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A synthesized thin film composite (TFC) nanofiltration membrane was prepared by incorporating Mg(OH) 2 nanosheets at different ratios (from 0 to 0.5 wt%) into polysulfone (PSf) support layer. The polypiperazinamide (PPA) layer was prepared on the polysulfone support layer by means of interfacial polymerization. Then TFC membrane was then etched with H 2 SO 4 and a PPA selective layer was established using trimesoyl chloride (TMC) and piperazine (PIP). The characterization results show that the modifications of the PSf substrate with Mg(OH) 2 alter the physicochemical properties of the poly(piperazine amide) selective layer. Through the introduction of Mg(OH) 2 , the hydrophilicity of the TFC membrane was increased (WCA: 20.5°), promoting more linear polypiperinamide. The addition of 0.4 wt% Mg(OH)₂ to the PSf substrate, followed by sulfuric acid etching, resulted in a 196 % increase in membrane flux and with Na₂SO₄ retention at 97.72 %. The change in matrix composition favoured the generation of a lighter and rougher selective layer. The two-dimensional nanochannels in the support layer provided additional channels for water molecule transport. The membrane with two-dimensional nanochannels exhibited excellent resistance to contamination, with a flux recovery of 92.8 % for bovine serum albumin (BSA). [Display omitted] • The high-flux TFC film prepared by the etching method is free of leaching nanomaterials. • Without sacrificing interception, the water flux increased by 196 % compared to the control membrane. • High-flux TFC membranes provide excellent film fouling resistance. [ABSTRACT FROM AUTHOR]

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 Na 2 SO 4 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. [Display omitted] • The effect of relative humidity during heat curing on TFC nanofiltration membranes was investigated. • Capillary stress was introduced to reveal the mechanism of nanofiltration membranes flux variation. • The surface morphology of nanofiltration membranes changed with the relative humidity. • The relative humidity affects the nanofiltration membrane uniformity. [ABSTRACT FROM AUTHOR]

ABSTRACT: In a previous study, we proved that tailoring the polyamide backbone stiffness is an effective way to fabricate high‐performance polyamide nanofiltration (NF) membranes. However, in the previous study, we mainly focused on the flat membrane and did not consider its chlorine tolerance. In this study, by regulating the aqueous‐phase compositions in the interfacial polymerization process, chlorine tolerance on NF hollow‐fiber membranes was endowed while the membrane performance stayed high. The experimental results show that when the ratio of Piperazine (PIP)–bisphenol F (BPF)/2,2′‐bis(1‐hydroxyl‐1‐trifluoromethyl‐2,2,2‐triflutoethyl)‐4,4′‐methylene dianiline (BHTTM) was 5:1:4, the NF membrane possessed a permeate flux of 21.0 L m−2 h−1 bar−1 and an Na2SO4 rejection up to 90.0%. X‐ray photoelectron spectroscopy analysis also confirmed that the polymerization degree of the PIP–BPF–BHTTM NF membrane was the highest. Moreover, the NF membrane could tolerate active chlorine to over 10,000 ppm h Cl. After the active chlorine treatment, the permeate flux increased over 30.0 L m−2 h−1 bar−1, and the Na2SO4 rejection was about 90.0%. Although the PIP–BHTTM NF membrane also possessed good chlorine tolerance, its permeate flux (after active chlorine treatment) was only 60% of that of the PIP–BPF–BHTTM NF membrane. Therefore, the PIP–BPF–BHTTM NF membrane possessed a combination of high flux and high chlorine tolerance and showed good potential in water treatment in rigorous environments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46482. [ABSTRACT FROM AUTHOR]

According to the Freeman theory, increasing the backbone stiffness to some extent is an effective way to obtain the remarkable membrane with both high permeability and selectivity. In this work, a high performance nanofiltration (NF) membrane was prepared via tailoring the polyester/polyamide backbone stiffness. The flexible monomer-piperazine (PIP) and the rigid monomer-bisphenol F (BPF) were selected as the aqueous phase monomers, and they were interfacial reacted with trimesoyl chloride (TMC) on the polyethersulfone (PES) UF membrane to generate the polyester/polyamide layer. By mixing PIP with BPF, both of the polyester/polyamide backbone stiffness and microporosity degree enhanced. As a result, the PIP/BPF NF membrane possessed a 2.6-fold pure water flux (PWF) of the PIP NF membrane (the salt rejection remained at the same level), and 4.8-fold PWF of the BPF NF membrane. Our results revealed a novel and facile way to improve the NF membrane performance. [ABSTRACT FROM AUTHOR]

A novel polypiperazine-amide nanofiltration (NF) membrane with very high salt rejection was successfully developed in this work. The NF membrane chlorine-tolerant ability were improved greatly after mixing a small amount of α,ω-diamino poly(ethylene glycol) (NH 2 -PEG-NH 2 ) with piperazine (PIP) in the aqueous phase. The XPS result demonstrated that the polymerization degree of the NF membrane was notably enhanced with the addition of NH 2 -PEG-NH 2 . The solute rejections and chlorine tolerance were improved remarkably, while the permeate flux remained almost at the same level. When the NH 2 -PEG-NH 2 (2 kDa) content in the total amine was 1%w/w (0.01%w/v in the aqueous solution), NF membrane performance was optimal. This membrane exhibited a pure water flux (PWF) of 34.9 L m −2 h −1 along with Na 2 SO 4 , MgSO 4 , MgCl 2 and NaCl rejections of 99.5%, 99.2%, 90.9% and 58.3% (2000 ppm, 6 bar, 25 °C), respectively. Moreover, the NF membrane performance was maintained after being treated by 14,000 ppm NaClO for 1 h. Therefore, adding a small amount of NH 2 -PEG-NH 2 in the aqueous phase could be considered to be an effective way to improve the polypiperazine-amide NF membrane chlorine-tolerant ability. [ABSTRACT FROM AUTHOR]

Good mechanical strength, high water flux and salt rejection, and highly chlorine-tolerant property are essential for nanofiltration (NF) membrane. To achieve these properties, polyethersulfone (PES) NF thin-film composite (TFC) membrane was prepared via interfacial polymerization using piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) as aqueous monomers, trimesoyl chloride (TMC) as organic monomers, and PES three-channel capillary ultrafiltration (UF) membrane as substrate. The prepared NF membrane displays pure water flux of 36.1 L m −2 h −1 and Na 2 SO 4 rejection of 96.8% at 4 bar. NaClO solution was used to treat NF membranes for the evaluation of NF membrane chlorine-tolerant property. The effects of NaClO concentration, contact time and operating pressure on the chlorine-tolerant property of NF membrane have been thoroughly investigated. Particularly, the durability of NF membrane versus Cl was tested though long-term test. The pure water flux and Na 2 SO 4 rejection of NF membrane after 5000 ppm-h NaClO immersion was 43.4 L m −2 h −1 and 99.8% at 4 bar, respectively. The fabricated NF membrane could tolerant 13000 ppm-h Cl under 4 bar, and the water flux and Na 2 SO 4 rejection are maintain at 51.6 L m −2 h −1 and 99.6% during NF running process, respectively. Moreover, NF membrane exhibits 3.84×10 5 ppm-h chlorine-tolerant at 0 bar. These results indicated that the fabricated PES three-channel capillary NF membrane could be applied to practical process of desalination or water softening. [ABSTRACT FROM AUTHOR]

