Amine Monomer Research Articles

Tailoring the pore size distribution of nanofiltration membranes via surfactants with different alkyl chain lengths: Towards efficient molecular separation

The diffusion of amine monomer during interfacial polymerization (IP) directly affects the structure and properties of the polyamide (PA) separation layer. Surfactants can regulate the diffusion rate of monomers and change the microstructure of the PA layer. In this study, a PA nanofiltration (NF) membrane with the tailor-made pore size is fabricated by modulating the diffusion rate of 1, 4, 7, 10-tetraazacyclododecane (Cyclen). Surfactants with different alkyl chain lengths are used to precisely regulate the diffusion rate of Cyclen monomer. The longer the alkyl chain length of the surfactant is, the faster the diffusion rate of the Cyclen monomer is, resulting in the formation of a PA layer with a narrow pore size distribution. The prepared composite membrane is qualified for on-demand desalting and antibiotic/salt separation performance by changing the length of the alkyl chain. For example, surfactants with short alkane chains (C4) endow the NF membranes with a high water permeance of 30.7 L−1 m−2h−1 bar−1 for tetracycline separation. Surfactants with long alkane chains (C12) endow the NF membranes with a high selectivity of 84.8 for tetracycline/NaCl separation. This study provides further evidence for surfactant-regulated IP reactions and offers new ideas for the tailor-made regulation of NF membrane properties.

Development and analysis of pH-sensitive surfactants for enhancing foam drainage gas retrieval

In this study, a novel surfactant with pH-responsive properties was developed to address the challenges associated with balancing foaming and defoaming properties in traditional foam drainage gas recovery processes. The surfactant was created by employing primary amine and aldehyde monomers based on the principles of reversible dynamic covalent bonds. Optimal synthesis conditions were determined through an extensive analysis of foaming performance: a molar reaction ratio of primary amine to aldehyde at 10:0.8, a 20-minute reaction time, and a stirring speed of 300 r/min.The formation of dynamic imine bonds was confirmed through infrared spectroscopy. Surface tension measurements revealed that at pH = 8, the surfactant achieved a minimum surface tension of 31.1 mN/m, while at pH = 3, the surface tension exceeded 40 mN/m. Particle size analysis demonstrated a 26.5-fold reduction in particle size as the pH decreased from 8 to 3. Zeta potential tests indicated excellent dispersion stability within the pH range of 3–8, with Zeta potential consistently exceeding 25 mV.Furthermore, the surfactant displayed remarkable foaming and foam stabilizing effects at pH = 8, with initial and 5-minute foam heights reaching 168 mm and 132 mm, respectively. When the pH dropped below 6, the surfactant exhibited rapid defoaming. After six cycles of alternating acid-base environments, it maintained excellent foaming performance, achieving a 5-minute foam height of up to 138 mm. Importantly, it retained its foaming capabilities in formation water solutions with a mineralization degree of 200 g/L.These findings hold significant implications for the development of intelligent environmental response treatments for foam drainage and gas production, enhancing the overall efficiency of drainage and gas production operations.

Tailored dendrimer interlayer based on Marangoni convection for high-performance reverse osmosis membranes

Advanced reverse osmosis (RO) membranes for desalination, typically thin-film composite (TFC) membranes, have emerged as a prominent research direction to combat water scarcity. The substrate properties, such as the amine monomer adsorption capacity, are considered important for the interfacial polymerization (IP) process. Herein, inspired by Marangoni convection, a tailored dendrimer interlayer based on the plasma-treated polyethylene substrate was developed via the in-depth modification driven by surface tension gradient to precisely adjust the substrate properties. In addition, sodium dodecyl sulfate (SDS) was introduced as an additive to synergistically improve the desalination performance, and its role was reinvestigated. The quantitative experiments of amine monomer adsorption show that the substrate with in-depth modification possesses enhanced adsorption capacity. Therefore, massive amines can be enriched at the substrate surface, which can erupt and react violently in IP, thereby forming a polyamide layer with thick apparent thickness and abundant nanovoids. The RO membrane after optimization exhibits 99.19 % of rejection to NaCl and 3.87 L m−2 h−1 bar−1 of permeance, which shows good competitiveness compared with the advanced polymer-based RO membranes. This work provides constructive suggestions for the screening of interlayers to RO membranes and the application of polyethylene-based TFC membranes.

