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Nanofiltration plays a crucial role in antibiotic desalination from high salinity water, but the membranes often have low water permeability and insufficient selectivity between antibiotics and salts. In this study, a Gemini-type quaternary diethanolamine monomer (QTDEA) containing quaternary ammonium and hydroxyl groups was synthesized. This monomer had a hybrid spatial structure combining both rigid and flexible components, allowing it to covalently graft to the acyl chloride groups on the nascent polyamide (PA) film. The resulting modified PA-QTDEA membrane exhibited enhanced hydrophilicity, reduced negative charge, and a looser structure. It demonstrated a high water permeance of 18.2 L m−2 h−1·bar−1 for chlortetracycline hydrochloride (CTC) desalination from a NaCl solution of 10 g L−1, and the NaCl/CTC selectivity was 21.2. This research presents an efficient method for improving the performance of antibiotic desalination through surface modification using the novel QTDEA monomer. [Display omitted] • Novel Gemini-type monomer QTDEA is synthesized and used for the surface modification. • Grafting is achieved by the esterification of –OH in QTDEA with acyl chloride in TMC. • QTDEA with rigid and flexible hybrid structure increases the pore size of PA film. • Quaternary ammonium in QTDEA reduces membrane charge and Donnan exclusion. • Modified membrane improves both water permeability and antibiotics/salt selectivity. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) is considered a competitive technique for acidic stream treatments. However, poorly reactive acid-resistant monomers normally cause thick and uneven separation layers with ultra-low permeability. Herein, catalyst-anchored secondary polymerization is employed after the interfacial polymerization (IP) reaction between trimesoyl chloride (TMC) and 3-aminobenzenesulfonamide (ABSA) to fabricate an extremely acid-resistant NF membrane. Acylation catalysts in ethanol are grafted on the nascent layer by reacting with residual acyl chloride groups to enhance the monomer reactivity, while the ethanol-induced nascent layer structure regulation greatly improves the surface uniformity. Benefiting from the improved self-inhibition effect and optimized phase integrity of the modified IP process, the resulting acid-resistant membrane has unprecedented water permeance (up to 31.4 Lm−2h−1bar−1), desirable Na 2 SO 4 rejection (92.8%), high dye/H+ selectivity and impressive acid stability (20 wt% of H 2 SO 4 for 50 days), outperforming almost all advanced acid-resistant NF membranes. Our work provides a versatile approach for the synthesis of high-performance specialty membranes. [Display omitted] • An acid-resistant NF membrane is fabricated by a catalyst-anchored secondary polymerization. • Anchored catalysts catalyze the secondary polymerization of low-reactive monomers. • Ethanol-induced swelling rearrangement greatly improves the phase interface uniformity. • The NF membrane has unprecedented water permeance up to 31.4 Lm−2h−1bar−1. • The membrane exhibits excellent acid-resistance in 20 wt% H 2 SO 4 for 50 days. [ABSTRACT FROM AUTHOR]

Co-solvent assisted interfacial polymerization (CAIP) has been widely used to increase the water permeability of thin-film composite (TFC) reverse osmosis (RO) membranes. However, its outcomes are often poorly understood or unpredictable. To bridge the gap between conventional wisdom and the real effects of the co-solvent, we report—for the first time, to the best of our knowledge—empirical evidence in terms of the actual interfacial tension between two immiscible solutions used in CAIP. According to our results, dimethyl sulfoxide (DMSO), which is frequently used as a co-solvent, influences IP by interacting with trimesoyl chloride (TMC). The dipole-dipole interaction between DMSO and TMC was estimated to increase the TMC concentration at the interface and, thereby, the reaction rate. Due to the fast reaction, the diffusion barrier forms quickly, reducing the thickness and roughness of the active layer. The cross-linking degree was also determined to decrease due to the incomplete reaction that occurs when one of three acyl chloride groups interacts with Sδ+−Oδ− electrostatic dipoles of DMSO at the interface, as evidenced by the variation in unreacted acyl chloride groups in the active layer and by the nitrogen/oxygen ratio. Such morphological changes were consistent with the trend in the performances of the RO membranes prepared with different amounts of DMSO, and were used to interpret the possible transport phenomena. Image 1 • The interaction between DMSO and TMC was considered as a parameter dictating IP. • DMSO increased the TMC concentration at the interface during IP. • The increase in the TMC concentration led to a faster but incomplete IP reaction. • The faster and incomplete IP changed the morphological features of polyamide films. • A new mechanism was proposed to clarify the DMSO effect based on empirical evidence. [ABSTRACT FROM AUTHOR]

