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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]

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]

Macroporous substrates have great potential in the development of high performance thin film composite forward osmosis (TFC FO) membranes. This paper reports on the preparation of TFC FO membrane via support-free interfacial polymerization (SFIP) technology on a macroporous substrate. SFIP technology can effectively break the bottleneck of conventional interfacial polymerization (IP) technology, which makes it difficult to form a complete polyamide (PA) film on the macroporous substrate. Briefly, the complete PA film is formed at the free water-organic phase interface and then attached to the macroporous substrate by vacuum filtration. The monomer concentration and filtration pressure were adjusted to form the optimal SFIP-PA film. Meanwhile, we chose a macroporous polyvinylidene fluoride (PVDF) microfiltration substrate and screened the pore size to reduce the structural parameters and then the internal concentration polarization, which caused the improvement of water flux. The performance of SFIP-PVDF membranes was investigated and discussed. Under the AL-FS mode with DI water and 1.0 M NaCl solution as the feed solution and draw solution, respectively, the SFIP-PVDF membrane, which used a macroporous PVDF substrate with a pore size of 0.45 μm exhibited a water flux (20 L/m2·h) and a reverse salt flux (2.5 g/m2·h). Besides, the membrane showed good stability in the 72 h test. The specific salt flux (J s /J w) of SFIP-PVDF membranes was much lower than that of IP-PVDF membranes prepared via IP technology, which were incomplete and defective, suggesting that SFIP technology was superior to IP technology. This work effectively exploits the potential of macroporous substrates for the development of high performance TFC FO membranes and provides an insight into the high performance FO membrane design. [Display omitted] • Support-free interfacial polymerization (SFIP) technology was proposed to prepare FO membranes on macroporous substrates. • Macroporous substrates with a pore size of 0.45 μm had high porosity and low tortuosity. • Low ICP, high water flux, and low reverse salt flux were exhibited. • SFIP technology was superior to IP technology on macroporous substrates. [ABSTRACT FROM AUTHOR]

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]

As a result of distinctive nanopores of two-dimensional material, graphene oxide (GO) has emerged as a new-generation membrane for high performance water separation. However, GO-based composed membrane applied to dye desalting gains less attention. A series of novel ultrathin and stable polydopamine/graphene oxide (PGO) membranes has been successfully fabricated via intercalation polymerization of dopamine using triple vacuum filtration. The polymerized dopamine (PDA) via intercalation polymerization in the interspace between the lamellar layers is used to simultaneously improve the stability of GO film and rapid passage of ions. The high permeation of pure water of as-prepared PGO membranes is investigated through adjusting the thickness (9–126 nm) of modified layers. In addition, the values decrease from 24.2 to 0.65 L m−2 h−1 bar−1 with increasing the layer. With the ultrafast ion transport and dyes rejection under cross-flow condition, the stability PGO membranes show a good capability for desalination dyes and concentration of dye (11.6 times of the initial dye solution). • A series of novel ultrathin and stable polydopamine/graphene oxide (PGO) nanofiltration membranes was successfully fabricated via intercalation polymerization of dopamine using triple vacuum filtration. • The intercalation polymerization method was applied to raise the stability of the GO film and increased the interspace of the lamellar layer which resulting in high permeation of pure water and ions. • The stability PGO membranes give an excellent capability for desalination dyes under the long-time testing, which show 99.6% rejection of methyl blue and 28.0% for Na 2 SO 4 , respectively. • The diafiltration process along with the mathematic simulation for preparation of digital inkjet printing dye were exploited. The result showed that the concentration of experiment date for dye was consist with the simulation date and obtain concentrated dye with 11.6 times. [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]

