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Porous silicate cement membranes (PSCMs) fabricated by the freeze casting method show great potential to be utilized in seawater pretreatment, fermentation broth separation, and industrial wastewater treatment due to its merit of high-temperature resistance, low-cost, and hierarchically ordered porous structures, while the freeze casting method is complex and time-consuming. In this work, a combination of freeze casting and heat-dry curing was initially applied to generate PSCMs. The preparation periods of PSCMs could be shortened by simplifying preparation processes and reducing curing time. The resulting membranes presented double-layer structures, containing a nucleation zone (N-zone) with dense structures and a stability zone (S-zone) with lamellar pore structures. The X-ray diffraction pattern of membranes displayed the mixed hexagonal and rhombohedral structures. This novel method could save more than half of energy consumption compared with the traditional preparation technology of silicate cement samples. The membranes with a mesopore size of 3.794 nm showed high permeation performance with pure water flux reaching 207.23 L m−2 h−1 under 0.15 MPa and room temperature. The separation efficiency of oil-water was 78.05% under operating pressure of 0.05 MPa. Molecular dynamics simulation was applied to narrate the microscopic process of transformation during heat-dry curing, and obtained a good similarity of consequences between the computational method simulation and experimental operation. [Display omitted] • Freeze casting combined with heat-dry curing to fabricate porous silicate cement membrane. • Freeze drying and steam curing were replaced using heat-dry curing. • Porous silicate cement membranes showed lamellar porous structures. • Molecular dynamics simulation was used to elucidate the hydration process of heat-dry curing. [ABSTRACT FROM AUTHOR]

Novel high boron removal thin film composite (TFC) membranes with semi-interpenetrating networks were fabricated by interfacial polymerization (IP) with m-phenylenediamine (MPD) and 1,3,5-benzenetricarbonyl trichloride (TMC). The polyisobutylene (PIB) was added to the organic phase prior to IP. The membranes were characterized by attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and the zeta potential and contact angle analysis. The results of this study demonstrate that the novel TFC membrane exhibited superior separation performance at a relatively low concentration of PIB (0.30%, m/v). As the concentration of the interpenetrating PIB in the membrane increased, the membrane morphology changed distinctly. Furthermore, the permeability coefficient of boron decreased from 20.84 to 3.26, and the rejection of boron increased from 81.36% to 93.12%. [ABSTRACT FROM AUTHOR]

The cosolvent-assisted interfacial polymerization (CAIP) has garnered significant attention due to its capacity to easily and effectively modify the performance of polyamide (PA) reverse osmosis (RO) membranes. To gain deeper understanding of the mechanism of a specific type of cosolvents on the IP reaction, namely N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N,N-dimethylpropionamide (DMPr) were used as aqueous-phase cosolvents to systematically investigate their effects on the membrane structures and properties under different conditions. Amide cosolvents in the aqueous phase facilitated the diffusion of the amine monomer and the formation of nanovoids within the PA layer as the C-chain length of amides increased. When 1,2-dichloroethane was also included in the organic phase, the extent of the two-phase miscible zone was further increased with its assistance, which contributed to generating the larger nanovoids within the layer, thicker PA layer and extensive exterior PA layers, as well as significantly enhancing the water permeability and selectivity of membranes. Importantly, this study successfully prepared high-performance RO membranes with multilayer nanovoid structures in situ by introducing cosolvents in the IP reaction with permeability up to 2.26 L·m−2·h−1·bar−1, providing theoretical and experimental bases for further enrichment of CAIP. [Display omitted] • Exploring the effects of different amides on the diffusion of amine monomers. • Longer chain DMPr contributes to the formation of multilayered nanovoid structures. • Correlating amine monomer diffusion rate with PA layer evolution. • TFC a-o -DMPr shows water permeability of 2.26 LMH/bar and NaCl rejection of 98.38 %. [ABSTRACT FROM AUTHOR]

The robust correlation between the performance of thin-film composite (TFC) reverse osmosis membranes and the polyamide (PA) active layer determines the necessity of precise design of the PA layer, and this regulation primarily involves the surface morphology and internal characteristics of the PA layer. In this study, we fabricated honeycomb Turing structure or nanovoid-rich TFC series membranes using polar/nonpolar organic phase additives. Characterization and simulation results confirmed that the enhancement of membrane performance relied more on the abundant nanovoids within the PA layer rather than the ordered honeycomb lattice surface. Notably, the TFC-nDCE membrane with multilayer nanovoids exhibited an approximately 89 % improvement in water permeability while maintaining satisfactory salt rejection (98.29 %). We emphasized the significant role of nanovoids in the diffusion process of amine monomers and investigated the potential relationship between nanovoids and the degree of surface cross-linking. Building upon this, a new insight into the formation of nanovoids induced by PA anisotropic growth was presented through a careful analysis of the amine monomer diffusion rate and the morphological evolution of nanovoids. The structure-property relationship between internal structures, surface morphologies, and performances was systematically and thoroughly investigated, pointing out the direction for the rational design of TFC membranes. [Display omitted] • Revealed effects of nanovoids on the water/salt flow in honeycomb Turing PA layer. • Impacts of nanovoids on the physicochemical structure of PA layer were emphasized. • New insights on the anisotropic growth of PA were provided. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel process to modify thin-film-composite polyamide membrane was developed. It involved surface treatment of the polyamide membrane by chlorine, followed by supramolecular assembly of chitosan on the membrane surface. While the original polyamide membrane was negatively charged, the surface modification led to a charge reversal due to skin layer of chitosanium in the resulting polyamide/chitosan composite membrane. The polyamide/chitosan (PA/CS) composite membrane was shown to perform better than the original polyamide membrane. The parameters involved in the chlorination of polyamide (e.g., chlorination time and chlorine concentration) and supramolecular assembly of chitosan (e.g., concentration and deposition time) on the membrane surface were investigated. The following conditions for membrane modification were found to be appropriate: NaClO concentration 200mg/L, chlorination time 2–5min, and chitosan concentration 1000mg/L; the PA/CS membrane so formed exhibited a permeation flux of 57.7L/(m2 h) and a salt rejection of 95.4% for a feed NaCl concentration of 1500mg/L at 0.8MPa. The PA/CS composite membrane also exhibited good performance for rejection of divalent salts (99.8% for MgCl2 and 98.5% for Na2SO4) at the same concentration. This modification technique is simple and practical because dilute solutions are used for surface treatment and commercial membrane units can be modified in their original modules. [Copyright &y& Elsevier]

Abstract: Interfacially polymerized polyamide thin film composite membrane was modified by electrostatic self-assembly of polyethyleneimine on the membrane surface, and the modified membrane showed significantly improved antifouling properties. The charge reversal on the membrane surface due to the application of the polyethyleneimine layer was shown to increase the fouling resistance of the membrane to cationic foulants because of the enhanced electrostatic repulsion, and the increased surface hydrophilicity would help minimize the flux reduction. The effects of parameters involved in the membrane surface modification (e.g., polyethyleneimine concentration and deposition time) on the membrane performance were investigated in terms of water permeation flux and salt rejection. The membrane modification was found to increase salt rejections when MgCl2 and NaCl were tested. The fouling behavior of the membranes was also studied with and without the presence of dodecyltrimethylammonium bromide (which is a common cationic surfactant present in waste water). It was shown that while the deposited polyethyleneimine surface layer tended to offer additional resistance to permeation, the improved fouling resistance and the increased surface hydrophilicity compensated for the reduction in membrane permeability due to the deposition of the polyethyleneimine layer. [Copyright &y& Elsevier]