In this work, a positively charged hollow fiber nanofiltration (NF) membrane based on twice interfacial polymerization (IP) reactions was developed for water soften and heavy metal ions removal. The first IP reaction was conducted on the polyethersulfone (PES) hollow fiber substrate using a mixture of branched polyethyleneimine (PEI) and piperazine (PIP) as the aqueous phase monomers in the aqueous phase reacting with trimesoyl chloride (TMC) in the cyclohexane solution. Then, a secondary IP reaction was performed between tris(2-aminoethyl) amine (TAEA) solution and the residual acyl chloride groups on the membrane to increase the positive charge density on the membrane surface. Consequently, a NF membrane with intensified positive surface charge density was successfully fabricated. The optimized membranes achieved a high rejection of MgCl 2 of 97.6% while maintaining a pure water permeability (PWP) of 16.0 L m−2 h−1 bar−1. Meanwhile, the membranes exhibit high rejection values of 99.8% to Cu2+ and 99.7% to Zn2+, respectively. In conclusion, this work provides a facile way to prepare a positively charged membrane for efficient water softening and metal ions removal. [Display omitted] • A novel polyamide NF hollow fiber membrane via a secondary IP reaction had been successfully fabricated. • The secondary IP reaction between TAEA and the residual acyl chloride groups effectively enhances the positive change density on membrane surface. • This modification method has no influence on membrane structure. • The optimum membrane shows more than 90% rejection of Mg2+ and Ca2+ and 99% rejection of heavy metals. [ABSTRACT FROM AUTHOR]

A method of assembling nanofilms for nanofiltration (NF) composite membranes with ultra-high desalination performance was developed in this work. A series of graphene quantum dots enhanced polyamide (GPA) nanofilms were primarily prepared via support-free interfacial polymerization. Subsequently, the NF composite membranes with two GPA nanofilms (GPA-GPA) layer-by-layer (LBL) assembly were elaborately designed to achieve effective desalination process. The residual amine groups and acyl chloride groups on the surfaces of GPA nanofilms reasonably formed a nascent polyamide (PA) interlayer between two functional layers. The separation performance of GPA-GPA assembly membranes was dramatically developed through the in-situ formed PA interlayer with network pore structure. Most of assembled NF membranes exhibited Na 2 SO 4 rejection rate above 99.5%, and the permeance was above 20.0 L m−2 h−1 bar−1. This creative strategy of in-situ constructing PA interlayer opened up an innovative path for the design of NF membranes with excellent desalination performance. [Display omitted] • Graphene quantum dots enhanced polyamide (GPA) nanofilms were fabricated by support-free interfacial polymerization. • The layer-by-layer assembly of GPA nanofilms was developed to prepare nanofiltration composite membranes. • The residual amine groups and acyl chloride groups of nanofilms formed polyamide interlayer via covalent bonds. • The ultra-high desalination performance was attributed to the in-situ formed network pores of interlayer. [ABSTRACT FROM AUTHOR]