Using Polysulfone (PSF) ultrafiltration (UF) membrane as porous support, a chlorine-tolerant nanofiltration (NF) membrane was prepared by interfacial polymerization of piperazine (PIP) and 2,2'-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4'-methylenedianiline (BHTTM) mixture with trimesoyl chloride (TMC). The XPS, SEM, AFM and contact angle methods were employed to characterize the physicochemical properties and morphology of the prepared NF membranes. The effects of preparation conditions such as reaction time, monomers mixing ratio and oxidation treatment on NF membrane performance were investigated. The salt rejection of the NF membrane met the order of Na 2 SO 4 >MgSO 4 >NaCl, indicating the membrane possessed a negative surface charge. The results showed the NF membrane prepared under the optimum conditions exhibited pure water flux (PWF) with 79.1 (L/m 2 h) and Na 2 SO 4 rejection of 99.5% under 0.6 MPa. The optimized post oxidation condition was treated by 3000 ppm NaClO solution for 1 h. The best NF membrane had a molecular weight cut-off (MWCO) less than 300 Da, corresponding to the pore size of 1 nm, which was calculated from the rejection of carbohydrates. The robustness of the NF membrane was proven by showing satisfactory stability in the long time running. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel nanofiltration (NF) membrane was prepared with cyclen and trimesoyl chloride by interfacial polymerization on a poly(ether sulfone) ultrafiltration membrane with a molecular weight cutoff of 50,000 Da. The effects of the reaction time, monomer concentration, and heat-treatment temperature are discussed. The physicochemical properties and morphology of the prepared NF membrane were characterized by Fourier transform infrared spectroscopy-attenuated total reflectance, scanning electron microscopy, energy-dispersive spectrometry, and atomic force microscopy. The NF performances were evaluated with solutions of Na2SO4, MgSO4, Mg(NO3)2, and NaCl. The salt-rejection order of the prepared NF membrane was as follows: Na2SO4 > MgSO4 > Mg(NO3)2 > NaCl. The resulting rejection of Na2SO4 and PEG600 (polyethylene glycol with the average molecular weight of 600) were more than 90%, whereas that of NaCl was approximately 10%. After the addition of silica sol in the aqueous phase (silica sol concentration = 0.1% w/v), the salt rejection of the membrane changed slightly. However, the water flux was from 24.2 L·m−2·h−1 (25°C, 0.6 MPa) up to 38.9 L·m−2·h−1 (25°C, 0.6 MPa), and the resulting membrane exhibited excellent hydrophilicity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42345. [ABSTRACT FROM AUTHOR]

Recent studies have documented that the incorporation of nanomaterials can effectively enhance the permselectivity of thin-film composite (TFC) membrane. The distribution and compatibility of molybdenum disulfide (MoS 2) nanosheets lack of functional groups within polymer matrices are research hotspots. Here we present polydopamine (PDA) modified MoS 2 (MoS 2 @PDA) nanosheets as nanofillers to prepare thin-film nanocomposite (TFN) nanofiltration (NF) membrane. PDA not only enhanced the dispersion and compatibility of MoS 2 in the polyamide matrices, but also resulted in defect-free TFN membranes due to its self-polymerization. The obtained TFN membrane loaded with 0.01 wt% MoS 2 @PDA nanosheets (TFN-0.01) had water permeability of 6.7 L m−2 h−1 bar−1, 1.45 times of the TFC membrane. The Na 2 SO 4 rejection increased from 97.1% to 98.2%, thus overcoming the long-standing permeability-selectivity trade-off of desalination membranes. Moreover, TFN-0.01 NF membrane had excellent long-term stability. Our results showed that PDA can effectively solve the dispersibility and compatibility problems of nanofillers in polymer matrices, especially for the nanofillers lack of functional groups. [Display omitted] • PDA generates molecular bridge between nanofillers and polymer matrices. • PDA enhances the dispersibility and compatibility of MoS 2 in PA matrices. • The obtained TFN-0.01 membrane showed 45% flux improvement with Na 2 SO 4 rejection of 98.2%. [ABSTRACT FROM AUTHOR]

Abstract: Poly(styrene sulfonic acid) sodium salt (PSSS)/polypiperazine-amide nanofiltration (NF) membrane and PSSS/SiO2/polypiperazine-amide NF membrane were prepared by interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on polyethersulfone (PES) supporting membrane. Effect of PSSS and silica concentrations were discussed. The active surface of the membrane was characterized by using SEM and AFM. The results showed that PSSS/polypiperazine-amide NF membrane prepared under the optimum conditions exhibited Na2SO4 rejection of 96.1% and water flux with 55.7Lm−2 h−1 at operation pressure of 0.6MPa. The rejection of Na2SO4, MgSO4, MgCl2 and NaCl follows a decreasing in order of 96.1%, 85.2% 45.4% and 21.1% respectively. After addition of 0.2% (w/v) silica in the aqueous phase, the water flux increased 42.7% compared with only polypiperazine-amide NF membrane. The PSSS/polypiperazine-amide NF membrane shows a promising capability for softening highly concentrated seawater from 8–20wt.%. [Copyright &y& Elsevier]

Highlights: [•] Silica sol is used for prepartion of silica–fluoropolyamide nanofiltration membrane. [•] Hexafluoroisopropanol group compound is used for prepartion of NF membrane. [•] Different polymerization conditions were investigated. [•] The resulting membrane showed better performance after oxidation treatment. [Copyright &y& Elsevier]

A novel composite nanofiltration (NF) membrane was prepared by interfacial polymerization of 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-trifluoroethyl)-4,4′-methylenedianiline (BHTTM) and trimesoyl chloride (TMC) on polyethersulfone (PES) supporting membrane. Different preparation conditions and NF membrane performances were discussed. The membrane structures of composite NF membranes were characterized by attenuated total reflectance infrared (ATR-IR), scanning electron microscope (SEM), and atomic force microscopy (AFM). The results showed that the NF membrane prepared under the optimum condition exhibited Na2SO4rejection of 85.3% and the water flux of 10.1 l.m−2.h−1. The NF membrane was treated by 5000 ppm chlorine solution for 1 h. The salt rejection and water flux of the treated membrane reached to 94.5% and 94.8 l.m−2.h−1. The rejection of two NF membranes for inorganic electrolyte solutions decreased in the order of Na2SO4, MgSO4, MgCl2, and NaCl, which were typical characteristics of negatively charged membranes. [ABSTRACT FROM PUBLISHER]

Abstract: Silica/polypiperazine-amide nanofiltration (NF) membranes were prepared by interfacial polymerization on polyethersulfone (PES) supporting membrane. Different preparation conditions and NF membrane performances were discussed, including silica concentrations, monomer concentrations, reaction time and salt rejections. The chemical structure characterizations of polyamide composite membrane were carried out by attenuated total reflectance infrared (ATR-IR). The surface images and cross sections were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM). The results showed that polypiperazine-amide NF membrane prepared under the optimum conditions exhibited Na2SO4 rejection of 97.4% and water flux of 46.8l.m−2.h−1. After addition of silica sol in the aqueous phase, the rejection of the resulting membrane changed slightly, but the water flux increased 21.1% than polypiperazine-amide NF membrane. According to the rejection of polyethylene glycols (PEGs), the molecular weight cut-off (MWCO) of the resulting membrane was under 600Da. [Copyright &y& Elsevier]

Using a coupling process of neutralization–nanofiltration–crystallization, pure ammonium metatungstate (AMT) was prepared. The effects of chemical neutralization of ammonium paratungstate (APT) by nitric acid, operating pressure, AMT concentration, the volume of washing water on the coupling process were systematically discussed. It was found that the better conditions of AMT preparation were as follows: the neutralization temperature was 80–95 °C, pH value was 2.0–3.5; the operating pressure of HDS-12-2 nanofiltration was 1.5–2.0 MPa, the density of AMT crystallization solution was 2.39 kg/L, and then cooling. APT conversion efficiency (δ) to AMT was more than 97.62%. The removal ratio of nitrate ion (NO3-) was more than 99% while AMT rejection (RAMT) was 99.9%. Besides, small-grained, even-proportioned, white-colored and high-purified AMT crystal was be obtained and analyzed. This method has several advantages such as simple technological process, short production cycle, lower environmental pollution and high quality. [Copyright &y& Elsevier]

