Thin Film Composite Polyamide Research Articles

Metal-assisted multiple-crosslinked thin film composite hollow fiber membrane for highly efficient bioethanol purification

Polyamide (PA)-based thin film composite (TFC) membranes have been extensively applied in various membrane-based separations. However, research works for bioethanol purification are relatively limited due to insufficient hydrophilicity and chain packing density of the PA selective layer by conventional interfacial polymerization. In this work, a new TFC hollow fiber (HF) membrane is fabricated by metal-assisted multiple crosslinking strategy, that is, metal-coordinated crosslinking of the pristine PA layer and coordination complexation between metal ions and phytic acid (PhA) for advanced water/ethanol separation. By tuning coordination abilities of metal ions with PA and PhA and the cycle number of PhA/metal ion assembly, PA-based TFC HF membrane is perfected. Additionally, a joint experiment/simulation characterization is deployed to reveal the coordination abilities of various metal ions with the pristine PA and grafted PhA. Ultimately, the synergistic effect between PA layer and PhA-metal ion complexes (i.e., 1 + 1 > 2 effect) is embodied in the separation performance of water/ethanol separation. The resulting TFC-Fe3+-PhA membrane with the strongest PhA-metal ion coordination ability exhibits the best water/ethanol separation performance, i.e., the separation factor of 1703 (34 times higher than pristine PA TFC HF membrane) and total flux of 1705 g/m2 h. This metal-assisted multiple crosslinking strategy is therefore believed to shed important lights on the development of next-generation high-performance TFC membranes for bioethanol purification.

High performance polyamide TFC reverse osmosis membrane fabricated on co-deposition hydrophilic modified polyethylene substrate

The separation performance of polyamide (PA) thin film composite (TFC) membrane is critically influenced by the substrates. Numerical models and experimental studies suggest that substrates with high porosity comprising small pores can effectively improve membrane performance. Here we report that a commercial polyethylene (PE) micro-porous membrane with high porosity was chosen as substrate for fabricating PA TFC membrane. The PE substrate was modified by co-depositing the copolymers of gallic acid and γ-aminopropyltriethoxysilane to improve its bulk hydrophilicity. The porosity, pore size, morphology and chemical properties of the modified PE substrates were characterized. The resultant PA TFC-PE membrane had a favorable water permeance of 2.33 ± 0.06 L m−2 h−1 bar−1 as well as a high NaCl rejection of 99.0 ± 0.4 % because of the suitable porosity, pore size and hydrophilicity for interfacial polymerization reaction. Our work is expected to provide an efficient way for the modification of hydrophobic porous membrane for fabricating PA TFC membrane.

Tailored nanofiltration membranes with enhanced permeability and antifouling performance towards leachate treatment

The leachate generated from the sanitary landfill or incineration poses serious environmental threats and it's difficultly disposed due to its complexity containing high concentration of organic matters and inorganic salts etc. Membrane technology stands out as a potential solution for leachate because of its beneficial advantages. Nanofiltration (NF) can reject organic compounds and separate divalent ions from mixed salts, which alleviates fouling and increases separation efficiency and flux of reverse osmosis (RO) in the popular combined processes (MBR-NF/RO) applicable for leachates. However, NF is often subject to low water permeance and membrane fouling for traditional polyamide thin film composite (PA-TFC) membranes. This work develops a high-performance NF membrane by grafting bipyridinium derivative monomer (BBD), an alternative antibacterial by interfering with the bacterial metabolism and reproduction and a hydrophilic compound endowing membrane hydrophilicity, onto PA-TFC membranes through the esterification reaction toward the leachate treatment. Resultantly, the BBD-TFC membrane achieves a reasonably high pure water permeability of 31.6 ± 2.1 L m−2 h−1 bar−1, ∼ 4 times higher than that of the pristine polyamide membrane. Notably, the resultant membrane exhibits excellent antifouling and antibacterial properties in the treatment of the leachate benefiting from the more hydrophilic surface and negative potential on BBD-TFC. Meanwhile, high rejection ratio of divalent ions and organic matter (R > 95%) was also attained companying with high separation efficiency of divalent/monovalent ions. The current work may provide an effective strategy to design high performance NF membranes for the leachate treatment or other wastewater treatment.