Cellulose triacetate (CTA) hollow fiber membrane for reverse osmosis (RO) desalination of brackish water with high salinity has been modified for pervaporation (PV) membrane of separating organic/organic mixture. The experiments presented that modified performance of CTA hollow fiber membrane treated by the organic solvent was affected by the modifying conditions. PV performance of CTA hollow fiber membrane modified mainly depends on the concentration of the modifying agent and the treatment time of CTA hollow fiber membrane in the aqueous acetone. The results showed that the membrane treated respectively by 5% acetone aqueous solution possesses a good PV separation performance, i.e. the separation factor 1998 and the permeate flux 45.1 (g/m2.h). It was exhibited from scanning electron microscope (SEM) photograph were produced. The structural changes from porous, defect to non-porous, even on the membrane surface and turn from asymmetric membrane of two layers consisting of the active and the support into the homogeneous membrane of single layer in the cross section of the membrane would indicated why the original RO membrane can become that of PV by means of modification treatment. [Copyright &y& Elsevier]

Novel acyl chloride monomer 5-(1-pyrrolidinyl)-1,3-benzenedicarbonyl dichloride (PIPC) featuring a rigid pyrrolidinyl group was proposed as an organic phase monomer to fabricate reverse osmosis (RO) membranes possessing exceptional water permeability and NaCl rejection via a two-step interfacial polymerization method. First, m -phenylenediamine (MPD) in the aqueous phase solution polymerized with PIPC in the first organic phase solution to form the much looser polyamide. After that the remaining MPD continued to diffuse to polymerize with trimesoyl chloride in the second organic phase solution to form the denser polyamide. The pyrrolidinyl group had steric hindrance effects and formed hydrogen bond with MPD, leading to decreasing the thickness significantly and increasing surface roughness of the separating layer. When the PIPC amount was 0.08 wt%, the PIPC-based RO membrane displayed optimal permselectivity with water flux increasing by 84.20 % compared to the original RO membrane (from 20.38 L·m−2·h−1 to 37.54 L·m−2·h−1) whereas retaining high NaCl rejection with 98.59 %. The PIPC-based RO membrane exhibited steady water flux and NaCl rejection within 120 h of filtration, as well as improved antifouling performance. Thus, preparation of the highly permeable RO membrane could be rationally achieved by the novel acyl chloride monomer with a rigid pyrrolidinyl group. [Display omitted] • The novel monomer PIPC was used to prepare RO membrane by a two-step IP method. • PIPC influenced the diffusion rate of MPD via hydrogen bonds and steric hindrance. • The PIPC-based membrane presented rougher surface and thinner PA layer. • Permeability of PIPC-based membrane was obviously enhanced without losing NaCl rejection. [ABSTRACT FROM AUTHOR]

Covalent Organic Frameworks (COFs) are of significant interest as promising crystalline building blocks for molecular separation due to their abundance of permanent, well-defined and size-selective micro-channels. However, thus far, the implementation of COFs-based membranes is limited by their poor scalability and impossibility of bridging the gap from molecular to ion separation. Herein, a novel thin-film nanocomposite (TFN) membrane comprising regular COFs nanosheets (CONs) with high crystallinity able to achieve an excellent H 2 O/NaCl selectivity is presented, accompanied with simultaneously over three times improvement on water permeability. The effectiveness of CONs cross-linked into polyamide matrix on hindering NaCl solubility and diffusivity is confirmed from both solution-diffusion mechanism and nanochannel-confined transport mechanism. Thanks to the protection of CONs with secondary amide linkages and strong steric hindrance from ortho- and meta-positioned methyl groups, the TFN membranes yield outstanding chlorine resistance of 18000 ppm h via inhibition of N-chlorination and ring-chlorination reaction. In addition, CONs incorporation also endows the TFN membranes with excellent anti-bacterial efficiency up to 99.8%. Our CONs-based membranes pave a new way towards the multifunctional composite membrane materials for highly efficient clean energy and environmental sustainability. Covalent organic framework nanosheets (CONs) with high crystallinity are pioneering utilization for fabrication of multifunctional thin-film nanocomposite (TFN) membranes, synchronously achieving three times improvement on water permeability, higher H 2 O/solutes separation selectivity, excellent chlorine resistance (tolerance of active chlorine up 18000 ppm h) and anti-bacterial efficiency against E. coli. Up to 99.8%. Image 1 • COFs nanosheets with high crystallinity was utilized to fabricate multifunctional TFN membranes. • CONs-based TFN membrane achieved a 3-fold of water permeability and synchronously an improved H 2 O/NaCl selectivity. • CONs-based TFN membrane yielded outstanding chlorine resistance of 18000 ppm h. • CONs-based TFN membrane yielded an excellent anti-bacterial efficiency up to 99.8%. [ABSTRACT FROM AUTHOR]

Most thin film nanocomposite (TFN) membranes with higher permeability are related to hydrophilic nanocomposites. Nevertheless, in nature, water permeates faster in hydrophobic pores (e.g. aquaporin) because of less affinity between water and wall of the pore. Here we show hydrophobic methyltrichlorosilane (MeSiCl 3 , MTS) functionalized polyamide TFN can be used to construct highly efficient desalination membranes. The TFN membranes were synthesized through the interfacial polymerization of aqueous amine and organic MTS/acyl chloride solutions. Both the water flux and water/salt selectivity increased. The water flux increased by more than a factor of 1.96, from 2.4 to 4.7 LMH/bar, as the fraction of MTS increased from 0 to 0.1 mM in the organic solution. Importantly, the water/salt selectivity ratio increased from 11.4 to 18.5 bar−1. Thus, MeSiCl 3 imparted narrow water channels to the polyamide matrix with higher flow rate and better selectivity. The enhanced compatibility and interactions between MTS and the polyamide polymers were attributed to their covalent (Si N) and hydrogen (O...H) bonds. MTS modified TFN membranes also show high water flux and recovery ratio in the bovine serum albumin (BSA) solution. This facile in situ modification provides a new insight into the high performance of hydrophobic TFN membranes. Unlabelled Image • MeSiCl 3 increased water permeability up to 196%. • More hydrophobic TFN membranes with higher water/salt selectivity. • MeSiCl 3 bonded with PA polymers by covalent and hydrogen bonds. • Narrow water channels created by MeSiCl 3. • High water flux and recovery ratio during the antifouling experiments. [ABSTRACT FROM AUTHOR]

The use of acidic nitrite as diazotization reagent has been adopted previously for performance improvement of finished polyamide-based reverse osmosis membrane through post-treatment under a low temperature. However, the mechanism of diazotization reagent treatment on the membrane intrinsic permeability coefficients for both solvent and solute is still not clear and low-temperature treatment is energy intensive. This work focused on the mechanism and the efficient regulation of perm-selectivity by surface treatment of polyamide-based reverse osmosis membrane with diazotization reagent under room temperature. Polyamide based membranes were treated with diazotization reagent under temperatures between 5.0 and 25.0 °C. Membrane physico-chemical property was characterized via instrumental analysis and membrane intrinsic permeation coefficient was evaluated via cross-flow permeation test. It was found that the diazotization reagent treatments under 5.0, 15.0 and 25.0 °C could effectively enhance membrane intrinsic permeability coefficient for water (A) by 14.1, 17.7 and 21.7%, lower membrane intrinsic permeability coefficient for NaCl (B) by 60.1, 50.0 and 40.3%, and improve membrane perm-selectivity (A/B) from 5.55 bar-1 to 15.76, 13.00 and 11.31 bar-1, respectively. Mechanism exploration revealed that both the diazotization reaction occurred with end amino groups and the N-nitrosylation reaction occurred with amide bonds had a great influence on the membrane performance. Diazotization reagent treatment under different pH demonstrated that the perm-selectivity of polyamide-based membrane could be finely regulated by controlling an optimized pH of diazotization reagent at 1.5. The performance regulation efficiency of diazotization reagent treatment was also found to be related with the initial performance of the treated membrane. Under the same condition, salt rejections of 96.5% and 98.0% could be improved up to 98.3% and 98.8%, respectively. This work not only explains the mechanism of diazotization reagent treatment on regulation of membrane perm-selectivity, but also provides a room-temperature modification method suitable for performance enhancement of newly produced membrane and performance restoration of used membrane. [Display omitted] • Diazotization reagent treatment was used to regulate perm-selectivity of PA membrane. • Room-temperature treatment was efficient in regulating membrane perm-selectivity. • Mechanism was explored with respect to diazotization and N-nitrosylation reactions. • Enhanced water permeability and lowed salt permeability were achieved simultaneously. • The method explored can be applied to both performance enhancement and restoration. [ABSTRACT FROM AUTHOR]

