High-performance Nanofiltration Research Articles

Facilely prepare ultra-high molecular weight polypropylene loose nanofiltration membrane for efficient dye/salt separation

The simple strategies and processes for preparing nanofiltration (NF) membranes with well-pore channels and high separation efficiency have received growing attention in academia. Herein, ultra-high molecular weight polypropylene (UHMWPP) has been successfully fabricated into high-performance loose NF membranes through thermally induced phase separation (TIPS). The results showed that the as-prepared UHMWPP loose NF membrane has a good water permeance (17.7 L m−2 h−1 bar−1), a high RB rejection (99 %), and a low inorganic salt retention rate (NaCl: 1.9 %), which makes the loose NF membrane a potential choice for dye/salt separation. In addition, the membrane also has good antifouling properties, acid and alkaline resistance, and long-term stability. Thus, this work offers a viable and pragmatic technical approach for addressing high-salt printing and dyeing wastewater, with broad prospects for application and practical value.

MXene Film as an Interlayer for Thin-Film Composite Membranes with High-Performance Nanofiltration

MXene Film as an Interlayer for Thin-Film Composite Membranes with High-Performance Nanofiltration

How to understand the effect of relative humidity on the morphology and performance of polypiperazine-amide NF membrane during heat curing process

Recent studies have shown that the temperature and time of the heat curing process have important effects on the nanofiltration (NF) membrane structure and properties. However, the mechanism of the relative humidity (RH), as one of the important factors in the heat curing of NF membranes, is still unclear. To analyze the specific effect of RH, we compared the heat curing results of the NF polyamide (PA) membranes fabricated with different monomer concentrations at various RH. The nanofiltration performance of the membranes appeared to be non-uniform when the RH was in the range of 40 %–60 %. Within the appropriate RH range, the rejection of Na2SO4 was preserved at about 98.5 % for the manufactured NF membranes. At high concentrations, the increasing RH created a discontinuous condensate layer on the PA layer surface, which affected the morphology and physicochemical properties of the NF membrane causing a doubling of pure water permeability (PWP) to 8.33 L m−2 h−1·bar−1. At low concentrations, the PA layer was not significantly changed with the increase of RH, but the evaporation of water from the smaller capillary pores in its PES substrate was slowed down, which reduced the capillary stress on the substrate and prevented the collapse of the substrate pore size, resulting in a nearly 20 times increase in its PWP to 39.7 L m−2 h−1·bar−1. This work reveals the effect of RH during heat curing and gives significant guidance to the design and synthesis of high-performance NF membranes.

Construction of TiO2-ZrO2 composite nanofiltration membranes for efficient selective separation of dyes and salts

The ceramic nanofiltration (NF) membrane exhibits excellent potential for textile wastewater treatment due to its efficient selective separation of dyes and salts. In this study, a high-performance TiO2-ZrO2 composite nanofiltration membrane was fabricated via a sol–gel method. Stable sols with an average particle size of approximately 2 nm were obtained. The addition of TiO2 effectively inhibits the phase transformation of ZrO2 during heat treatment, thus improving the integrity and ensuring separation accuracy of the membrane. Moreover, an optimal balance between membrane integrity and thickness was achieved, promoting efficient selectivity towards dyes and salts. The optimized NF membrane exhibited a MWCO of 1 kDa, a membrane thickness of 100 nm, and pure water permeance of 44 L∙m−2∙h−1∙bar−1. Additionally, the NF membrane demonstrated exceptional performance in dye/salt separation as evidenced by rejection rates exceeding 97.71% for Reactive Blue 19 while maintaining rejections below 5% for NaCl/Na2SO4 solutions. A stable permeance of 21.65 L∙m−2∙h−1∙bar−1 was achieved during the separation process. In conclusion, this study presents a high-performance ceramic NF membrane which exhibits significant potential for treating dye/salt containing wastewater.

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.

