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This study reports highly permeable ultrathin film composite (uTFC) membranes whose rejection layer was reinforced by polymer chains during the interfacial polymerization of trimesoyl chloride (TMC) and m-phenylenediamine (MPD) to achieve enhanced salt rejection. A rejection layer of approximately 20 nm was formed at an MPD concentration of 0.01 wt%. This reinforced membrane had a water permeability of about 16.7 L/(m2 h bar), while exhibiting an improved divalent salt (Na 2 SO 4) to monovalent salt (NaCl) selectivity compared with the control TFC membrane without reinforcement (3.44 vs. 1.06). The role of the reactable polymer chains in interfacial polymerization was discussed as MPD adsorbent and reactant, according to the measurements by quartz crystal microbalance and X-ray photoelectron spectroscopy. This work provides a new pathway for the design and construction of uniform ultrathin layers as well as the preparation of high performance separation membranes. [ABSTRACT FROM AUTHOR]

Abstract Using hydroxypropyl-β-cyclodextrins (OH-β-CD) as aqueous phase additive, nanocavity-contained thin film composite (TFC) nanofiltration (NF) membranes were prepared by interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). Attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopy analysis confirmed the successful incorporation of OH-β-CDs into the thin polyamide rejection layers. The rejection layer morphologies and structures, surface properties and separation performances of the prepared TFC membranes were greatly influenced by the OH-β-CD mass ratio in aqueous phase during interfacial polymerization. With appropriate OH-β-CD mass ratios (20–60%), the prepared TFC membranes showed enhanced water flux, reduced R NaCl , increased R Na2SO4 and R MgSO4 , which led to highly improved divalent to monovalent ions selectivity. These nanocavity-contained TFC membranes exhibited the potential to apply in desalination pretreatment. Graphical abstract Unlabelled Image Highlights • Nanocavity-contained TFC membrane was formed by interfacial polymerization. • β-CDs were incorporated into the polyamide rejection layer to form nanocavities. • Nanocavity-contained TFC membrane showed enhanced water permeability. • The prepared TFC membrane showed high divalent to monovalent ion selectivity. [ABSTRACT FROM AUTHOR]

In this study, we investigate the use of reactable substrates for interfacial polymerization of polyamide membranes. Two reactable group (hydroxyl group) contained substrates were prepared. Using m -phenylenediamine (MPD) and trimesoyl chloride (TMC) as monomers, thin film composite (TFC) membrane formed thereon displayed varying film morphology, chemical composition and separation performance. The substrate participating TFC membrane showed a thicker rejection layer with greater crosslinking density. The latter was caused by the formation of ester bonds in addition to amide bonds. This polyamide/polyester composite rejection layer had greatly enhanced NaCl and Na 2 SO 4 rejection compared to the control membrane prepared on inert substrate. We further proposed a conceptual model that highlighted the important role of amphiphilic copolymers as (1) MPD enrichment loaders, (2) reactive monomers and (3) surfactants in the interfacial polymerization process. [ABSTRACT FROM AUTHOR]

We applied a polydopamine (PDA) coating on a thin film composite (TFC) forward osmosis (FO) membrane and investigated the effects of coating on FO mass transport and antifouling behavior. The PDA coating significantly improved membrane surface hydrophilicity as well as reduced membrane surface roughness. Using a short PDA coating duration of 0.5 h, the coated membrane TFC-C0.5 achieved enhanced FO water flux and reduced reverse solute diffusion simultaneously. The reduced reverse solute diffusion can be attributed to the enhanced membrane selectivity: TFC-C0.5 had better rejection and similar water permeability compared to the original TFC membrane. This reduction in reverse solute diffusion further reduced the internal concentration polarization inside the coated membrane, leading to an enhanced FO water flux. Nevertheless, longer PDA coating duration of 1–4 h resulted in reduced FO water flux due to the significantly increased hydraulic resistance of the coated membranes. The PDA coated membrane TFC-C0.5 also presented an improved antifouling performance compared to the control membrane using alginate as a model foulant. Our results reveal the great room for the development of effective coating materials in FO: a well-designed coating with high selectivity and low hydraulic resistance can improve solute rejection, reduce reverse solute diffusion, mitigate internal concentration polarization and enhance FO water flux in addition to control fouling. Such unprecedented opportunities break the traditional trade-off between water flux and antifouling performance when coating pressure driven reverse osmosis membranes. [ABSTRACT FROM AUTHOR]

We performed chlorination experiments to understand the impact of hypochlorite exposure on both cation exchange membranes (CEMs) and anion exchange membranes (AEMs) regarding their properties and performance in a reverse electrodialysis (RED) stack. Changes in membrane morphology, surface elemental composition and chemical bounding suggested the chlorine incorporation in the form of C-Cl bonds and side-chain cleavage of –SO 3 - or –NR 3 + containing molecular fractions. These observations were further supported by observed increases in hydrophobicity and decreases in fixed charged groups of the membranes, respectively. Compared to CEMs, AEMs were less chlorine resistant such that the development of more extensive cracks in the membrane structure further increased water content and dramatically decreased membrane conductivity. The performance of both chlorinated CEMs and AEMs were tested in an RED stack and the results showed the reduced RED power density was largely attributed to the deteriorated electrical properties of AEMs. [ABSTRACT FROM AUTHOR]

We report a fast, simple, and green coating method using the coordination complex of tannic acid (TA) and ferric ion (Fe3+) to enhance the removal of trace organic contaminants (TrOCs) by polyamide membranes. The entire coating process can be completed in less than 2 min; quartz crystal microbalance characterization revealed that a TA-Fe thin film formed in merely 10-20 s. Coating this TA-Fe thin film on a commercial nanofiltration membrane (NF270) reduced its effective pore size from 0.44 to 0.40 nm. The TAFe-coated NF270 showed significantly increased rejection of both NaC1 and trace organic contaminants. In comparison with the more-time-consuming polydopamine coating (e.g., 0.5 h), the TA-Fe coating presented greater resistance to TrOC permeation (i.e., lower permeability of TrOCs). The advantages of the fast coating process, greatly improved rejection performance, and use of green accessible materials make TA-Fe a highly promising coating material for large-scale applications. [ABSTRACT FROM AUTHOR]

Four tertiary amine based amphiphilic copolymers with similar composition but different sequence structures in terms of diblock (Poly(dimethylamino-2-ethyl methacrylate- b -methyl methacrylate) (P(MMA- b -DMAEMA))), triblock (P(DMAEMA- b -MMA- b -DMAEMA)), four-armed diblock (P(MMA- b -DMAEMA) 4 ) and random (P(MMA- r -DMAEMA)) were synthesized and used for fabricating functional porous membranes by blending method. The retention ratios and surface enrichment ratios of the copolymers in blend membranes were determined by hydrogen nuclear magnetic resonance ( 1 H-NMR) and X-ray photoelectron spectroscopy (XPS). The composition of the formed membranes was investigated and the durability was experimentally tested. The hydrophilicity of the membranes was evaluated by water contact angle measurement. The performance of membranes under different conditions including water fluxes at different pH and various ionic strength, the adsorption capabilities for Cr(VI) and negatively charged dye sunset yellow at different pH was studied. The results show that tertiary amine based amphiphilic copolymers with block and multi-armed sequence structures enable the blend membranes with higher copolymer retention ratios, more surface tertiary amine groups contents and better composition stability as well as more sensitive to the variation of pH, ionic strength, higher equilibrium anions, and negatively charged dyes uptakes. [ABSTRACT FROM AUTHOR]