Nanofiltration (NF) is considered a promising candidate to improve the separation efficiency in water desalination, and the membranes with incomparable water permeance and great selectivity are urgently requried to reduce the energy consumption. Iron oxohydroxides (FeOOH) nanorods, goethite (α-FeOOH) with a diameter of 30–40 nm and length of about 340 nm, were synthesized and deposited on PES microfiltration (MF) membrane with the pore size of 0.1 μm by the assistance of vacuum filtration. Then a high flux NF membrane intercalated by well-dispersed FeOOH nanorods was fabricated using piperazine (PIP) and trimesoyl chloride (TMC) as monomers. The influence of FeOOH deposition on the surface properties and the nanofiltration performance of the fabricated membranes was studied. XPS, SEM, TEM, AFM, water contact angle (WCA) and NF measurements were utilized to investigate membrane performance. The optimum membranes showed a high water permeability (34.1 L·m−2·h−1·bar−1), high rejection for Na 2 SO 4 (95.0%) and good ion selectivity towards Cl−/SO 4 2− (23.9). Furthermore, the optimized NF membranes are acid-stable to some extent, and showed good stability in long-term NF operations. This work presents a facile and low-cost strategy for constructing high performance NF membranes. • FeOOH nanorods were synthesized via hydrothermal method. • FeOOH-interlayed thin-film NF membranes were fabricated by interfacial polymerization. • The prepared NF membrane showed a pure water flux of 34.1 L·m−2·h−1·bar−1 and Na 2 SO 4 rejection of 95.0%. [ABSTRACT FROM AUTHOR]

To obtain high-performance polyester (PE) nanofiltration (NF) membranes for desalination, most PE NF membranes are fabricated with high aqueous monomer concentration, or high reaction temperature, or long reaction time. The interfacial polymerization (IP) reaction rate between hydroxyl groups and acyl chloride groups is promoted but the cost of membrane fabrication is also increased. In this work, Bis-tris (bis(2-hydroxyethyl)-amino-tris(hydroxymethyl)methane) with rich hydroxyl groups is first utilized as an aqueous monomer to fabricate PE membranes under conventional IP conditions. The fabricated Bis-tris PE membranes feature strong hydrophilicity, excellent electronegativity, and ultra-thin selective layers, which are conducive to improving desalination performance. The optimized Bis-tris PE membrane shows excellent water permeance of 22.5 L m−2 h−1 bar−1 and a satisfactory Na 2 SO 4 rejection of 96.9 %. Additionally, the Bis-tris PE membrane displays superior long-term stability and chlorine resistance under 96 h cross-flow filtration. This research enlightens the promising potential of Bis-tris as a novel and economic aqueous monomer for the fabrication of high-performance PE NF membranes. [Display omitted] • Bis-tris was first utilized to fabricate polyester NF membranes. • Polyester NF membrane for desalination was fabricated via interfacial polymerization. • The optimized Bis-tris membrane exhibited high water permeance and Na2SO4 rejection. • The fabricated membrane had high electronegativity and an ultra-thin selective layer. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membranes with both high permeability and salt rejection are in dire need for water treatment. Generally, heat treatment is an essential step for fabricating polyamide NF membranes. Conventional heat treatment in an oven causes membrane pore shrinkage and over cross-linking, which often leads to a severe loss of permeation performance. Herein, we report a single-step method by heat-treating membranes in non-neutral solutions to avoid pore shrinkage and generate graded hydrolysis in membrane selective layer. As confirmed by the XPS result, the polyamide NF membrane fabricated via controlled hydrolysis possesses a gradient cross-linking degree vertically along the membrane surface. This optimal polyamide NF membrane had a superior pure water permeability (PWP) of 27.5 L m−2 h−1 bar−1 and high Na 2 SO 4 rejection of 98.5%. Such controlled hydrolysis approach provides novel strategy for fabricating high performance polyamide membranes. • Heat treatment in water was employed to avoid pore shrink and over cross-linking of the polyamide active layer. • The performance of NF membrane with gradient cross-linked structure can be easily tuned by adjusting the pH value of water. • The optimal membrane owns a superior pure water permeability of 27.5 L m−2 h−1 bar−1 and a high Na 2 SO 4 rejection of 98.5%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of COFs modified Nylon microfiltration substrates by interfacial polymerization. • The COFs layer has an impact on subsequent IP processes confirmed by MD simulation. • The polyester layer has hydrophilicity and anti-fouling properties. • The COF-PE/Nylon membrane shows excellent separation performance. Currently, polyester (PE) membranes prepared using green materials have gained more attention in the membrane separation field. Most of the previously reported PE membranes are synthesized on ultrafiltration substrate, which hinders the enhancement of water permeance. This paper proposes a new strategy to fabricate PE membranes with covalent organic frameworks (COFs) modified microfiltration substrate via interfacial polymerization (IP). On the one hand, COFs modify the Nylon microfiltration substrate while affecting the subsequent IP process to obtain the thinner and smoother selective layer. This process was also analyzed by molecular dynamics (MD) simulation. On the other hand, the excellent hydrophilicity of the PE layer also endowed the anti-fouling properties of the covalent organic frameworks-polyester/Nylon (COF-PE/Nylon) membrane. The optimal COF-PE/Nylon membrane had 99.6 % Congo red (CR) rejection, and dye/salt (CR/NaCl) selectivity was 63.1. Meanwhile, the pure water permeance reached 157.5 L m−2h−1 bar−1, higher than the PE membrane prepared on the ultrafiltration substrate. The present work demonstrated the excellent separation performance of COF-PE/Nylon membranes and provided a reference for subsequent PE membrane preparation on various substrates. [ABSTRACT FROM AUTHOR]

Despite the prosperity of membrane technology, the separation efficiency for Mg2+/Li+ mixture is still far from satisfactory. Herein, a novel thin‐film nanocomposite (TFN) membrane was developed by loading polyhydroxylated fullerene (PHF) via interfacial polymerization. The effects of the PHF dosages on the as‐developed membranes were investigated comprehensively by XPS, SEM, AFM, contact angle measurements, as well as nanofiltration tests. The results revealed the TFN membrane containing 0.01% (w/v) PHF exhibited the optimum performances. The membrane showed a pure water flux of 6.7 L·m−2·h−1·bar−1 and salt rejections with the order of Na2SO4 (95.6%) > MgSO4 (93.6%) > MgCl2 (89.9%) > NaCl (22.6%) > LiCl (16.3%). The membrane not only presented a separation factor of 13.1 in separating Mg2+/Li+ mixtures, but also demonstrated excellent antifouling ability, which enables membrane regeneration without operation break, suggesting its great potentials in the recovery of Li+ from brine or seawater. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48029. [ABSTRACT FROM AUTHOR]

This study investigated the chemical stability differences between dry and wet nanofiltration membranes when immersed in strong acid and base environments. Systematic experimental studies were conducted on both types of nanofiltration (NF) membranes, supplemented by Molecular Dynamics (MD) simulations and Density Functional Theory (DFT) calculations. The results indicate that wet NF membranes, soaked in deionized water for a week, exhibit higher chemical stability compared to dry membranes treated only with air. Traditional air heating causes membrane pore contraction and excessive crosslinking. However, after a week of immersion in water, the polyamide (PA) layer gradually becomes a loose and well-extendable PA layer. MD simulations revealed that H+ and OH− ions possess lower diffusion coefficients and extended residence times in dry NF membranes, making them more prone to damage. Additionally, DFT calculations disclosed that the Gibbs free energy (ΔG) for amide bond hydrolysis in wet NF membranes, in the presence of water molecules, is elevated, significantly delaying their hydrolysis rate under extreme conditions. This study highlights the pivotal role of membrane wetness in the chemical durability of NF membranes and offers a novel perspective for improving membrane lifespan and efficiency. [Display omitted] • Wet NF membranes show markedly higher chemical stability in acidic and basic environments. • MD simulations indicate lower ion diffusion and longer residence times in dry NF membranes. • DFT calculations reveal slower amide bond hydrolysis in wet membranes, enhancing durability. • Study offers new insights for extending NF membrane lifespan and improving filtration efficiency. [ABSTRACT FROM AUTHOR]