In this work, a novel coating layer of polyvinyl alcohol (PVA)/polyquaternium-10 (PQ10) was constructed onto the surface of polyamide-based RO membrane via the method of surface coating followed by cross-linking. Permeation tests demonstrated that the incorporation of PQ10 into PVA could efficiently improve the water permeation ability of surface coating layer, showing a significant decrease of hydraulic resistance from 5.9 × 1012 m−1 of the PVA-1.0 coating layer to 2.5 × 1012 m−1 of the PVA-1.0/PQ10-0.2 coating layer. Anti-fouling performance evaluation revealed that the PVA/PQ10-coated membrane not only possessed the good anti-fouling property of the PVA-coated membrane to negatively charged foulants and protein but also exhibited more excellent anti-fouling performance to positively charged foulant due to its relatively lower surface charge density and pseudo-zwitterionic surface character. Long-term filtration tests with dye wastewater illustrated that although the initial water permeability of membrane coated with PVA-1.0/PQ10-0.2 surface layer was lower than that of the virgin RO membrane under the same operation condition, the PVA-1.0/PQ10-0.2-coated membrane exhibited a higher salt rejection, lower flux decline rate and larger cumulative volume of permeated water during a filtration period of 48.0 h. Soaking tests further demonstrated the improvement of membrane chemical durability against acid, alkaline and chlorine by the PVA/PQ10 coating layer. [Display omitted] • A novel surface coating layer of PVA/PQ10 was constructed on PA-based RO membrane. • PQ10 was adopted to satisfy permeability, hydrophilicity and charge of coating layer. • PVA/PQ10 coating layer improves membrane salt rejection and anti-fouling property. • PVA/PQ10-coated membrane exhibits enhanced separation efficiency to dye wastewater. • PVA/PQ10-coated membrane has improved durability against acid, alkaline and chlorine. [ABSTRACT FROM AUTHOR]

Hollow porous nanoparticles were proposed to transform the skin layer structure for enhancing the performance of reverse osmosis (RO) membrane in this work. Amino-modified hollow mesoporous silica nanospheres (AHMSS) with a size from 110 to 130 nm were successfully prepared via the hard template method. AHMSS were added in the organic phase and then incorporated into the RO membrane skin layer after the interfacial polymerization process. The hydrophilicity of RO membrane was improved by AHMSS. The performance evaluation results showed that AHMSS improved the RO membrane flux (improved by 41.5%) with rejection decreasing slightly. Amino-modified mesoporous silica nanospheres without hollow cores were also prepared and incorporated into the RO membrane skin layer to investigate the effects of the hollow cores of AHMSS on the membrane performance. The results showed that the hollow cores of AHMSS contributed to the improvement of membrane performance. This work demonstrates that AHMSS have huge potential in preparing RO membranes with both high flux and high rejection. Image 1 • Amino-modified hollow mesoporous silica nanospheres (AHMSS) were synthesized. • AHMSS improved the performance of RO membrane. • The hollow cores of AHMSS improved the flux by 18.9% with improving the rejection slightly. • The RO membranes prepared using AHMSS exhibited both high flux (63.4 L m2 h−1) and high rejection (98.98%). [ABSTRACT FROM AUTHOR]

The removal of boron from seawater remains a challenge and now receives increasing attention worldwide. Boron removal rates offered by conventional reverse osmosis membranes through one-pass desalination processes are not sufficient to achieve WHO standard. In this paper, the UiO-66 nanoparticles, a metal-organic framework (MOF), are proposed to incorporate into the polyamide (PA)-based thin film nanocomposite (TFN) reverse osmosis (RO) membrane for boron removal due to their inherent porous structure, narrow pore size, and strong adsorption to boron. At an optimum blending concentration of 0.05% (w/v), The UiO-66 TFN membrane showed a ∼50% increase in water flux and a marginal increase in rejection compared with the benchmark thin film composite (TFC) membrane in the brackish water desalination test. In a simulated seawater desalination test, the UiO-66 blended TFN membrane promotes the boron rejection by ∼11% compared with the benchmark membrane. The simultaneous increase of water flux and boron rejection at low blending concentrations are likely attributed to the highly porous structure which provides additional pathways for water transport and the strong adsorption to boron which indued a further pore narrowing effect to its intrinsic pore size of ∼6.1 Å. Therefore, this work provides a new and facile approach to enhance the boron removal rate of the polyamide-based RO membrane via the incorporation of UiO-66 nanoparticles. • The UiO-66 nanoparticle was incorporated into the polyamide (PA)-based TFN RO membrane for boron removal. • Effects of UiO-66 particles on the membrane structure and performances were investigated systematically. • The UiO-66 based TFN membrane showed a ∼50% increase in water flux in brackish water desalination test. • The UiO-66 based TFN membrane promotes the boron rejection by ∼11% in seawater desalination test. [ABSTRACT FROM AUTHOR]

Highlights • Hydrophilic MPEG brushes were grafted onto the surface of PA TFC RO membrane. • Membrane performance in tertiary treatment of textile effluent was investigated. • Membrane water permeability and fouling resistance to textile effluent were improved. • Membrane COD removal and conductivity rejection to textile effluent were enhanced. • Membrane durability against chlorine was also improved. Abstract To improve the separation performance and durability of the aromatic polyamide thin-film composite reverse osmosis membrane in tertiary treatment of textile effluent, grafting of hydrophilic polymer brushes was performed in this work through sequential surface treatment using acidic aqueous glutaraldehyde and monomethoxy-poly(ethylene glycol) (MPEG) solutions. ATR-FTIR and XPS analyses confirmed that MPEG brushes were grafted on membrane surface at the sites of N H group of amide linkages and end amino groups in the polyamide active layer. The modification was found to enhance membrane fouling resistance, water permeability and rejections to both COD and conductivity in tertiary treatment of textile effluent. The steady-state flux of the modified membrane to secondary textile effluent was higher by 24.0% compared with the virgin membrane and comparable with that of the commercial membrane BW30FR. The grafting of MPEG brushes was also found to make the membrane less susceptible to chlorine. After ten times of intensified chlorine exposure, i.e. total chlorine exposure of 42,000 ppmh NaClO of 35.0 °C and pH 9.0, the membrane grafted with MPEG brushes maintained COD and conductivity rejections of 97.9% and 98.5%, respectively, to textile effluent, showing better durability against chlorine than the virgin membrane and compared membrane BW30FR. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • In situ modification was performed with polyamide reverse osmosis membrane module. • Modification was implemented via EDC/NHS-activated amidation of carboxyl groups. • Fouling resistance to model foulant could be improved via grafting specific monomer. • Membrane hydrophilicity and charge were in charge of the improved fouling resistance. • Modification also enhanced membrane salt rejection at no sacrifice of water flux. Abstract In situ improvement of fouling resistance of the state-of-the-art polyamide reverse osmosis membrane module on the basis of the fouling characteristic of the fluid to be treated is of great practical significance. In this work, in situ modification was performed with the spiral wound polyamide reverse osmosis membrane module for improved fouling resistance to specific foulant. Small molecular monomers of amidosulfonic acid (ASA), diethanolamine (DEA) and piperazine (PIP) were grafted onto the surface of the flat-sheet polyamide-based thin-film composite membrane within the module separately through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-activated amidation of carboxyl groups. The results of fouling experiments indicated that the fouling resistance of the polyamide reverse osmosis membrane module to the model foulants of bovine serum protein (BSA), sodium alginate (SA) and dodecyl trimethyl ammonium bromide (DTAB) could be effectively improved through grafting monomers ASA, DEA and PIP, respectively, showing significant reduction in declines of membrane flux to aqueous BSA, SA and DTAB solutions by 47.2%, 41.3% and 34.4%. The changes of membrane surface hydrophilicity and negative charge were in charge of the improved antifouling property. The in-situ modification was also found to slightly enhance membrane salt rejection and have nearly no influence on membrane water flux. [ABSTRACT FROM AUTHOR]