To obtain ultrafiltration (UF) membranes with multi-functions in permeation, macromolecule sieving and specific heavy metal removal by adsorption, tertiary amine groups containing amphiphilic block copolymers (poly(methyl methacrylate- b -dimethylamino-2-ethyl methacrylate) (P(MMA- b -DMAEMA))) were designed and synthesized. Then the block copolymers were used to fabricate the tertiary amine block copolymer containing blend membranes with poly(vinylidene fluoride) (PVDF) via a non-solvent induced phase separation (NIPS) process. Hydrogen nuclear magnetic resonance ( 1 H NMR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the bulk and the surface layer compositions of the prepared membranes. It was found that P(MMA- b -DMAEMA) stably retained in the blend membranes and greatly enriched onto the surface layers. The pH-dependent performances of the membranes were investigated in details. With the change of pH values, the surface hydrophilicity, water permeation, dextran sieving behaviors and hexavalent chromium (Cr(VI)) adsorption properties varied greatly. And the membrane performed obviously reversible pH-dependent property. From the results, a feasible method could be inferred for fabricating UF membranes with tunable filtration, macromolecule sieving and anion adsorption properties under different pH conditions. [ABSTRACT FROM AUTHOR]

We report a novel forward osmosis (FO) membrane prepared by a green tannic acid/iron (TA/Fe) coordination chemistry to selectively separate and recover organic source from salty water. The microscopic and x-ray photoelectron spectroscopy (XPS) characterizations confirmed the formation of a thin continuous TA/Fe rejection layer with a thickness of 20–30 nm on a polyacrylonitrile (PAN) substrate. This TA/Fe-PAN membrane showed a high water permeability (A) of 14.2 ± 1.7 Lm−2h−1bar−1, a high rejection of 99.5 ± 0.1% for a low-molecular dye sunset yellow and low rejection of 27.6 ± 2.7% for NaCl under reverse osmosis (RO) mode. The membrane selectivity to sunset yellow was nearly three orders of magnitude greater than that of NaCl, revealing its preference towards organic dye retention and salt passage. As a result of its higher water permeability and the prevention of salt accumulation during FO tests, the TA/Fe-PAN membrane showed significantly higher FO water flux compared to that of a commercially available polyamide thin film composite membrane. It could concentrate sunset yellow from a salty FS solution with a concentration ratio of 9.6 and mild salt accumulation at the water recovery ratio of 90%. The results demonstrated the feasibility of selective separation and resource recovery for target solutes from salty even more complicated water matrix via proper membrane chemistry design in FO. Image 1 • A green TA/Fe-PAN FO membrane was fabricated. • The membrane had much higher selectivity of dye than that of NaCl. • The membrane achieved remarkable concentration ratio of dye from salty water. • The membrane could be used for selective separation and resource recovery. [ABSTRACT FROM AUTHOR]

A nanofiltration-like (NF-like) forward osmosis (FO) membrane was prepared by interfacial polymerization and applied for seawater pretreatment. The prepared NF-like FO membrane shows much higher water permeability and higher divalent salt to monovalent salt selectivity compared to a commercial reverse-osmotic-like (RO-like) FO membrane. The comparison between NF-like FO membrane and RO-like FO membrane in FO process was systematically investigated by using an antiscalent (sodium polyacrylate, PAANa) solution as draw solution. Both NF-like and RO-like FO process showed high rejection of alginate and sulfate. However, the water flux and monovalent salt (NaCl) passage in NF-like FO process were much higher, which enables the NF-like FO membrane to be a better candidate for pretreating seawater. The findings provide new insights on the design and preparation of FO membranes for seawater pretreatment. Unlabelled Image • NF-like forward osmosis membrane was used to pretreat seawater. • Efficiency of NF-like and RO-like FO for desalination pretreatment was compared. • NF-like FO had much higher water flux than RO-like FO. • NF-like FO had adequate removal of alginate and sulfate. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Thin film composite (TFC) polyamide membranes set the golden standard for reverse osmosis technology, but tuning their permeability and selectivity remains a major challenge because of the inherent permeability-selectivity trade-off. Creating nano-sized voids within the polyamide rejection layer can tune the membrane roughness and increase its effective filtration area to improve the water permeability. Here we prepare nano-foamed polyamide rejection layers by adding sodium bicarbonate into the aqueous solution of amine monomers. We show a systematic evolution of the roughness structure of polyamide membranes, with increasingly leaf-like and belt-like features appearing under enhanced nano-foaming conditions. These nano-foamed features can result in remarkable improvements in both water permeability and salt rejection and reduce membrane fouling propensity at the same time. Our study paves a new research direction for designing future generation of desalination membranes, which holds vast potential to reduce the cost and energy consumption of desalination while achieving improved product water quality. [ABSTRACT FROM AUTHOR]

We designed a highly selective surface coating to achieve enhanced rejection of endocrine disrupting compounds (EDCs) by nanofiltration membranes. A commercial NF90 membrane was first coated with polydopamine (PDA) followed by in situ immobilization of silver nanoparticles (AgNPs). This PDA/AgNPs coating greatly improved EDC rejection at the expense of slight water permeability loss (4–10%). This improvement in rejection can be attributed to a combination of enhanced size exclusion and suppressed hydrophobic interaction. A resistance-in-series analysis further reveals that the coating was highly permeable to water but highly resistant to EDCs, leading to an EDC selectivity that was an order of magnitude greater than those of the bare PDA coating and the base membrane NF90. The current study provides important insights into the design of highly selective coatings for effective retention of targeted trace organic contaminants. [ABSTRACT FROM AUTHOR]

A novel composite nonwoven separator exhibiting high heat resistance, high ionic conductivity and high lithium ion transference number is fabricated by a simple dip-coating and heat treatment method. The thermal stable polyimide (PI) nonwoven matrix is chosen as a mechanical support and contributes to improving the thermal shrinkage of the composite nonwoven separator (abbreviated as IACS). The cross-linked poly(2-acrylamido-2-methylpropanesulfonic acid) PAMPS(Li + ) gel polymer electrolyte (GPE), lithium ion sources of a single ion conductor, is introduced into the PI nonwoven matrix and acts as a functional filler. This PAMPS (Li + ) GPE is proved to be able to provide internal short circuit protection, to alleviate liquid electrolyte leakage effectively, to supply more lithium ions dissociating from PAMPS (Li + ) by liquid electrolyte solvent, to contribute a more stable interfacial resistance, and thus resulting in an excellent cyclability. More notably, the migration and mobility rate of anions could be hindered by the −SO 3 − group in the PAMPS (Li + ) polymer based on electrostatic interaction, giving rise to a very high lithium ion transference number. These fascinating characteristics endow the IACS a great promise for the application in the high power and high safety lithium ion batteries. [ABSTRACT FROM AUTHOR]