A novel chitosan (CS)-piperazine (PIP) composite nanofiltration (NF) membrane with satisfied characteristics for brackish water and seawater desalination was successfully developed. PIP was mixed with CS during the interfacial polymerization (IP) process to enhance the NF membrane permeate flux. The resultant NF membranes were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM), contact angle. Effects of CS concentration, trimesoyl chloride (TMC) concentration, reaction time and the mixing ratio of CS/PIP on NF membrane performance were investigated thoroughly. When PIP in the aqueous phase monomers reached to 25% (w/w), the PWF (60.6 L·m−2·h−1) was synergistically improved by nearly 2 times without a significant reduction of Na2SO4 rejection (89.1%). Moreover, the NF membranes possessed excellent performance for the desalination of brackish water and seawater, which showed high potential to be applied in the desalination process for water treatment. [ABSTRACT FROM AUTHOR]

Recent research has focused on the acid resistance of polyamide nanofiltration (NF) membranes, a critical aspect for their stability during practical applications. However, the impact of different acids, particularly the role of various anions, on NF membrane acid resistance remains unexplored. Our research systematically evaluates NF membrane performance and property alterations under various acids at identical pH levels, supplemented by density functional theory (DFT) simulations. Results reveal that membranes treated with H₃PO₄ retain desirable NF performance, in stark contrast to those treated with H₂SO₄ and HCl, which undergo significant degradation. Specifically, H₃PO₄-treated membranes showed only a 4.2 % decline in Na₂SO₄ rejection, compared to a dramatic 83.3 % decline for HCl-treated membranes under identical pH. This degradation is linked to the acids infiltrating the polyamide structure. The membrane's enhanced resistance to H₃PO₄ is primarily due to the strong negative charge of phosphate ions, influenced by the Donnan effect, which prevents deep penetration into the membrane. This is further supported by DFT simulations, which reveal that the interaction energy between the membrane surface and phosphate ions is over twice as high as with chlorine ions, highlighting the importance of ion-specific interactions. This research highlights the crucial role of anions in acidic environments for the maintenance and operation of NF membranes in industrial applications. It provides key insights for enhancing membrane efficiency and longevity under acidic conditions. [Display omitted] • Filled the research gap in polyamide membranes resistance to different acids. • Revealed the variance in acid resistance for anionic charge-induced Donnan effect. • Provides insights for optimizing acid utilization in industrial processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PEI interlayer regulated the PA layer structure and enhanced the positively charged property of NF membranes. • NH 2 -MIL-101(Cr) NPs improved the permeability and provided fast transport paths for Li+. • The obtained membrane presented high flux of 17 L m-2h−1 bar−1 with a superior Li+/Mg2+ separation factor of 102. Nanofiltration (NF) technology has exceptional mono/divalent ion separation performance, providing considerable application potential for lithium extraction. However, polymeric NF membranes provided only restricted amounts of practical applications since of their low permeability and limited selectivity. Herein, a positively charged membrane designed for Li+/Mg2+ separation was developed, this achievement was accomplished by incorporating NH 2 -MIL-101(Cr) nanoparticles (NPs) into the polyamide (PA) layer situated atop the polyethyleneimine (PEI) interlayer. The PEI interlayer controlled the amine monomer distribution, regulated the PA nanofilm morphology, and improved the membrane positively charged properties. Meanwhile, the NH 2 -MIL-101(Cr) could provide Li+ with fast transport paths to further enhance the membrane Li+/Mg2+ separation capability. The improved membrane possessed MgCl 2 rejection of 96.1 %, LiCl rejection of 42.3 %, and Li+/Mg2+ separation factor of 102 with outstanding permeance of 17.0 L m-2 h−1 bar−1. This research made a valuable contribution to applying NF membranes in lithium extraction processes. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a new periodic porous crystalline material, that has nano pore sizes. Herein, a novel COFs MPDTp was introduced into nylon microfiltration substrate to reduce polyamide (PA) infiltration condition for highly permselective nanofiltration (NF). The resultant PA-COF/nylon membrane was achieved after twice interfacial polymerization (IP) processes. The first was the introduction of COFs, and the second was the preparation of PA selected layer. The optimal membrane showed outstanding pure water permeance (PWP) of 27.3 L m−2 h−1 bar−1, which was about three times larger than the PA/nylon membrane, and rejection of 98.4 % for Na 2 SO 4. The excellent performance was benefit from the existence of COFs, on the one hand, the COFs on the surface and inside could be seem as a net which prevented PA infiltration and blockage. On the other hand, a thinner PA separation layer was generated due to the slower piperazine (PIP) diffusion rate, which was also certified by molecular dynamics (MD) simulation. Therefore, this work not only demonstrates the high application value for desalination of the PA-COF/nylon membrane, but also provides a new strategy to adjust the relationship between the microporous substrate and the PA layer. Herein, a novel COFs MPDTp was used to reduce polyamide (PA) infiltration phenomenon of nylon microfiltration substrate to fabricated highly permselective nanofiltration (NF) membrane. COFs on the surface and inside could be seem as a net which prevented the PA infiltration. The obtained membrane showed outstanding pure water permeance, which was about three times larger than the membrane without COFs existence, and the rejection of Na 2 SO 4 remained stable. [Display omitted] • A novel COFs was introduced to nylon substrate by interfacial polymerization method. • COFs net reduced the polyamide infiltration phenomenon on microfiltration support. • Slower diffusion rate of amine with COFs participation was certified by MD simulation. • The optimal membrane exhibited excellent desalination performance. [ABSTRACT FROM AUTHOR]

Although covalent organic frameworks (COFs) membranes have promising applications in water treatment due to their ordered structure and adjustable pore size, most of them are imine-linked ones, which severely limits their application in harsh environments. Herein, we offer a stable novel COFs membrane which is composed of hydrazone bonds and β-ketoenamine structures. Such β-ketoenamine based COFs composite membrane was fabricated via interfacial catalytic polymerization on a nylon substrate, which was generated at the water (P-Toluenesulfonic acid)/n-hexane (2,5-dimethoxyterephthalhydrazide, 1,3,5-triformylphoroglucinol) interface. The resultant COFs membrane demonstrates excellent chemical stability in strong acidic (2 mol/L)/alkaline (9 mol/L)/organic solvents (dioxane, acetone, methanol, and ethanol) media. The optimized COFs membrane achieved 109.73 L m−2 h−1 bar−1 permeance in Congo Red aqueous solution and 99.56 % CR rejection. This study exploits a novel approach to produce robust COFs membranes under extreme conditions. [Display omitted] • TpDMTH COFs membranes were fabricated via interfacial catalytic polymerization. • The combination of hydrazone bonds and β-ketoenamine structures makes membranes show stable chemical structure. • Such COFs membranes maintained excellent separation performance in 9 M NaOH solution. • Such COFs membranes showed excellent dye/salt separation performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • VA-based polyphenol coated loose PEI NF membrane was developed. • NH 2 -MIL-101(Fe) was utilized to enhance the deposition of polyphenol coating. • High dye/salt selectivity, dye sieving capacity, and water permeability were achieved. • XDLVO theory results show the membrane with outstanding antifouling property. • Good membrane stability offered a potential solution to textile wastewater treatment. Effective dye sieving and dye/salt separation could recycle valuable resources during textile wastewater treatment. In this work, a loose nanofiltration (NF) membrane with outstanding performance was constructed with facile materials including the surface polyphenol coating and the polyetherimide (PEI) support. Firstly, the mixed matrix support membrane was prepared by incorporating Fe-based MOF NH 2 -MIL-101(Fe) into PEI membrane via non-solvent induced phase separation (NIPS) method, then the polyphenol coating based on vanillyl alcohol, which was the characteristic component derived from Gastrodia elata Blume, was co-deposited on the support PEI membrane, followed by the treatment of 1,3-propane sultone. In this way, the optimal loose NF membrane could have a high good pure water permeability (87.9 L·m−2·h−1·bar−1) while high dye/salt selectivity was reached (Selectivity: 58.9 for Congo Red/NaCl; 46.8 for Conge Red/Na 2 SO 4). Moreover, a mixture of large molecule dye and small molecule dye could be sieved and the optimal loose NF membrane showed outstanding antifouling capacity with the flux recovery ratio of 85.7%, 98.1%, and 97.9% respectively for bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA), which was further analyzed and calculated by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The long-term stability during EBT/Na 2 SO 4 mixture filtration endowed the membrane with great potential in treating textile wastewater. [ABSTRACT FROM AUTHOR]