Abstract Preparation of novel swelling resistance membrane by interpenetrating an immiscible flexible polyisobutylene (PIB) polymer into a rigid polyamide (PA) network by interfacial polymerization. Due to the force interlocking of flexible PIB, polyamide network has high strength and excellent resistance to methanol. The PA layer was characterized by mechanical strength, attenuated total reflection fourier transforms infrared spectroscopy (ATR-FTIR), small angle X-ray scattering (SAXS), contact angle, field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM). RO membrane performances were evaluated based on small molecule alcohol (methanol and ethanol) solution of Safranin O. The results show that the flexible PIB interpenetrates well in the rigid polyamide network and improves mechanical strength and swelling resistance. With an increasing concentration of PIB from 0% to 0.30% in the organic phase during the fabrication, the mechanical strength of the PA layer becomes 2.8 times that of the original, and the rejection of Safranin O increased from 95.43% to 99.43%, and the permeability coefficient (B s) decreased from 5.22 to 0.47. Graphical abstract fx1 Highlights • Flexible polyisobutylene (PIB) binding polyamide aggregate pore. • Rigid-flexible interlocking enhanced mechanical strength of polyamide network. • Reinforced concrete structure enhanced polyamide for swelling resistance. [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]

Polyamide/polyethylene thin film composite (PA/PE-TFC) NF membranes were prepared from reverse-phase interface polymerization (RIP) for improved Mg(II)/Li(I) separation. RIP processes between 1,3,5-benzenetricarbonyl chloride (TMC) in bottom organic phase and piperazine (PIP) in upper aqueous phase were developed to form continuous and intact surface PA separation layers on PE porous substrates thinner than traditional polysulfone (PSF) based substrates. After activation with isopropyl alcohol (IPA), PA/PE-TFC-IPA NF membranes were formed, whose NF performance could be tuned by adjusting the preparation conditions. When TMC concentration was kept at 0.15 % w/v, RIP with low PIP concentration (0.025 wt%) yield PA/PE-TFC-IPA NF membranes with negatively charged surfaces, high Na 2 SO 4 rejection rate (95 % ± 3 %) and water permeance (13–19 L·m−2·h−1·bar−1). RIP with high PIP concentration (0.3 wt%) formed PA/PE-TFC-IPA NF membranes with less negative surfaces, high MgCl 2 rejection rate (94.3 ± 0.7 %), low water permeance (4.8 ± 0.3 L·m−2·h−1·bar−1), and high Mg(II)/Li(I) separation coefficient S Li/Mg (18 ± 1) for 1000 ppm LiCl and MgCl 2 mixed solution. PA/PE-TFC-IPA NF membranes also showed good long-term stability and improved anti-fouling performance for positively charged pollutants, bearing high potential for applications in the lithium extraction processes. Polyamide/polyethylene thin film composite NF membranes (PA/PE-TFC-IPA) with superior NF performance for Mg(II)/Li(I) separation had been prepared by using thinner and lower cost PE porous substrates to replace the thicker and more expensive PSF substrates, coupled with reverse phase interface polymerization and isopropanyl alcohol activation strategies. [Display omitted] • PE based PA TFC NF membranes showed superior Mg(II)/Li(I) separation. • Reverse phase IP (RIP) led to NF surfaces with less negative charge. • NF performance could be tuned by RIP reaction conditions. • Anti-fouling property controlled mainly by the surface charges. • Activation by isopropanol could survive long term testing. [ABSTRACT FROM AUTHOR]

Customization of thickness and roughness of thin film composite reverse osmosis (TFC-RO) membranes provides opportunities to optimize the membrane permeability and fouling resistance. We propose a novel strategy to synthesize ultrathin multi-layered polyamide (ML-PA) membranes with the versatile maneuverability of the salt rejecting layer thickness and roughness. We have employed advanced quartz crystal microbalance with dissipation (QCMD) techniques to study the deposition rate of the ultrathin PA nanolayers with a resolution of approximately 8, 15 and 25 nm per deposition cycle. At brackish water desalination condition, the ML-PA membrane exhibited ~ 60% flux increase and higher salt rejection compared with the home-made TFC membrane fabricated by the conventional method. Benefit from the low roughness, the ML-PA membrane shows much better fouling resistance to Bovine serum albumin (BSA). [ABSTRACT FROM AUTHOR]