Anion exchange membranes (AEMs) with excellent antifouling property are essential for treating highly saline organic wastewater through electrodialysis (ED). In this study, we proposed a strategy of surface charge inversion to construct a blocked- nanolayer based on in-suit dopamine (DA) deposition followed by grafting negative-charged 2-acrylamide-2-methylpropanesulfonic acid (AMPS) for promoting the antifouling performance of AEM. It's indicated that the surface hydrophilicity and negative charge density was gradually enhanced with the increase of AMPS grafting density without sacrifices of ion exchange capability, swelling ratio and desalination performance. In the simulated fouling experiments, the optimal AEM-AMPS-105 membrane exhibited excellent antifouling property due to the improved surface hydrophilicity and high electrostatic repulsion against organic matter. It's highlighted that the transmembrane voltage of modified membrane after operating 200 min was reduced from 7.12 V to 4.85 V with a significant decrease of energy consumption by 55.1 % while maintaining a high current efficiency level of 85.5 %. Moreover, the modified membrane performed significantly enhanced salt/contaminant selectivity and high stability in dye wastewater treatment. We anticipated that the construction of charge-blocked nanolayer by surface charge inversion offered a practical method for improving the organic fouling-resistance of AEMs. [Display omitted] • An anion exchange membrane with a negative-charged blocking nanolayer was developed by surface charge inversion. • Surface hydrophilicity and negative charge density was gradually improved with the increase of AMPS grafting density. • The constructed AMPS nanolayer contributed to formationing the hydration layer and enhancing the electrostatic exclusion effect. • Modified AEM exhibited excellent antifouling ability and stability. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) hollow fiber membrane holds tremendous potential for the treatment of complex wastewater due to its outstanding chemical and thermal stability. However, its treatment efficiency is often hindered by the low water permeate flux arising from the inherent hydrophobicity of PTFE. Here, we present a gentle and convenient hydrophilic modification method that involves immersion in a nonionic surfactant aqueous solution, followed by dopamine self-polymerization. The nonionic surfactant facilitated the penetration of the dopamine solution into the membrane, where dopamine self-polymerized to form a hydrophilic layer on the surface and inner pores of the membrane. The hydrophilicity-modified PTFE hollow fiber membranes demonstrated an impressive increase in water permeate flux, reaching 10231.4 L m−2 h−1, nearly ten times that of the original membrane. Even after prolonged exposure to a strong acid solution (pH = 1) or an oxidant solution (1000 mg L−1 NaClO) for two weeks, this membrane still maintained its favorable water permeability. Furthermore, the modified PTFE membranes also exhibited remarkable resistance to fouling by humic acid. These results showcased a straightforward method for designing a hydrophilic layer on PTFE hollow fiber membranes, underscoring their significant potential for real wastewater treatment applications. [Display omitted] • Mild and convenient method for hydrophilic modification of PTFE membranes. • Overall hydrophilic modification on the surface and within pores. • Maintaining excellent water permeability under acidic and oxidizing conditions. • Improved resistance to humic acid (HA) and high flux for tap water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crosslinking the copolymer enhanced its migration resistance and membrane stability. • The membrane exhibited pH-dependent adsorption and easy recovery properties. • The membrane removal/regeneration process resulted in the concentration of purified target pollutants. In this study, a blend membrane consisting of polyvinylidene fluoride (PVDF) and tertiary amine containing random copolymer poly(methyl methacrylate-r-dimethylamino-2-ethyl methacrylate) (P(MMA- r -DMAEMA)) was fabricated and utilized as an adsorptive membrane for micropollutants (anionic dye and heavy metal ions) removal from aqueous solutions. Cross-linking the random copolymer by p-xylylene dichloride (XDC) produced the membrane with improved copolymer retention ratio and stability, while slightly variated physicochemical properties. Besides, the fluxes of crosslinked blend membranes dramatically increased from 0.7 ± 0.1 L/(m2h) to 118.6 ± 5.9 L/(m2h). Then the present blend membrane was carried out adsorption and filtration experiments to investigate the influence of various of operation parameters including initial solution pH value, contacting time, initial solution concentration, and recycling efficiency on micropollutants removal. The experimental results showed that the removal of the anionic dyes and heavy metal ions on this tertiary amine containing blend membrane was a pH-dependent process with the maximum adsorption capacity at the initial solution pH of 3.5 for anionic dyes and 6.0 for metal ions, respectively. The membrane showed highly efficient capture of sunset yellow (above 99%). Meanwhile, the captured sunset yellow was recovered and concentrated with a small volume of alkaline solutions at pH 10.0, which simultaneously regenerated the membrane for its reuse. In a 3-cycle capture-recovery test, the membrane demonstrated a high sunset yellow recovery ratio and a volumetric concentration ratio as high as 400%. Our study provides an alternative strategy for functionalized membrane fabrication, micropollutants removal and recovery. [ABSTRACT FROM AUTHOR]

Antibacterial electrospun nanofibrous membranes for PM 1.0 filtration. [Display omitted] • Green antibacterial peptide was employed to modify nanofibrous membrane. • The grafting density of peptide reached to 387.24 ng cm−2. • This membrane exhibited excellent PM 1.0 segregation performance. • The antibacterial efficacy of E. coli and B. subtilis can reach to 99.86% and 99.99%. Segregating airborne particulate matters (PMs, especially PM 1.0) with high transmissibility of bacterial and viral pathogens is crucial for ensuring outdoor breathing safety. Electrospun nanofiber membranes (ENMs) have shown great promise for this purpose. However, the application of traditional ENMs is usually plagued by bacterial growth causing severe public health concern. Although some research has been done to overcome this challenge by doping antibacterial materials, the potential negative effects of these materials on the human body cannot be ignored. In this study, the ε-Poly-L-lysine (ε-PL), a green broad-spectrum antibacterial reagent, was grafted onto the surface of polydopamine (PDA) coated polyacrylonitrile (PAN) ENM via addition of Schiff base and Michael reaction. Experimental results indicated that the introduction of the ε-PL is key to the antibacterial performance of the membranes, and the antibacterial efficacy of E. coli and B. subtilis can reach to 99.86 % and 99.99 % respectively. Even after 7 days, the antibacterial efficiency of membrane remained at a high level. Additionally, the uniform structure of membranes endowed it with a high filtration efficiency of 80.9 % for PM 1.0 particles with a moderate transmembrane pressure drop (TMP) of 250 Pa and the corresponding quality factor is approximately 0.0066 Pa−1. This study has far-reaching implications for the design of green antibacterial nanofibrous membranes to realize the segregation of harmful PMs. [ABSTRACT FROM AUTHOR]