Nanosheet thickness control of nitrogen-doped polyimide/ammonium phosphotungstate composite for photocatalytic mineralization of imidacloprid

A series of polyimide/ammonium phosphotungstate composite photocatalysts were prepared by varying the the amine monomers, including melamine (MAPIPW), melem (MEPIPW), and carbon nitride (CNPIPW). As the heterocycle in these molecules gets larger, the nano-layer thickness reduces progressively. This results in an increased specific surface area for those photocatalysts possessing thin layers. For instance, the specific surface areas recorded for MAPIPW, MEPIPW and CNPIPW are 8.1863, 51.3379, and 142.6756 m2/g respectively. Thanks to their high surface areas, these composites exhibited improved substrate adsorption and demonstrated significant enhancement in imidacloprid degradation rates increasing to 70.06%, 76.39%, and 71.39% for MAPIPW, MEPIPW, and CNPIPW respectively. MEPIPW exhibited the highest degradation efficiency due to its superior physical adsorption, besides exhibiting excellent photovoltaic properties. An intricate POM-π interaction exists between polyimide and the Keggin structure of ammonium phosphotungstate, extending ligand conjugation to this framework so as to disperse electrons across the hybrid material's backbone. Nonetheless, this interaction may be weakened with reduced nano-sheet thickness, impacting composite photon absorption ability. Further enhancing photocatalysis was possible via nitrogen doping using urea, resulting in degradation rates of 93.69%, 95.13%, and 91.39%, for MAPIPW-20%U, MEPIPW-20%U and CNPIPW-20%U respectively.

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

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

Green synthesis of Dextrin‐graft‐poly(allyl amine‐co‐methacrylic acid)/reduced graphene oxide composite and its application for dye and pesticide removal from the aqueous medium

AbstractA Dextrin‐graft‐poly(allyl amine‐co‐methacrylic acid)/reduced graphene oxide (DEXTGP/RGO) is synthesized through the grafting of a combination of allyl amine (AAM) and methacrylic acid (MAA) monomers onto the dextrin polysaccharide backbone by using the free radical copolymerization technique in an aqueous medium, with potassium peroxydisulfate serving as the initiator followed by the partial reduction of graphene oxide (GO). Various characterization techniques including FTIR, 1H/13C NMR, XRD, FESEM, EDAX, and BET analysis are utilized to characterize both the synthesized DEXTGP/RGO composite and graft copolymer. Investigations are conducted on multiple operational variables, including adsorption kinetics, isotherms, and thermodynamic parameters, for the adsorption of both MB and PL. Both intra‐particle diffusion kinetic model and pseudo‐second‐order kinetics are observed to follow for the adsorption of MB, while the Langmuir isotherm model provided a good fit for the equilibrium data. In contrast, the adsorption of PL displayed solely pseudo‐second‐order kinetics, while the equilibrium data shows good agreement with both the Langmuir and Dubinin‐Radushkevich isotherm models. Maximum adsorption capacity ( ) of the RGO composite is found to be 932.56 mg/g for MB and 311.63 mg/g for PL. The thermodynamic analysis revealed that the adsorption of dye and pesticide onto the RGO composite is a spontaneous process.