Monomers are elementary units that constitute the polyamide layer, which determines the properties of nanofiltration membranes. The design of nanofiltration membranes with both high separation performance and outstanding chemical stability remains a challenge. In this study, two typical monomers, heterocyclic monomer molecule-piperazine (PIP) and carbon ring molecule-1,4-cyclohexane diamine (CHDA), were applied as aqueous monomers for interfacial polymerization to generate polyamide nanofiltration membranes. The physicochemical properties of the two nanofiltration membranes were comprehensively investigated. The results demonstrated that the nanofiltration membrane fabricated via CHDA exhibited more chemical stability than that fabricated via PIP. The mechanisms influencing the chemical stability difference were elucidated via multiscale simulation. The CHDA polyamide has higher levels of HOMO-LUMO energy and Gibbs-free energy, which make it more stable under harsh chemical environments. Overall, this work presents the effect of the diamine structure on the chemical stability of polyamide NF membranes, which can inspire highly chemically stable nanofiltration membrane fabrication. [Display omitted] • Effect of diamine structure for NF membrane chemical stability was investigated. • Carbon ring molecule had better chemical stability than heterocyclic molecule. • Experimental study showed a high correlation with simulation calculations. [ABSTRACT FROM AUTHOR]

This work describes a novel nanofiltration membrane fabrication strategy in which the octadecylamine-grafted GO with the organophilic property is incorporated in organic phase during interfacial polymerization (IP) in order to protect the polyamide backbone from the attack of free chlorine. Meanwhile, the aqueous phase containing mixed amines of piperazine (PIP) and the fluorine-containing monomer (2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline, BHTTM) enables further improvement in chlorine resistance of the thin film nanocomposite (TFN) membrane. The modified GO was systematically characterized by TEM, FT-IR, TGA and XRD. And the membrane properties were investigated by XPS, TEM, AFM and dynamic contact angle. The octadecylamine-grafted GO TFN membrane (TFNMA-GO-ODA) exhibits measurably smoother and less hydrophilic surface compared to TFC membrane with mixed amines as well as the similarly fabricated GO TFN membrane. The TFNMA-GO-ODA demonstrated a pure water flux of 49.6 L m −2 h −1 (0.6 MPa), which was nearly 2.5 times than that of pristine PIP TFC membrane and 1.6 times than that of mixed-amine TFC membrane, while keeping high Na 2 SO 4 rejection of 98.4%. More importantly, the TFNMA-GO-ODA presented excellent chlorine resistance, benefiting from the existence of fluorine-containing groups in BHTTM and the protective effect of stable graphene nanosheets. The results indicate great potential of such membrane in water desalination and purification in industrial scale. [ABSTRACT FROM AUTHOR]

Thin film composite (TFC) hollow fiber nanofiltration (NF) membranes were fabricated via interfacial polymerization, with mixed diamines of piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) as water phase and trimesoyl chloride (TMC) as organic phase. Fabricated membranes were characterized for ATR-FTIR, SEM, AFM, and water contact angle. Formation conditions of the selective polyamide layer have been optimized for a good NF membrane performance. The pure water flux of NF membrane prepared under optimized conditions was 31.2 L·m − 2 ·h − 1 and the rejection for Na 2 SO 4 was 99.7% at 6 bar. The rejections of NF membranes for different salts followed the order: Na 2 SO 4 > MgSO 4 > NaCl > MgCl 2 . The molecular weight cut-off of NF membrane was around 300 Da. The performance of NF membranes was stable during a 7-day filtration process for rejecting different species ions including heavy metal ferric ion (FeCl 3 and Fe 2 (SO 4 ) 3 ) and oxyanions (SO 4 2 − and HPO 4 2 − ), in addition to different inorganic salts. Also, the NF membranes exhibited chlorine tolerant property. This work demonstrates the potential of PES outer-selective TFC hollow fiber membranes for desalination or water softening process, provides database to fabricate suitable NF membranes for long-term salts removal and raise a simple technique to form a thin chlorine-tolerant polyamide layer. [ABSTRACT FROM AUTHOR]

γ-Al 2 O 3 /α-Al 2 O 3 hollow fiber nanofiltration (NF) composite membranes with different molecular weight cut-offs (MWCOs) ranging from 1.4 kDa to 14.5 kDa were prepared by dip-coating γ-AlOOH sol on the ceramic membrane with a mean pore size of 229 nm. The effect of the preparation conditions including soaking time and coating times were investigated by scanning electron microscopy (SEM), dynamic contact angle and membrane performance. The optimal inorganic NF membrane demonstrated a high pure water permeance with high retentions of multivalent ions and low retentions of monovalent ions. The γ-Al 2 O 3 /α-Al 2 O 3 inorganic hollow fiber NF membrane shows excellent solvent resistance and good stability. [ABSTRACT FROM AUTHOR]

Novel high-flux thin film composite (TFC) nanofiltration (NF) membranes were fabricated by the sodium hypochlorite (NaClO) pre-oxidation of the mixed diamine monomers of piperazine (PIP) and 2,2′-bis(1-hydroxyl-1-trifluoromethyl-2,2,2-triflutoethyl)-4,4′-methylenedianiline (BHTTM) in the aqueous phase solution, and via interfacial polymerization (IP) with trimesoyl chloride (TMC) on the polysulfone (PSF) ultrafiltration (UF) membrane. The chemical change of the pre-oxidation aqueous phase solution was characterized by LC-MS. By optimizing the NaClO and NaOH content in the aqueous phase solution, the pure water flux was improved greatly and the salt rejection kept on a high level (>90%). The properties of NF membranes were characterized by XPS, SEM, AFM and contact angle. Through the NaClO pre-oxidation of the mixed diamine monomers of PIP and BHTTM in the aqueous phase solution, the active layer of NF membrane became thinner and the pore size of NF membrane was enlarged. Besides, after oxidation treatment by 3000 ppm active chlorine solution for 1 h, the NF membrane exhibited pure water flux (PWF) with 161 (LMH) and Na 2 SO 4 rejection of 92.1% under 0.6 MPa. The molecular weight cut-off (MWCO) of the NF membrane was greater than 500, which was calculated from the carbohydrates rejection. The good performance and the satisfactory stability of the novel high-flux NF membrane demonstrated its good potential in the practical application. [ABSTRACT FROM AUTHOR]