The cationic covalent organic frameworks (COFs) with editable pore environment and pore size are promising candidates for constructing the ion channel of anion exchange membranes (AEMs) with excellent separation properties, but the high reversible linking bond (e.g. imine) makes these membranes unstable in the industrial applications. In this work, the keto-linked COF (TpTG Cl) with high acid-stability was fabricated on the surface of carboxyl-modified polyacrylonitrile (CPAN) ultrafiltration membrane. The COF active layer with positively charged property in pore channels afforded high separation factor of H+/Fe2+ up to 450 under batch dialysis process. Owing to the electrostatic repulsion, the cationic nanopore demonstrated a screening feature that transmitted H+ and rejected Fe2+. Moreover, the membranes (TpTG Cl /CPAN) exhibited outstanding acid-stability, which could maintain high separation performance after 10 cycle under strong-acid conditions. The result suggested that COF with chemical stability and functional embellishment offered opportunities to synthesis high performance ion exchange membrane, and it could further be leveraged to tackle other challenges in membrane separation field. [Display omitted] • TpTG Cl is in-situ fabricated on surface of CPAN. • TpTG Cl /CPAN shows the outstanding separation factor (H+/Fe2+). • TpTG Cl /CPAN maintains the excellent acid-stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • COFs (Covalent organic frameworks) was chosen as the shell material in heterogeneous catalyst. • A yolk-shell (Pd/C)@TpPa COFs catalyst was synthesized via a template method. • The catalytic performance was tested in Suzuki reaction. • The heterogeneous catalyst showed a high conversion with only 0.05 mol% Pd loading. • Catalytic selectivity by size exclusion due to COFs was observed, amounting to 100%. • The heterogeneous catalyst also showed good recyclability. • Environment-friendly, stable, and robust nano catalyst for cross-coupling reactions. A novel catalyst with a yolk-shell structure was designed to overcome the leaching of noble metals in heterogeneous catalysis. Through a template method, palladium (Pd) nanoparticles were encapsulated by hollow spherical covalent organic frameworks (COFs) consisting of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) and p-phenylenediamine (Pa). The final catalyst with a yolk-shell structure was denoted as (Pd/C)@TpPa COFs. The unique morphology and chemical structure of this novel composite (Pd/C)@TpPa COFs were confirmed by a transmission electron microscope (TEM), a laser particle analyzer, X-ray diffraction (XRD), and N 2 adsorption and desorption. Subsequently, to demonstrate its catalytic performance brought by structural design, this novel catalyst was applied to catalyze the Suzuki reaction. Interestingly, this catalyst exhibited a brilliant size cutoff efficiency for aryl benzene amounting to 100% and achieved a high conversion with only 0.05 mol% Pd loading. Besides, this catalyst could be readily recovered via filtration and reused for at least five consecutive cycles without any significant loss in its activity. [ABSTRACT FROM AUTHOR]

The aminated electrospun nanofiber membrane (ENFM) was synthesized via facile method and used as the PRB material to remediate Cr(VI) contaminated soil. • A facile strategy for fabricating aminated electrospun nanofiber membrane was developed. • This membrane exhibited excellent Cr(VI) adsorption performance. • The interaction between Cr(VI) and amino group was systematically investigated. • This membrane was used as PRB material for Cr(VI) contaminated soil remediation. Electrokinetic remediation (EKR) combined permeable reactive barrier (PRB) is an emerging technique for the in-situ hexavalent chromium (Cr(VI)) heavy metal contaminated soil remediation. In the EKR-PRB technique, PRB materials with high Cr(VI) adsorption capacity and regenerability are severe desired. Here, a promising PRB material of aminated electrospun nanofiber membrane (ENFM) was synthesized by a facile short time thermal treatment of an hyperbranched polyethylenimine (HPEI)-enriched polyacrylonitrile (PAN) ENFM. The as-prepared PAN/HPEI ENFM exhibited a remarkable Cr(VI) adsorption capacity (~206 mg g−1) and excellent reusability (>9 cycles) owing to its amine group-rich membrane surface and interpenetrating porous structure. More importantly, a bench-scale Cr(VI) contaminated soil remediation test using a EKR-PRB technique showed that this PAN/HPEI ENFM could effectively immobilize and remove the Cr(VI) in soil. [ABSTRACT FROM AUTHOR]

The ion-ion precise separation is of paramount importance but presents significant technical challenges. Achieving such an accurate separation utilizing nanofiltration (NF) membranes demands ion-selective channels with appropriate pore geometry structure and charge property. In this work, thinner polyamide (PA) NF membranes with narrower pore size distribution than conventional NF membranes were fabricated via the porous organic polymer (POP) interlayer-mediated interfacial polymerization. The dual-rigid-distorted POP interlayers were incorporated in situ onto the substrates through azo-coupling reactions. The POP interlayers exhibited a high-density adsorption capacity of amine monomers and acted as a space manipulator that regulated their diffusion behavior into the oil phase, enabling their reaction with the acyl chloride. The synergistic effects engendered a uniform PA active layer and impeded further growth of the membrane, compared with the typical PA membranes, facilitating the generation of a thin and a narrow pore size distribution PA active layer with a nanostripe surface. The prepared NF membranes showed an outstanding ion-ion separation factor of Li+/Mg2+ (up to 78.56), almost 18 times that of the pristine NF membrane (4.32), along with a two-fold increase in water permeance. Furthermore, the newly developed NF membranes demonstrate long-term stability under operational pressure, thus highlighting the promising potential of these NF membranes for extracting Li+ from salt-lake brines. [Display omitted] • Dual-rigid-twisted POP interlayers were used to modulate NF membranes. • NF membranes with narrow pore size distribution and small mean pore size were prepared. • A high Li+/Mg2+ separation factor up to 78.56 was achieved. • Extraction of Li+ from the mixed salt solution showed efficiency and stability. [ABSTRACT FROM AUTHOR]

Bilirubin, a severe endogenous toxin, underscores the critical need for the development of bilirubin adsorbents exhibiting both high removal efficiency and exceptional hemocompatibility. Such advancements are pivotal for augmenting the efficacy of hemoperfusion therapy in managing hyperbilirubinemia. Here, a polyacrylonitrile-polyethyleneimine (PAN-PEI) nanofiber membrane (NFM) with elevated amino content was prepared using a facile reflux method for bilirubin adsorption. The PAN-PEI NFMs exhibited a significantly augmented surface amino density of 23.5 mmol.m−2, consequently achieving a remarkable bilirubin adsorption capacity of 87.65 mg.g−1, along with an impressive removal efficiency of 92.3% for bilirubin. Additionally, these nanofiber membranes displayed excellent hemocompatibility, including minimal hemolysis rates, significant anti-protein and anti-hemocyte adhesion properties, as well as a certain degree of anticoagulant activity. These results indicate that the vast potential of using PAN-PEI nanofiber membranes for hyperbilirubinemia hemoperfusion therapy. [Display omitted] • The amino-rich nanofiber membrane was fabricated via a facile reflux method. • This membrane exhibited excellent bilirubin adsorption ability. • The hydrophilic surface promoted the hemocompatibility. [ABSTRACT FROM AUTHOR]

Developing polyamide (PA) reverse osmosis (RO) membrane with chlorine resistance is of great significance for simplifying pretreatment processes and saving operating costs. Herein, we constructed an active layer capable of highly chlorine stability and regenerative chlorine resistance by introducing p-amino diphenylamine (p-ADA) with redox activity via a facile secondary interfacial reaction (s-IR) on PA membrane surface. The calculation of resistance-in-series model indicated that the introduction of p-ADA facilitated the increase of NaCl transmembrane resistance without sacrificing membrane permeance. Chlorination experiments under acid conditions proved the protection effect of p-ADA grafted layer due to its oxidation resistance, avoiding the direct attack by free chlorine to amide bonds of polyamide membrane. By virtue of the convertible modality of the p-ADA molecule between the quinone and benzene structures during redox process, modified membranes presented the capability of regenerative chlorine resistance. After the "chlorination-reduction" cycle experiments, the normalized flux of modified membranes remained 0.522 while contrasted PA membranes showed a flux of 0.278; and the corresponding normalized NaCl rejection of modified membranes maintained at 0.998 significantly higher than that of PA membranes (0.963). This study presents a straightforward and efficient approach to enhance the chlorine resistance of PA RO membranes. [Display omitted] • p-ADA was adopted to modify the PA RO membrane by a secondary interfacial reaction. • The grafted p-ADA could cover and heal the defects of the PA membrane. • The modified membranes showed improved chlorine resistance with a higher salt rejection. • The redox feature of p-ADA molecules endowed the modified membranes with regenerative chlorine resistance. [ABSTRACT FROM AUTHOR]