Constructing highly rough skin layer of thin film (nano)composite polyamide membranes to enhance separation performance: A review

AbstractThe thin‐film (nano)composite (TFC or TFN) polyamide membrane prepared by interfacial polymerization method has a wide range of applications in water treatment. The preparation of TFC or TFN membrane with a highly wrinkled morphology in the selective layer can significantly improve the permeability of the membrane and is an effective way to break the “trade‐off” effect. However, the formation mechanism of highly rough skin layer and the membrane fouling performance associated with the rough structure have been underexplored. In this review, the formation mechanisms of crumpled membranes were summarized into four aspects: interfacial nanobubbles effect, template method, diffusion‐driven instability, and co‐solvent effects. On the basis of these mechanisms, researchers have explored different methods to construct membranes with highly rough structures. This article summarized these construction methods including introduction of additives, construction of functional interlayer, sacrificial template and some other strategies. The advantages and disadvantages of these fabrication methods and the separation performance comparison of the crumpled membrane and the original membrane were discussed in detail. Furthermore, the review analyzed the recent research status of the anti‐fouling performance of the pleated membrane, and finally put forward the research opinions on the future in fabricating highly roughness membranes.

Vacuum-Assisted Interfacial Polymerization Technique for Enhanced Pervaporation Separation Performance of Thin-Film Composite Membranes.

In this work, thin-film composite polyamide membranes were fabricated using triethylenetetramine (TETA) and trimesoyl chloride (TMC) following the vacuum-assisted interfacial polymerization (VAIP) method for the pervaporation (PV) dehydration of aqueous isopropanol (IPA) solution. The physical and chemical properties as well as separation performance of the TFCVAIP membranes were compared with the membrane prepared using the traditional interfacial polymerization (TIP) technique (TFCTIP). Characterization results showed that the TFCVAIP membrane had a higher crosslinking degree, higher surface roughness, and denser structure than the TFCTIP membrane. As a result, the TFCVAIP membrane exhibited a higher separation performance in 70 wt.% aqueous IPA solution at 25 °C with permeation flux of 1504 ± 169 g∙m−2∙h−1, water concentration in permeate of 99.26 ± 0.53 wt%, and separation factor of 314 (five times higher than TFCTIP). Moreover, the optimization of IP parameters, such as variation of TETA and TMC concentrations as well as polymerization time for the TFCVAIP membrane, was carried out. The optimum condition in fabricating the TFCVAIP membrane was 0.05 wt.% TETA, 0.1 wt% TMC, and 60 s polymerization time.

Dissecting the structure-compaction-performance relationship of thin-film composite polyamide membranes with different structure features

Thin film composite (TFC) polyamide (PA) membranes experience compaction at high pressure applications, resulting in the reduction in water permeability. However, the compaction mechanism is still unclear especially for different PA morphologies and substrate structures. In this work, we systematically studied the compaction of TFC PA membranes with different structures and morphologies. We first examined 2 main types of commercial reverse osmosis (RO) membranes: brackish water RO and seawater RO membranes. After that, we synthesised four types of TFC membranes with tailored PA and substrate structures to further understand the compaction behaviors. TFC membrane with a PA layer of low protuberances or nodules and dense substrate showed excellent resistance against high pressure (50 bar), with only a slight irreversible decrease of 2.1–3.5% in water permeability when retested at 5 bar. However, the PA layer of high protuberances experienced significant compaction even when it was supported by a similar dense substrate. The permeability of the TFC membrane decreased ∼10% as a result of the decrease in the effective area of the active layer. On the other hand, the TFC membrane with a PA layer of low protuberances formed atop a loose substrate showed a greater decrease (∼18.5%) in water permeability. The densified skin layer and collapsed macro-voids within the loose substrate resulted in a ∼40% decrease in the overall height of the PA layer and a 65% decline in substrate surface porosity, respectively, which are identified as the reasons for the reducing water permeability. Notably, the water-salt selectivity of this particular membrane was seriously deteriorated after compaction due to the presence of subtle defects in the PA layer caused by the drastic deformation of the loose substrate. This work deepens the understanding of the compaction behaviors of TFC PA membranes, providing a clear fundamental guidance on designing membranes applied at high operating pressures.