The interfacial polymerization based on the interlayer is an effective method for enhancing thin-film composite (TFC) nanofiltration (NF) membranes permeability. In this study, a polyvinyl alcohol (PVA) interlayer was constructed on a polyethersulfone substrate through a physical deposition method. Then the TFC NF membranes regulated by PVA interlayer were prepared, and conducted a quantitative analysis of the impact of the PVA interlayer on the permeation resistance of TFC NF membranes. The results indicated that after regulated by the PVA interlayer, the permeation resistance of the polyamide layer decreased slightly, from 0.130 to 0.106 bar h m−1, while the permeation resistance of the substrate decreased significantly, from 0.277 to 0.087 bar h m−1. These results indicated that the dramatic decrease in permeation resistance of substrate caused by PVA interlayer was main reason for enhanced permeability, enriching our understanding of the mechanism of the interlayer. [Display omitted] • TFC NF membranes regulated by PVA interlayer were fabricated. • A striped structure was formed on polyamide layer. • PVA interlayer greatly reduced the permeation resistance of substrate. • Reveal the main battleground for the PVA intermediate layer's role. [ABSTRACT FROM AUTHOR]

Creating a gradient structure in a separation layer is an effective approach for enhancing separation performance of thin film composite membranes. Here we present the preparation of a positively charged nanofiltration membrane with a gradient structure. An inner layer consisting of a loose polyester separation layer with large pores was formed through the interfacial polymerization (IP) reaction between triethanolamine (TEA) and trimesoyl chloride (TMC). And a dense and thin top layer composed of a polyamide separation layer was obtained by secondary interfacial polymerization (SIP) reaction using polyethyleneimine (PEI) along with unreacted TMC and residual acyl chloride groups of IP reaction. The influences of TEA concentration, PEI concentration and SIP time on the physicochemical properties and separation performances of the membrane were systematically analyzed. Our results show that the presence of the gradient structure optimized mass transfer pathways and reduced mass transfer resistance, resulting in significantly improved permeability of 13.0 ± 0.5 L·m−2·h−1·bar−1 (over 3 times compared with control-PEI), high MgCl 2 rejection of 91.7 ± 0.6 %, and an excellent stability and anti-fouling performance. Our work provides valuable insights and guidance for developing high-performance positively charged NF membrane with gradient structures. • A positively charged nanofiltration membrane with gradient structure was designed and obtained. • The gradient structure significantly improves the permeability of the nanofiltration membrane (over 3 times). • The T0.2-P0.5–10 membrane exhibits excellent stability and anti-fouling performance. [ABSTRACT FROM AUTHOR]

The synthesis of high selectivity and permeance thin-film composite (TFC) membranes frequently encounters a significant challenge in balancing the permeance-selectivity trade-off. Recent research has demonstrated that the incorporating of nanomaterials into fabricated thin film nanocomposite (TFN) membranes is a feasible strategy to overcome this permeance-selectivity trade-off. Here we proposed using calcium carbonate nanoparticles (n-CaCO 3) as organic phase additives to modulate interfacial polymerization (IP) reaction to prepare TFN membrane. Molecular dynamics (MD) simulation was employed to explore the effects of n-CaCO 3 addition on the dispersion of organic phase monomers and on the diffusion of water phase monomers. The prepared TFN membrane (TFN-0.03) loaded with very little n-CaCO 3 (0.03 wt%) exhibited a high permeability of 16.9 ± 0.5 L m−2 h−1 bar−1, which was 1.7 times greater than that of the TFC membrane, and also maintained a high selectivity (Na 2 SO 4 rejection: 98.8 %). Our work furnishes the theoretical and experimental basis for the development of high performance TFN nanofiltration (NF) membranes. [Display omitted] • TFN membrane was prepared by adding nano-CaCO 3 in organic phase to modulate IP reaction. • Molecular dynamics simulation shows nano-CaCO 3 affecting the dispersion of TMC and the diffusion of PIP. • The obtained TFN membrane has a thinner, smoother, and looser PA layer. • The TFN membranes exhibits excellent separation performance and good stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • TFN(O) membrane exhibits a high flux of 30.4 L∙m−2∙h−1∙bar−1 with 96% rejection for TCE. • The molecular orientation of n-hexane is affected by UiO-66. • The asymmetric distribution of UiO-66 in PA layer has been studied. • The tandem model of dissolution and diffusion in NF is applied to the MD simulation. Chlorinated hydrocarbons (CHC) are highly toxic to human health and the ecological environment. In this study, thin-film nanocomposite (TFN) membranes doping with UiO-66 were prepared and applied to the CHC removal in groundwater. TFN membranes with UiO-66 asymmetrically distributed in the polyamide (PA) layer were prepared by incorporating UiO-66 in the aqueous phase and the organic phase, respectively. Molecular dynamics (MD) simulation was applied to do further mechanism research. The water boundary layer surrounding UiO-66 induces a wrinkled phase interface when UiO-66 is dispersed in the aqueous phase. Also, the dissolution-diffusion model was used for investigating nanofiltration (NF) process. Water molecules show a faster dissolution rate and a higher dissolution equilibrium on the UiO-66 surface. UiO-66 exhibits twice the water number density relative to the PA due to super-hydrophilicity, which provides a greater driving force for the mass transfer of water. In addition, the diffusion coefficient of water in the UiO-66 pore is about 1.5 times that in PA. As a result, TFN(O) membrane exhibits a high pure water flux of 30.4 L∙m−2∙h−1∙bar−1 with the trichloroethylene (TCE) and trichlorobenzene (TCB) rejection above 96%. This work provides a solution for CHC removal of groundwater and a mechanistic explanation for the interfacial polymerization (IP) and separation process of doped nanoparticles. [ABSTRACT FROM AUTHOR]

Layer-by-layer self-assembly of polyelectrolytes is one of the most promising methods for preparing nanofiltration membranes. Here poly (sodium 4-styrenesulfonate) (PSS) and poly (diallyldim-ethylammonium chloride) (PDADMAC) were chosen to prepare polyelectrolyte multilayer (PEM) membrane. The effects of background salt concentration, PSS concentration, background salt types, the number of layers and the outermost functional groups on the separation performance of the PEM were investigated systematically. Molecular dynamic simulation was employed to simulate the influence of background salt on the diffusion of PDADMAC. The simulation results agree well with the experimental results. The optimized (PSS/PDADMAC) 4.5 membrane with Na 2 SO 4 as background salt shows permeance of 15.9 LMH/bar, Na 2 SO 4 rejection of 98.2 %, and an excellent stability. Our study provides both theoretical and experimental supports for the preparation of PEM membranes using LBL method. [Display omitted] • Affecting factors were systematically investigated for polyelectrolyte membrane prepared by layer-by-layer self-assembly. • MD simulation results show that different ions influence the diffusion rate of polyelectrolyte. • The obtained membrane shows excellent separation performance for corresponding salts. [ABSTRACT FROM AUTHOR]