Nanofiltration represents an efficient technology for mono/divalent ions separation, such as Mg2+/Li + mixtures which are crucial for lithium extraction from salt lakes. This work shows that charge intensification of loose structure nanofiltration membranes is an effective way to reconcile high flux with Mg2+/Li+ selectivity. A new electrolyte monomer (QTHIM) containing quadruple imidazolium and hydroxyl groups was synthesized to react with residual acyl chloride groups on the nascent polyethyleneimine-based polyamide membranes (PEI-TMC), leading to the formation of a high-permeance nanofiltration membrane (PEI-TMC-QTHIM). The modified membrane highlights loose structures combined with enhanced positive charge, exhibiting high water permeance (∼33 L m−2 h−1 bar−1), good MgCl 2 rejection (∼92%) and high flux to 100 Mg2+/Li+ ratio mixture (∼170 L m−2 h−1). Notably, flux of the modified membrane is ca. 6 times as high as that of the nascent membrane. A new monomer containing quadruple imidazoliums was effectively modified to polyethyleneimine-based polyamide membranes, leading to loose structures, intensified positive charge, highly improved permeance and good Mg2+/Li+ separation performance. [Display omitted] • A new monomer (QTHIM) containing quadruple imidazolium salts was synthesized. • High-permeance Mg2+/Li+ NF membranes were prepared via the QTHIM modification. • QTHIM modification leads to enhanced positive charge and loose structures. • The permeance and MgCl 2 rejection of NF membranes is 33 Lm−2h−1bar−1 and 92%. [ABSTRACT FROM AUTHOR]

Solvent resistant membrane distillation (SR-MD) is a novel technology to effectively separate water from waste streams containing solvents with high boiling points, avoiding the high chemical costs and release of harmful gas in conventional treatments. Ceramic membranes are promising for this process as they are highly stable chemically but they require modification to tune the hydrophilicity to hydrophobicity. However, the widely used silanization for hydrophobic modification often involves expensive chemicals and may produce toxic substances. Here, we present a new hydrophobic modification method with the use of fatty acid chloride (FAC), as a greener and cheaper alternative to silanes. In the grafting reaction, the acyl chloride groups react with the –OH groups on the ceramic membranes to form strong ester bonds. We successfully grafted stearoyl chloride (SC) and palmitoyl chloride (PC) on the ceramic tubular membranes. With long carbon chains grafted, the modified membranes exhibited high hydrophobicity with a water contact angle >141° and a liquid entry pressure >3 bar. When tested in SR-MD with a feed solution containing 50 wt% dimethyl sulfoxide, the PC-modified membrane demonstrated a flux of 3.2 kg m−2 h−1, with rejection >98% and separation factor >110 at 60 °C, and a high flux of 4.5 kg m−2 h−1 with rejection >96% at 70 °C. The FAC-modified membranes allow a cost-effective treatment of challenging wastewater containing organic solvents through SR-MD. [Display omitted] • Hydrophobic ceramic membranes for solvent resistant MD were synthesized through fatty acid chloride grafting. • The acyl chloride groups formed strong ester bonds on ceramic surface and the modified membranes had high hydrophobicity. • Flux of 3.2 kg m−2 h−1, rejection >98% and separation factor >110 can be achieved when treating 50 wt% DMSO in SR-MD. • The hydrophobicity and separation performance are comparable to ceramic membrane grafted with silanes. • This study presents a greener and cheaper surface modification chemistry to synthesize hydrophobic ceramic membranes. [ABSTRACT FROM AUTHOR]