A method to quantify composition, purity, and cross-link density of the active polyamide layer in reverse osmosis composite membranes using 13C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy

A method for harvesting and purifying the thin polyamide (PA) active layer from thin-film composite (TFC) reverse osmosis (RO) membranes was developed, enabling quantitative nuclear magnetic resonance (NMR) measurements of the composition and cross-linking in the PA layer that can be directly related to membrane performance. Using our chemical separation process, we report on four trimesoyl chloride (TMC)/isophthaloyl chloride (IPC)/ m -phenylene diamine (MPD)-based TFC membranes in which the cross-link density was intentionally reduced by replacing trifunctional cross-linking TMC monomers with their linear IPC difunctional analog. While the NMR results show a two-fold decrease in cross-linking that causes a 30% increase in salt passage, the addition of the difunctional analog leads to increased polar amine groups that reduce water permeance due to tighter binding of water in the PA membrane. Our results demonstrate that 13 C cross polarization magic angle spinning (CPMAS) is a powerful method for quantitatively monitoring the purity, cross-linking, and chemical composition in PA membranes and will be an essential tool in ascertaining atomistic models of PA structure. • A method for purifying the polyamide layer from TFC RO membranes was developed. • 13 C CPMAS quantifies composition and crosslinking in harvested polyamide TFC RO films. • Crosslinking is controlled by IPC/TMC ratio. • With a two-fold decrease in crosslinking, a 30% increase in salt passage. • With a two-fold increase of amine content, a 30% decrease in water permeance.

Proteoliposome-Incorporated Seawater Reverse Osmosis Polyamide Membrane: Is the Aquaporin Water Channel Effect in Improving Membrane Performance Overestimated?

The water channel feature of the aquaporin (AQP) is considered to be the key in improving the permselectivity of AQP-based thin-film composite (TFC) polyamide (PA) membranes, yet much less attention has been paid to the physicochemical property changes of the PA layer induced by AQP-reconstituted proteoliposomes. This study systematically investigated the roles of proteoliposome constituents (liposome/detergent/AQP) in affecting the physicochemical properties and performance of the membranes. For the first time, we demonstrated that the constituents in the proteoliposome could facilitate the formation of a PA layer with enlarged protuberances and thinner crumples, resulting in a 79% increase in effective surface area and lowering of hydraulic resistance for filtration. These PA structural changes of the AQP-based membrane were found to contribute over 70% to the water permeability increase via comparing the separation performance of the membranes prepared with liposome, detergent, and proteoliposome, respectively, and one proteoliposome-ruptured membrane. The contribution from the AQP water channel feature was about 27% of water permeability increase in the current study, attributed to only ∼20% vesicle coverage in the PA matrix, and this contribution may be easily lost as a result of vesicle rupture during the real seawater reverse osmosis process. This study reveals that the changed morphology dominates the performance improvement of the AQP-based PA membrane and well explains why the actual AQP-based PA membranes cannot acquire the theoretical water/salt selectivity of a biomimetic AQP membrane, deepening our understanding of the AQP-based membranes.