To minimize the internal polarization concentration (ICP) in FO process and improve the structural stability of thin film composite (TFC) forward osmosis (FO) membrane, a reactable hydrophilic nanofiber substrate was prepared by vacuum filtrating an interlayer composed of polydopamine nanoparticles (PDA NPs) onto an electrospun polyacrylonitrile nanofiber substrate. Then a TFC FO membrane with dense selective layer, low structure parameter, high water permeability and low salt permeability was prepared by the interfacial polymerization thereon. According to the T-peel test, the resulting TFC FO membrane showed greatly improved adhesion strength between selective layer and substrate due to the chemical bonding and entanglement between polyamides and the PDA NPs, and the strong adhesion between PDA NPs and the nanofibers. The ICP in FO process for the resulting membranes were minimized due to the application of the nanofiber substrates with low structure parameter (in the range of 290 ± 36 μm–354 ± 20 μm). These FO membranes performed well in the heavy metal ions contained water treatment, showed 1–2 times higher water flux (29.2 ± 0.3 L/m2h) compared with commercial TFC membrane (HTI-TFC) and high heavy metal ions rejection (99.5% ± 0.4%, 99.1% ± 0.5%, 98.1% ± 0.7% for Cr3+, Cu2+ and Ni2+, respectively) when using 2.0 M NaCl as draw solution. The findings provide the pathway for the design of nanofiber based FO membrane with improved structure stability and high performance by interfacial polymerization. Image 1 • PDA NPs composed interlayer was filtrated onto the nanofiber substrate. • TFC FO membrane was prepared on the PDA NPs modified nanofiber substrate. • Adhesion strength was greatly improved by using the PDA NPs modified substrate. • The ICP in FO process was minimized by using the prepared FO membrane. • The prepared FO membrane performed well in heavy metal ions removal. [ABSTRACT FROM AUTHOR]

Electrodialysis is a commonly used desalination method. In this study, we investigate its hybridization with its reverse process, where reverse electrodialysis (RED) harvests the salinity gradient power to provide the driving force for electrodialysis. In particular, the desalination performance (rejection and recovery) and their tradeoff relationship are simulated for the first time for an energy self-sufficient RED-ED desalination stack (REDD). The simulation results show that these two parameters can be simultaneously optimized by tailoring ion exchange membranes in the stack, i.e., using more selective membranes in the ED sub-cell (ED cell) and less selective membranes in the RED sub-cell (RED cell). Our analysis shows that a considerable driving force (e.g., a salinity ratio of high salinity stream to low salinity stream over 30 and a volumetric ratio over 0.5) is required to fully unleash the desalination performance of REDD, leading to a favorable shift of the rejection-recovery tradeoff line. In addition, multi-pass treatment is demonstrated to further enhance rejection at the expense of lower recovery. Similarly, a multi-stage configuration can be applied for higher recovery. This study reveals the operational constraints of a novel desalination REDD technique and provides insights into performance enhancement. Image 1 • Energy self-sufficient desalination is realized by the hybridization of RED and ED. • The performance of an energy self-sufficient RED-ED desalination stack is modeled. • There is a clear tradeoff between recovery and equivalent salt rejection. • A considerable driving force is required (e.g., c ‾ H 0 ≥ 30) for satisfactory performance. • Multi-pass and multi-stage enhance overall rejection and recovery, respectively. [ABSTRACT FROM AUTHOR]

Superhydrophobic polyvinylidene fluoride (PVDF) membrane is a promising material for membrane distillation. Existing approaches for preparing superhydrophobic PVDF membrane often involve separate manipulation of surface roughness and surface chemistry. Here we report a one-step approach to simultaneously manipulate both the surface roughness and surface chemistry of PVDF nanofibrous membranes for enhanced direct-contact membrane distillation (DCMD) performances. The manipulation was realized in a unique solvent-thermal treatment process, during which a treatment solution containing alcohols was involved. We demonstrate that by using different chain-length alcohols in the treatment solvent, surface roughness can be promoted by creating nanofin structures on the PVDF nanofibers using an alcohol which has moderate affinity with PVDF. Meanwhile, surface chemistry can be tuned by adjusting the fraction distribution of crystal phases (nonpolar α phase and polar β phase) in the membrane using different alcohols. PVDF membranes with different surface wettabilities were used to evaluate the effects of surface roughness and surface energy on the DCMD performances. Combining both low surface energy and multi-scale surface roughness, pentanol-treated PVDF membrane achieved best anti-water property (water contact angle of 164.1° and sliding angle of 8.1°), and exhibited superior water flux and enhanced anti-wetting ability to low-surface-tension feed in the DCMD application. [ABSTRACT FROM AUTHOR]

Diversified ion-selective separation applications have dramatically incentivized the exploitation and performance modulation of highly ion-selective nanofiltration (NF) membranes. However, the ion selectivity of NF membranes is synergistically governed by multi-scale factors of membrane structural parameters and operational parameters, with the intrinsic ion-selective mechanism still ambiguous. Herein, we proposed an ensemble machine learning (ML) method to decouple key factors affecting the ionic selectivity of polyamide NF membranes. Membrane structural parameters and operational parameters were typically extracted as input variables and linked to mono−/divalent ion selectivity by model training based on Random Forest and XGBoost algorithms. The feature importance assessment indicated the critical role of membrane structure parameters on ion selectivity, wherein pore radius dominated the mono−/divalent anionic selectivity while zeta potential for mono−/divalent cationic selectivity. Partial dependence analyses further depicted intensive insights regarding the influence of membrane structural parameters on ion selectivity. Moreover, stochastic dataset splitting measurements demonstrated the accurate predictive capability of the model simultaneously possessing excellent stability and reliability. We anticipated that the implementation of ensemble ML in explicating the intricate ion-selective mechanism created platforms for understanding the structure-membrane performance correlation and orientally manufacturing highly ion-selective NF membranes. [Display omitted] • Ensemble machine learning was implemented to decouple the key features affecting ion selectivities of polyamide membranes. • RF and XGBoost algorithms were adopted to learn from relevant variables and evaluate permutation features importance. • Mono-/divalent anionic selectivity was dominated by pore size while zeta potential for mono-/divalent cationic selectivity. [ABSTRACT FROM AUTHOR]

The lifetime of reverse osmosis (RO) membranes would be shortened by membrane fouling during the applications, resulting in the generation of a huge number of discarded RO membrane modules each year. To extend the lifetime of RO membranes, in this work, end-of-life RO membranes collected from four typical RO applications, including boiler feed water treatment, water reuse, surface water treatment, and seawater desalination were autopsied to reveal the fouling layer characteristics. The morphologies and primary compositions of the membrane fouling layers were evaluated. It was found that proteins, polysaccharides, and the scales of Si, Fe, and Al presented in all the fouling layers of the analyzed end-of-life RO membranes, while the contents varied depending on the applications. On this basis, the formation process of the fouling layers was revealed; the general and specific lifetime extension strategies of the RO membrane for various water treatment processes were proposed. [Display omitted] • Fouling characteristics of RO membranes in different applications were revealed. • The main foulants on the RO membrane varied seasonally. • Proteins, polysaccharides, and Si, Al, Fe scales were the main foulants. • Strategies to extend the lifetime of RO membranes were proposed. [ABSTRACT FROM AUTHOR]