Effect of a novel pH-responsive tertiary amine monomer dodecylmethylaminoethyl methacrylate modified resin adhesive on biofilm formation of Streptococcus mutans and Lactobacillus casei in vitro

Objective: To explore the application prospect of a new pH-responsive tertiary amine monomer dodecylmethylaminoethyl methacrylate (DMAEM) modified resin adhesive (DMAEM@RA) in the prevention and treatment of secondary caries. Methods: Five percents DMAEM was added to the resin adhesive to synthesize DMAEM@RA for modifying. Streptococcus mutans (Sm) and Lactobacillus casei (Lc) biofilms were cultured on resin adhesive and DMAEM@RA, respectively. The culture systems were set up at pH=7.4, 6.0, 5.5, and 5.0. The antimicrobial activity of DMAEM@RA was evaluated by quantitative PCR. The effects of DMAEM@RA on biofilm thickness, bacterial amount, and extracellular polysaccharides were studied by scanning electron microscope (SEM) and extracellular polysaccharide staining. Real-time fluorescence quantitative PCR was used to study the effect of DMAEM@RA on the expression levels of cariogenic genes in Sm. Results: DMAEM@RA could significantly reduce the amount of Sm and Lc under acidic conditions, especially Lc. At pH=5.0, the logarithm value of co-cultured Sm bacteria [lg (CFU/ml)] in DMAEM@RA group (7.58±0.01) was significantly lower than that in control group (7.87±0.03) (t=14.32, P<0.001), and the logarithm value of Lc bacteria [lg (CFU/ml)] (7.29±0.04) was also significantly lower than that in control group (7.93±0.15) (t=6.93, P=0.002). SEM observed that the bacteria decreased and the cell fragments appeared in DMAEM@RA group. In addition, DMAEM@RA significantly reduced the biomass of extracellular polysaccharides in the dual-species biofilm under acidic conditions. At pH=5.0, the biomass of extracellular polysaccharides in DMAEM@RA group [(25.13±3.14) mm3/mm2] was significantly lower than that in the control group [(42.66±7.46) mm3/mm2] (t=3.75, P=0.020). DMAEM@RA could significantly up-regulate the expressions of gtfB and gtfC genes in Sm under acidic conditions. At pH=5.0, gtfB and gtfC genes were significantly up-regulated by (14.64± 0.44) times and (2.99±0.20) times, respectively (t=-42.74, P<0.001; t=-13.55, P<0.001). Conclusions: The DMAEM@RA has a good antibacterial effect under acidic conditions, demonstrating that it has a good potential to prevent the occurrence and development of secondary caries.

Acetone extraction induced piperazine diffusion reaction for regulating thin film composite nanofiltration membrane

The regulation of monomer diffusion in interfacial polymerization played a vital role in manipulating structure and enhancing separation performance of nanofiltration (NF) membrane. The co-solvent strategy has been recognized to be valid and applicable for improving membrane performance. However, the underlying mechanism for its effect on the diffusion progress of amine monomers was still unclear and contradictory. In this study, we found that the added co-solvent (acetone) induced piperazine diffusion flood through interfacial co-solvent extraction effect due to the interfacial enrichment of acetone and innovatively proposed a concept of “acetone extraction effect”. The mechanism and molecular dynamics simulation (MD) were used to systematically explain the effect of diffusion on the morphology and properties of the membranes. The prepared NF membranes exhibited improved separation performance for Calcium (CaCl2, 71.5 ± 0.6 %) and Magnesium (MgCl2, 83.1 ± 0.8 %) ions, which were better than many of the recorded membranes. This study provided a new idea for the co-solvent effect in interfacial polymerization and promising guidance for the preparation of superior NF membranes.

Enhanced performance polyamide membrane by introducing high-porosity SOD/GO composite interlayer to tailor the interfacial polymerization process

Controllable preparation of high-performance polyamide nanofiltration (NF) membranes that can be used in various applications such as seawater desalination and wastewater treatment is very promising. In this work, a high-performance polyamide NF membrane was designed using high-porosity hydroxy sodalite/graphene oxide (SOD/GO) composite interlayer to slow down the diffusion of amine monomer and control the interfacial polymerization (IP) process. The unique tortuous effect and hydrogen bonds with amine monomers caused by the dense interlayer significantly inhibit the diffusion of amine monomers (reduction of 50 % in diffusion rate), thereby resulting in the controllable slow IP process. The slowing IP process facilitates the formation of thinner dense polyamide (PA) layer with stripe morphology and narrow pore size. Consequently, the optimal polyamide membrane with composite interlayer possesses a superior water permeability of 22.05 L m-2h−1⋅bar−1, nearly 2.5 fold that of the controlled one, while retaining an excellent rejection of Na2SO4 (97.25 ± 0.81 %). Moreover, the polyamide membrane depicts outstanding antifouling propensity (flux-recovery ratio (FRR) = 82 %), long-term stability (80 h) and pressure resistance (9 bar). This work provides a novel strategy for controllable construction of high-performance NF membrane and deepens the slights into the interlayer influences IP process.