Negatively charged nanofiltration membrane with high performance via the synergetic effect of benzidinedisulfonic acid and trimethylamine during interfacial polymerization

Negatively charged surface is preferred for thin film composite (TFC) nanofiltration (NF) membrane with excellent separation performance for divalent anions, and ultra-smooth surface is beneficial for antifouling in practical application. Herein a kind of high-flux sulfonated polyamide TFC NF membrane, termed as TFC-BDSA, was successfully fabricated via interfacial polymerization (IP) between the aqueous monomers, 2,2-benzidinedisulfonic acid (BDSA) mixed with piperazine (PIP), and the organic monomer, trimesoyl chloride (TMC), with triethylamine (TEA) as aqueous catalyst. The results proved that BDSA and TEA have synergetic effect on the performance of the fabricated NF membrane. BDSA enabled the formation of more negatively charged, more hydrophilic and much smoother surfaces, which greatly improved the separation performance and antifouling capability of the prepared TFC-BDSA membrane. TEA not only act as an acid receiver, but could form a complex salt with BDSA and thus help to manipulate the diffusion rate of BDSA and PIP as well as the interfacial polymerization process, which helps to form a more smooth, more hydrophilic, more negatively charged, as well as more antifouling and defect-free membrane skin layer. With 1.0 wt% BDSA in the aqueous monomer solution and at pH 11.2 which is adjusted by TEA, the resultant TFC-BDSA membrane displays an excellent water permeance of 122 L m−2h−1 MPa−1, which is more than twice the pristine baseline TFC membrane. Meanwhile, the resultant TFC-BDSA membrane achieved an extremely higher Na2SO4 rejection of 99.6 %, which is more than 2.0 % higher than that of the latter. Moreover, the flux recovery ratios were 101.1 % and 99.5 % (after two cycles of filtration - cleaning) for the TFC-BDSA membrane fouled with sodium alginate and humic acid, respectively, indicating its excellent antifouling performance. Furthermore, the TFC-BDSA membrane shows an excellent operation stability over a 120 h filtration process. In summary, this study provides a new approach to prepare high performance NF membranes for water treatment.

Nanofiltration Membranes Formed through Interfacial Polymerization Involving Cycloalkane Amine Monomer and Trimesoyl Chloride Showing Some Tolerance to Chlorine during Dye Desalination.

Wastewater effluents containing high concentrations of dyes are highly toxic to the environment and aquatic organisms. Recycle and reuse of both water and dye in textile industries can save energy and costs. Thus, new materials are being explored to fabricate highly efficient nanofiltration membranes for fulfilling industrial needs. In this work, three diamines, 1,4-cyclohexanediamine (CHD), ethylenediamine (EDA), and p-phenylenediamine (PPD), are reacted with TMC separately to fabricate a thin film composite polyamide membrane for dye desalination. Their chemical structures are different, with the difference located in the middle of two terminal amines. The surface morphology, roughness, and thickness of the polyamide layer are dependent on the reactivity of the diamines with TMC. EDA has a short linear alkane chain, which can easily react with TMC, forming a very dense selective layer. CHD has a cyclohexane ring, making it more sterically hindered than EDA. As such, CHD’s reaction with TMC is slower than EDA’s, leading to a thinner polyamide layer. PPD has a benzene ring, which should make it the most sterically hindered structure; however, its benzene ring has a pi-pi interaction with TMC that can facilitate a faster reaction between PPD and TMC, leading to a thicker polyamide layer. Among the TFC membranes, TFCCHD exhibited the highest separation efficiency (pure water flux = 192.13 ± 7.11 L∙m−2∙h−1, dye rejection = 99.92 ± 0.10%, and NaCl rejection = 15.46 ± 1.68% at 6 bar and 1000 ppm salt or 50 ppm of dye solution). After exposure at 12,000 ppm∙h of active chlorine, the flux of TFCCHD was enhanced with maintained high dye rejection. Therefore, the TFCCHD membrane has a potential application for dye desalination process.