Abstract In this study, the novel technique, namely interfacial polymerization (IP) coupled with surface amidation, was proposed to fabricate polyamide thin-film composite (TFC) membranes for improved reverse osmosis performance. TFC membrane with loose polyamide separation layer was firstly prepared through conventional IP process. Surface amidation was then performed through covering the surface of the loose polyamide layer with aqueous 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) solution. Amidation reaction between the free carboxylic and amino groups on membrane surface was confirmed through ATR-FTIR and XPS analyses. Permeation tests revealed that the step of surface amidation could effectively improve the ability of membrane rejection to solute, showing significant increases of NaCl, NaNO 3 and glycerol rejections from about 96.4%, 90.5% and 78.4% to 97.8%, 93.7% and 91.3%, respectively. The water permeability of the membrane obtained via IP followed with surface amidation was at least 22.3% higher than the membrane of the same NaCl rejection obtained via conventional IP process. Thus, the method developed was attractive for the fabrication of TFC reverse osmosis membranes with improved permeability to water and rejection ability to solutes. Additionally, the step of surface amidation of present work can be potentially applied to the in-situ rejuvenation of used polyamide reverse osmosis membranes. Highlights • TFC membrane was fabricated via interfacial polymerization and surface amidation. • Surface amidation was facilely implemented via using acidic EDC aqueous solution. • PA selective layer composed of a top dense skin on loose bulk was obtained. • PA TFC membrane with improved reverse osmosis performance could be obtained. [ABSTRACT FROM AUTHOR]

This work reports the repairing of partially degraded polyamide TFC RO membrane for restored salt rejection and simultaneously enhanced resistance to both chlorine and fouling through adopting an in-situ, simple and upscalable approach of cross-flow filtration of sericin aqueous solution followed by flushing with de-ionized water. The attachment of sericin molecule on membrane surface was confirmed by XPS analysis and was found to be effective in recovering membrane reverse osmosis performance. The membrane with a degraded salt rejection higher than 94.0% exhibited a restored salt rejection the same as or a little higher than that of the new membrane (before chlorination). The deposition of sericin was also found to make membrane surface smoother and more hydrophilic and negatively charged under neutral condition, and thus endow the restored membrane with enhanced fouling resistance to bovine serum albumin compared with the new membrane. Furthermore, the chlorine exposure experiments demonstrated that the restored membrane with the coating of sericin exhibited better resistance to chlorine compared to the new membrane. The simplicity and good reproducibility of the restoration treatment procedure and the satisfactory performance stability of the restored membrane reveal that the in-situ restoration approach of present work is attractive for practical applications. [ABSTRACT FROM AUTHOR]

This work focused on salt rejection restoration and simultaneous anti-fouling and anti‑chlorine functionalization of partially deteriorated polyamide-based reverse osmosis membrane by surface chemical deposition of tannic acid (TA) followed with polyethyleneimine (PEI). TA molecules were chemically deposited onto membrane surface with glutaraldehyde as bridging and cross-linking agent. The deposited TA molecules were then employed for sequential chemical deposition of PEI molecules through Schiff base reaction under hot alkaline condition. Restoration process was optimized and its influences on membrane physico-chemical properties were systematically studied. Under desired restoring conditions, deposition of TA molecules was found to recover NaCl rejection from 93.2 % to 96.5 %, the sequential deposition of PEI molecules further improved NaCl rejection up to 98.6 %. The depositions of TA and PEI were found to greatly improve membrane surface hydrophilicity and make the membrane hardly charged under neutral pH. The fouling resistance of restored membrane was better than the new polyamide based membrane for its excellent hydrophilicity and surface brushes induced by the PEI molecules grafted. Chlorination tests proved that the antioxidant structures of the deposited TA and PEI molecules endowed the restored membrane with better chlorine stability compared to the new polyamide membrane. • Performance of deteriorated RO membrane was restored by reconstructing selective layer. • Selective layer was reconstructed by chemical deposition of TA followed with PEI. • Membrane rejection to NaCl was effectively recovered from 93.2 % to 98.6 %. • Anti-fouling and anti‑chlorine functionalizations were achieved simultaneously. • Chlorine and fouling resistances of restored membrane were better than new membrane. [ABSTRACT FROM AUTHOR]

Forward osmosis has motivated practical applications in seawater desalination and agricultural irrigation due to its potential advantage of osmotic dilution. However, water flux decline accompanies with continuous dilution of the DS, which will cause extra membrane expenditure, until final osmotic equilibrium. Without the help of additional driving force, it is impossible to reduce driving force loss in OD. In this study, concentration-dependent hydraulic pressure is exactly introduced as an auxiliary driving force. Investigations on water flux decline behavior in OD showed that water fluxes at lower initial concentration difference, lower initial solution volume and AL-DS orientation suffered more severe decline; furthermore, it implied that additional hydraulic pressure could alleviate adverse effects of greater concentration difference variation generated by pressure-induced water flux increment on water flux. For given dilution of the DS, minimized change in bulk FS concentration was conducive to ensure the effectiveness of constant hydraulic pressure on reducing water flux decline. Validation experiments demonstrated that current model equations were more appropriate under lower hydraulic pressures, and stable water flux also relied on concentration difference variation corresponding to applied hydraulic pressure. Potential implications were highlighted in the context of technical progress of membrane preparation and application potential of OD. [ABSTRACT FROM AUTHOR]

Tight ultra-filtration (TUF) membranes with in-situ grown zeolitic imidazole framework (ZIF) particles embedded in and packed under porous polysulfone (PSF) separating layers were prepared using non-solvent induced phase separation (NIPS) processes. Imidazole ligands contained in casting solutions were released and reacted with divalent Zn2+ cations pre-loaded on non-woven fabric supporting layers. The capillary filling pore size and molecular-weight-cut-off (MWCO) Stokes solute rejection pore size of the formed ZIF/PSF TUF were tuned by varying the loading levels of Zn (II), polyvinylpyrrolidone (PVP) and imidazole, as well as the NIPS reaction time. With thinned PSF separating layer (200–500 nm) and embedding water permeating short-cuts from the ZIF particles, ZIF/PSF TUF membranes showed 7 times higher water permeance (up to 250 L/(m2 h bar)) and greatly enhanced dye/salt retention selectivity, bearing high potential for applications in dye and textile waste water treatment processes. Tight ultra-filtration (TUF) membranes with in-situ grown zeolitic imidazole framework (ZIF) particles embedded in and packed under porous polysulfone (PSF) separating layers were prepared using non-solvent induced phase separation (NIPS) processes. With thinned PSF separating layer (200–500 nm) and embedded water permeating internal channels in the ZIF particles, these membranes showed ultra-high water permeance (up to 250 L/(m2 h bar) and greatly enhanced dye rejection selectivity over salts. [Display omitted] • High flux and high dye/salt selective TUF membranes were developed. • In situ formed ZIF particles could increase water flux and dye rejection of TUF. • Porosity and performance could be effectively tuned by NIPS parameters. [ABSTRACT FROM AUTHOR]

