layer enabled uniform pre-polymerization of UiO-66-(OH)2 at the reaction interface by pre-exposing it to down-diffusing acyl chloride monomers. This ensured the continuity of membrane structure while creating additional free volume within the membrane. This work presented a scalable method for manufacturing ultra-thin, defect-free, homogeneous, and high-performance nanofiltration membranes.

Ionic liquid-functionalized antibiofouling nanofiltration membranes

Nanofiltration membranes hold great potential for water treatment applications, but are susceptible to fouling issues. In this study, we demonstrate the fabrication of NF membranes with high permeability, high rejection, antibiofouling and scaling resistance. The membrane was prepared through interfacial polymerization by doping the aqueous phase with 1-aminoethyl-3-methylimidazolium tetrafluoroborate ionic liquid. The TFC-0.2 membrane exhibited a more open nanoporous structure, resulting in an increased permeability from 5 ± 0.5 L·m−2·h−1·bar−1 (LMH/Bar) to 11.1 ± 0.4 LMH/Bar, while maintaining a comparable salt rejection performance to the original TFC membrane. Additionally, the TFC-0.2 membrane demonstrated excellent retention performance, with a removal efficiency exceeding 90 % for emerging contaminants such as antibiotics and PFOA. Notably, the TFC-0.2 membrane exhibited significant differences in the rejection of Na2SO4 and CaCl2, indicating its strong resistance to gypsum fouling. Furthermore, it is worth highlighting that the TFC-0.2 membrane displayed remarkable antibiofouling performance due to the bactericidal properties of AMIT. This capability allowed for the sterilization of bacteria at the early stage of attachment to the membrane surface, effectively mitigating biofouling. The findings of this study offer a simple yet effective strategy for fabricating high-performance nanofiltration membranes with exceptional antifouling properties.

The metal organic framework of UiO-66-NH2 reinforced nanofiltration membrane for highly efficient ion sieving

Metal organic framework (MOF) with fine pore structures, ultra-high porosity and large specific surface area can provide more water transport channels while achieving precise sieving of different sizes of ions, which is a promising material for high efficiency desalination. However, particle agglomeration, interface incompatibilities and interface defects severely restrict the performance of MOF-based membranes. It is still a challenge to construct MOF-based desalination membranes with both high water permeability and high ion sieving. Herein, the UiO-66-NH2 based nanofiltration membrane was fabricated by in-situ growth of UiO-66-NH2 on Nylon membrane and composed with polyamide (PA) layer by interfacial polymerization (IP). With 12 h solvothermal reaction, the UiO-66-NH2 nanoparticles are found uniformly loaded on the Nylon substrate. Therefore, the water molecule transport channels provided by UiO-66-NH2 nanoparticles reduce the transport resistance, which can improve the water permeability. More importantly, UiO-66-NH2 nanoparticles are found to be involved in the IP process, which can reduce the interfacial defects and thus enhance the bonding force between the PA layer and base film. The synergistic effect of the UiO-66-NH2 and PA layer improves the nanofiltration performance of the membrane with rejection rate of 92.97% for Na2SO4 and the pure water permeance (PWP) of 11.55 L m−2 h−1 bar−1. The N-UN12 @PA membrane also has excellent antifouling performance (flux recovery ratio (FRR) of 95.86%, reversible fouling ratio (Rr) of 33.93%, irreversible fouling ratio (Rir) of 4.14%). Unlike the mixed-matrix membrane (MMM) and polycrystalline MOF membrane, this strategy provides a promising method to prepare high-performance nanofiltration membrane for desalination.

Polyamide nanofiltration membrane fabricated via a metal-chelate strategy for high-flux desalination

Nanofiltration (NF) technology, utilizing polyamide (PA) membranes fabricated through interfacial polymerization (IP), has found extensive application in desalination processes. The pursuit of enhancing water permeance while maintaining high rejection rates of NF membranes has garnered substantial research attention. This study proposed a metal-chelate strategy by incorporating calcium chloride (CaCl2) as an aqueous additive during the IP process and employing EDTA-4Na for post-treatment. In the presence of Ca2+, the EDTA-4Na-soaked membrane achieved suitable swelling to better regulate membrane pores, which benefited water flux enhancement and avoided severe structural defects. Meanwhile, the modified membrane also showed a more hydrophilic and negatively charged surface, leading to a significant performance in removing Na2SO4. As a result, the optimized membrane exhibited a water flux of 24.6 L m−2 h−1 bar−1, nearly 3 folds that of the initial PA membrane, while maintaining a satisfactory Na2SO4 rejection (97.2 %). Moreover, the obtained membrane showed good operation stability and anti-fouling properties during long-term use. This work proves that the metal-chelate strategy can be an efficient modification method and inspires the fabrication of high-performance NF membranes with coupling processing.

