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Ion-selective membranes are necessary components of many electrochemical systems including fuel cells, electrolyzers, redox flow batteries, and electrodialyzers. Perfluorinated sulfonated membranes (PFSMs) dominate these applications due to their excellent combination of fast ion transport, stability, and processability. However, perfluorinated cation exchange membranes (CEMs) are expensive, and their production process involves chemistry that generates toxic perfluorinated chemicals. The development of affordable, nonfluorinated membranes with a competitive combination of high ion selectivity, transport, and stability could help enable the widespread use of the technologies listed above while hastening the development of emerging electrochemical systems, including aqueous alkaline CO2 sorbent regeneration. To this end, we pursue the use of thin-film composite polyamide (PA-TFCs) membranes─those that typically find application in reverse osmosis and nanofiltration desalination─as cation-selective exchange membranes. Given their negative surface charge under neutral-to-alkaline conditions, PA-TFCs can serve as effective CEMs in these pH regimes. We prepared a series of PA-TFCs from traditional monomers (trimesoyl chloride and piperazine) and compared their thicknesses, charge densities, water transport properties, ion transport properties, and long-term stability in a high pH environment to traditional CEMs (Nafion and FKE) and commercial nanofiltration and reverse osmosis membranes. We find that some of the best-performing PA-TFC membranes have similar resistances and Na+ transference numbers compared to Nafion 117 in Na2SO4 and NaHCO3-containing solutions. This proof-of-principle study suggests that further optimization of PA-TFCs could enable cost-effective ion exchange membrane alternatives to PFSMs.

This study explores the utilization of electrospun polysulfone (PSF) as a thin-film support in the pressure-retarded osmosis (PRO) system, leveraging its notable thermal, chemical, and oxidative stability. To enhance the efficiency of the PRO system, the inherently hydrophobic PSF surface is modified through functionalization with benzenesulfonamide groups (BSA-PSF). The modification process involves chloromethylation of PSF, followed by substitution with BSA, and subsequent electrospinning to produce BSA-PSF fibers. A thin-film composite forward osmosis membrane, composed of an electrospun BSA-PSF support layer and a polyamide thin layer synthesized through interfacial polymerization (BSA-PSF/PA), is developed. The incorporation of BSA improves the hydrophilicity of the membrane surface, while also imparting antibacterial features to the electrospun BSA-PSF. Comparative analyses with pristine PSF membranes reveal that the pure water flux of the BSA-PSF membrane achieves a notable 65 LMH, surpassing the pristine PSF membrane’s flux of 45 LMH. Moreover, protein absorption is significantly reduced in the BSA-PSF membrane (40.6 μg cm−2) compared to the unmodified PSF membrane (64.2 μg cm−2). The establishment of a hydration layer near the surface, facilitated by hydrogen interactions between water units and the hydrophilic sulfonamide chains in the polymer, contributes to lower protein adsorption than observed in the pristine PSF membrane. Notably, the prepared BSA-PSF/PA membrane exhibits advanced surface hydrophilicity, commendable antibacterial properties, exceptional fouling resistance, and high water permeability. These attributes position it as a promising candidate for widespread applications in power generation and large-scale water treatment. BSA functionalized the electrospun PSF used as the PRO membrane’s thin-film support. The introduction of BSA to PSF improved the hydrophilicity, water flux, antibacterial properties, and fouling resistance of thin-film composite PRO membraneArticle Highlights: BSA functionalized the electrospun PSF used as the PRO membrane's thin-film support. The introduction of BSA to PSF improved the membrane's hydrophilicity and water flux. BSA-PSF nanofibers exhibit antibacterial properties. BSA-PSF/PA membrane has satisfactory fouling resistance [ABSTRACT FROM AUTHOR]

Thin-film nanocomposite (TFN) forward osmosis (FO) membranes have attracted significant attention due to their potential for solving global water scarcity problems. In this study, we investigate the impact of titanium oxide (TiO2) and titanium oxide/reduced graphene (TiO2/rGO) additions on the performance of TFN-FO membranes, specifically focusing on water flux and reverse salt diffusion. Membranes with varying concentrations of TiO2 and TiO2/rGO were fabricated as interfacial polymerizing M-phenylenediamine (MPD) and benzenetricarbonyl tricholoride (TMC) monomers with TiO2 and its reduced graphene composites (TiO2/rGO). The TMC solution was supplemented with TiO2 and its reduced graphene composites (TiO2/rGO) to enhance FO performance and reverse solute flux. All MPD/TMC polyamide membranes are characterized using various techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. The results demonstrate that incorporating TiO2/rGO into the membrane thin layer improves water flux and reduces reverse salt diffusion. In contrast to the TFC membrane (10.24 L m−2h−1 and 6.53 g/m2 h), higher water flux and higher reverse solute flux were detected in the case of TiO2and TiO2/rGO-merged TFC skin membranes (18.81 and 24.52 L m−2h−1 and 2.74 and 2.15 g/m2 h, respectively). The effects of TiO2 and TiO2/rGO stacking on the skin membrane and the performance of TiO2 and TiO2/rGO skin membranes have been thoroughly studied. Additionally, being investigated is the impact of draw solution concentration. [ABSTRACT FROM AUTHOR]

Poly(acrylonitrile-co-methyl acrylate) (PAN-co-MA) electrospun nanofiber (ENF) was used as the support for the formation of polyamide (PA) thin films. The ENF support layer was post-treated with heat-pressed treatment followed by NaOH hydrolysis to modify its support characteristics. The influence of heat-pressed conditions and NaOH hydrolysis on the support morphology and porosity, thin-film formation, surface chemistry, and membrane performances were investigated. This study revealed that applying heat-pressing followed by hydrolysis significantly enhances the physicochemical properties of the support material and aids in forming a uniform polyamide (PA) thin selective layer. Heat-pressing effectively densifies the support surface and reduces pore size, which is crucial for the even formation of the PA-selective layer. Additionally, the hydrolysis of the support increases its hydrophilicity and decreases pore size, leading to higher sodium chloride (NaCl) rejection rates and improved water permeance. When compared with membranes that underwent only heat-pressing, those treated with both heat-pressing and hydrolysis exhibited superior separation performance, with NaCl rejection rates rising from 83% to 98% while maintaining water permeance. Moreover, water permeance was further increased by 29% through n-hexane-rinsing post-interfacial polymerization. Thus, this simple yet effective combination of heat-pressing and hydrolysis presents a promising approach for developing high-performance thin-film nanocomposite (TFNC) membranes. [ABSTRACT FROM AUTHOR]

Spray coating has been exploited to fabricate and tailor the morphologies of various components in thin film composite membranes separately. For the first time, here we exploit this technology to construct and assemble both the selective layer and porous support of a thin-film composite membrane in a single process. In our approach, spray-assisted non-solvent induced phase inversion and interfacial polymerization reduced the time required to fabricate thin-film composite membranes from 3 – 4 days to 1 day and 40 ​min. Our approach did not sacrifice membrane separation performances during desalination of a mixture comprising 2000 ​ppm of NaCl in water at 4 ​bar and room temperature. At these conditions, compared to traditional thin film composite membranes, the water permeance of our spray coated membranes was higher by 35.7 %, reaching 2.32 ​L ​m−2 ​h−1 bar−1, while achieving a NaCl rejection rate of 94.7 %. This demonstrated the feasibility of fabricating thin film composites via spray coating in a single process, potentially reducing fabrication time during scale-up production.

Positively charged nanofiltration (NF) membranes show great potential in the fields of water treatment and resource recovery. However, this kind of NF membrane usually suffers from relatively low water permeance. Herein, a positively charged NF membrane with a porous interlayer is developed, where the interlayer is formed by assembling dendritic mesoporous silica nanoparticles (DMSNs) after the formation of a polyamide layer. This post-assembly strategy avoids the adverse effect of the interlayer on the formation of positively charged NF membranes. The porous DMSN interlayer provides abundant connected channels for water transport, thus endowing the NF membrane with enhanced water permeance. A series of DMSNs with different sizes was synthesized, and their influence on membrane formation and membrane performance was systematically investigated. The optimized membrane exhibits a CaCl2 rejection rate of 95.2% and a water flux of 133.6 L·h−1·m−2, which is 1.6 times that of the control group without an interlayer. This work represents an approach to the fabrication of a positively charged NF membrane with porous interlayers for high-efficiency cation rejection. [ABSTRACT FROM AUTHOR]

Polyamide membranes made with surfactant-assisted interfacial polymerization (IP) have demonstrated the potential for excellent membrane performance. The presence of surfactants accelerates amine diffusion into the organic phase causing a more complete IP reaction. Even though surfactant-assisted IP has been used in polyamide membranes, the structure-property relationship of the surfactants on amine transport into the organic phase has not been explored in a systematic manner. In this work, MPD diffusion from a membrane support into n-dodecane in the presence of seven different surfactants, which were anionic, cationic, and non-ionic, was evaluated. When the surfactants were used at different concentrations, the MPD concentration was increased in the presence of anionic (48–80%), cationic (32–75%) and non-ionic (26%) surfactants. The MPD concentration was increased in the presence of anionic (by 48–72%), cationic (by 32–75%), and non-ionic surfactants (by 26%) at 15–60 s contact time. For further understanding, the interfacial tension in n-dodecane for the surfactants was measured, however, it did not correlate with our data. This study provides a better understanding of MPD diffusion in the presence of different types of surfactants during RO membrane synthesis, which will help us to engineer membranes with better permeability and selectivity.