Monodispersed spherical MCM-48 nanoparticles with three-dimensional cubic mesostructure were synthesized and used as nanofillers dispersed in the aqueous or organic phase to prepare thin film nanocomposite (TFN) membranes through the interfacial polymerization of m -phenylenediamine and trimesoyl chloride. Scanning and transmission electron microscope images of the isolated polyamide (PA) active layer confirm that MCM-48 nanoparticles were embedded throughout the PA layer with dispersion in the organic phase as they were clipped between the PA layer and the polysulfone support with dispersion in the aqueous phase. Water flux was measured at 16 bar with 2000 ppm NaCl solution. Furthermore, water flux increased gradually from 24 L/m 2 ·h to 40 L/m 2 ·h with the increase in MCM-48 content in the organic phase, without significantly affecting salt rejection (>95%). Water flux increased from 24 L/m 2 ·h to 68 L/m 2 ·h, whereas salt rejection decreased from 97% to 80% with the increase in MCM-48 content in the aqueous phase. Less MCM-48 can be used in the aqueous phase than in the organic phase with similar performances. The two kinds of TFN membranes exhibit enhanced long-term durability, which confirms that MCM-48 can stably reside in the TFN membranes by dispersing whether in the organic or aqueous phase. [ABSTRACT FROM AUTHOR]

The effective removal of boron from water is highly desirable for many chemical processes. Reverse osmosis (RO) membrane technology has been considered to be a competitive technology for boron removal. However, in addition to seawater, RO membrane technology is rarely used in the treatment of other industrial wastewaters containing boron. In this work, a high boron removal RO membrane with broad industrial application prospect was developed. Specifically, sulfonate groups were grafted onto the surface of the RO membrane through the acetal reaction of polyvinyl alcohol (PVA) with benzaldehyde disulfonic acid disodium salt (BADSA Na). In this process, PVA was coated on the membrane surface in advance. The possibility that large complexes can form due to the reaction between PVA and boric acid and the characteristic of the sulfonate group which can decrease the hydrogen bonding sites work together to reduce the rate of boron diffusion, and then a high boron removal rate is achieved. Under seawater conditions, the boron removal rate of the membrane was improved obviously from 85.71% to 91.63%, while a high flux of 44.41 L m−2 h−1 and a high salt rejection of 99.63% was maintained. In addition, the membranes developed were able to maintain excellent boron removal performance in three other industrial water scenarios (geothermal water, nuclear power plant wastewater and oilfield fracturing flowback fluid). Furthermore, the overall performance of the membrane is better than that of other commercially available membranes and existing processes, showing that the membrane developed has a bright promise for various industrial applications. [Display omitted] • A high boron removal reverse osmosis membrane with broad industrial application prospect was developed. • The introduced sulphonate groups and PVA coating worked synergistically for improving the boron removal rate. • The boron removal rate of membrane could be significantly improved to 91.63% meanwhile maintaining a high permselectivity. [ABSTRACT FROM AUTHOR]

Thin-film nanocomposite (TFN) membrane with polyamide (PA) layer containing nanofillers have attracted extensive attention due to their excellent properties. In this study, hollow polymer phenolic resin nanospheres (HPS) and silver nanoparticles immobilized HPS (Ag/HPS) were synthesized with 2,4-dihydroxy benzoic acid and hexamethylene tetramine, and used as nanofillers to prepare TFN-HPS and TFN-Ag/HPS membrane. In this paper, the effects of HPS and Ag/HPS addition (0.002 wt%, 0.004 wt%, 0.006 wt%, 0.008 wt% and 0.010 wt%) on TFN membranes separation performance were investigated. The results showed that the water fluxes of TFN-HPS and TFN-Ag/HPS membranes reaches 64.7 L·m−2·h−1 and 64.0 L·m−2·h−1, respectively, when the addition amount of HPS and Ag/HPS was 0.006 wt%, which is about 80 % higher than that of TFC membranes (36.0 L·m−2·h−1). Furthermore, the TFN-HPS and TFN-Ag/HPS membrane have excellent long-term stability. After seven days of continuous operation, the water flux of TFN-HPS and TFN-Ag/HPS membranes remains at 50.0 L·m−2·h−1 and 45.6 L·m−2·h−1, respectively. In addition, the fouling resistance of TFN-HPS and TFN-Ag/HPS membranes is significantly improved, with flux recovery rates reaching 88.8 % and 91.4 %, respectively. Importantly, the sterilization rate of TFN-Ag/HPS membrane containing antibacterial silver to Escherichia coli is up to 96.7 %. [Display omitted] • Hollow polymer nanospheres (HPS) and Ag immobilized HPS nanofillers were prepared. • Two new-type TFN membranes containing HPS and Ag/HPS nanofillers were prepared. • HPS and Ag/HPS greatly improved the permselectivity and stability of TFN membranes. • TFN-Ag/HPS membrane showed high water flux (64 LMH) with NaCl rejection of 97.9 %. • TFN-Ag/HPS membrane showed a high antibacterial ratio of 96.7 % against E. coli. [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]

Montmorillonite (MMT), a cationic clay, and layered double hydroxide (LDH), an anionic clay were prepared through “top-down” and “bottom-up” methods, respectively, with lateral dimension on hundred-nanometer scale as well as high aspect ratio. These two types of nanosheets, served as additives in interfacial polymerization process, were utilized to fabricate thin film nanocomposite (TFN) reverse osmosis (RO) membranes containing cationic and anionic clay nanosheets. The properties of TFN membranes were effectively modified with the advantage of unique charged properties and hydrophilic nature of these nanoclay filler materials,. Both MMT and LDH filled TFN membranes showed increased hydrophilicity and improved desalination performance. More importantly, the incorporation of MMT and LDH nanoclays resulted in a more and less negatively charged membrane surface, respectively, and thus exhibited different electrostatic repulsion effects and improved antifouling performances towards protein, cationic surfactant, and natural organic matter foulants. The results indicate that clay nanosheets are effective filler materials to tailor membrane surface properties and fouling resistance. Since the modification by nanoclays can be achieved in the membrane preparation process without altering existing procedures, this approach can be considered as a facile way to produce novel high-performance and fouling-resistant TFN RO membrane for desalination. [ABSTRACT FROM AUTHOR]

Tailoring excellent polyamide (PA) seawater reverse osmosis (SWRO) membranes for boron (B) removal is a key challenge. Herein, we developed a facile surface engineering design strategy to improve the boron removal and desalination performance of SWRO membranes by controlling the reaction kinetics of interfacial polymerization. The functional groups and density of the oligomers covering the surface of PA skeleton were tuned to reduce the pore size and hydrogen bonds interaction inside the PA active layer with an enhanced the selectivity of the membranes. The designed membrane exhibits a high boron removal rate of 95.34%, while displaying a NaCl rejection of 99.8% and an acceptable water flux. This work offered a basic framework for the design of outstanding SWRO membranes, and also provided some insights for the formation and structure-property relations of polyamide membranes based on interfacial polymerization. [Display omitted] • A surface engineering strategy was proposed for enhancing membrane selectivity. • The boron removal ability of the tailor-made SWRO membrane was as high as 95.34%. • The oligomeric overlay of PA separation layer was rationally designed and switched. • The formation and structure-property relations of PA membranes were further disclosed. [ABSTRACT FROM AUTHOR]

The integrated membrane technology, consisting of MF, UF, and RO membrane, was used for the concentration of biogas slurry to realize the recovery of fertilizer and water. The pilot test proved the feasibility of the integrated membrane technology in this application. The RO membrane can concentrate the biogas slurry with the concentration factor of 5. RO membrane shows over 97% removal for COD and NH 3 -N, allowing less than 50 ppm of COD and NH 3 -N transport to the permeate side. The RO membrane suffered both organic and inorganic fouling. The optimal strategy for eliminating the fouling in this study is the receipt of NaOH + SDS + STPP → HCl. The salt rejection maintained at around 97.0% by this strategy, and the flux recovery had a sharp increase (~ 50.0%) after the addition of this multiple agent. [ABSTRACT FROM AUTHOR]