Deciphering the Role of Amine Concentration on Polyamide Formation toward Enhanced RO Performance

Polyamide surface morphology and its underneath nanosized voids have crucial influence on the separation performance of thin film composite (TFC) polyamide reverse osmosis membranes. Although there have been numerous studies reporting the impact of amine monomer concentration on polyamide formation and membrane performance, the observations and interpretations in the existing literature remain controversial. In this study, we performed interfacial polymerization (IP) of polyamide films over a wide range of m-phenylenediamine (MPD) concentration (0.05–8.0 w/w %). For the first time, we demonstrate that the water permeance of the resultant TFC membranes is governed by the competing effects of (1) promoted polyamide film growth for forming thicker polyamide films and (2) improved nanofoaming effect that results in more extensive nanovoids at higher MPD concentrations. To dissect these competing mechanisms, we further adopted a free-interface IP strategy to suppress the nanofoaming effect. The corresponding polyamide nanofilms had negligible nanovoids and monotonously increased film thickness, leading to decreased water permeance at high MPD concentrations. In contrast, the conventional TFC membranes exhibited optimal water permeance at the intermediate MPD concentration of 2.0 w/w %, which results from the trade-off between improved nanovoid formation (which promotes higher permeance) and increased film growth (which limits permeance). On the other hand, the better film growth at greater MPD concentration was generally beneficial for achieving better membrane rejection. The current study unveils the fundamental chemistry–morphology–performance relationship of TFC polyamide membranes and provides important implications on their synthesis and environmental applications.

Effect of colder stream temperature control on energy utilization, flux, RSF, and membrane integrity in asymmetric temperature FO systems

Water and energy are key components to assess the feasibility of any water treatment technique. For industrial applications of forward osmosis (FO), energy optimization needs to be explored further. Asymmetric temperature conditions, having different feed solution (FS) and draw solution (DS) temperatures, are likely to occur in industrial FO applications and are least explored. Some standard practices are followed without any scientific evidence of their impact on the system performance and energy utilization, like maintaining the colder stream temperature instead of letting it reach a steady state with the hotter stream. This study compares water flux, reverse solute flux (RSF), and energy utilization when the colder stream temperature is maintained and not maintained. Thin film composite-poly amide (TFC-PA) and cellulose triacetate (CTA) membranes were used at laboratory-scale in 24 h batch experiments with 0.75 M NaCl as DS and DI water as FS. All possible configurations of membrane orientation (AL-DS and AL-FS) and streams heating and cooling strategies were studied. The module material was made up of plexi-glass with 4 cm thick plates and flexible tubing of PVC was used. Results revealed that under not maintained conditions, on average, the water flux increased by 9.1–17%, RSF increased by 13.8–27.3%, and energy consumption reduced by 75.8–67% with CTA and TFC membranes, respectively. Therefore, if the RSF is not the primary concern of the application, it is advantageous not to maintain the colder stream temperature. However, it is recommended that scientists verify and compare the efficiencies between maintained and not maintained temperatures under their specific experimental conditions.

Optimizing interfacial polymerization with UV-introduced photo-fries rearrangement for enhancing RO membrane performance

To conveniently and environmentally friendly improve the performance of polyamide thin film composite (PA-TFC) membrane, a novel method associated with UV was presented in this study. In the process of the interfacial polymerization (IP), the UV irradiation procedure was performed to initiate photo-Fries rearrangement of PA, optimizing the membrane properties (i.e. thickness, membrane charge, hydrophilicity), and enhancing the membrane performance (i.e. permeability, selectivity, and anti-fouling performance). In comparison with the virginal PA-TFC membrane (virgin-RO), the resulting membrane (UV-13) exhibited an increased water flux of 75.9 L/m2·h (LMH, increased by 15.5%), and NaCl rejection of 99.34% (increased by 0.87%). Especially, the selectivity of UV-13 was dramatically enhanced, which can be concluded from that the salt permeability coefficient of UV-13 (5.04 × 10-4 m/h) is only half of that of virgin-RO (10.21 × 10-4 m/h). Furthermore, a series of membranes were fabricated by changing MPD concentration, TMC concentration and IP duration, and the corresponding separation performance were enhanced more or less, which may demonstrate that UV irradiation has the potential to be widely applied for enhancing PA-TFC RO membrane performance. Furthermore, UV-13 presents enhanced antifouling performance in comparison of virgin-RO, according to the results of artificial pollution tests of bovine serum albumin (BSA) and lysozyme (LYZ). Theoretically, for the RO membranes synthesized via IP process with aromatic amine monomers and aromatic acyl chloride monomers, this method is able to effectively improve the membrane performance, and has enormous potential in industrialization.