Thin-film composite (TFC) membranes have gained significant attention as an appealing membrane technology due to their reversible fouling and potential cost-effectiveness. Previous studies have predominantly focused on improving the selective layers to enhance membrane performance. However, the importance of improving the support layers has been increasingly recognized. Therefore, in this review, preparation methods for the support layer, including the traditional phase inversion method and the electrospinning (ES) method, as well as the construction methods for the support layer with a polyamide (PA) layer, are analyzed. Furthermore, the effect of the support layers on the performance of the TFC membrane is presented. This review aims to encourage the exploration of suitable support membranes to enhance the performance of TFC membranes and extend their future applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thin selective skin layer was prepared using NGQDs and CD as the aqueous monomers. • Separation performance experiments of the membrane were performed at low pressure. • The addition of NGQDs significantly elevated the rejection for small molecular dye. • Excellent rejection obtained not only for larger molecular dye but for smaller dye. • The NGQDs-CD-MWCNTs-5 membrane exhibited superior antifouling property. For better sustainable resource recovery and elevating the separation efficiency of dye/salt mixture, it is essential to develop an appropriate nanofiltration membrane for the treatment of textile dyeing wastewater containing relatively smaller molecule dyes. In this work, a novel composite polyamide-polyester nanofiltration membrane was fabricated by tailoring amino functionalized quantum dots (NGQDs) and β -cyclodextrin (CD). An in-situ interfacial polymerization occurred between the synthesized NGQDs-CD and trimesoyl chloride (TMC) on the modified multi-carbon nanotubes (MWCNTs) substrate. The incorporation of NGQDs significantly elevated the rejection (increased by ∼ 45.08%) of the resultant membrane for small molecular dye (Methyl orange, MO) compared to the pristine CD membrane at low pressure (1.5 bar). The newly developed NGQDs-CD-MWCNTs membrane exhibited enhanced water permeability without compromising the dye rejection compared to the pure NGQDs membrane. The improved performance of the membrane was primarily attributed to the synergistic effect of functionalized NGQDs and the special hollow-bowl structure of CD. The optimal NGQDs-CD-MWCNTs-5 membrane expressed pure water permeability of 12.35 L m-2h−1 bar−1 at the pressure of 1.5 bar. Noteworthily, the NGQDs-CD-MWCNTs-5 membrane not only showed high rejection for the larger molecular dye of Congo Red (CR, 99.50%) but also for the smaller molecular dye of MO (96.01%) and Brilliant Green (BG, 95.60%) with the permeability of 8.81, 11.40, and 6.37 L m-2h−1 bar−1, respectively at low pressure (1.5 bar). The rejection of inorganic salts by the NGQDs-CD-MWCNTs-5 membrane was 17.20% for sodium chloride (NaCl), 14.30% for magnesium chloride (MgCl 2), 24.63% for magnesium sulfate (MgSO 4), and 54.58% for sodium sulfate (Na 2 SO 4), respectively. The great rejection of dyes remained in the dye/salt binary mixed system (higher than 99% for BG and CR, <21% for NaCl). Importantly, the NGQDs-CD-MWCNTs-5 membrane exhibited favorable antifouling performance and potential good operation stability performance. Consequently, the fabricated NGQDs-CD-MWCNTs-5 membrane suggested a prospective application for the reuse of salts and water in textile wastewater treatment owing to the effective selective separation performance. [ABSTRACT FROM AUTHOR]

Highly permeable acid‐resistant nanofiltration (NF) membranes are of critical significance for the efficient treatment of acidic streams. Enhancing permeability while maintaining the high solute rejection of acid‐resistant NF membranes remains a great challenge due to the low reactivity of monomers. In this work, a novel catalytic template assisted interfacial polymerization (IP) strategy of 3‐aminobenzenesulfonamide (ABSA) and trimesoyl chloride (TMC) was provided to prepare a poly(amide‐sulfonamide) membrane. Aminopyridine doped graphene quantum dots rich in acylation catalytic sites and ZIF‐8 nanoparticles are co‐loaded on a substrate as template. Benefiting from the enhanced phase integrity and self‐inhibition effect of the template assisted IP process, the resulting ultra‐thin acid‐resistant membrane exhibits an excellent water permeance (20.4 Lm−2h−1bar−1) with a high Na2SO4 rejection of 90.5%, which outperforms almost all the reported acid‐resistant NF membranes. Our work paves a versatile way for synthesis of special separation membranes. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a promising thermal desalination technology, but its application is largely limited by membrane wetting. This study introduces a thin‐film composite (TFC) membrane comprising a polyamide (PA) surface layer, a polydopamine (PDA) interlayer, and a hydrophobic polyvinylidene fluoride (PVDF) membrane substrate for anti‐wetting MD operations. With a PDA reaction time of 1 h, a compact and hydrophilic PDA interlayer forms on the PVDF membrane substrate, facilitating the subsequent formation of the PA surface layer. With 2 cycles of interfacial polymerization process, a dense PA surface layer forms on the PDA interlayer, rendering a TFC membrane with robust wetting resistance. From diffusion experiments and breakthrough pressure measurements, the TFC membrane exhibits excellent wetting resistance because the dense PA surface layer can prevent the wetting contaminants from reaching the hydrophobic membrane substrate due to the combination of the size exclusion effect and capillary effect. The results from this study shed lights on a new approach for the fabrication of robust MD membranes for practical applications. [ABSTRACT FROM AUTHOR]

The development of highly permeable and selective thin-film composite (TFC) membranes is essential for organic solvent nanofiltration (OSN) applications. However, overcoming the permeability–selectivity trade-off in polymer membranes remains highly challenging owing to the difficulty in controlling the thickness and nanostructures of the selective layers. In this study, TFC OSN membranes with sandwich-like structures were developed via interfacial polymerization on Cu-TCPP nanosheet-modified microporous polyvinylidene fluoride (PVDF) substrate surface. The interfacial polymerization was done by using mixed amine (polyethyleneimine and piperazine) in the aqueous phase and the 1,3,5-benzenetricarbonyl trichloride in the hydrophobic ionic liquid phase as monomers. It was found that the Cu-TCPP nanosheets of micrometer lateral dimensions and nanometer thickness (1.5 ± 0.6 nm) can be deposited on the PVDF substrate as an interlayer to facilitate the following interfacial polymerization reaction. The Cu-TCPP interlayer also can be served as a binder between the polyamide selective layer and the microporous PVDF substrate to enhance their mechanical strength. As compared with the PVDF/PA membrane, the PVDF/t-Cu-TCPP/PA membrane exhibited higher elongation (8.0 vs. 4.6%) while ensuring slightly lower tensile strength (36.0 vs. 48.6 MPa). Under optimal synthetic conditions, the TFC membranes could achieve 2.7 L m–2 h–1 bar–1, and 98.9% and 95.0% rejection to Brilliant Blue R (826 Da) and Congo red (697 Da), respectively, in ethanol. Furthermore, the membranes showed steady performance throughout the 36 h nanofiltration of the Rose bengal/ethanol mixture and exhibited good performance in the concentration of lecithin in methanol. Accordingly, this work highlights the potential of using thin metal–organic framework nanosheets as interlayers to develop high-performance TFC membranes for OSN applications. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) technology has the merit potential to remove heavy metal ions from wastewater. However, the deficiency of FO membranes with low selectivity and permeability has hampered the scale-up and development of this technology. In this work, we coated a hydrophilic alginate/Ca2+ thin layer through the layer-by-layer (LbL) assembly as an interlayer on polyethersulfone (PES) microfiltration (MF) substrate to enhance the separation performance of the thin-film composite (TFC) membrane. The interlayer thickness was controlled by the LbL cycles (1–7 cycles), and its effect on surface properties of substrates in terms of hydrophilicity and pore size was investigated thoroughly. Then the influence of interlayer LbL cycles on the polyamide (PA) synthesis through interfacial reaction was studied. Results show that the interlayer prevents the PA layer's intrusion into the substrate pores and provides a hydrophilic and smooth surface to synthesize a defect-free PA layer. SEM images show that a dense, uniform, and defect-free PA rejection layer was formed on interlayer-coated MF substrates. FO performance result also verified the positive effect of interlayer on TFC membrane performance, where TFC-LbL.5 membrane (with 5 LbL cycles of alginate/Ca2+) showed 2 times higher water flux than control TFC membrane (23.3 LMH compared to 9.2 LMH). In the TFC-LbL.5 membrane, the defect-free PA active layer formed on the alginate/Ca2+ interlayer acted as a favorable barrier for different heavy metal ions (Cr3+, Co2+, and Hg2+) with the rejection of more than 99% under FO mode. This work offers a novel opportunity for the practical construction and development of high-efficiency TFC-FO membranes for heavy metal removal applications. [Display omitted] • Alginate/Ca2+ interlayer is coated on porous MF substrate via LbL assembly method to fabricate novel TFC-FO membrane. • The alginate/Ca2+ interlayer has a vital role in the synthesis of PA selective layer. • A smooth and ultrathin PA selective layer is achieved by using alginate/Ca2+ interlayer. • Water flux and selectivity is significantly improved in interlayered TFC membrane. [ABSTRACT FROM AUTHOR]