Improving fouling resistance and chlorine stability of aromatic polyamide (PA) thin-film composite (TFC) reverse osmosis membrane is still of considerable need in desalination membrane technology. Here, we reported the chemical linkage of neutral hydrophilic polymer polyvinyl alcohol (PVA) on the surface of a commercial PA TFC membrane through a single step of grafting with potassium persulfate as thermal dissociation initiator and its role on the improvement of membrane resistance to both chlorine and fouling. Membrane characterization was conducted through ATR-FTIR spectroscopy, SEM, AFM, measurements of streaming potential and contact angle and cross-flow permeation tests. It was found that membrane surface became smoother, more hydrophilic and less charged after modification and the modified membrane exhibited an increased slat rejection, a slightly declined water flux and improved fouling resistances to the model foulants of bovine serum albumin (BSA), sodium dodecyl sulfate (SDS) and dodecyltrimethyl ammonium bromide (DTAB). The chlorine exposure tests under accelerated conditions also indicated that the membrane chlorine stability has been enhanced effectively. The PVA molecules on the membrane surface could effectively enhance membrane anti-adsorption capability and prevent the underlying polyamide backbones from chlorine attack, and thereby improving membrane resistance to both fouling and chlorine. [ABSTRACT FROM AUTHOR]

This study explored the effect of increasing nanofiltration (NF) permeate recovery ( R NF ) by recirculation and dosage of chemicals on NF separation performance, concentration polarization ( CP ) and accumulation of scaling-prone ion concentration on NF membrane surface. The related coupling effect on seawater reverse osmosis (SWRO) desalination was also evaluated. The results show that when R NF for a single NF membrane element increased from 40% to 65%, pH of NF retentate and recycling ratio ( R r) increased from 5.02 and 0.75 to 5.10 and 3.58, respectively, with the dosage of both acid and antiscalant. In the same R NF range, the rejection of Ca 2 + , CO 3 2 − , SO 4 2 − , TDS and total hardness decreased from 35.1%, 78%, 96.3%, 18.2% and 56.1% to 28%, 76.9%, 96.1%, 10.9% and 33.9%, respectively, for NF in without chemical dosage. The CO 3 2 − and SO 4 2 − ion concentrations both in SWRO brine and on SWRO membrane surface were only around 0.12, 98, 0.12 and 99 mg·L − 1 , respectively, which were much lower than those in typical SWRO brine. Higher rejection for SO 4 2 − ion and higher selectivity of divalent ions over monovalent ions by the NF element were demonstrated in this study, which indicates that ESNA3 membrane yields a relatively higher efficiency of seawater pretreatment. [ABSTRACT FROM AUTHOR]

Thin film nanocomposite (TFN) membranes incorporated with NaY zeolite nanoparticles were prepared via interfacial polymerization (IP) of trimesoyl chloride and m-phenylenediamine on nanoporous polysulfone supports. The isolated zeolite-filled polyamide layer was observed by transmission electron microscopy, and the nanoparticles dispersed in the dense nodular polyamide on the polysulfone side. The effects of IP reaction time and zeolite loading on membrane separation performance were investigated. The results showed that a longer IP reaction time was necessary to form a denser zeolite–polyamide layer for higher salt rejection, and the optimum zeolite loading was determined to be 0.15 wt%. Under the optimum conditions, the water flux increased from 0.95 to 1.78 m 3 /m 2 /day (23.3 to 43.7 gal/ft 2 /day (gfd)) with the incorporation of the zeolite nanoparticles, while providing a high salt rejection of 98.8% (2000 ppm NaCl solution, 225 psi (1.55 MPa), 25 °C). The TFN membranes were then post-treated with aqueous solutions containing glycerol, camphorsulfonic acid-triethylamine salt, and sodium lauryl sulfate to further improve the water flux. By optimizing the post-treatment solution composition, an improved brackish water desalination performance was achieved with 2.06 m 3 /m 2 /day (50.6 gfd) water flux, which was more than double compared to that of the TFC membrane without the zeolite nanoparticles, along with 98.4% salt rejection. [ABSTRACT FROM AUTHOR]

In this study, a novel approach, namely surface mineralization, was adopted to modify the commercial thin-film composite (TFC) polyamide (PA) reverse osmosis (RO) membrane for improved membrane properties. BaSO 4 -based mineral coating was deposited on the surface of the PA-RO membrane by alternate soaking process (ASP) using aqueous solutions containing barium chloride (BaCl 2 ) and sodium sulfate (Na 2 SO 4 ), respectively. Membranes with different mineralization degrees were prepared by varying the number of ASP cycles. The mineralized TFC PA-RO membranes were characterized through FESEM microscopy, AFM analysis, EDX analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. It was found that the mineral coating composed of BaSO 4 particles distributed evenly on membrane surface. The surface of the membrane became more hydrophilic and negatively charged after mineralization and the membranes modified under certain conditions exhibited both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution also demonstrated that the BaSO 4 -based surface coating layer could effectively alleviate the adsorption and deposition of foulant molecules on the membrane surface through enhancing electrostatic repulsion and lowing hydrophobic interaction between BSA molecules and membrane surface, and that the mineralized membrane possessed improved fouling resistance to BSA aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: Polyamide reverse osmosis membranes incorporating carboxy-functionalized multi-walled carbon nanotubes (MWNTs) were prepared by interfacial polymerization of metaphenylene diamine and trimesoyl chloride. The pristine MWNTs were pre-treated with mixed acids before being modified with diisobutyryl peroxide to enhance their dispersity and chemical activity. The prepared nanocomposite membranes had a 100–300nm skin layer and the modified MWNTs were embedded within the skin layer, which was confirmed by scanning electron microscopy and transmission electron microscopy. The surface of the nanocomposite membrane was shown to be more negatively charged than bare polyamide membrane. It was shown that with an increase in the carbon nanotube loading in the membrane, the membrane morphology changed distinctly, leading to a significantly improved flux without sacrificing the solute rejection. Meanwhile, the nanocomposite membranes showed better antifouling and antioxidative properties than MWNT-free polyamide membranes, suggesting that the incorporation of modified MWNTs in membranes is effective for improving the membrane performance. [Copyright &y& Elsevier]

Abstract: Pilot-scale tests were carried out on a nanofiltration (NF)–seawater reverse osmosis (SWRO) integrated membrane system (IMS) using a kind of ultra-low pressure and high selectivity NF membrane (ESNA3, Hydranautics). Three different schemes were investigated for the NF seawater softening processes. The effect of increasing NF permeate recovery rate (R NF) on the potential of scaling in the NF and RO modules was investigated in term of concentration polarization modulus (CP) of scalant ions, Stiff and Davis Stability Index (S&DSI), and Supersaturation Index (SI) of CaCO3 and CaSO4. The results show that within the test range, high R NF, large permeate flux and low specific energy consumption (Es) could be achieved simultaneously for the loosen NF membrane. The Es for ESNA3 membrane could be lower than 0.95kWh·m−3. CP SO4 2− was larger than CP CO3 2− in the NF module under the NF retentate recycling operating conditions. The SI data indicated that at R NF of higher than 65% and with antiscalant addition and pH adjustment, CaSO4 would preferentially precipitate on NF membrane surface. However, with pH adjustment, the S&DSI values on the NF and SWRO membrane surface remained negative, which indicated that CaCO3 scaling could not form in the pilot test operating range. [Copyright &y& Elsevier]

Abstract: Surface modifications including physical and chemical treatments are effective approaches to improve the fouling and chlorine resistances of the commercial thin-film composite (TFC) aromatic polyamide reverse osmosis (RO) membranes. However, the major problem facing the modification is the influence on membrane performance. In this study, surface modification of a commercial TFC RO membrane was performed through redox initiated graft polymerization of N-isopropylacrylamide (NIPAm) followed by acrylic acid (AA) and the modified membrane showed improved membrane properties. Membrane characterization was conducted through ATR-FTIR analysis, zeta-potential analysis, contact angle measurement and cross-flow permeation test. Changes in surface characteristics confirmed the graft polymerizations of NIPAm and AA. The surface of the membrane became more hydrophilic and negatively charged after modification. The membrane modified under certain conditions showed both increased water flux and salt rejection. Fouling experiments with bovine serum albumin (BSA) aqueous solution demonstrated that the modification could mitigate the deposition of foulants on the membrane surface through enhancing electrostatic repulsion and lowering hydrophobic interaction between BSA molecules and membrane surface and thereby improving fouling resistance. Furthermore, chlorination tests also showed that surface modification through graft polymerization of NIPAm followed by AA could effectively enhance the chlorine stability of the polyamide membrane. [Copyright &y& Elsevier]