Surface-engineered sulfonation of ion-selective nanofiltration membrane with robust scaling resistance for seawater desalination

Inorganic fouling is one of the most critical issues in the seawater desalination process; it significantly deteriorates the desalination performance of the current seawater reverse osmosis (SWRO) membranes. Conventional nanofiltration (NF) membranes, which act as the pretreatment medium, are unable to effectively fractionate the scaling ions, Ca 2+ and SO 4 2− , resulting in fouling transfer from SWRO to the NF membranes. To address this issue, a new class of nanofiltration membranes was proposed and designed by surface engineering a custom-made sulfonated polyamide thin-film composite. Specifically, a new functional monomer, 4-aminobenzenesulfonic acid (ABSA), was chemically grafted onto a membrane surface via carbodiimide crosslinking chemistry. Due to the intentional optimization of mean pore sizes and surface charges, the as-prepared NF membranes (named BM-ABSA) exhibited extremely low Ca 2+ rejections (6.1 ± 0.4%) and moderate SO 4 2− rejections (57.5 ± 0.1%), corresponding to a higher ion selectivity (9.5) toward seawater compared to that of the benchmark commercial NF270 membrane (1.5). More importantly, the replacement of carboxylate groups in the substrate membrane matrix with the sulfonate groups considerably lowered the probability of the Ca–COOH chelation effect, which, in turn, facilitated steady NF-pretreatment processes without significant fouling. The subsequent SWRO process, using the BM-ABSA membrane-pretreated permeate as the feed solution, also proceeded well over a short-term operation with limited gypsum fouling. Overall, this study highlighted the effective inhibition of scaling by sulfonated NF membranes in the pretreatment process, validating their potential application for robust and efficient seawater desalination. • ABSA was chemically grafted onto the surface of NF membrane through EDC/NHS coupling reaction. • BM-ABSA-5 membrane showed a high ion-ion selectivity toward Ca 2+ and SO 4 2− . • The anti-scaling mechanism of –SO 3 H groups was investigated by molecular dynamics simulation. • Gypsum scaling on NF membrane and RO membrane was both inhibited in the hybrid NF-RO process for seawater desalination.

Covalent Organic Framework-Mediated Thin-Film Composite Polyamide Membranes toward Precise Ion Sieving.

Covalent organic frameworks (COFs) have evinced a potential solution that promises for fast and efficient molecular separation due to the presence of orderly arranged pores and regulable pore apertures. Herein, the synthesized COF (TPB-DMTP-COF) with the pore aperture matching the pore size of the nanofiltration (NF) membrane was utilized to modulate the physicochemical characters of the polyamide (PA) membranes. It is demonstrated that COFs with superior polymer affinity and hydrophilicity not only circumvent the nonselective interfacial cavities but also improve the hydrophilicity of the resultant thin-film nanocomposite (TFN) membranes. Furthermore, the predeposited COF layer is able to slow down the diffusion rate toward the reaction boundary through hydrogen bonding, which is consistent with the results of molecular dynamic (MD) and dissipative particle dynamic (DPD) simulations. In this context, COF-modulated TFN membranes show a roughened and thickened surface with bubble-shaped structures in contrast to the nodular structure of original polyamide membranes. Combined with the introduced in-plane pores of COFs, the resultant TFN membranes display a significantly elevated water permeance of 35.7 L m2 h-1 bar-1, almost 4-fold that of unmodified polyamide membranes. Furthermore, the selectivity coefficient of Cl-/SO42- for COF-modulated TFN membranes achieves a high value of 84 mainly related to the enhanced charge density, far exceeding the traditional NF membranes. This work is considered to provide a guideline of exploring hydrophilic COFs as an interlayer for constructing highly permeable membranes with precise ion-sieving ability.