The major scope of this study is the fabrication and development of a substrate and polyamide rejection layer for an efficient thin-film hydrophilic composite forward osmosis (TFC-FO) membrane. Fabrication of a thin-film nanocomposite forward osmosis membrane employing interfacial polymerization and modification of substrate characteristics using titanium dioxide (TiO2) nanoparticles as additives (TFNC-FO) are studied. Characterizations of the prepared TFC-FO and TFNC-FO membranes were determined. The morphologies of cross-section, upper and bottom surfaces for the TFC-FO and TFNC-FO membranes were studied using scanning electron microscopy (SEM). Energy-dispersive X-ray (EDX) spectroscopy was used to examine the compositions of different elements for both membranes. The hydrophilicity of the prepared TFC-FO and TFNC-FO membranes was investigated using the measurement of the contact angle test. A Fourier Transform Infrared (FT-IR) spectrophotometer was used to observe the existing functional groups of the TFC-FO and TFNC-FO membranes. The thermal stability of the membrane was evaluated via thermogravimetric analysis (TGA). The overall performance of TFC-FO membranes was evaluated with and without adding TiO2 nanoparticles through different parameters, such as membrane flux, initial feed concentration, draw solution concentrations, reverse solute fluxes, membrane permeabilities, and finally, the effect of FO membrane orientations. FO membrane performance was successfully enhanced by adding different concentrations of TiO2 nanoparticles from 0.5 to 1.5 wt%. The findings indicated that an increase in the concentration from 0.5 to 1 wt% leads to a clear increase in both the porosity and hydrophilicity of the nanocomposite substrate and consequently, an increase in the water flux. However, further increasing the concentration of TiO2 nanoparticles to more than 1 wt% affects the membrane performance. HIGHLIGHTS Preparation of a TFNC-FO membrane.; Incorporating TiO2 nanoparticles into polysulfone membrane matrix.; Evaluation of FO performance.; FO membrane permeability.; Characterization of the synthetic FO membranes.;

• PA/PEI-TA@MOF-808 thin film composite (TFC) membrane was fabricated. • TA@MOF-808 in support layer could regulate interfacial polymerization. • The TFC membrane achieved a retention rate of over 96.7% for rare earth ions. • Evaluated the acid resistance and operational stability of the TFC membrane. • The TFC membrane exhibited excellent selectivity for trivalent cations. Retrieval of rare earth ions from dilute wastewater produced from in-situ leach mining is a crucial approach to effectively mitigate the shortage of rare earth resources, and the employment of the membrane technology for recuperation of ionic rare earths is an energy-efficient and eco-friendly solution. In this study to optimize the use of the membrane technology for ionic rare earths recovery, TA@MOF-808 was fabricated by combining tannic acid (TA) with MOF-808 and then incorporated as nanoparticles into a polyetherimide (PEI) base membrane. On this basis, PA/PEI-TA@MOF-808 thin-film composite membranes were prepared via interfacial polymerization. TA@MOF-808 with its hydroxyl and carboxyl functional groups generated hydrogen and covalent bonds with the secondary amine groups of piperazine (PIP), which stored PIP and regulated its diffusion rate into the organic phase. Thereby, the membrane surface charge was modulated under acidic conditions, and a separation layer was reconstituted, improving the structural and operational stability of the membranes. The PA/PEI-TA@MOF-808 membrane exhibited a water flux of 42.1 L·m−2·h−1, and La3+, Y3+, and Gd3+ retention rates of 97.7 %, 96.7 % and 97.4 %, respectively. Separation tests, acid resistance tests, long-term operational stability tests and actual rare earth wastewater treatment tests revealed the PA/PEI-TA@MOF-808 membrane possessed outstanding ionic rare earth separation capability, consistent membrane flux, notable acid resistance, and operational stability, suggesting a bright future in the application for ionic rare earth recovery. [ABSTRACT FROM AUTHOR]

The commercial polyethylene (PE) battery separator is well-suited as support for nanofiltration owing to its thickness of 7 um, high porosity, and strong mechanical properties. A new polyethylene based thin-film composite membrane was fabricated on the catechol/polyethyleneimine (CCh/PEI) modified PE support by pre-diffusion interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). By regulating the properties of the CCh/PEI layer and the PIP to influence the diffusion of PIP, a distinct worm-like structure in the polyamide (PA) layer was found, which provides more water penetration sites. After grafting melamine on the surface of PA layer, the TFC membrane exhibited outstanding chlorine resistance and the permeability of 12.5 L·m−2·h−1·bar−1 with the Mg2+ rejection of 94.5 %. Due to its small pore size, strong positively charged, and high adsorption capacity, the TFC membrane showed high rejection of heavy metal ions through pore size sieving, Donnan effect and adsorption. Therefore, it has great potential for water purification from heavy metal ions. [Display omitted] • The PE support is favorable for enhancing water flux. • Melamine enhances the chlorine resistance, pollution resistance, and selectivity of the membrane. • The NF-0.5 membrane exhibits high flux and high selectivity for removing salt. • NF-0.5 membrane shows great potential for water purification from heavy metal ions. [ABSTRACT FROM AUTHOR]

The intrinsic structure of the aromatic polyamide (APA) layer which is decisive for permeability and permselectivity of the state-of-art thin film composite (TFC) reverse osmosis (RO) membranes should be analyzed precisely in-depth. In this work, seawater reverse osmosis (SWRO) membranes with different APA microstructures are prepared by introducing the environmental-friendly solvent Gamma-valerolactone (GVL) into the organic phase to modulate the diffusion rate of m-phenylenediamine (MPD), thereby altering the packing density and morphology of APA aggregates. Small-angle X-ray scattering is utilized to obtain the fractal dimension of APA aggregates which quantitatively reflects the irregularity and complexity of the APA aggregates based on the principle of statistics. Confirmed by the cross-section images, fractal dimensions of APA aggregates transform from pseudo-1-dimension to pseudo-2-dimension structures due to the weakened folding property and the enhanced structural flexibility of the APA colloid particles, along with the looser stacking morphology of the APA aggregates. By correlation analysis, the fractal dimension possessed strong linear and positive correlation with water permeability coefficient A (R 2 =0.9945), together with strong linear and negative correlation with water-salt permselectivity A/B (R 2 =0.9896). As a demonstration, parameter of fractal dimension was supposed to be the critical structural parameter which played the most important role in water permeability of SWRO membranes, and the permeability and the permselectivity of SWRO membranes could only be simultaneously improved on the basis of the fractal dimension infinitely close to 1-dimension with the nodular and linear structures of the APA aggregated mostly maintained. [Display omitted] • SWRO membranes with ultra-high permeability and NaCl rejection were prepared using Gamma-valerolactone. • The intrinsic structure of the aromatic polyamide was defined by fractal dimension. • Strong linear and positive correlation between fractal dimension and the water permeability coefficient was figured out. • Strong linear and negative correlation between fractal dimension and water-salt permeability was revealed for the first time. • Chemical and morphological properties of polyamide were systematically analyzed. [ABSTRACT FROM AUTHOR]