Highlights: [•] Natural hydrophilic polymer sericin was coated on the surface of TFC RO membrane. [•] Membrane surface hydrophilicity was improved and negative charge was enhanced. [•] Membrane surface morphology was smoothed. [•] Membrane pure water permeability and salt permeability coefficient were decreased. [•] Modified membrane showed improved fouling resistance to BSA. [Copyright &y& Elsevier]

[Display omitted] • Oxygen-containing azido functionalized GO were synthesized via facile EMR-FD method. • Novel MMMs were synthesized by incorporating azido functionalized GO nanosheets. • Oxygen-containing AGO enhanced interaction with polymer to achieve high compatibility. • AGO/PSF membranes displayed high permeability and good antibacterial performance. Bio-fouling of membranes caused by microorganisms seriously limited the development of membrane technology in practical applications. Design and synthesis of antifouling and antibacterial membranes with high quality are of paramount importance. In this study, we report a facile and safe method of extended Mitsunobu reaction (EMR)-freeze drying (FD) method to achieve oxygen-containing azido functionalized GO (AGO) nanosheets and synthesize novel azido-group functionalized graphene/polysulfone mixed matrix ultrafiltration membranes with enhanced permselective, antifouling and antibacterial property. Unlike reported thermochemical or chemical reactions to modify GO nanosheets, GO nanosheets were functionalized at low temperature which effectively prevented the decomposition of structural frame of pristine GO materials and the self-stacking phenomenon. Because of strong interactions between oxygen-containing AGO nanosheets and polymer matrices, high dispersity and interfacial compatibility were obtained in polysulfone membranes, resulting in sharp decrease of interfacial defects. Different kinds of techniques include SEM, ATR-FTIR, XPS, XRD, TEM and EDX were used to investigate the structure and morphology of AGO nanosheets and blended membranes, and cross-flow filtration experiments, anti-fouling and antibacterial test were applied to predict the behavior of hybrid membranes. High performance AGO/PSF mixed matrix membranes with excellent anti-fouling ability were successfully synthesized, which exhibited pure water flux as large as 245.1 L m−2h−1 with satisfactory rejection of 95.8% for BSA. Moreover, the prepared membranes displayed good antibacterial activity against E. coli and S. aureus in long-term duration. [ABSTRACT FROM AUTHOR]

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

Abstract: Monodispersed spherical mesoporous nanosilicas were synthesized by the hydrothermal method using tetraethoxysilane as silica source, cetyltrimethylammonium bromide as template, ethanol as co-solvent, and sodium hydroxide as alkali source. The synthesized silica has an average particle diameter of 164nm with a relative standard deviation of 4.87%, specific surface area of 1141m2·g−1, pore size of 2.47nm, pore volume of 0.77cm3·g−1, and a pore structure radiating from the heart to the outer surface of the sphere. The spherical mesoporous nanosilica–polyamide thin film composite reverse osmosis (TFC RO) membranes were obtained by interfacial polymerization. The silica nanoparticles are visible in the TFC RO membranes based on the surface and cross-sectional SEM images. Correspondingly, energy dispersive X-ray spectroscopy analysis confirms that the silica has been successfully doped into the TFC RO membranes. The hydrophilicity of the TFC RO membranes is improved and water flux is increased from 19L·h−1·m−2 (without nanosilica) to 53L·h−1·m−2 (with 0.1% (w/v) mesoporous nanosilica loading), whereas all solute rejection rates are greater than 96%. [Copyright &y& Elsevier]

Abstract: The role of thermo-responsive polymer (TRP) in the cleaning of organic-fouled polyamide-based reverse osmosis membranes was systematically investigated in this study. Fouling and cleaning experiments were performed employing a laboratory-scale cross-flow test unit. Following accelerated organic fouling runs with bovine serum albumin (BSA), cleaning experiments were conducted using de-ionized water and de-ionized water containing TRP with low critical solution temperature under various conditions, respectively. The separation performances of the fresh, fouled and cleaned membranes were characterized through permeation tests. It was found that the phase transition of the TRP that had diffused into the fouling layer would facilitate the removal of foulants located on membrane surface, and thereby improve the cleaning efficiency. The efficiency of the intensified cleaning with TRP solution was largely affected by the type and concentration of TRP, as well as the soaking time of TRP solution. The efficiency of the intensified cleaning could be enhanced by increasing the concentration and/or prolonging the soaking time of TRP solution. Moreover, membrane surface characterization via scanning electron microscopy, attenuated total reflectance infrared and surface contact angle measurements also confirmed the beneficial effect of TRP on the removal of the deposited foulants from the membrane surface. [Copyright &y& Elsevier]

Abstract: This study aimed to evaluate and compare the effectiveness of reverse osmosis (RO) and nanofiltration (NF) membranes in the treatment of biologically treated textile effluent in terms of COD removal, salinity reduction as well as permeate flux. Cross-flow filtration tests of the textile effluent were conducted under various hydrodynamic conditions employing BW30 reverse osmosis and NF90 nanofiltration flat-sheet membranes. The experimental results showed that, under the same operating pressure, the nanofiltration membrane NF90 exhibited higher water permeability and more severe flux decline than membrane BW30 because of its higher porosity and more serious concentration polarization and membrane fouling; while under the same initial flux, the reverse osmosis membrane BW30 experienced more serious flux decline than membrane NF90 due to its tendency towards fouling. Both the membranes could reduce COD to a desirable level of less than 10.0mg/L. However, the nanofiltration membrane showed better COD removal efficiency compared to the reverse osmosis membrane, possibly due to its sieving removal mechanism. Additionally, the reverse osmosis membrane BW30 reduced salinity to a greater extent than the nanofiltration membrane NF90. The treated water could be recycled back into the process, thereby offering economical benefits by reducing the water consumption and wastewater treatment cost. [Copyright &y& Elsevier]

Abstract: Polyelectrolyte complexes (PECs) constitute a large family of multi-component polymeric materials with rich functionalities. PEC membranes (PECMs) have already been utilized in pervaporation, nanofiltration and fuel cells. In literature, these PECMs were prepared in different methods so that they have the desired structures suitable for targeted applications. For instance, there have been two-ply PECMs, blend PECMs, multilayered PECMs, and homogeneous PECMs that have been utilized for different applications. A systematic retrospect on PECMs will not only propel present research but also stimulate new application potentials of PECMs. This review article focuses on the physical background, preparation and application aspects of PECMs in pervaporation, nanofiltration and fuel cells. [Copyright &y& Elsevier]

Abstract: This study focus on the surface modification and the improved acid stability and chlorine resistance of the commercial thin-film composite polyamide reverse osmosis membranes coated with hydrophilic copolymers poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)) surface layer. The virgin flat-sheet polyamide membranes were modified in situ with dilute P(NIPAM-co-Am) aqueous solution, and the modified membranes were then tested for their acid stability and chlorine resistance through long-term cross-flow permeation tests with aqueous solution containing 0.5mol/l HCl and 2000ppm NaCl and chlorine exposure experiments with hypochlorite aqueous solutions of different concentrations, respectively. The membrane properties were characterized in terms of reverse osmosis performance and surface chemical structure. The membrane modification was found to improve the chlorine tolerance and acid stability significantly. The P(NIPAM-co-Am) surface coating layer would impede the hydrolysis and the replacement of hydrogen with chlorine on the amide groups of the aromatic polyamide thin-film through enhancing intermolecular hydrogen bonding, and prevent the attack of acid and chlorine on the underlying polyamide film as a protective and sacrificial layer. The P(NIPAM-co-Am)-coated membrane would offer a potential use as a new type of thin-film composite polyamide membrane with improved acid stability and chlorine resistance. [Copyright &y& Elsevier]