Novel carboxyl-functionalized graphene oxide (CFGO)/polyamide (PA) nanofiltration (NF) membranes were prepared via interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC). CFGO was fabricated by a chemical modification (ring opening followed by esterification) to the epoxide ring of GO. CFGO was then introduced in the PIP aqueous phase as an additive in the IP reaction. Compared with a pristine PA reference membrane, both the GO/PA and CFGO/PA membrane have an enhanced permeability (the optimum concentration of GO and CFGO in the membrane was 0.05% and 0.07%, and the corresponding water flux is 96.5 and 112.1 L/m 2 /h, respectively),with a slight decrease of the salt rejection. In dye desalination experiment, the permeation flux of 0.05%GO/PA membrane is only 75.5 L/m 2 /h, with 98.1% rejection of New Coccine (a dye with negative charge) and 28.7% retention for NaCl. For 0.07%CFGO/PA membrane, it can cut off 25.0% NaCl and 95.1% New Coccine, and its permeation flux can reach 110.4 L/m 2 /h, which shows that the CFGO/PA membrane could be potentially applied to the dye desalination and concentration process. The CFGO/PA membrane shows better performances in permeability and dye desalination than GO/PA membrane, due to the significantly increased hydrophilicity and enhanced surface charge density. [ABSTRACT FROM AUTHOR]

Graphene oxide with lamellar structure has attracted research interest in various fields. In this study, sulfonated reduced graphene oxide (S-rGO) nanosheets with negatively charged sulfonic acid groups were synthesized via a facile distillation-precipitation polymerization, followed by hydrazine reduction. The sulfanilic acid was grafted on the graphene oxide sheets to separate GO nanosheets each other and provide anion channels for anions selectivity. These nanosheets were used to modify anion exchange membranes (AEMs), and to enhance the membrane monovalent anions selectivity and the modification layer conductivity, in order to meet industrial requirements. The permselectivity and separation efficiency were used to evaluate selectivities of the modified membranes. The results show that the unmodified AEM has no monovalent selectivity, while the permselectivity and separation efficiency of S-rGO modified AEMs (reduced by hydrazine hydrate steam in 10 min) increases from 0.65 to 1.80 and from −0.13 to 0.31 (in 40 min), respectively; and from 0.72 to 2.30 and from −0.07 to 0.28 (in 80 min), respectively. [ABSTRACT FROM AUTHOR]