The TFC RO/NF membranes are the predominant membranes applied in desalination, and heat curing is an essential step in its industrial production, which increases the polyamide cross-linking degree and facilitate packing but leads permeability decrease. Nevertheless, the mechanism of heat curing on TFC membranes permeation resistance changes is still ambiguous. Figuring it out will aid in crafting a more effective optimization strategy in high flux membrane preparation. Herein, we prepared a range of TFC RO/NF membranes with various monomer concentrations on different substrates and quantified the permeation resistance changes by a resistance-in-series model. For nascent TFC RO/NF membranes, the PA layer provided almost all permeation resistance. After heat curing, the substrate exhibited a marked increase in permeation resistance. The change in the permeation resistance composition was further exacerbated by the decrease in monomer concentration. For TFC NF membranes with heat curing, the proportion of substrate permeation resistance increased significantly, rising from 31.62 % to 75.05 %. This study made a comprehensive analysis of the impact of the permeation resistance in TFC RO/NF membranes caused by heat curing, enriched the insight into the impact of heat curing on TFC membranes, and helped to prepare TFC membranes with better desalination performance. [Display omitted] • The resistance proportions of RO/NF membranes are quantitatively revealed. • The substrate resistance increases significantly due to heat curing. • Low monomer concentration results in high substrate resistance. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) exhibits significant promise in tackling the worldwide water crisis, and the endeavor to develop high-performance NF membranes constitutes an essential long-term goal. In this study, an ionic liquid, [tetrakis(hydroxymethyl) phosphonium chloride, THPC], was employed as structural modifiers to prepare NF membranes. Hydrogen bonding effects between the hydroxyl group in THPC and the amino group in piperazine (PIP) decelerated the diffusion rate of PIP, which is verified by molecular dynamic simulations. This, together with the spatial effect provided by the unique tetrahedral structure of THPC, allowed to form a thinner, smoother, looser, and more hydrophilic polyamide selective layer. The resultant NF membrane achieved an ultra-high permeance (43.2 L m−2 h−1 bar−1) with satisfactory Na 2 SO 4 rejection (97.8%), and a significant enhancement in its antifouling performance. Our work has achieved simultaneous optimization of NF membrane permeation-selectivity and antifouling performance through simple and cost-effective measures, which will inspire the construction of the coming version of high-performance NF membranes. [Display omitted] • Molecular dynamics simulations confirm that tetrakis(hydroxymethyl) phosphonium chloride can reduce the diffusion rate of piperazine. • The obtained membrane shows high water permeance of 43.2 L m−2 h−1 bar−1 and Na 2 SO 4 rejection of 97.8%. • The TIP-0.01 membrane exhibits enhanced antifouling performance. [ABSTRACT FROM AUTHOR]

Given the critical requirements of environmental preservation and resource reutilization, the recovery of lithium from spent lithium-ion (LIBs) batteries holds immense significance. This study investigates the viability of nanofiltration (NF) membranes for selectively separating lithium from spent LIBs leaching solution. A membrane-based approach uniquely sidesteps the significant metal losses often encountered in traditional methods that necessitate initial pH adjustments. The NF270 and DK membranes were characterized and evaluated. DK demonstrated superior rejection capabilities for high-valence metal ions with over 99.0 % rejection, while allowing a notable 40.1 % lithium passage rate. Furthermore, DK showcased enhanced acid resistance compared to NF270. The findings underscore the characteristics essential for NF membranes in this application, and the study affirms the feasibility of membrane-based lithium recovery, marking a stride in battery recycling research. [Display omitted] • Proposed a novel membrane-based process for spent lithium battery recycling • The battery-grade lithium carbonate can be obtained through two-stage nanofiltration. • DK membrane exhibits excellent acid resistance and high-valence metal ion rejection to the leaching solution. [ABSTRACT FROM AUTHOR]

Active layers with outstanding organic solvent nanofiltration (OSN) performances were designed novelly by adopting host-guest (HG) interaction to realize adamantane structure immobilization. During the fabrication process, β -cyclodextrin (β -CD) served as the "host" while adamantylamine/adamantanemethylamine (AMA/AMmA) worked as the "guest". Stechiometrical experiment results demonstrated that one half molar ratio of the "guest" to the "host" molecular (1.0%, w/v) led to the best OSN performance. The successful immobilization of adamantane structure was verified by XPS , FT-IR and EDX results, and the adamantane immobilized membrane showed weakened "nodule-like" pattern and reduced surface roughness values compared with the control membrane. Acetone, for the first time, was proposed as the activation solvent for enhancement of OSN performance. After acetone activation, the morphology and topography of the adamantane immobilized membranes seldom changed but their pure methanol (MeOH) flux were quintupled (29.0 ± 2.6 L m−2 h−1) and the rose bengal (RB) removed from MeOH reached to 98.2 ± 0.1%. Those HG complexes also resulted in the reduction of molecular weight cut-off (MWCO) values from 466.6 Da to 436.9 and 428.4 Da of PCA10 1/2 + and PCAm10 1/2 +, respectively. Besides, the PCAm10 1/2 + demonstrated excellent OSN performances in the long-term operation of active pharmaceutical ingredients (APIs) concentration of clarithromycin (CLA)/acetone. Novel designed active layer immobilized adamantane structure with outstanding stability and membrane performances for organic solvennt nanofiltration (OSN). Image 1 • Host-guest chemistry was firstly utilized in OSN membrane development. • Adamantane structure was successfully immobilized into the active layer. • Activation of the OSN membrane using pure acetone was firstly proposed. • The mechanism of experimental errors of MWCO values was illuminated. • Outstanding performance in the potential application of API concentration was made. [ABSTRACT FROM AUTHOR]

[Display omitted] • MD simulations confirm that crown ether can reduce the diffusion rate of PIP. • Crown ether facilitates the formation of ultra-thin and highly cross-linked polyamide selective layers. • The obtained membrane shows high water permeance of 23.6 L m−2h−1 bar−1 and Na 2 SO 4 rejection of 99.2%. Nanofiltration (NF) membranes with high selectivity and high permeability are essential for efficient water purification. However, improving the performance of NF membranes by simple and effective methods remains challenging, as many of the reported improvements are difficult to scale up practically. In this work, we successfully prepared high-performance NF membranes using the hydrogen bonding interactions and host–guest interactions of crown ether (CE) and piperazine (PIP). Molecular dynamics (MD) simulation shows that the introduction of CE slows down the diffusion rate of PIP, thus effectively modulating the interfacial polymerization (IP) process, resulting in an ultra-thin (∼28 nm) and highly cross-linked polyamide selective layer. The TFC-CE0.5 membrane prepared under optimized conditions combines surprising permeability (water permeance: 23.6 L m−2 h−1 bar−1) and selectivity (Na 2 SO 4 rejection: 99.2%). Our work demonstrates an elegant and efficient approach to prepare high-performance NF membranes without major modifications to existing manufacturing processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultra-permeable PA NF membranes were prepared through porous 2D MOF nanosheets. • Ultra-thin porous 2D Al-MOF nanosheets provide additional water transport channels. • High water permeance of 42.4 L m−2 h−1 bar−1 and Na 2 SO 4 rejection of 97.0%. High-performance nanofiltration membrane is of great importance to alleviate the worldwide freshwater crisis. Recent studies have shown that the performance of nanofiltration membranes can be enhanced by optimizing the properties of the substrates. Substrates with large pores are favorable to mass transfer but difficult to prepare highly selective polyamide layers on them by interfacial polymerization reaction. Here we employed porous two-dimensional (2D) aluminum-metal organic framework (Al-MOF) nanosheets to tune the commercial Nylon microfiltration substrate, and then prepared polyamide nanofiltration membranes by interfacial polymerization. 2D Al-MOF nanosheets were chosen for the tuning material except for their obvious advantages of easy synthesis and structural stability, the most important thing was their high porosity, which provided additional water transport channels. The morphologies as well as the separation properties were analyzed systematically. The best-performing Nylon-2.5 TFC membrane achieved an ultrahigh permeability (42.4 L m−2 h−1 bar−1), 13 times that of a control (PES-0) TFC membrane prepared on commercial PES substrate under the same interfacial polymerization conditions while ensuring the high rejection of Na 2 SO 4 (97.0%). Our work provides insights for optimizing substrate properties to prepare high-performance nanofiltration membranes. [ABSTRACT FROM AUTHOR]