Atomically dispersed Ni active sites on covalent organic frameworks for heterogeneous metallaphotocatalytic C–N cross-coupling

Covalent organic frameworks (COFs) have been acknowledged as a potential platform for heterogeneous photoredox cross-coupling due to their excellent chemical stability, admirable controllability, and extremely prominent surface area. However, synthesizing COFs with bidentate ligand units and utilizing active sites remain a grand challenge. Herein, we report a promising new family of 2,6-pyridinedicarboxaldehyde-bis-(p-aminophenylimine)-based two-dimensional (2D) COFs (PP-COF) using an amine monomer and classic tri-aldehydes. On this basis, dispersed Ni single-atom sites were immobilized on three-types imine-based bi-coordinated 2D COFs (Ni SAS-PP-COF) as heterogeneous dual photoredox catalysts for photo/Ni dual-catalyzed C–N cross-coupling between aryl bromides and alkyl/sulfo amines. Under solar energy irradiation, PP-COF could absorb light to generate electrons and holes, then the photogenerated electrons are transferred to Ni sites to reduce divalent nickel to monovalent nickel. Monovalent nickel is necessary to drive the nickel catalytic cycle. Due to the increased charge separation and abundant active sites, the state-of-the-art Ni SAS-PP-COFs catalyst achieves excellent catalytic performance in comparison of pristine PP-COF. The heterogeneous Ni SAS-PP-COF catalytic system not only confirms the prospect of COFs as potential photoredox/transition-metal dual catalysts, but also provides in-depth insights into the synthesis of functional COFs toward practical metallaphotocatalytic application.

Surfactant-assisted interfacial polymerization towards high-crystallinity COF membranes for organic solvent nanofiltration

Preparing high-crystallinity covalent organic framework (COF) membranes by interfacial polymerization remains a grand challenge. Herein, a monomer pre-assembly process is proposed to prepare high-crystallinity COF membranes by surfactant-assisted interfacial polymerization (SAIP) strategy. The self-assembled chains of amphiphilic surfactants across interface can gather and pre-assemble monomers and improve their interphase transport for complete topological growth. Apart from the reduction in polymerization time from over 72 h–48 h, the crystallinity and pore uniformity of COF membranes are highly enhanced. This strategy is universal and four kinds of amine monomers are utilized to tune COF pore size. The 1.8 nm-sized COF membrane shows highly enhanced rejection from 65.5% to 95.7% for reactive black with a size of 2.0 nm, when compared to that without surfactants. Importantly, the orderly stacked pores permit fast molecule transport with a 76% increase in acetonitrile permeance (366.9 L m−2 h−1 bar−1). Meanwhile, the robust crystal properties endow this COF membrane with excellent solvent resistance, compressive strength, and hence operational stability for over 100 h. The amphiphilic molecule-assisted interface engineering may represent a technology for scalable fabrication of high-crystallinity framework materials for molecule separation.