Enhancing the removal of organic micropollutants by nanofiltration membrane with Fe (III)–tannic acid interlayer: Mechanisms and environmental implications

Nanofiltration technology has been applied in a variety of water treatment scenarios. However, conventional thin-film composite (TFC) membranes fail to remove emerging organic micropollutants (OMPs) efficiently. Here we applied thin-film nanocomposite membrane with an interlayer (TFNi) of Fe (III)-tannic acid to remove various types of OMPs, such as endocrine disrupting chemicals (EDCs), pharmaceutically active compounds (PhACs), and perfluoroalkyl substances (PFASs). Compared to the pristine TFC membrane, TFNi membrane exhibited crumpled morphology and its rejection layer was denser, better cross-linked and possessed smaller average pore size with narrower distribution. Significant enhancement in water-OMPs selectivity of PhACs and PFASs was observed. The mechanism lies in the effects of interlayer in improving the membrane permeance to water and meanwhile reducing the permeance to some OMPs by enhancing size exclusion effects. This work confirms the effectiveness of using TFNi membrane to simultaneously enhance the OMPs rejection and water permeance. The unraveled mechanism might inspire the future development of high-performance nanofiltration membranes targeting OMPs removal.

EMT-NH2 zeolite interlayer induces the formation of high-performance polyamide membrane

Conventional nanofiltration (NF) thin-film composite (TFC) membranes are strongly restricted by the trade-off between their water permeance and selectivity as well as the poor structural stability for desalination and wastewater treatment. Herein, we report an interlayer-based thin-film composite (i-TFC) NF membrane with high performance using amino-functionalized EMT zeolite (EMT-NH2) nanocrystals as the interlayer. By adjusting the distribution density of EMT-NH2 on the substrate, a thin and dense polyamide (PA) layer with heterogeneity multi-level morphology (nanosized nodules and nanoscale stripes) can be formed and regulated. The EMT-NH2 zeolite nanocrystals with numerous hydrophilic groups (hydroxy and amino groups) and internal cavities can provide an additional priority water channel, increase the amine monomer storage on the substrate, and slow down the diffusion of amine monomer, thereby leading to the construction of a dense PA layer with high performance. As a result, the i-TFC-15 membrane depicted a water permeability of 13.82 ± 0.47 L m-2h−1⋅bar−1 (2.5 times that of the controlled one), while maintaining an excellent retention ability for divalent salts (98.55% for Na2SO4, 98.42% for MgSO4 and 97.40% for MgCl2). Additionally, the rigid hydrophilic interlayer containing zeolite nanocrystals endowed the i-TFC-15 membrane with excellent pressure resistance (up to 2.4 MPa), long-term operating stability, and antifouling propensity (flux-recovery ratio, 90.1%). This work provides an approach for fabricating a novel high-performance NF membrane and deepens our understanding of the role of porous interlayer affecting the formation of the PA layer.

High-performance thin film composite nanofiltration membranes with MoS2 nanosheet interlayer

High-performance polyamide thin film composite (TFC) nanofiltration membranes have received great attention in recent years. Herein, we report the preparation of TFC nanofiltration membranes by interfacial polymerization using MoS2 nanosheets as the nanomaterial interlayer. The aqueous monomer and MoS2 nanosheets are distributed on the surface of microporous membrane substrates by a one-step method. The MoS2 interlayer improves the uniformity and smoothness of the microporous substrates, helping to form polyamide nanofilms at ultralow monomer concentration. Moreover, the hydrophilic and negatively-charged MoS2 nanosheets enhance the water permeability and negative charges of the nanofiltration membranes. The composite membranes show both high water permeance of 33.5 L m−2 h−1 bar−1 and Na2SO4 rejection of 97.5%, as well as significantly improved mono-/divalent anions selectivity and antifouling property. It is proved that the interfacial polymerization strategy assisted by the MoS2 interlayer is effective for preparing high-performance nanofiltration membranes.