Abstract Novel polyamide/TiO 2 composite nanofiltration (NF) membranes were fabricated by interfacial polymerization of polyethyleneimine and trimesoyl chloride on TiO 2 -sol-modified ceramic hollow fibre microfiltration substrates. X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and dynamic contact angle measurements were utilised to characterise the chemical structures and morphologies of the prepared membranes. The effects of monomer concentration, reaction time, and immersion time in the aqueous phase were thoroughly investigated in this study. The composite NF membrane prepared under optimised conditions exhibited a high pure water flux (PWF) of 105.5 L m−2 h−1 and MgCl 2 rejection of 95.5% at 4 bar. In addition, the membrane had excellent antifouling properties with high permeate recovery and low flux decline for bovine serum albumin and humic acid. During a 168 h long-run test, the membrane maintained a high PWF (> 100.0 L m−2 h−1) and high MgCl 2 rejection (> 95.0%). Graphical abstract fx1 Highlights • Novel high-flux polyamide/TiO 2 composite nanofiltration membranes were fabricated on ceramic hollow fibre substrates. • The NF membrane showed a high pure water flux of 105.5 L m−2 h−1 and MgCl 2 rejection of 95.5% at 4 bar. • The NF membrane exhibited good antifouling property and stability. [ABSTRACT FROM AUTHOR]

Currently, most nanofiltration membranes exhibit satisfactory separation performance on the anions or cations, and few membranes could concurrently separate anion and cation. Therefore, preparing nanofiltration membranes with excellent separation performance for both anionic and cationic ions remains a challenge. Herein, we have developed a series of nanofiltration membranes using conventional interfacial polymerization with different ratios of trimesoyl chloride (TMC) and piperazine (PIP) concentrations. In the interface polymerization process, the amine groups carried by PIP imparted a positive charge, while the hydrolysis of acyl chloride groups resulted in the generation of carboxylic acid groups that introduced a negative charge. The mix-charged nanofiltration membrane could be fabricated by varying PIP/TMC concentration ratios. The optimized membrane exhibited high rejection rates for bivalent ions (Na 2 SO 4 rejection of 96.6 %, MgCl 2 rejection of 93.0 %), and its selectivity for Mg2+/Li+ mixed solution was improved significantly. This work provides a novel approach for the development of nanofiltration membranes capable of effectively separating mono-/divalent ions. [Display omitted] • Fabrication of mixed-charged polyamide membranes via regulating the PIP/TMC ratio directly. • High PIP/TMC ratio leads more unreacted amine groups in the polyamide which was beneficial to MgCl 2 rejection. • Such NF membrane showed excellent separation efficiency to Mg2+/Li+ and SO 4 2−/Cl−. [ABSTRACT FROM AUTHOR]

A novel positively charged nanofiltration (NF) membrane was fabricated by incorporating metal-organic frameworks (MOFs) into chitosan polymeric matrix for enhanced removal of multivalent cations. The synthesized MOFs, NH 2 -MIL-101(Al) and NH 2 -MIL-101(Cr), could be homogeneously dispersed in the chitosan polymeric matrix. The morphologies of MOFs had a significant influence on the permeability of NF membranes. NF membrane filled with NH 2 -MIL-101(Al) with rod-like structure attained two times higher flux but similar rejection compared with that filled with NH 2 -MIL-101(Cr) with grainy structure. The effect of MOF loadings (NH 2 -MIL-101(Al)) on the membrane performance were evaluated by XRD, FTIR and SEM. These positively charged MOF/chitosan NF membranes were able to reject up to 93.0% of MgCl 2 , and the salt rejection followed the order of MgCl 2 >CaCl 2 >NaCl>Na 2 SO 4 . [ABSTRACT FROM AUTHOR]

[Display omitted] • Four hierarchical structures of the selective layer of NF membrane are proposed. • Dot-field reconstruction describes PA layer structures and pore characteristics. • A new indicator is found to evaluate the uniformity of pore structure. Organic solvents have important influences on the morphology and performance of nanofiltration (NF) membranes. However, it is still unclear how organic solvents affect the polyamide (PA) selective layer of NF membrane. In this work, dissipative particle dynamics (DPD) simulation is employed to reveal the four hierarchical structures (Surface Structure Layer , Smooth Structure Layer , Heterogeneous Layer , Homogeneous Layer) of PA selective layer due to organic solvent (Pentane-PEN, Hexane-HEX, Heptane-HEP and Octane-OCT) gradients. And the method of dot-field reconstruction is proposed to analyze the morphology and pore structure of Homogeneous Layer. Moreover, the separation performances of Homogeneous Layer formed in different solvents were evaluated. It is proposed how to choose a suitable solvent, indicating the theoretical feasibility of preparing large-flux and high-rejection NF membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The solvation effects of organic anions are investigated in OSN. • Solvation structures exhibit solvent-separated ion pairs and contacting ion pairs. • Pseudo-solvation structure undergoes desolvation due to Na+ transmembrane. • Mixed solvents can be used to regulate solvation size for efficient separations. The solvation effect plays a critical role in chemical reactions and ion transport process, but most studies focus on the solvation effect of metal ions, such as Li+, Mg2+ and so on. Few studies have explored the solvation of organic ions with more complex structures than metal ions. In this work, the solvation effect of organic ions in the organic solvent nanofiltration (OSN) process is investigated, in which methyl orange (MO) is selected as the model organic anions. The solvent-separated ion pairs (SSIP) and contact ion pairs (CIP) are found to form in protic and aprotic solvents, respectively, caused by the differences in solvent polar groups, and the transmembrane mechanism of organic anions in protic and aprotic solvents. Then, the solvation structure of mixed solvent is studied from molecule level, which is further validated by experiment. The addition of water can regulate the solvent environment around MO and weaken adverse effect on rejection performance due to the desolvation process in aprotic solvents. This work is of great significance for achieving high-efficiency separation by adjusting solvation structures, which expands the application scenarios of single membranes. [ABSTRACT FROM AUTHOR]

Heavy metal ions in drinking water severely threaten public health in various places worldwide. Nanofiltration (NF) membrane technology is an attractive option for heavy metal ions removal; however, improving NF membrane filtration performance is required to make their industrial application viable. In this study, a positively charged THPC/PEI-TMC NF membrane was designed via simple one-step incorporation of Tetrakis (hydroxymethyl) phosphonium chloride (THPC) biocide on the surface of PEI-TMC membranes, significantly optimizing surface morphology, roughness, hydrophilicity, and zeta potential of PEI-TMC membranes. It was found that the pure water permeability (11.6 Lm−2h−1bar−1) of the THPC modified membrane was three times larger than that of the original PEI-TMC membrane (3.4 Lm−2h−1bar−1) while maintaining a high level of ion rejections (around 95% for Zn2+, Cd2+, Ni2+, Cu2+ and about 90% for Pb2+). Additionally, the incorporation of the THPC on the original PEI-TMC membrane surface also conferred good antibacterial properties, which protect the organic membrane from bacterial growth and prolong the lifespan of the membrane. [Display omitted] • Improved significantly hydrophilicity due to the incorporation of THPC. • More than three times increased for PWF from 3.4 Lm−2h−1bar−1 to 11.6 Lm−2h−1bar−1. • Outstanding antibacterial properties were obtained due to the incorporation of THPC. • THPC/PEI-TMC membranes with excellent rejection performance for removing heavy metal ions. [ABSTRACT FROM AUTHOR]

Electrospray-assisted interfacial polymerization has recently raised researchers' attention during membrane fabrication process due to the thickness of the polyamide layer is tunable in nanometers. Here we report that 2D molybdenum disulfide (MoS 2) nanosheets could endow the electrospray-assisted interfacial polymerization polyamide membrane with improved selectivity at a short spray time. The nanosheets dispersed uniformly under the electric field. The optimal TFN-15 membrane demonstrated water permeance of 9.23 L m−2 h−1·bar−1 and Na 2 SO 4 rejection of 95.4%. Furthermore, the obtained polyamide membranes showed splendid stability and antifouling. Our research provides an effective strategy for the optimization of the fabrication process of the electrospray-assisted interfacial polymerization polyamide membrane with high-performance. [Display omitted] • 2D nanosheets optimize the electrospray-assisted membrane fabrication process. • MoS 2 nanosheets dispersed well under electric field. • The obtained polyamide membrane had excellent separation performance. [ABSTRACT FROM AUTHOR]