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membranes are widely used for the treatment of water and wastewater treatment. However, the membrane surface properties could be further modified during interfacial polymerization (IP) process to achieve higher water flux and salt rejection. Herein, the effects of sodium bicarbonate (NaHCO3) and co-amine monomer—2-(2′aminoethoxy) ethylamine (AEE) on the characteristics of piperazine (PIP)-based TFC membranes were investigated for water purification and aerobically treated palm oil mill effluent (AT-POME) treatment. Characterizations based on field emission scanning electron microscopy (FESEM), Fourier transform infrared analysis (FTIR) and contact angle were carried out to provide support to the filtration results. Our findings showed that 0.5 wt% NaHCO3 was the best loading to be added to improve the membrane performance by enhancing water permeability by 37% without affecting Na2SO4 rejection. In the presence of 0.5 wt% NaHCO3, it is found that the introduction of AEE into PIP solution could further improve the Na2SO4 rejection of PIP-based membrane from 97.1 to 98.5% while producing a permeate of better quality. Further evaluation using AT-POME indicated that the AEE-modified membrane was able to enhance the separation performance of PIP-based membrane, increasing its conductivity, colour (ADMI) and COD reduction from 74.31, 92.79 and 83.4%, respectively, to 79.15, 94.26 and 89.3%. This work demonstrated the positive features of using inorganic additive and secondary amine monomer in improving characteristics of TFC membrane for water and wastewater treatment. [ABSTRACT FROM AUTHOR]

Interlayered thin-film composite (i-TFC) membranes based on 2D materials have been widely studied due to their high efficiency in mass transfer. However, the randomly stacked 2D nanosheets usually increase the fluid path length to some extent. Herein, in situ -grown quasi-vertically oriented 2D ZIF-L was introduced as an interlayer for preparing high-performance reverse osmosis (RO) membranes. Through the optimization of the crystal growth based on the inert polyethylene substrate, the novel i-TFC RO membrane via interfacial polymerization shows an outstanding water permeance (5.50 L m -2 h -1 bar -1 ) and good NaCl rejection (96.3%). The membrane also shows promising potential in domestic water purification and organic solvent separation applications. Compared with the randomly stacked ZIF-L interlayer, the advantages of the vertically oriented one were ascribed to the excellent storage capacity of the amine monomers and the intensified gutter effect. This work will encourage more exploration on the interlayer architectures for high-performance i-TFC membranes.

Herein, polyamide thin-film composite forward osmosis (TFC-FO) membranes were fabricated using beta-cyclodextrin-graft-poly acrylic acid (ß-CD-g-PAA), as a nature-based graft polymer. The polymer was synthesized by free radical graft polymerization and was consequently incorporated into the active layer to enhance the hydrophilicity, anti-fouling, and overall performance of the conventional TFC-FO membrane. The effect of synthesized polymer concentration on characteristic features such as roughness, morphology, and hydrophilicity of the polymer-modified membranes was thoroughly investigated using different characterization techniques. Apart from that, the separation performance of the newly developed membranes was investigated in FO and reverse osmosis (RO) filtration systems. The transport data revealed increased water flux of around 1.5 times for the membrane which was modified with 1250 ppm of ß-CD-g-PAA solution (TFC-1250) compared to pristine TFC in the FO mode. Interestingly, the mentioned membrane showed demonstrably perm-selectivity of 0.043 bar in RO filtration system. The antifouling investigations of the TFC-1250 membrane against protein and organic foulant in FO mode, not only showed minor fouling tendency, but also revealed great flux recovery ratio (FRR>98%) with a simple washing step. These observations prove the reversible characteristic of fouling in FO process. Hence, this project opens a new way to surface functionalization of TFC membranes with nature-based polymers to render selectivity as well as antifouling features to them. [Display omitted] • A novel natural-based graft polymer was utilized to fabricate novel TFC-FO membrane. • Hydrophile ß-CD-g-PAA polymer led to improved water flux in various filtration systems. • The newly developed membranes were of smooth surface and ultra-thin PA layers. • Superior anti-fouling and reverse fouling feature was observed against protein and organic foulants. [ABSTRACT FROM AUTHOR]

A series of thin-film composite membranes with polyurea as the active layer were fabricated by interfacial polymerization of different multi-amine and 1,4-phenylene diisocyanate (PDI) on porous poly(ether sulfone) support. By XPS and SEM analysis, polyethylenepolyamine (PP) was confirmed to be more suitable to react with PDI to form denser and thinner polyurea-based active layer. The best-optimized sample was obtained by varying PP and PDI content during interfacial polymerization process, exhibiting a MgSO4 rejection of 99.0%, with a water flux of 15.4 L m−2 h−1 at 2.0 MPa. The acid/alkali-tolerant property of the best-optimized membrane was investigated by both static acid/alkali soaking tests and long-term permeation tests under extremely acidic or alkaline condition. It should be noted that the optimal membrane fabricated by PP can still retain a MgSO4 rejection higher than 93.0% at neural pH testing condition, after exposure to extreme pH condition for 1 year, and the pH stability of the membrane can be comparable to that of the commercial MPS-34 membrane produced by Koch industries. On the other hand, during long-term permeation tests, the optimal membrane fabricated by PP showed stable Na2SO4 rejection higher than 90%, with higher than 90% permeability for H2SO4, implying potential application in the separation of the acid from metal salts. [ABSTRACT FROM AUTHOR]

High-performance, additive-free, all-polymeric thin-film composite (TFC) membranes were developed for CO₂ capture, focusing on a comparison between block and random copolymers (referred to as PTF) composed of hydrophobic poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) and CO 2 -philic polar poly(oxyethylene methacrylate) (POEM) chains. The PTF random copolymer, synthesized via free-radical polymerization (FRP), exhibited a disordered morphology. In contrast, the PTF block copolymer, synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, formed a well-ordered hexagonally packed cylindrical structure, creating an amphiphilic, microphase-separated nanostructure. Molecular dynamics (MD) simulations revealed that in both copolymers, there was minimal interaction between the gases (CO₂ and N₂) and the hydrophobic PTFEMA segments, while CO₂ showed strong affinity for the hydrophilic POEM segments. The block and random copolymers demonstrated similar CO₂ permeance, which can be attributed to their comparable CO₂ diffusivity and solubility. However, the block copolymer exhibited significantly lower N₂ permeance than the random copolymer, resulting in nearly quadruple the CO₂/N₂ selectivity. This increase in selectivity was supported by the lower N₂ mean squared displacement (indicating reduced diffusivity) observed in the block copolymer. The PTF block copolymer outperformed the commercial Pebax block copolymer, achieving CO₂ capture efficiencies that surpass industrial standards for CO₂ separation and capture. This positions the single-matrix PTF block copolymer as a promising alternative to mixed-matrix membranes for practical applications in gas separation technologies. [Display omitted] • Additive-free, single-matrix TFC membranes were created using PTF block copolymer. • The well-ordered cylindrical structure of the PTF block copolymer reduced N₂ permeance, enhancing CO₂/N₂ selectivity. • MD simulations were used to characterize diffusivity and solubility. • The PTF block copolymer outperformed Pebax, meeting the industrial standards required for efficient CO₂ capture. [ABSTRACT FROM AUTHOR]