Aiming at enhancing the permeability of reverse osmosis (RO) membranes, polyaniline-co-polypyrrole hollow mesoporous nanospheres (PPHMNs) were synthesized with aniline and pyrrole monomers via a simple and rapid one-step method, and then added to the aqueous phase of interfacial polymerization to fabricate thin-film nanocomposite (TFN) membranes. Hollow cores of the PPHMNs embedded in polyamide layers could reduce the interior transfer resistance of the membrane and shorten the transmission pathway of water molecules. Mesoporous shell of PPHMNs provided more channels for rapid transmission of water molecules. Moreover, amino groups in PPHMNs originated from the monomer of aniline could not only be bonded to polyamide (PA) layer by reacting with acyl chloride groups to prevent the leakage but also improve hydrophilicity of the membrane. Water flux of TFN membrane doped with PPHMNs (TFN-Ps) of 0.005 wt% addition concentration was 34.1 L·m−2·h−1 which is 76.7% higher than that of thin-film composite (TFC) membrane, and the NaCl rejection all kept over 99.0%. The TFN-Ps also showed excellent long-term stability, chlorine resistance and anti-fouling performance. This work opens an avenue for application of mesoporous hollow nanospheres with amino groups synthesized by simple and time-saving methods in developing TFN membranes with improved water flux. [Display omitted] • Mesoporous hollow nanosphere with amino groups was synthesized via a one-step method. • Nanospheres have uniform sizes of 130 nm and spherical shell ranges from 21 to 35 nm. • Water flux of RO membranes raised from 19.3 to 34.1 LMH with NaCl rejection over 99%. • TFN membrane showed long-term stability, chlorine-resistant and antifouling property. [ABSTRACT FROM AUTHOR]

The weak interfacial force among the substrate with polyamide layer is always a non-ignorable issue for the traditional thin-film composite (TFC) membrane during actual operation. To solve this issue, herein, we have proposed an effective strategy, which is enhancing the long-term separation durability of the TFC membrane by fixing the polyamide layer on the substrate through covalent bonding. To start with, an amino-substituted polyethersulfone (PES-NH 2) was synthesized and blended with polyethersulfone (PES) to prepare a hydrophilic PES/PES-NH 2 substrate. Next, the amino group in the substrate could effectively react with a part of acyl chloride groups in the organic phase to form the stable covalent bond with the polyamide layer formed by interfacial polymerization. The prepared PES/PES-NH 2 TFC membrane possessed a denser polyamide layer with a higher cross-linking degree, as well as exhibited greatly increased separation performance at 0.6 MPa. Significantly, the PES/PES-NH 2 TFC membrane still maintained excellent separation performance under a long-term filtration period of 15 days, which is also much longer than the PES TFC membrane. This effective and promising method provides a valuable way to maintain the separation stability of TFC membrane in long-term operation. [Display omitted] • An amino-substituted polyethersulfone (PES-NH 2) resin was successfully synthesized. • The hydrophilic PES/PES-NH 2 substrate membrane containing amino groups was firstly prepared. • The PES/PES-NH 2 TFC polyamide membrane showed good long-term separation stability. • The mechanism of strengthening the interface connection between the substrate and the polyamide layer was elaborated. [ABSTRACT FROM AUTHOR]

Sugar-based nanofiltration membranes were successfully developed through a facile interfacial polymerization reaction. Glucose, maltose and raffinose, representing the most classic mono-, di- and tri-saccharides, were used as the aqueous monomers to react with trimesoyl chloride. Importantly, NaOH was utilized to accelerate the reaction between acyl chloride groups and the lowly active hydroxyl groups, forming a dense polyester separation layer. The optimal sugar-based membrane shows a high water permeance of 33.7 ± 1.4 L m−2 h−1 bar−1 and a Na 2 SO 4 rejection of ~95%, demonstrating the potential of rapid desalination. Systematic characterizations by chemical analyses and optical microscopy were carried out. The results revealed that the high separation performance of the sugar-based membrane mainly benefited from its negatively charged, hydrophilic surface and super thin polyester layer. Considering the sustainable and green nature of saccharides, the sugar-based membrane is promising to stand out in the next-generation membrane field. Our findings enlighten the development of sugar as bio-monomer in fabricating high-performance nanofiltration membranes. Image 1 • Sugar-based membranes have been synthesized by interfacial polymerization. • Glucose, maltose and raffinose were used as aqueous monomers. • The optimized membrane had a high water permeance of 33.7 ± 1.4 L m−2 h−1 bar−1. • The effect of monomers on NF membrane performance was investigated. [ABSTRACT FROM AUTHOR]