Tailoring morphology for improved dispersibility of hydrophilic silica nanoparticles to fabricate thin-film nanocomposite membranes

Improving the dispersibility of nanomaterials is a promising approach to enhance the performance of thin-film nanocomposite (TFN) membranes. In this study, hydrophilic nonporous, mesoporous, and dendritic mesoporous silica nanoparticles (NSNs, MSNs, and DMSNs) with a uniform particle size were utilized as aqueous phase additives to prepare TFN membranes through in-situ polymerization. The electrostatic adsorption of nanoparticles increased the concentration of amine monomers on the surface of the polysulfone (PSF) substrate. In collaboration with the steric hindrance effect, nanoparticles restricted the diffusion of piperazine (PIP) into the organic phase to polymerize with the acyl chloride monomers. Compared to TFC-0, the TFN membranes exhibited a rougher surface with increased negative charge and had more channels that facilitated the transportation of water molecules. Among the nanoparticles, DMSNs exhibited excellent dispersibility, ensuring their uniform distribution within the polyamide (PA) matrix. Furthermore, DMSNs possessed an open central-radial pore structure, offering more efficient channels for water molecules to cross the membrane. Therefore, a highly crosslinked, defect-free, and hydrophilic PA layer of TFN-DMSNs was achieved. In the performance characterization, TFN-DMSNs demonstrated a high water/salt permselectivity (A/B) of up to 32.25 bar−1, and exhibited good resistance to acidic/alkaline environments as well as foulants during the operation. This study proposes a novel approach to prepare advanced TFN membranes by optimizing the morphological structure of nanoparticles.

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

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

Polytetrafluoroethylene hollow fiber membranes with thru hydrophilic channels for enhancing water transfer and anti-oil-fouling properties

Herein, a feasible method for hydrophilic modification of polytetrafluoroethylene (PTFE) hollow fibers via interfacial polymerization (IP) was proposed. 1, 3-Diamino-2-propanol (DAP) and trimesoyl chloride (TMC) were selected as monomers and a three-time IP method was adopted to construct hydrophilic channels within the membrane pores, thus effectively improving the hydrophilicity and permeability of membranes. The solvent of aqueous phase in conventional IP process was replaced by ethanol for better introducing amine monomers into membrane pores. The characterization results of Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and water contact angle (WCA) tests indicated the successful formation of polyamide (PA) layer within the membrane pores. In comparison to the ethanol pre-wetted control membrane, the PTFE hollow fibers modified under optimal IP conditions exhibited higher water flux (from 136.8 to 1059.1 kg m−2 h−1) and showed better resistance to both BSA (FRR from 53.4% to 92.3%) and soybean oil (FRR 16.4% from to 78.1%) after four cycles of filtration and cleaning. Simultaneously, the modified membranes demonstrated a favorable oil removal capacity (≥ 92%), and still maintained good stability after 24 h ultrasonic treatment and 8 d immersion tests in acid, alkali and oxidation solutions. This membrane holds significant application value in the treatment of oily wastewater.

Liquid-solid interfacial polymerization of thin-film composite nanofiltration membrane

Interfacial polymerization prepared polyamide (PA) nanofiltration membranes are widely used for desalination and wastewater recovery due to their lower operating pressure compared to reverse osmosis desalination and ease of scalability. The diffusion behavior of amine (PIP) and acyl chloride (TMC) monomers make a significant impact on PA structure and performance. In this paper, through freezing the aqueous amine reactive solution which turned the liquid–liquid reaction process into liquid–solid and regulated the amine monomer diffusion behavior, an ultra-thin, defect-free PA layer was achieved. The effect of PIP solution temperature in the range of −15 to 25 °C on membrane morphology, chemical composition and surface properties was investigated. The results indicated that PIP diffusion rate had a positive effect on the crosslinking degree of formed PA layer. However, frozen amine solution effectively inhibited the diffusion rate of PIP and hydrolysis of TMC which simultaneously improve the permeability and selectivity. The fabricated membrane by liquid–solid reaction process showed hydrophilic, dense and ultrathin PA layer with a high pure water permeance (23.7 L·m−2·h−1·bar−1) and good retention of salt (95.4 % for Na2SO4). Also, the good selectivity to divalent cation and anion, and excellent stability of the membrane prefigured its potential in application of various water treatment fields.