In response to the growing demand for efficient water treatment solutions, thin-film composite (TFC) membranes have gained prominence due to the versatility in various separation processes. Tannic acid (TA), derived from plants, exhibits unique properties such as hydrophilicity, metal ion chelation, and antioxidant activity, positioning it as a promising agent for membrane modification. This review comprehensively explores recent advancements in enhancing TFC membranes through TA modification. It delves into synthesis methodologies and performance enhancement mechanisms, aiming to provide a foundational resource for membrane design and application. The focus is on how TA contributes to improved membrane performance through selective layer and interlayer synthesis, optimizing the interfacial polymerization (IP) reaction process, and post-treatment surface modification. Additionally, the review highlights innovative non-IP TFC membranes incorporating TA, such as metal-phenolic network membranes, co-deposited membranes, layer-by-layer self-assembled membranes, and two-dimensional laminar membranes. Challenges are addressed, and future research directions are suggested to optimize TA utilization and evaluate its long-term performance and stability in membrane applications. [Display omitted] • The research progress of TA-modified TFC membranes is systematically reviewed. • TA-modified TFC membranes based on IP and non-IP methods are introduced. • Performance data of 76 kinds of TA-modified TFC membranes are summarized. • Future research gaps and outlooks in TA-modified membranes are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • DAR was first used for fabricating a novel PA TFC membrane. • The morphology of this PA nanofilm was regulated by DAR content. • Water flux of the membrane was up to 212.5 LMH/bar while 100 % rejection for BBR. • Efficient fraction was achieved with 98 % CR rejection and >95 % salt passage. • The prepared membrane exhibited excellent antifouling and stability. Developing ultrathin polyamide thin-film composite (PA TFC) membrane with ultrahigh performance to overcome the perm-selectivity upper bound of molecular separation is still the major challenge for practical applications. Herein, we first designed an ultrahigh performance PA TFC membrane fabricated by interfacial polymerization of 4,6-diaminoresorcinol dihydrochloride (DAR) and trimethyl chloride (TMC) on the substrate. The structural morphology of the PA active layer and the separation performance of the resultant membrane were tuned by DAR dosage. This ultrathin PA TFC membrane breaks the trade-off between water permeance and dye (NOM) selectivity. Accordingly, the optimal membrane had a water flux of 212.5 LHM/bar with superior rejection of 98.6 % and 100 % for BBR and CR, respectively, surpassing the upper-bound limit of most reported polymeric membranes thus far. The membranes also exhibited a high salt passage (>95 %), achieving an impressive screening capacity for the dye/salt mixture as well as excellent antifouling and operation stability performance. This work sheds light on the regulation of the PA selective layer via new amine monomer featuring ultrahigh performance. [ABSTRACT FROM AUTHOR]

Ceramic membranes with multi-channel configurations exhibit superior mechanical strength, high packing density, and high separation efficiency, making them more suitable for industrial applications than single tube and hollow fiber membranes. However, the preparation of thin-film composite (TFC) membranes on multi-channel ceramic supports remains a challenge because of the poor compatibility between organic and inorganic materials and their special configuration. In this study, nanofiltration membranes with a stabilized structure supported by 19-channel ceramic membranes were successfully prepared with improved adhesion strength and dynamic interfacial polymerization. TFC membranes with different channels exhibited uniform microstructure and stable performance. Specifically, polyethyleneimine, which served as a polymerization reactant, can be tightly wound on the surface of ceramic membranes via hydrogen bonding and van der Waals forces during interfacial polymerization. Owing to the enhanced cross-linked network interactions between the support and separation layers, the adhesion strength was significantly improved. Consequently, the optimized membranes maintained excellent rejection to MgCl 2 of ∼94 % after the back-flush test under the pressure of 4 bar. Additionally, the multi-channel TFC membranes exhibited stable performance, with a pure water permeance of ∼14.9 LMH/bar and a molecular weight cut-off of 450 Da. When filtering sunset yellow for 10 h, the prepared membranes exhibited stable permeance and excellent rejection performance. [Display omitted] • PEI served as linking agent to enhance the adhesion of ceramic supports and PA layer. • The performance of optimized TFC membranes changed slightly after the back-flush test at 4 bar. • The TFC membranes supported by the 19-channel ceramic supports was prepared. • The membranes of each channels show uniform microstructure and stable performance. [ABSTRACT FROM AUTHOR]

Worldwide water shortage and significant issues related to treatment of wastewater streams, mainly the water obtained during the recovery of oil and gas operations called produced water (PW), has enabled forward osmosis (FO) to progress and become advanced enough to effectively treat as well as retrieve water in order to be productively reused. Because of their exceptional permeability qualities, thin-film composite (TFC) membranes have gained increasing interest for use in FO separation processes. This research focused on developing a high water flux and less oil flux TFC membrane by incorporating sustainably developed cellulose nanocrystal (CNC) onto the polyamide (PA) layer of the TFC membrane. CNCs are prepared from date palm leaves and different characterization studies verified the definite formations of CNCs and the effective integration of CNCs in the PA layer. From the FO experiments, it was confirmed that that the membrane with 0.05 wt% of CNCs in the TFC membrane (TFN-5) showed better FO performance in PW treatment. Pristine TFC and TFN-5 membrane exhibited 96.2% and 99.0% of salt rejection and 90.5% and 97.45% of oil rejection. Further, TFC and TFN-5 demonstrated 0.46 and 1.61 LMHB pure water permeability and 0.41 and 1.42 LHM salt permeability, respectively. Thus, the developed membrane can help in overcoming the current challenges associated with TFC FO membranes for PW treatment processes.

The discharge of wastewater containing dyes not only causes serious environmental pollution but also poses a severe threat to human health. The selective separation of dyes and reuse of inorganic salts are vital in the textile industry. In this work, nitrogen-doped graphene quantum dots (N-GQDs) was successfully synthesized via the "one-step solvothermal method", and the N-GQDs composite membranes were innovatively fabricated by constructing a thin selective layer top the modified multi-walled carbon nanotubes (MWCNTs) matrix membrane via interfacial polymerization process. The pore size of the N-GQDs membranes could be flexibly modulated by regulating the contents of the N-GQDs. The suitable N-GQDs membrane (M4, 0.35 wt % of N-GQDs) possessed over 96 % rejection rate for diverse charged dyes, which was higher than that of the piperazine polyamide (PA3) membrane. Notably, the rejection of the smaller molecular weight of Methylene Blue by the M4 membrane reached ∼98.93 %, which was higher than that reported in most literature, mainly owing to the relatively smaller average pore size and stronger electronegativity of the membrane. Especially compared with our previous work, the prepared M3 and M4 membranes exhibited an enhancement of ∼37.79 % and 39.48 % in rejection of Methylene Blue, ∼ 78 % and 19 % in pure water permeability, respectively. On account of the size sieving and charge effect, the N-GQDs membrane (M4) could maintain high rejection for dyes and exhibited efficient separation for dye/salt with a separation factor of 115 for the Congo Red/sodium chloride mixture after continuous cross-flow filtration for 24 h in the simulated wastewater condition. Furthermore, the N-GQDs membrane also exhibited favorable acid-base resistance and satisfactory anti-fouling performance. Importantly, the N-GQDs membranes presented excellent decolorization efficiency for the practical textile wastewater. These results revealed that the as-prepared N-GQDs membrane possessed great potential for actual textile wastewater advanced treatment and purification. This study also offers a new candidate to rationally manipulate the separation properties of nanofiltration membranes adopting new aqueous monomers. [Display omitted] • The pore size of the membrane could be flexibly regulated by N-GQDs contents. • The custom-tailored N-GQDs membrane was suitable for efficient dye separation. • N-GQDs membranes show worthy durability and selectivity even in harsh conditions. • N-GQDs membranes present superior decolorization for actual dye wastewater. [ABSTRACT FROM AUTHOR]

In this study, highly hydrophilic TiO2/Fe3O4 nanoparticles with a high level of photocatalytic activity were used to improve the performance of thin-film nanocomposite (TFN) membranes in forward osmosis (FO) process. The influence of TiO2/Fe3O4 nanoparticles binary metal oxides incorporation on the properties of the TFC FO membrane in terms of hydrophilicity, porosity, pore size, and cross-sectional morphology was thoroughly studied. Results demonstrate that with the addition of TiO2/Fe3O4 nanoparticles, the structure of the membrane top layer has changed due to nanoparticles’ reaction with the amino and organic monomers in the surface polymerization process. Furthermore, the thickness of the membrane cross section has changed with the addition of TiO2/Fe3O4 nanoparticles due to changes in the rate of the amine monomer penetration into the sublayer. The TiO2/Fe3O4 loading caused changes in the overall porosity and improved membrane hydrophilicity. The effect of UV light on the synthesized membranes was also tested. It was found that in the presence of UV light, the high photocatalytic activity of TiO2/Fe3O4 nanoparticles is the primary cause of their excellent performance in the membrane structure. As the membrane was exposed to UV light, the increase in hydrophilicity increases the membrane flux and decreases its structural parameter. These changes resulted in a 43% improvement in membrane water permeability and reduced the structural parameter up to 410 μm. Water flux of improved membrane also increased by 74% in the forward osmosis process, which was achieved without significantly decreasing membrane selectivity. [ABSTRACT FROM AUTHOR]