Abstract: Commercial thin-film composite aromatic polyamide reverse osmosis membranes were modified by depositing N-isopropylacrylamide-co-acrylic acid copolymers (P(NIPAm-co-AAc)) on the membrane surface, and the modified membranes showed improved membrane properties. P(NIPAm-co-AAc) copolymers were synthesized by free radical copolymerization and their aqueous solutions of different concentrations were used to modify the polyamide membranes through in situ surface coating technique. The deposition of P(NIPAm-co-AAc) layer was shown to increase membrane surface hydrophilicity and surface charge at neutral pH, but offer additional resistance to water permeation. The effect of surface modification on membrane salt permeability was investigated through permeation tests with different salts under different pHs. The membrane modification was found to decrease the salt permeability of NaCl and Na2SO4 under neutral and alkaline conditions, and the decrease was significant for Na2SO4 that has divalent anions than for NaCl that has monovalent anions. The results of the fouling experiments with bovine serum albumin (BSA) aqueous solution and washing experiments with de-ionized water of different temperatures also revealed that the P(NIPAm-co-AAc) coating layer improved the fouling resistance to BSA and the cleaning efficiency. The phase transition of the coating layer under temperatures above its LCST would facilitate the removal of foulants located on the membrane surface. [Copyright &y& Elsevier]

Abstract: Interfacially synthesized thin-film composite (TFC) aromatic polyamide reverse osmosis membranes were modified by depositing a thermo-responsive polymer poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)) with low critical solution temperature (LCST) on membrane surface, and the modified membranes showed significantly improved antifouling properties and cleaning efficiency. In the experiments, membrane modifications were conducted in situ with dilute P(NIPAM-co-Am) solutions under different modifying conditions (e.g., P(NIPAM-co-Am) concentration and deposition time), after which fouling properties of the virgin and modified membranes were studied through cross-flow fouling experiments using bovine serum albumin (BSA) aqueous solution under different feed concentrations and pHs, and membrane cleaning tests were also carried out with the fouled membranes using de-ionized water under different feed temperatures. The membrane properties were also characterized by ATR-FT-IR, contact angle and streaming potential measurements as well as permeation tests. It was found that membrane modification improved the water permeability and fouling resistance to BSA due to the increased membrane surface hydrophilicity, and that the phase transition of the thermo-responsive polymer surface coating layer above LCST facilitated the removal of foulant located on membrane surface. Furthermore, the in situ membrane surface modification approach would be of particular interest for treating existing commercial membranes in their original module assembly. [ABSTRACT FROM AUTHOR]

Abstract: This study focuses on the surface modification of the commercial aromatic polyamide (PA) thin-film composite (TFC) reverse osmosis (RO) membranes with thermo-responsive copolymers poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)) for improved membrane properties. Firstly, thermo-responsive copolymers P(NIPAM-co-Am) with certain lower critical solution temperature (LCST) were synthesized by free radical copolymerization in aqueous solution. The resultant copolymers were then used to modify the commercial TFC RO membranes through surface coating technique under different conditions, and the surface properties of the resulting modified membranes were characterized by ATR-FTIR, XPS, SEM, AFM, and contact angle measurement. Finally, the reverse osmosis performance of the modified RO membranes was evaluated by permeation experiment with salt aqueous solution. The experimental results revealed that thermo-responsive copolymer P(NIPAM-co-Am) could be successfully deposited on the surface of the commercial aromatic polyamide TFC RO membrane by dip-coating method under certain conditions and the surface hydrophilicity of the modified membrane would change with the environmental temperature; that while the deposited copolymer P(NIPAM-co-Am) surface layer tended to offer additional resistance to permeation, the increased surface hydrophilicity would compensate for the reduction in membrane permeability; and that the surface coating layer of copolymer P(PNIAM-co-Am) had little influence on the salt rejection of the modified TFC membrane. [Copyright &y& Elsevier]

Abstract: This paper aims to enhance the performance of the machine-made flat sheet thin-film composite (TFC) polyamide-urethane seawater reverse osmosis membranes and their spiral wound elements by modifying the manufacture technique. Continuous flat sheet TFC membranes were fabricated employing a reaction line through interfacial polymerization of m-phenylenediamine with 5-chloroformyloxyisophthaloyl chloride on porous polysulphone support membrane under optimum conditions, and spiral wound elements were manufactured from the resulting membrane sheets. In the process, a modified laminating method of one-side-contacting reaction and an additional procedure of thermo-sealing on the membrane sheet along the glue line were adopted for membrane fabrication and element manufacture, respectively. The effects of the modifications involved in the manufacture technique on the performance of the resulting membranes and elements, and the separation characteristics of the machine-made membranes were investigated in terms of permeate flux and salt rejection through permeation experiments with synthetic seawater. It was found that, the flat sheet TFC membranes and spiral wound elements manufactured adopting the modified technique showed significant improved seawater reverse osmosis performance. Additionally, the results of pilot test on a desalination plant indicated that the developed TFC membranes and spiral wound elements possessed good performance stability and were suitable for single-pass seawater desalination. [Copyright &y& Elsevier]

Abstract: Aromatic-cycloaliphatic polyamide thin-film composite (TFC) reverse osmosis (RO) membranes with improved chlorine resistance as well as good RO performance were developed by the interfacial polymerization of m-phenylenediamine-4-methyl (MMPD) and cyclohexane-1,3,5-tricarbonyl chloride (HTC) on polysulfone supporting film. Parametric studies were carried out to optimize the performance of the TFC membrane. The RO performance including salt rejection and water flux of the resultant membrane was evaluated through permeation experiment, the properties of TFC membrane were characterized by AFM, SEM, XPS, ATR-IR and contact angle measurement, and the chlorine resistance was studied by measuring the chlorine uptake rate of the polyamide and the evaluation of membrane performance before and after hypochlorite exposure. The results reveal that the TFC membrane prepared from MMPD and HTC exhibits higher chlorine resistance and better-matched water flux compared with that prepared from m-phenylenediamine (MPD) and trimesoyl chloride (TMC) at the expense of some salt rejection. The desired membrane prepared under the optimum condition exhibits a typical salt rejection of 97.5% and a water flux of 53.0l/m2 h for brackish water desalination, and an attractive chlorine resistance of more than 3000ppmh Cl. The high chlorine resistance is attributed to the reduced probability of N-chlorination and Orton-rearrangement by using monomer MMPD. [Copyright &y& Elsevier]

Abstract: This paper aims to study the structure–property relationship and make several reasonable suggestions for tailoring special separation performance and surface properties of thin-film composite polyamide membranes. In the experiments, composite membranes of different thin films with small structural differences were prepared through interfacial polymerization of trimesoyl chloride (TMC), 5-isocyanato-isophthaloyl chloride (ICIC), and 5-chloroformyloxy-isophthaloyl chloride (CFIC) with m-phenylenediamine (MPD) separately, after which their reverse osmosis performances were evaluated by permeation experiment with salt aqueous solution, and film properties were characterized by AFM, SEM, XPS, ATR-IR, contact angle and streaming potential measurements. Chlorine stability was also studied through the evaluation of membrane performance before and after hypochlorite exposure. The results show that the polyacyl chloride structure strongly influences the reverse osmosis performance, surface properties and chlorine stability of the composite membranes; that the introduction of isocyanato group into polyacyl chloride improves the hydrophilicity, water permeability and surface smoothness of the thin-film composite membrane, and increases the absolute value of zeta potential at both low and high pH, but reduces the chlorine stability; and that the introduction of chloroformyloxy group increases the salt rejection rate and the surface roughness of the composite membrane, but lowers the water permeability. [Copyright &y& Elsevier]