Antifouling performance of membranes is the key obstacle limiting their practical applications for oil/water separation. In this study, a sustaining antifouling membrane was fabricated by constructing polydopamine (PDA) micro-/nano-spheres on a polyacrylonitrile (PAN) nanofibrous membrane. The secondary PDA nano-spheres not only strengthened the bonding of primary micro-spheres with the substrate, but also diversified the hierarchical structure and chemistry. The composite showed enhanced superhydrophilicity and underwater superoleophobicity. Permeability of PAN-PDAc membrane was maintained as high as 11666 ± 978 Lm−2h−1bar−1 with separation efficiency of higher than 99.9% over a 2-h continuous filtration. This permeability was about 2.7 times of pristine PAN membrane (4260 ± 430 Lm−2h−1bar−1). The extrusion and cutting demulsification on the confined space of PAN-PDA surface was proposed. Antifouling mechanism of the superhydrophilic membrane was first theoretically elucidated based on hydration ability and adhesion free energy with recourse to thermal analysis and Derjaguin-Landau-Verwey-Overbeek theory respectively. It was found that PDA micro-/nano-spheres mediated membrane showed strong hydration ability (higher fraction of non-freezable water) and weak adhesion towards toluene (low free energy of adhesion) compared to pristine PAN membrane. These findings would lead to a better understanding of antifouling demulsification mechanism and improved design of sustaining antifouling membranes for oil/water separation. • Sustaining fouling resistant oil/water separation membranes. • Extrusion and cutting demulsification of the nanofibrous membrane. • High permeability (11666 ± 978 Lm −2h−1bar−1). • Oil antifouling mechanism analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract We report a novel membrane surface modification method using a fast polydopamine coating (fPDAc) strategy. Specifically, NaIO 4 was introduced in the coating process to accelerate the polydopamine deposition rate. Surface properties and separation performances of fPDAc-coated reverse osmosis membranes were characterized and compared to those obtained using the conventional slow polydopamine coating (sPDAc) strategy. Quartz crystal microbalance measurements showed greatly increased polydopamine deposition rate using the fPDAc method, resulting in a reduction of 97% coating time to reach an areal mass of 2000 ng/cm2. Both fPDAc and sPDAc enhanced the surface hydrophilicity and reduced the membrane surface charge. At relatively low areal mass deposition (<1000 ng/cm2), fPDAc-coated membranes showed improved NaCl rejection together with only mild loss of pure water flux. Nevertheless, this rejection enhancement effect was not noticeable when extensive polydopamine coating was applied due to the undesirable cake-enhanced concentration polarization effect. The extensive polydopamine coating was further accompanied with severe loss of membrane permeability, suggesting that shorter coating time (e.g., 4 min) is preferred using the fPDAc method. Our study provides a more rapid and effective membrane surface coating method compared to the conventional sPDAc method. [ABSTRACT FROM AUTHOR]

Abstract Thin film nanocomposite (TFN) membranes, which incorporate nanomaterials in a crosslinked polyamide matrix, often show enhanced separation properties thanks to the additional pores or channels offered by these materials. In this study, we deliberately created nanovoids in the dense polyamide rejection layer by acid-etching copper nanoparticles (CuNPs) contained in a TFN membrane. Systematic membrane characterization confirmed the complete removal of CuNPs using 1% HNO 3 , which formed nanovoids of approximately 10 nm in size. The water flux of the etched membrane TFC-Cu50X was nearly quadrupled compared to that of the CuNPs loaded membrane TFC-Cu50. This significantly improved water flux can be ascribed to the enhanced water transport through these nano-sized voids. The nanovoids-enhanced approach provides new possibilities for synthesizing high performance membranes. Graphical abstract fx1 Highlights • A nanovoids-enhanced TFC membrane was prepared. • Systematic characterization results confirmed the complete removal of CuNPs. • The nanovoids containing TFC membrane achieved 4-fold water flux than that of CuNPs loaded membrane. • The nanovoids-enhanced TFC membrane showed linear relationship between water flux and applied pressure. [ABSTRACT FROM AUTHOR]

[Display omitted] • An amino-rich nanofiber membrane for efficient bilirubin removal was developed. • Membrane was prepared by electrospun with polyacrylonitrile and polyethyleneimine. • Bilirubin removal rate exceeds 96% with membrane addition greater than 120 mg. • The adsorption capacity of free bilirubin is 142.79 mg/g at clinical concentration. • Nanofiber membrane showed satisfying results for all hemocompatibility evaluations. Bilirubin is a serious toxin in the blood of liver failure patients, and the development of bilirubin adsorbent with high removal efficiency, excellent hemocompatibility is crucial to improve the efficacy of hemoperfusion therapy. Herein, PAN/PEI nanofiber membrane (NFM) with amino-rich and smooth surface structure was prepared through a more facile co-blended electrospun method. During simulated adsorption experiments in vitro , PAN/PEI NFMs exhibited a high adsorption capacity of 142.79 mg g−1 for free bilirubin at clinical bilirubin concentration (100 mg L-1) in patients with liver failure. In addition, the bilirubin removal efficiency in static adsorption exceeded 96% when the PAN/PEI NFMs addition was greater than 120 mg. In particular, PAN/PEI NFMs displayed excellent hemocompatibility, presented a low hemolysis rate (0.4%), favorable anti-adhesion properties for hemocyte and plasma protein, and had no significant effect on coagulation. The development of this facile method promotes the feasibility of nanofibrous membranes for the treatment of hyperbilirubinemia with significant implications for improving therapeutic efficacy. [ABSTRACT FROM AUTHOR]

We proposed a facile method of using polyelectrolyte additive to tune interfacial polymerization reaction and tailor polyamide NF membrane with better separation performance and lower bio-fouling potential for groundwater treatment. A moderate concentration of negatively charged poly(4-styrene sulfonate) (PSS) was introduced to the aqueous phase solution during the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). The presence of PSS hindered the diffusion of PIP, leading to the formation of polyamide layer with a looser structure, increased thickness, and additional negative charges on the membrane surface. The fabricated TFC-P 6 membrane possessed enhanced water permeance (21.8 ± 0.7 L m−2 h−1 bar−1) and better selectivity (α = 11.5 ± 1.0) of calcium chloride over sodium sulfate which can be beneficial to achieve higher water recovery compared to the control TFC membrane. In addition, the TFC-P 6 membrane demonstrated enhanced rejection of perfluorooctane sulfonate (~95 %) and the biofouling was inhibited by its additional negative charge and smoother surface. Our results introduced a robust and scalable strategy of polyelectrolyte-assisted interfacial polymerization for designing high performance NF membranes in groundwater treatment. • Negatively charged polyelectrolyte was applied as an additive to the aqueous solution during interfacial polymerization. • PSS hindered the diffusion of piperazine. • TFC membrane fabricated with the aid of PSS showed enhanced water permeance and higher selectivity of CaCl 2 over Na 2 SO 4. • The TFC membrane fabricated with the modified recipe demonstrated higher rejection of PFOS and reduced bio-fouling potential. [ABSTRACT FROM AUTHOR]