The escalating global demand for clean water has driven a growing interest in developing thin-film composite (TFC) membranes with high permeability and selectivity for wastewater treatment and desalination processes. Engineering polymer materials with precisely tunable properties for selective molecular separation remains a challenging step toward achieving this goal. Herein, we have fabricated a highly permselective asymmetric polyamide nanofilm with a dual-layer structure in which the bottom layer is a porous hyperbranched aromatic polyamide (HBPA) interlayer, and the top layer is a dense polyamide layer with a nanostrip structure. The HBPA porous layer was covalently assembled in situ via oxidative coupling reaction with ammonium persulfate on a polysulfone (PSF) substrate. The hydrophilic porous HBPA interlayer forms nanosized cavities that may enhance the storage and confine amine monomer diffusion, leading to the construction of a striped pattern PA nanofilm. The resulting asymmetric PA membrane exhibits excellent water permeability of 18.39 ± 1 L m−2 h−1 bar−1 (3.98 times that of control membranes) and improved divalent salt (Na 2 SO 4) rejection (≥98 %), surpassing most of the commercial and reported nanofiltration membranes. The HBPA-regulated interfacial polymerization provides a groundbreaking framework for developing high-performance membranes for precisely controlled nanofiltration. [Display omitted] • In situ covalent assembly of hyperbranched aromatic poly (amidoamine) via oxidative coupling reaction. • Hyperbranched aromatic poly (amidoamine) interlayer plays a pivotal role in regulating the IP process. • Hyperbranched aromatic poly (amidoamine) interlayer endows the TFC membranes with multi-scale morphology. • Asymmetric PA nanofilm exhibits outstanding permeability and ion separation performance. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) technology has the potential to separate and purify organic solvents in high efficiency. The self-supporting structure and ease scaling-up merit of hollow fiber (HF) type membrane make it an attractive option for OSN application. Nevertheless, low solvent permeance is one of technical limitation in conventional HF OSN membranes due to their excessively dense separation layer and limited free volume. Herein, we propose a straightforward methodology to fabricate HF thin-film composite (TFC) OSN membranes having exceptional solvent permeance and solute rejection. This methodology is conducted through the incorporation of macrocyclic molecules, 1,4,7,10-tetraazacyclododecane (Cyclen), into the aqueous monomer solution of m -Phenylenediamine (MPD) during the interfacial polymerization to modulate the separation layer. In this way, the average pore size of the separation layer could be precisely enlarged and narrowed on a sub-nanometer scale. Consequently, the Cyclen-modulated HF TFC OSN membrane exhibits excellent separation performance, with a pure methanol permeance of 76.7 L m−2 h−1 MPa−1 and a pure ethanol permeance of 26.5 L m−2 h−1 MPa−1, which is nearly 60 % increase compared with the baseline TFC membrane, while the Rhodamine B (RDB) rejection only shows a neglectable decrease from 99.7 % to 99.6 % at optimal fabrication conditions. Furthermore, the optimal membrane exhibits remarkable solvent resistance, withstanding a 35 d immersion in N, N -dimethylformamide (DMF) at room temperature without a significant decline in RDB rejection. Additionally, the optimal membrane shows higher than 99 % rejection for Rifampicin (823 Da), which is considerable potential for applications in the separation and recovery of pharmaceuticals. In summary, incorporating macrocyclic polyamine Cyclen into the polyamide layer is a viable method for regulating the physical structure and strengthening the performance of HF OSN membrane. [Display omitted] • Hollow fiber OSN membrane doped with macrocyclic polyamine Cyclen. • The incorporation of Cyclen results in an enlarged average pore size. • Ethanol permeance increases nearly 60 % with Rhodamine B rejection of 99.6 %. • No significant decrease in Rhodamine B rejection during 35 d immersion in DMF. [ABSTRACT FROM AUTHOR]

The structure parameter of the forward osmosis membrane has been defined as the characteristics of the support membrane, not related to the separation layer. Therefore, studies for improving the performance of the forward osmosis (FO) membranes have been focused on the optimization of the support structure. This study demonstrates that the separation thin-film polyamide (PA) layer has a strong impact on the performance of the FO membrane thus the structure parameters (S). We intentionally utilized a polyethersulfone hollow fiber substrate and two types of active separation skin were prepared at the inner surface: the first MPD/TMC and the second by adding triethylamine (TEA) into the aqueous phase during the interfacial polymerization (IP). By adding TEA, a rough PA layer with a leaf-like structure and a high crosslinking degree was obtained followed with high FO flux and low reverse salt flux attributed to the increased effective filtration area and crosslinking degree. The structure parameter of the FO membrane was reduced from 0.78 mm (for MPD/TMC system) to 0.45 mm (for MPD-TEA/TMC system). The result indicated that for the same substrate, lower structure parameter corresponded to the skin layer with higher permeance and rejection. This study confirmed that the structure parameter is more an inherent property of the entire TFC FO membrane than the character of the porous substrate. Future design for FO membranes needs to regulate the substrate, but more importantly to optimize the separation layer. • An approaching ratio (α) was designed as a simple guideline for control the structure parameter of FO membranes. • Diethylene glycol was used as the nonsolvent to control the approaching ratio. • Lowest structure parameter and highest FO performance were obtained at α = 50 %. • The optimized TFC membrane is of practical interest for lithium concentration. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile interface polymerization modification scheme is developed. • The introduction of PEI results in an unprecedented positive charge (IEP = 9.55) for the membrane. • The PSA group introduced by BDSC improves the acid-resistance of the membrane. • The doping of TMC greatly improves the separation performance of traditional PSA membranes. Adjusting the TMC content to control the structural pore size of the membrane. • The modified membrane has good separation performance for dye/metal ions. The selection of separability and surface positive charge is of significant importance for treating acidic industrial wastewater with acid-resistant nanofiltration (NF) membranes. In this work, polyvinylidenefluoride (PVDF) flat membrane was used as the base membrane material, with polyethyleneimine (PEI) as the aqueous monomer and trimesoyl chloride (TMC)/benzene-1,3-disulfonyl chloride (BDSC) as the organic phase monomers, to prepare PEI-polyamide-sulphonamide (PASA) NF membrane through interfacial polymerization (IP). The influence of reaction conditions on membrane separation performance and corrosion resistance were studied, and the performance differences of the membrane under different ratios of TMC and BDSC were explored. PEI-PASA NF membrane was characterized by FTIR, XPS, SEM, contact angle tester, and mechanical strength tester. The results showed that the PEI-PASA NF membrane prepared under optimal conditions had a strong positive charge on the surface, with a water flux of 17.54 L·m−2·h−1 at 5 bar, and after static assessments in 10 % H 2 SO 4 solution at 55 °C for 24 h, the methyl orange rejection remained kept over 95 %; after dynamic filtration in 1 % HCl for 120 h, the rejection performance of the membrane remained stable (FeCl 3 96.88 %, CuCl 2 93.72 %), indicating the potential application inharsh conditions, especially acid wastewater treatment. [ABSTRACT FROM AUTHOR]

Preparing polyamide (PA) composite membranes with high gas separation performance requires rational control for the interfacial polymerization (IP) process. In this study, the monomer supply of piperazine (PIP) and trimesoyl chloride (TMC) in the IP process was precisely manipulated to generate an ultrathin PA film on the polydimethylsiloxane (PDMS) gutter layer for CO 2 separation. Concretely, the PIP supply was regulated from the homogeneous, slow, and excess mode to the inhomogeneous, fast, and small mode by constructing a sodium dodecyl sulfate (SDS) array at the phase interface; subsequently, the TMC supply was increased by elevating the TMC concentration. Therefore, the amine-to-acid chloride concentration ratio in the reaction zone was optimized and, as a consequence, the IP reaction rate was significantly increased. As a result, the thickness of the PA film was reduced from ∼92 nm to ∼37 nm through the optimization of SDS and TMC concentrations, and accordingly, the CO 2 permeance was increased from 501 GPU to 1498 GPU under 0.1 MPa without sacrificing selectivity. Moreover, the membrane preparation efficiency was greatly improved with an IP reaction time of less than 30 s. The insights provided could promote the industrial application of interfacial polymerization in the scale-up preparation of high-performance CO 2 separation membranes. [Display omitted] • The interfacial polymerization was regulated by manipulating monomers supply. • High membrane-preparation efficiency was achieved. • PA TFC membrane with the ultrathin selective layer of ∼37 nm was prepared. • The CO 2 permeance had nearly tripled without sacrificing selectivity. [ABSTRACT FROM AUTHOR]

Thin-film composite (TFC) polyamide membranes have a wide range of applications in forward osmosis, but tuning the water flux remains a significant challenge due to concentration polarization. The generation of nano-sized voids within the polyamide rejection layer can change the roughness of the membrane. In this experiment, the micro-nano structure of the PA rejection layer was adjusted by adding sodium bicarbonate to the aqueous phase to generate nano-bubbles, and the changes of its roughness with the addition of sodium bicarbonate were systematically demonstrated. With the enhanced nano-bubbles, more and more blade-like and band-like features appeared on the PA layer, which could effectively reduce the reverse solute flux of the PA layer and improve the salt rejection of the FO membrane. The increase in roughness raised the area of the membrane surface, which led to a larger area for concentration polarization and reduced the water flux. This experiment demonstrated the variation of roughness and water flux, providing an effective idea for the preparation of high-performance FO membranes.