Thin Film Composite Polyamide (Tfc-Pa) Total Heat Exchange Membranes with Ultrahigh Sensible Heat Recovery and Co2 Barrier Properties

Thin Film Composite Polyamide (Tfc-Pa) Total Heat Exchange Membranes with Ultrahigh Sensible Heat Recovery and Co2 Barrier Properties

Thin Film Composite Polyamide (Tfc-Pa) Total Heat Exchange Membranes with Ultrahigh Sensible Heat Recovery and Co2 Barrier Properties

Thin Film Composite Polyamide (Tfc-Pa) Total Heat Exchange Membranes with Ultrahigh Sensible Heat Recovery and Co2 Barrier Properties

Structures and Performance of Alcohol Activated Thin Film Composite Polyamide (Tfc-Pa) Nanofiltration (Nf) Membranes Prepared with and Without Co(Ii) Modulation

Structures and Performance of Alcohol Activated Thin Film Composite Polyamide (Tfc-Pa) Nanofiltration (Nf) Membranes Prepared with and Without Co(Ii) Modulation

Modifying the surface of active polyamide layer in thin-film composite tubular membranes with polyethylene glycol for improved separation and antifouling

BackgroundMembrane fouling can deteriorate the membrane performance for the long term. Surface modification of the membrane using hydrophilic moieties improves the antifouling property of the membrane. In this study, thin-film composite (TFC) polyamide tubular membrane was modified using glutaraldehyde (GA) and polyethylene glycol (PEG). MethodsPolyamide layer was formed through interfacial polymerization of piperazine (PIP) with trimesoyl chloride (TMC). Before modification using PEG on the surface of the TFC membrane, the TFC membrane was post-treated using GA. The aldehyde group of the GA reacted with free amines on the polyamide surface, producing enamine. PEG modified the GA-TFC membrane through the reaction of excess aldehyde group of the GA on the membrane surface. FindingsPEG-GA-TFC membrane shows a better hydrophilicity and membrane surface charge than pristine and GA-TFC membrane. Consequently, during nanofiltration test, it delivered the highest membrane performance and antifouling property (tested using 100 ppm BSA solution). Furthermore, the modified membrane exhibited good stability in a wide range of pressure and salt concentration.

High-flux polyamide membrane with improved chlorine resistance for efficient dye/salt separation based on a new N-rich amine monomer

• Guanazole was firstly used as diamine monomer to fabricate novel TFC membrane by interfacial polymerization. • The membranes showed optimum separation selectivity for dye and NaCl with higher pure water flux (95.1 L m −2 h −1 bar −1 ). • The membranes maintained outstanding chlorine resistance after 120 h immerse in NaClO solution. Interfacial polymerization is the gold standard for manufacturing thin film composite (TFC) membranes for nanofiltration (NF) and reverse osmosis (RO). However, typical polyamide (PA) thin film composite (TFC) membranes fabricated by interfacial polymerization are inappropriate for dye wastewater zero discharge and are susceptible to oxidizing agents. In this study, by using a new N-rich amine monomer 3,5-diamino-1,2,4-triazole (DAT), a novel PA TFC membrane was fabricated for the separation of dyes and salts. It is speculated that the unique molecular structure of DAT can conducive to the formation of a less compact polyamide layer with improved chlorine resistance. The optimum membrane shows an ultrahigh pure water permeability (95.1 L/m 2 ·h·bar) and an excellent dye/salt separation selectivity for Congo red and NaCl (rejection, 99.1% and 5.8%, respectively). This is superior to that of the two commonly used dye/salt separation commercial membranes (Sepro NF 6 and NF 2A, Ultura). Furthermore, the resultant DAT/TMC TFC membranes maintained their original separation efficacy after 120 h of immersion in NaClO solution, demonstrating their good chlorine resistance. In summary, this study not only expands the application of interfacial polymerization, but also provides a new inspiration for the preparation of advanced membranes for efficient dye/salt separation.