Tailoring nanofiltration (NF) membrane with low scaling potential and high energy efficiency is of critical importance to its practical implementation for groundwater remediation. In this study, interfacial polymerization was performed on the surface of an intermediate layer of TA-Fe/CNTs coated polyether sulfone (PES) substrate to obtain a loose NF membrane (TFNi-x) with negative surface charges and optimized water transport path for selective permeation of scaling ions and higher water permeance. The obtained TFNi-10 intermediated with a moderate amount of CNTs (10 μg/cm2) exhibited 80.5 % higher selectivity of Ca2+ over SO 4 2− and 156 % higher water permeance compared to the control TFC while maintaining a high PFOA rejection (∼97.3 %). For the gypsum scaling measurements, TFNi-10 showed better anti-scaling behavior and 40 % less pressure energy consumption for the same recovered water volume (2.2 L), resulting in the higher water recovery and lower energy cost of specific volume of the permeate. It was contributed by the synergistic effects of the strong affinity of TA-Fe to piperazine monomer and the gutter effect of TA-Fe/CNTs interlayer. Our results paved a new way of fabricating novel NF membrane with tailored intermediate layer for optimized interfacial polymerization to realizing groundwater remediation in a cost-effective manner. • Tannic acid-Fe(III) complexes stabilized CNTs was synthesized for fabricating thin film nanocomposite membrane with an interlayer (TFNi). • The obtained TFNi membrane demonstrated enhanced selectivity of calcium over sulfate and maintained a high PFOA retention. • The gypsum scaling experiments of TFNi exhibited better anti-scaling properties compared to the control TFC and NF270. • The energy consumption of TFNi was reduced due to the higher water permeance. [ABSTRACT FROM AUTHOR]

Nanofiltration is a promising technology to recover dye from textile wastewater with highly saline for sustainable resource recovery. However, it is difficult for the conventional piperazine-based nanofiltration membranes, which usually have a tight polyamide matrix structure, to precisely separate dye and salt in wastewater. In this study, 5,5,6',6'-tetrahydroxy-3,3,3',3'-tetramethyl spirobisindane (TTSBI) with rigidly contorted structure has been used instead of piperazine as aqueous-phase monomer to fabricate polyarylate (PAT) nanofiltration membranes with quasi-PIMs structure via interfacial polymerization (IP) with three types of acyl chloride, i.e., rigid trimesoyl chloride (TMC), short-chain glutaryl chloride (GC) and long-chain sebacoyl dichloride (SDC). The contorted structure of TTSBI introduces extra microporosity in nanofiltration membranes, and the differentia of three acyl chlorides in molecular flexibility further endows with tailoring the stacking density of as-formed PAT networks. The PAT NF membranes thereby exhibited high permeability and tunable size-selectivity in desalination from dye effluent. Among these PAT membranes, TTSBI-TMC membranes had the highest water flux of 480.5 LMH, nearly 7-fold increase compared traditional PA NF membranes, whereas TTSBI-SDC membranes had the highest dye rejection of 97.4%, and TTSBI-GC membrane had the relatively balanced dye desalination performance with high rejection 95.4% for Congo Red and 8.3% for NaCl accompanied by high flux of 402.4 LMH. Therefore, this study provides a new prospective for the fabrication of highly permeable nanofiltration membranes for precise separation. [Display omitted] • A quasi-PIMs nanofiltration membrane with TTSBI served as water-phase monomer was developed. • Three types of acyl chlorides with different molecular flexibility were used as oil-phase monomer respectively. • Ultrahigh water permeability was achieved by the introduction of extra microporosity. • Dye/salt selectivity was tailored by the differentia of molecular flexibility. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) plays an increasingly central role in water/salts separation, which puts forward tailored requirements on NF membranes in a variety of application scenarios. However, the ambiguous separation mechanisms of NF including membrane structure parameters and operating conditions hinder the rational design of versatile NF membranes. Herein, machine learning was used to explore the correlation between membrane structure parameters and operating conditions with water/salts selectivity, and reveal the importance of the diverse features based on literature data. Two structural features of polyamide NF membrane (pore radius and zeta potential) and two operating parameters (pressure and feed concentration) were typically extracted and associated with water/salts selectivity. Random Forest and XGBoost models were employed to learn from relevant variables and assess their importance. The results showed that membrane structure parameters attached more importance to water/salts selectivity than that of operating conditions accompanying the variable influence for different typed salts, where symmetrical salts were mainly governed by size sieving while Donnan exclusion for asymmetrical salts. Structure-performance relationships between pore radius, zeta potential and diverse water/salts selectivity were established using partial dependence plot analysis. It is anticipated that the constructed comprehensive insights can be further leveraged to tackle performance modulation and oriented design of multi-scenarios NF membranes. [Display omitted] • Machine learning was used to understand NF separation mechanisms. • Random Forest and XGBoost models were employed to learn from relevant variables and assess features importance. • Symmetrical salts were mainly governed by size sieving while Donnan exclusion for asymmetrical salts. • The integrated management of pore size and zeta potential for the oriented design of versatile NF membranes was highlighted. [ABSTRACT FROM AUTHOR]

Endotoxin has been recognized as the crucial inducer for sepsis, and selective removal of endotoxin from plasma in vitro is the popular therapeutic strategy, such as hemoperfusion technology based on adsorption. Construction of hemoperfusion adsorbents with high endotoxin adsorption capacity in plasma is critical to meet the demands of hemoperfusion therapy for sepsis. However, it has proven to be challenging because of the adhesion of plasma protein. Inspired by the antiadhesion property of mixed-charge polymers and the endotoxin adsorption property of polyethyleneimine, here, a charge-bias, endotoxin selectively adsorbable and hemocompatible layer was constructed on nanofibrous surface of polysulfone (PSF) electrospun nanofibrous membrane (ENM) by the co-deposition of positively-charged polyethyleneimine (PEI) and negatively-charged polydopamine (PDA). The charge-bias degree of PEI/PDA co-deposition layer was quantified through zeta potential measurement, and firstly visualized through Kelvin probe force microscopy (KPFM) measurement. The continuity and integrity of PEI/PDA layer were characterized by XPS and TEM. We showed that the light positive charge-bias of the PEI/PDA layer in physiological environment (pH = 7.4) can macroscopically drove the adsorption selectivity towards endotoxins via electrostatic interaction, and uniformly distributed positive and negative charges can microscopically drove the anti-protein adhesion property. The resultant PEI/PDA@PSF ENM exhibited high adsorption capacity of 9049 EU/g in plasma, which is much higher than commercial endotoxin adsorbents. Notably, PEI/PDA@PSF ENM possessed satisfactory anti-plasma protein adhesion property, hemocompatibility and had no adverse effects on blood components, especially plasma protein. This work suggests a feasible approach for producing ENMs-based hemoperfusion adsorbent matrix for endotoxin-induced sepsis. [Display omitted] • A facile strategy for fabricating charge-biased electrospun nanofibrous membrane was developed. • This membrane exhibited excellent endotoxin adsorption performance in plasma. • The charge distribution and charge-bias degree was quantitatively investigated and visually characterized. • This membrane was used as hemoperfusion material for sepsis. [ABSTRACT FROM AUTHOR]