A novel non-equilibrium molecular dynamics (MD) model was presented to investigate the transport mechanisms and desalination performance of thin-film composite membranes (TFC). Firstly, polyamide (PA) and polysulfone (PSF), or PSF/UiO-66 models, were constructed as active and support layers. Subsequently, feed solution and draw solutions with 0.5, 1.0, and 1.5 M salt concentrations were generated. Thirdly, these aqueous and membranes were combined to build forward osmosis (FO) models. The FO process was simulated to anatomise the membrane fouling, water flux, and salt rejection, which JAVA and MD programs were combined to calculate. The results indicated that the PA-PSF/UiO-66 membrane exhibited a stable water transport and salt rejection performance compared to the pristine PA and PA-PSF membranes. Finally, experiments and simulations were compared, and the same trends were found. Therefore, this simulation work provided significant insight in guiding the design and synthesis of the FO membrane. [ABSTRACT FROM AUTHOR]

[Display omitted] • FO regeneration of an MEG aqueous solution was conducted using novel TFC membranes. • The polyamide layer was synthesized on PPSU/CAP/vertically aligned FMWCNTs support. • The effect of MMPD concentration and IP reaction time on the top layer was studied. • Using MMPD in the synthesis of polyamide layer improved its chlorine resistance. Monoethylene glycol (MEG) aqueous solution was regenerated in the forward osmosis (FO) process for further use. For this purpose, a novel thin-film composite (TFC) membrane was prepared and applied. To mitigate the internal concentration polarization (ICP), a proper support with a low structural parameter and high hydrophilicity was utilized. In addition, a chlorine-tolerant polyamide layer was synthesized using trimesic acid trichloride (TMC) and 4-methyl-m-phenylenediamine (MMPD) monomers. The latter aimed to improve the chlorine resistance of the polyamide layer and increase the membrane lifespan in practical applications where oxidants are utilized for membrane cleaning. The effect of MMPD concentration and interfacial polymerization (IP) reaction time on the characteristics of the top layer was studied thoroughly. During the FO test, the TFC membrane whose polyamide layer was prepared with 2 wt. % MMPD concentration and 1.4 min reaction time exhibited the highest reverse flux selectivity at 5.71 L/g, while its water flux and MEG rejection during the regeneration of a MEG aqueous solution sampled from a gas processing plant were 35.40 LMH and 93.85%, respectively. The chlorine exposure test confirmed a significantly higher chlorine resistance for the MMPD/TMC polyamide layer compared to the conventional MPD/TMC one. [ABSTRACT FROM AUTHOR]

Fabricating acid resistant nanofiltration (NF) membranes with precise solute separation performance is highly demanded for acidic wastewater treatment but remains a challenge. Herein, we propose a facile strategy for preparing dually charged acid resistant NF membranes with both high cations and anions rejections via a two-layer reverse interfacial polymerization (r-IP) process. Organic monomers of trimesoyl chloride (TMC) and 1,4-phenylene diisocyanate (PPDI) are firstly applied to react with 3-aminobenzenesulfonamide (ABSA) to construct a negatively charged loose intermediate layer, followed by the r-IP of TMC/PPDI and polyethyleneimine (PEI) to engineer a dense positively charged top layer. The highly cross-linked polyurea (PU) formed by isocyanate and amine leads to an enhanced size sieving effect, and the well-arranged dually charged layer endows the membrane stronger electrostatic exclusion. The resultant membrane has 97.7% rejection of Na2SO4 and 93.0% of MgCl2, and it exhibits fairly high rejections to various heavy metals, as well as impressive long-term stability after exposure to strong acid (10 wt% of H2SO4 for 400 h).

This work was focused on the mitigation of physical aging in thin-film composite (TFC) membranes (selective layer ~1 μm) based on polymer intrinsic microporosity (PTMSP) by the introduction of both soft, branched polyethyleneimine (PEI), and rigid, porous aromatic framework PAF-11, polymer additives. Self-standing mixed-matrix membranes of thicknesses in the range of 20–30 μm were also prepared with the same polymer and fillers. Based on 450 days of monitoring, it was observed that the neat PTMSP composite membrane underwent a severe decline of its gas transport properties, and the resultant CO2 permeance was 14% (5.2 m3 (STP)/(m2·h·bar)) from the initial value measured for the freshly cast sample (75 m3 (STP)/(m2·h·bar)). The introduction of branched polyethyleneimine followed by its cross-linking allowed to us to improve the TFC performance maintaining CO2 permeance at the level of 30% comparing with day zero. However, the best results were achieved by the combination of porous, rigid and soft, branched polymeric additives that enabled us to preserve the transport characteristics of TFC membrane as 43% (47 m3 (STP)/(m2·h·bar) after 450 days) from its initial values (110 m3 (STP)/(m2·h·bar)). Experimental data were fitted using the Kohlrausch–Williams–Watts function, and the limiting (equilibrium) values of the CO2 and N2 permeances of the TFC membranes were estimated. The limit value of CO2 permeance for neat PTMSP TFC membrane was found to be 5.2 m3 (STP)/(m2·h·bar), while the value of 34 m3(STP)/(m2·h·bar) or 12,600 GPU was achieved for TFC membrane containing 4 wt% cross-linked PEI, and 30 wt% PAF-11. Based on the N2 adsorption isotherms data, it was calculated that the reduction of the free volume was 1.5–3 times higher in neat PTMSP compared to the modified one. Bearing in mind the pronounced mitigation of physical aging by the introduction of both types of fillers, the developed high-performance membranes have great potential as support for the coating of an ultrathin, selective layer for gas separation.

This paper presents a comprehensive study of the performance of a newly developed titania nanotube incorporated RO membrane for endocrine-disrupting compound (EDC) removal at a low concentration. EDCs are known as an emerging contaminant, and if these pollutants are not properly removed, they can enter the water cycle and reach the water supply for residential use, causing harm to human health. Reverse osmosis (RO) has been known as a promising technology to remove EDCs. However, there is a lack of consensus on their performance, especially on the feed concentrations of EDC that vary from one source to another. In this study, polyamide thin-film composite (PA TFC) membrane was incorporated with one-dimensional titania nanotube (TNT) to mitigate trade-off between water permeability and solute rejection of EDC. The characterization indicated that the membrane surface hydrophilicity has been greatly increased with the presence of TNT. Using bisphenol A (BPA) and caffeine as model EDC, the removal efficiencies of the pristine TFC and thin-film nanocomposite (TFN) membranes were evaluated. Compared to TFC membrane, the membrane modified with 0.01% of TNT exhibited improved permeability of 50% and 49% for BPA and caffeine, respectively. A satisfactory BPA rejection of 89.05% and a caffeine rejection of 97.89% were achieved by the TNT incorporated TFN membranes. Furthermore, the greater hydrophilicity and smoother surface of 0.01 TFN membrane led to lower membrane fouling tendency under long-term filtration.