Regulation of interfacial polymerization by organic base for high-permselective nanofiltration

In the synthesis of the polyamide nanofiltration (NF) membrane, the hydrogen chloride is a by-product generated at the organic interface from interfacial polymerization, which reduces the reactivity of amine monomers due to protonation. Herein, a strategy of addition of an organic base in the organic phase to neutralize the H+ was reported. The performances of the membranes produced using three organic bases with different chain lengths were explored. The results showed that the organic base neutralized the H+ and promoted the rate of interfacial condensation reaction, which facilitated the formation of a dense and thin polyamide layer. Moreover, compared to control membrane, the membrane modified by organic base exhibited higher water permeance without sacrificing salt rejection. Higher diffusion rate of HCl through PES substrate compared to NF membrane indicated that HCl diffusion was mainly affected by the resistance of polyamide layer. Molecular simulations demonstrated that triethylamine (TEA) has lower energy barrier of neutralization and higher reaction heat in comparison with tripropylamine and N, N-diisopropylethylamine. The TEA modified membrane thereby displayed a permeance up to 24.3 L h−1 m−2 bar−1 and Na2SO4 rejection of 98.8 %. This work provided a promising strategy for the regulation of interfacial polymerization in achieving high-permselective nanofiltration.

Facile fabrication of ceramic-based highly permeable composite nanofiltration membranes by in-situ interfacial polymerization

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 Na2SO4, 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.

Efficient separation of Li+/Mg2+ via positively charged TFN membrane based on the PEI interlayer

Nanofiltration (NF) technology has exceptional mono/divalent ion separation performance, providing considerable application potential for lithium extraction. However, polymeric NF membranes provided only restricted amounts of practical applications since of their low permeability and limited selectivity. Herein, a positively charged membrane designed for Li+/Mg2+ separation was developed, this achievement was accomplished by incorporating NH2-MIL-101(Cr) nanoparticles (NPs) into the polyamide (PA) layer situated atop the polyethyleneimine (PEI) interlayer. The PEI interlayer controlled the amine monomer distribution, regulated the PA nanofilm morphology, and improved the membrane positively charged properties. Meanwhile, the NH2-MIL-101(Cr) could provide Li+ with fast transport paths to further enhance the membrane Li+/Mg2+ separation capability. The improved membrane possessed MgCl2 rejection of 96.1 %, LiCl rejection of 42.3 %, and Li+/Mg2+ separation factor of 102 with outstanding permeance of 17.0 L m-2h−1 bar−1. This research made a valuable contribution to applying NF membranes in lithium extraction processes.

Porous organic polymer interlayers modulated nanofiltration membranes for ultra-permselective Li+ /Mg2+ separation

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.

Ternary deep eutectic solvent enhanced the diffusion control of amine monomer for highly permeable and anti-fouling polyamide nanofiltration membranes

Thin-film composite nanofiltration (TFC NF) membranes have been widely used in water treatment, while the common active polyamide (PA) separation layer suffers the problems of excessive mass transfer resistance and fouling. In this work, a novel ternary deep eutectic solvent (DES) of citric acid/choline chloride/glycol as an additive in the aqueous phase was focused on regulating the formation of PA layer. The ternary DES can interact with piperazine (PIP) via hydrogen bonding and electrostatic interaction, synergistically enhancing the diffusion control of PIP with viscosity modulation during interfacial polymerization. Notably, a thinner and rougher separation layer with a cellular-like structure was obtained by optimizing the ratio of citric acid in ternary DES. Accordingly, the optimized TFC10%-3 membrane maintained an excellent Na2SO4 rejection (98.8 %) and a 104.7 % increase in pure water permeance (39.5 L·m−2·h−1·bar−1) compared to the original membrane, outperforming commercial membranes and the most NF membranes reported in the literature. Besides, the introduction of citric acid in PA layer increased the surface hydrophilicity and electronegativity of TFC10%-3 membrane, resulting in a higher flux recovery rate (FRR = 93.2 %) of TFC10%-3 membrane than that of TFC10%-0 membrane (FRR = 83.9 %). This study provides a feasible design strategy for the preparation of highly permeable and anti-fouling TFC NF membranes and enrichs the application of ternary DES in water treatment.