Asymmetrically charged polyamide nanofilm of intrinsic microporosity containing quaternary ammonium groups for heavy metal removal

High-performance nanofiltration (NF) is a highly hopeful approach for removing heavy metals from water, which can effectively solve the hazards of heavy metals to the public health and environment security. In this study, a polyamide (PA) nanofilm of intrinsic microporosity was fabricated through interfacial polymerization of the novel spirocyclic diamine monomer (SBI) with trimesoyl chloride (TMC). The PA nanofilm demonstrated high microporosity due to the porous structure formed by the covalent cross-linking of SBI with TMC and the stacking of the SBI monomers due to its rigidly-contorted structure. Consequently, its free volume was high with the water permeance of 19.3 L m−2 h−1·bar−1. Meanwhile, the PA nanofilm exhibited asymmetrical charges on both sides with a positively charged bottom and a negatively charged top. The quaternary ammonium moieties in SBI produced positively charged nanochannels in the PA nanofilm, reinforcing the Donnan exclusion against multivalent cations. The proposed SBI-TMC membrane was able to effectively remove heavy metals from water, with rejections of Cu2+, Ni2+, Zn2+, and Pb2+ at 93.3%, 93.0%, 91.8%, and 88.3%, respectively. This study confirmed that the fit-for-purpose design of monomer with rigidly-contorted structure is a feasible approach to fabricate NF membrane with enhanced separation performance.

Construction of a high-performance hollow fiber composite NF membrane via the simultaneous modification of substrate and selective layer

Hollow fiber composite (HFC) nanofiltration (NF) membrane demonstrates significant commercial potential profiting from its self-supporting characteristic, high packing density and strong fouling resistance. In this work, a high-performance HFC NF membrane was successfully developed through simultaneous modification of the substrate via alkaline hydrolysis and incorporation of iopamidol (IPD) into the selective layer. Alkaline hydrolysis enhanced the hydrophilicity of the polyacrylonitrile (PAN) substrate by converting –CN groups into –COOH, thereby sharply improving the success rate of HFC NF membrane fabrication. The addition of IPD into piperazine (PIP) solution effectively increased the water permeability of the HFC NF membrane without compromising its salt rejection. Specifically, the optimized membrane sample denoted as NF-0.15P + 0.5I with 0.5 w/v% IPD added demonstrated a 44 % increase in PWP from 21.8 L·m−2·h−1·bar−1 to 31.5 L·m−2·h−1·bar−1, while maintaining a Na2SO4 rejection over 96.8 %. This improvement can be attributed to the decreased selective layer thickness and reduced MWCO. Furthermore, the membrane exhibited exceptional dye/salt separation performance. This work represents a novel approach leading to the development of a HFC NF membrane suitable for dye/salt separation.

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.

Water recovery from the high salinity brine: Effect of the interlayer structure in the polyamide nanofiltration membrane

Water recovery by nanofiltration (NF) from the high salinity brine is emerging as a promising technology to alleviate the water shortage. Thin film composite membranes with polyamide (PA) selective layer are the mainstream in the field of NF. Nevertheless, the trade-off between permeance and retention as well as the structural stability of the mainstream PA membrane still restrict their widespread application. Herein, a novel interlayered thin-film nanocomposite (TFNi) nanofiltration membrane was fabricated based on the interfacial polymerization. The PDA@MXene hybrid was employed as the interlayer to modulate the adsorption and diffusion process of amine monomers, giving rise to the formation of thin and rough PA selective layer, which could accelerate the transport of water molecules. Moreover, PM-TFNi membrane demonstrated higher crosslinking degree and more negatively charged surface, significantly benefiting the repulsion of inorganic salt ions. In this context, PM-TFNi membrane rendered a competitive permselectivity with the water flux of 18.3 L m−2 h−1 bar−1 and the Na2SO4 rejection of 98.0%. In addition, PM-TFNi membrane exhibited distinguished long-term stability and pH resistance. Overall, this work would provide a paradigm shift in designing high-performance and robust NF membrane for the water treatment.

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.

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.

C3N4-interlayer-mediated interfacial polymerization of homopolymer nanofiltration membranes for efficient water purification

Interlayered thin film composite (TFNi) membranes have been shown to achieve high-quality polyamide (PA) skin layers with enhanced permeability and selectivity. Herein, we demonstrate the construction of a hydrophilic interlayer by polymeric graphitic carbon nitride (g-C3N4) for optimizing the interfacial polymerization of the nanofiltration membrane. Due to the effective enrichment and the slowed diffuse rate of amine monomer solutions, g-C3N4 modification decreases the thickness of the PA skin layer and increases the electronegativity of membranes. The best TFNi membrane exhibits a high water permeance of 31.82 L m−2 h−1 bar−1, nearly twice as high as that of the membrane without g-C3N4 interlayer, while maintaining a comparably Na2SO4 rejection efficiency. The stronger hydrophilicity and more negatively charged surface of the TFNi membrane effectively retarded membrane fouling, contributing to the high-efficiency removal of harmful drugs from actual surface water, with more than two times higher water flux that of commercialized NF270 membrane. This work provides a facile strategy to synthesize TFNi membranes with great application potential for high-performance nanofiltration.

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.