In this study, aminated PES substrates were prepared and applied for the investigation on the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) thereon, with relatively low (PIP: 0.1 wt%, TMC: 0.01 wt%) and high (PIP: 0.5 wt%, TMC: 0.05 wt%) monomer concentration. In low concentration condition, thin, dense, and defect-free selective layers were synthesized on the aminated substrates. In high concentration condition, thin film composite (TFC) membranes with thin selective layers and without the intrusion of polyamide into the substrates were formed. The reactions between the aminated substrate and selective layer were confirmed by XPS analysis on the back surface of the selective layer. The aminated substrates based TFC membrane (TFC-48-H) showed high separation performance, including high water permeability as 20.6 ± 0.1 L/m2 h bar and high Na 2 SO 4 to NaCl selectivity as 86.7, indicating the application potential in divalent to monovalent salts separation process. A conceptual model was proposed to highlight the role of the aminated substrates in the interfacial polymerization process as (1) PIP loaders, (2) PIP diffusion hinders, and (3) polyamide intrusion chemically inhibitors in high monomer concentration condition. [Display omitted] • Interfacial polymerization process on the aminated substrate was investigated. • Thin, dense and defect-free selective layer was formed in low C PIP concentration. • In high C PIP condition, TFC membrane without the intrusion of polyamide was formed. • Aminated substrate based TFC membrane showed greatly improved Na 2 SO 4 to NaCl selectivity. • Conceptual model that highlighted the role of aminated substrate was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The cationic COF was used to synthesis AEMs. • DhaTG Cl /HPAN showed high selectivity based on electrostatic repulsion. • DhaTG Cl /HPAN exhibited the excellent acid stability by building the intramolecular H-bonding. Diffusion dialysis (DD) based on the anion exchange membranes (AEMs) is considered as a promising technology for acid recovery. Two-dimensional (2D) cationic covalent organic frameworks (COF) with uniform pores and intrinsic cationic-type skeleton structures are excellent candidates for the synthesis of the AEMs. However, the sustaining of crystallinity and porosity in acid environments is still a key challenge for the existing COF, which severely restricts their applicability in the acid recovery. Herein, by introducing OH functionalities adjacent to the Schiff base centers, we synthesized the acid-stable cationic COF (DhaTG Cl) layers with intralayer hydrogen bond on the surface of hydrolytic polyacrylonitrile (HPAN) ultrafiltration membrane. The strong electrostatic repulsion, endowed by cationic guanidine-based knots, as well as well-aligned proton channel, constructed by OH functionalities, rendered extremely high separation factor (S) of 4589 ± 684.2 for HCl recovery from HCl/FeCl 2 solution. The membrane maintained high selectivity toward H+/Fe2+ after 10 cycles during DD process, while the one without OH degraded during cycling experiments. Our results imply that building the intralayer H-bonding interactions could be a promising approach for expanding the application of the COF membranes for acid recovery. [ABSTRACT FROM AUTHOR]

The electrical neutrality of ionic liquids (ILs) was exploited to enhance the antifouling property of polyamide (PA) reverse osmosis (RO) membranes in this work. We solely tethered the aminated imidazolium cation of ILs [AVIM] Br onto the top-surface of PA RO membranes via mild amidation. The molecular simulation results confirmed that the tethered imidazolium cation and the dissociated bromine anion were stably existed in the form of ion pairs on PA RO membrane surface. In virtue of the electrical neutrality of these ion pairs, the ionic-solvation induced hydration layer formed in ILs above the modified membrane surface was thick and evenly distributed, similar to that formed in conventionally electroneutral zwitterion antifouling materials. Thereby, the cation-tethered membrane surface intuitively achieved balanced charge and strong hydrophilicity, and stably exhibited low protein adsorption and excellent antifouling behaviors to diverse foulants, even when the imidazolium cation was paired with anions of different molecular size. Meanwhile, the typical ridge-and-valley surface morphology for PA RO membrane was well preserved due to the mild modification condition, and thereby harvested satisfactory separation performance. The integration of high performance, abundant ILs and mild conditions was expected to expand the application of superb antifouling materials in a variety of biofouling areas. [Display omitted] • The electroneutrality of ionic liquids was exploited for antifouling application. • The PA RO membrane surface was solely tethered with the aminated cation of ILs. • The tethered cation and dissociated anion were still stably existed as ion-pairs. • The ionic-solvation of ion pairs induced a strong hydration layer above membrane. • The cation-tethered PA RO membrane exhibited enhanced antifouling properties. [ABSTRACT FROM AUTHOR]

The separation of Li+ and Mg2+ is a decisive step for achieving high-grade lithium extraction from salt-lake brines to circumvent the lithium supply shortage and sustainability. However, polymer nanofiltration membranes suffer from low lithium selectivity and are hindered by complicated preparation and miniaturized scales. Here, we report a facile surface charge-inversion strategy via a unique secondary non-aqueous medium interfacial reaction of polyethyleneimine to construct a selective positive-nanolayer on nanofiltration membranes surface for selective separation of lithium ions from concentrated magnesium/lithium mixtures. The introduction of amine moieties not only increases the Donnan potential but also improves the compactness of the membrane, which simultaneously enhances the Donnan exclusion and size sieving for the Mg2+ ion with higher valence and larger hydration ion size. The surface interaction theory (DLVO) verified that the high positive-charge density provided an excellent selectivity to allow passage of Li + but reject Mg2+, and the separation factor (S Li/Mg) achieved 12.37 at a high Mg2+/Li+ mass ratio of 150. Such highly positive transmembrane potential barrier simultaneously endowed the membrane surface with the anti-fouling performance against Ca2+. We anticipate that our facile and scalable surface charge-inversion will greatly advance lithium ions permselectivity membranes design and application in lithium extraction. [Display omitted] ● A nanofiltration membrane with a positive-charged blocking layer was developed. ● The surface charge inversion strategy of secondary non-aqueous medium reaction was effective and facile for scalable preparation. ● The constructed positive-charged blocking layer implemented synchronous reinforcement of Donnan exclusion and size sieving conjunct effects. ● Modified membranes exhibited excellent Li+/Mg2+ separation efficiency under high Mg2+/Li+ ratio of 150 and remarkable anti-fouling against Ca2+. [ABSTRACT FROM AUTHOR]

Superhydrophilic-underwater superoleophobic (SUS) membranes have been demonstrated to be promising materials for oily wastewater treatment. However, development of facile, low cost and robust SUS membrane with high flux and less membrane fouling is still challenging. In this study, we reported a simple electrospinning/in-situ growth strategy to prepare SUS SiO 2 @PVA nanofibrous membrane for gravity-driven separation of oil/water mixture. In specific, a highly porous PVA nanofibrous membrane was first fabricated by electrospinning technique, followed by an in-situ growth of silica nanoparticles on the pristine PVA nanofibers through a modified Stöber reaction. The abundant hydroxyl groups on PVA nanofibers enabled uniform and stable deposition of silica nanoparticles, thus simultaneously realizing high surface energy surface (hydrophilic nature of PVA and silica) and multi-scale roughness. As expected, the resultant membrane exhibited excellent in-air "water-loving" (instantaneous in-air water wetting) and underwater "oil-hating" properties (underwater oil contact angle of 161.8° and sliding angle of 6.2°). The SUS SiO 2 @PVA membranes exhibited efficient separation of both free oil/water mixture and a variety of surfactant-stabilized oil-in-water emulsions in a gravity-driven filtration process. In addition, oil density played an important role during the separation process, due to superior separation performance was achieved for lighter-than-water oil when compared to heavier-than-water oils. Moreover, the membrane showed robust reusability that it maintained stable oil rejection and permeate flux in cyclic experiments. Image 1 • In situ silica growth on PVA nanofibers to achieve superwetting property. • Excellent in-air water-loving and under-water oil-hating properties achieved. • The membrane realized efficient oil-in-water emulsion separation under gravity. • Oil density plays an important role in the oil/water separation process. • The membrane maintained stable rejection and flux in cyclic experiments. [ABSTRACT FROM AUTHOR]