Featured Application: This article presents a discussion on the gains from enhancing salt rejection from a broad perspective, which includes the specific energy consumption and some insights into a technical direction to improve salt rejection of TFC-RO membranes. Since the specific energy consumption (SEC) required for reverse osmosis (RO) desalination has been steeply reduced over the past few decades, there is an increasing demand for high-selectivity membranes. However, it is still hard to find research papers empirically dealing with increasing the salt rejection of RO membranes and addressing the SEC change possibly occurring while increasing salt rejection. Herein, we examined the feasibility of the process and material approaches to increase the salt rejection of RO membranes from the perspective of the SEC and weighed up a better approach to increase salt rejection between the two approaches. A process approach was confirmed to have some inherent limitations in terms of the trade-off between water permeability and salt rejection. Furthermore, a process approach is inappropriate to alter the intrinsic salt permeability of RO membranes, such that it should be far from a fundamental improvement in the selectivity of RO membranes. Thus, we could conclude that a material approach is necessary to make a fundamental improvement in the selectivity of RO membranes. This paper also provides discussion on the specific demands for RO membranes featuring superior mechanical properties and excellent water/salt permselectivity to minimize membrane compaction while maximizing the selectivity. [ABSTRACT FROM AUTHOR]

In this study, we deployed a modified interfacial polymerization process to incorporate multifunctional crown ethers (CEs) into thin‐film composite (TFC) polyamide membranes. CE additives acted as both the phase‐transfer catalyst and co‐solvent to facilitate the diffusion of amine monomers into the organic phase via interacting with amine monomers (form the host‐guest inclusion complex), and enhanced the free volume content of the selective layer, therefore facilitating water transport and inhibiting the diffusion of salt ions. Various characterization techniques were employed to elucidate the modification mechanism as a function of CE chemical and physical properties on the microstructure of resultant TFC membranes and consequently separation performances. Compared to TFC membranes produced from traditional interfacial polymerization method, CE‐modified membranes exhibited a 146% water flux enhancement and 59% lower reverse salt fluxes with a suitable draw solution. CE‐modified membranes also showed the improved antifouling behavior and chemical stability in various harsh conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • PA nanofilms were prepared via support-free IP with a series of anionic surfactants. • Longer alkyl tails or smaller/weaker-bound cations of surfactants more deformed PA. • Marangoni instability was triggered by binding of surfactant–MPD complexes to PA. • Longer tails or smaller/weaker-bound cations induce greater Marangoni instability. • Larger Marangoni instability led to larger PA structure and performance alterations. Polyamide (PA) nanofilm membranes are key materials for water treatment and desalination. Although surfactants are widely used to tune the interfacial polymerization (IP) process for PA nanofilm formation, their regulatory mechanisms remain incompletely understood. Herein, we synthesized PA nanofilm membranes at a support-free interface in the presence of anionic surfactants with different tail lengths and counterions and comprehensively characterized them to identify the IP mechanism regulated by the surfactant structure. The use of the surfactant with a longer alkyl tail or a smaller/weaker-bound counterion resulted in greater alterations in the structural and physicochemical properties and separation performance of the PA nanofilm membranes. Collaborated with computational simulations, this phenomenon could be attributed to solutal Marangoni instability triggered by the interfacial migration (via binding to PA) of the surfactant complexed with amine monomers during IP. A longer alkyl chain or smaller/weaker-bound counterion of the surfactant intensified Marangoni instability by promoting the interfacial formation of surfactant–amine complexes and/or facilitating their binding to PA, leading to greater PA deformations. Our work provides new insights into the surfactant-regulated IP mechanism as well as a facile means to rationally tailor the properties and performance of IP-assembled nanofilm membranes for various environmental applications. [ABSTRACT FROM AUTHOR]

Polyamide (PA)/ferroferric oxide/oxidized multi-walled carbon nanotubes (Fe 3 O 4 /o-MWCNTs)/polyvinyl chloride (PVC) composite nanofiltration (NF) membranes were prepared by the interfacial polymerization (IP) process with the Fe 3 O 4 /o-MWCNTs/PVC porous membrane as the substrate membrane, which was prepared by the magnetic field assisted non-solvent induced phase separation method (NIPS) with the synthesized superparamagnetic Fe 3 O 4 /o-MWCNTs nanoparticles (NPs) as the additives of the functional intermediate layer integrated with the substrate. The effects of the magnetic carbon nanotubes modified PVC porous substrate membrane on the surface chargeability, PA layer thickness, mechanical properties, pressure resistance and permeability of the composite NF membranes were investigated, and the comprehensive performance of composite NF membranes was enhanced. The results indicated that the porosity and hydrophilicity of the Fe 3 O 4 /o-MWCNTs/PVC porous substrate membrane were improved by the migration of magnetic Fe 3 O 4 /o-MWCNTs NPs to the upper edge of the substrate membrane and uniform enrichment under magnetic field induction, which further affected the structure and properties of the PA/Fe 3 O 4 /o-MWCNTs/PVC composite NF membrane. The prepared NF membrane presented smaller roughness, thinner PA layer, larger pore size, with excellent mechanical properties and better pressure resistance. Meanwhile, the PA/Fe 3 O 4 /o-MWCNTs/PVC composite NF membrane presented excellent divalent salt rejection, with the rejection of MgSO 4 and Na 2 SO 4 maintaining more than 95.2% and 93.4%, respectively, while the permeation flux could reach 35.4 L·m−2·h−1. In summary, the modification of the substrate integrated with the functional intermediate layer had certain enlightening significance for the preparation of the NF membrane with excellent comprehensive performance. [Display omitted] • The NF membrane was prepared with the magnetic Fe 3 O 4 /o-MWCNTs/PVC porous substrate membrane. • The functional intermediate layer was integrated with the substrate to form a whole. • Adding hydrophilic magnetic NPs as intermediate layer optimized the PA structure with better permeability. • TFC NF membrane showed better comprehensive performance on the modified substrate. [ABSTRACT FROM AUTHOR]

The preparation of thin-film composite (TFC) membranes with both extraordinary permeance and excellent rejection performance are still a challenge due to the irreversible and rapid interfacial polymerization (IP). The high reactivity of amine monomers helps to form a defect-free membrane instantaneously during the IP process, but also ultimately leads to low water permeance. Here, a facile strategy was proposed to improve the performance of TFC membrane by conducting in-situ IP on the nanoporous ceramic membranes. First, it was confirmed that the hydrophilic ceramic membrane, which serves as an oil-water interface, can provide a uniform aqueous layer. The free-like interface is conductive to the formation of defect less polyamide layer even at ultra-low monomer concentrations and very short reaction times. Then, the performance of TFC membranes using ceramic membranes with different pore sizes as supports was systematically investigated. The result indicates that supports with smaller pore size and narrower distribution enable facilitate the formation of a thinner membrane. Moreover, the nanofiltration membrane exhibited ultra-high pure water permeances of 42.9 LMH/bar and a rejection of 93.4 % to Na 2 SO 4 , utilizing a ceramic membrane with a pore size of 10 nm as support under PIP of 0.025 wt% and reaction times of 10 s. [Display omitted] • TFC membranes were prepared by in-situ IP at ultra-low PIP concentrations. • The ceramic support can provide a uniformly distributed water/organic interface. • A simple way was used to tune the thickness and microstructure of the PA film. • The TFC membranes exhibited water flux of 42.9 LMH/bar and rejection of 93.4 % to Na 2 SO 4. [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]

The high temperatures and aggressive chemical conditions of many relevant industrial processes such as the hydrogen production from hydrocarbon fuel sources restrict the use of polymeric membranes for gas separations (GS) that could make such processes more efficient and environmentally friendlier whilst reducing their operational costs. Therefore, this work was centered on the development of a thin-film composite membrane (TFCM) prepared with high-performance polymeric materials capable of withstanding temperatures above 200 °C in industrial GS applications and which could eventually be integrated to perform in situ separations in a reactor. An innovative prototypical three-layered TFCM featuring the polyimide 6FDA-6FpDA as selective layer deposited on a cross-linked (CL) Matrimid® 5218 (Matrimid) porous support prepared on a thermally stable polyphenylene sulfide (PPS) nonwoven was investigated in two different gas permeation experimental facilities in a range from 30 to 200 °C and feed pressures of up to 10 bar. The TFCM exhibited low permeances compensated by outstanding ideal selectivities for H 2 /CO 2 , H 2 /CH 4 and O 2 /N 2 gas pairs. This behavior was attributed to the formation of an interpenetrating network between 6FDA-6FpDA and Matrimid, caused by a swelling effect of the solvent used to form the selective layer on the surface of the cross-linked Matrimid porous membrane. A drop in membrane performance was observed above 170 °C due to a reduction in the thermal stability of the CL Matrimid resulting from the opening of the imide rings of the polyimide backbone during the cross-linking reaction. [Display omitted] • A Matrimid membrane support with improved microporous structure was prepared. • The porous support was cross-linked with propandiamine and rendered insoluble in THF. • A TFCM comprising 6FDA-6FpDA on top of a porous cross-linked Matrimid and PPS nonwoven supports was developed. • The membrane featured outstanding ideal selectivities for the H 2 /CO 2 , H 2 /CH 4 and O 2 /N 2 gas pairs. • The TFCM demonstrated a stable performance up to 170 °C and feed pressures up to 10 bar. [ABSTRACT FROM AUTHOR]