In this study, a kind of thin film composite (TFC) membrane with two-dimensional (2D) covalent organic frameworks (COFs) as interlayer, termed as iTFC, which has integrally covalent bonding structure, ultra-thin and ultra-smooth surface, as well as high separation performance was fabricated via interfacial polymerization (IP) and subsequent chemical cross-linking and solvent activation for organic solvent nanofiltration (OSN). The COFs interlayer was in situ constructed using 1,3,5-triformylphloroglucinol (Tp) and hydrazine (Hz) on polyimide (PI) substrate prior to the IP. The optimization of the membrane fabrication process shows that very low concentration for both the COFs aqueous monomer Hz and the IP aqueous monomer m-phenylenediamine (MPD) was conducive to the formation of very smooth (roughness of 2.4 nm), very thin and defect-free cortex, thus improving the organic solvent permeation while remaining the dye rejection. Under optimal conditions, the prepared iTFC OSN membrane has an ethanol permeance of 63.4 L m−2 h−1 MPa−1, a Rhodamine B (RDB) rejection of greater than 99 %, and a molecular weight cut-off (MWCO) of as low as 380 Da. In addition, after filtration of 100 mg L−1 RB/DMF solution for 408 h, the optimized iTFC OSN membrane remained Rose Bengal (RB) rejection above 97 %, which proves its excellent solvent resistance performance. [Display omitted] • Ultra-low content Tp and Hz monomers are used for in situ construction of ultra-thin TpHz COFs interlayer. • Ultra-low content MPD, TMC monomer are used during the interfacial polymerization process. • Integrally covalent bonding forms between the adjacent layers of substrate, COFs interlayer and skin layer. • The iTFC OSN membrane achieves a much higher ethanol permeance of 63 L m−2 h−1 MPa−1 and 99 % high RDB rejection. • The integrally covalent bonding TFN OSN membrane achieves superior solvent resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wetting-induced reversible superlyophobic membranes were fabricated. • A novel method of direct surface decoration during phase inversion was proposed. • The membrane could efficiently separate W/O and O/W emulsions in alternation. • The membrane exhibited excellent durability and recyclability. Super-wettable membranes have been extensively investigated due to their prospective applications in oily wastewater remediation. However, it is still a big challenge to develop super-wettable membranes via a facile and rationally designed method. In this work, we proposed a novel strategy to develop wetting-induced superlyophobic polyacrylonitrile (PAN) membranes with reversible wettability via in situ cross-linking polymerization and surface immobilization of nanoparticles during phase inversion process. The resulting membranes exhibited super-amphilic property in air, and were capable of converting their wetting behavior from underwater superoleophobicity to underoil superhydrophobicity with excellent dynamic stability. The membranes also displayed outstanding separation capability toward various surfactant-stabilized emulsions with separation efficiencies exceeding 99.2% under gravity. Moreover, the membranes could be regenerated with high performance preserved using a facile rinsing-and-drying method, and could be repeatedly applied to separate surfactant-stabilized emulsions. This work has made progress in the fabrication of super-amphiphilic membranes with superior separating performance through a facile method, providing great potential in practical application for oily wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • TFC polyamide-polyarylate OSN membrane prepared via IP reaction with non-planar rigid twisted structure monomer. • Non-planar rigid twisted monomer effectively manipulates the interfacial polymerization process. • The separation performance of the prepared OSN membrane with PIM structure is remarkably enhanced. • High permeability of ethyl acetate, DMF and methanol and greater than 99% RDB rejection was achieved. • Superior solvent resistance was maintained after immersion in DMF at 80 °C for 63 d. Organic solvent nanofiltration (OSN) has become an emerging green and efficient technique for the separation and purification of organic solvents. The key of the industrial application of this technique is OSN membrane. Till now, current OSN membranes still have relatively low solvent permeance due to the high hydraulic resistance of the dense structure of the OSN barrier layer. Herein, a thin-film composite (TFC) polyamide-polyarylate OSN membrane containing polymers of intrinsic microporosity (PIMs) structure was successfully prepared via interfacial polymerization (IP) using a kind of hydrophilic monomer with rigid twisted structure as aqueous co-monomer together with m -phenylenediamine (MPD). The added co-monomer remarkably enhanced the perm-selectivity of the prepared OSN membrane, with an increase of more than 1.5 times for ethanol permeance, while maintaining the rejection of rhodamine B (RDB, 479 Da) above 99% under the optimal conditions. Moreover, the prepared OSN membrane has a much high permeance to polar solvents, e.g., 110.5, 112.6 and 95.8 L m−2h−1 MPa−1, for ethyl acetate, methanol and DMF, respectively. The most exciting aspect of the prepared OSN membrane is its superior solvent resistance in strong polar organic solvent. It maintained an essentially unchanged solute rejection during 63 d immersion in DMF at 80 °C, and during 120 h continuous cross-flow filtration of the RB-DMF solution at room temperature, which is superior over most of the state-of-the-art literature works, indicating its broad application prospects for separation and purification of polar organic solvent systems. [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: 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]

Divalent metal nitrates were pre-loaded on polysulfone support to modulate the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). It is found that the nano-porosity and nano-morphology of thus formed thin film composite polyamide (TFC-PA) nano-filtration (NF) membranes as well as their filtration performance could be effectively tuned by the type and concentration of the divalent metal salts, especially the divalent cations used. Main group cations, such as Mg (II) and Ca (II), increased the water flux of the NF membranes by increasing their surface nano-scale nodular arrays without altering the pore sizes and rejections of the membranes, while transitional metal cations such as Zn (II), Cu (II) and Co (II) increased the water flux of the NF membranes not only by the formation of high surface area nano-scale Turing type crisscrossed ridge networks, but also by the increase of their nano-pore sizes due to their coordination with the >NH groups of the PIP. The prepared NF membranes pore sizes adjustable from 0.54 Å to 0.90 Å could be developed to have varied selectivity and rejections among inorganic salts and organic dyes. [Display omitted] • Nano-porosity of NF membranes could be tuned in the IP processes. • Retention selectivity of TFC-PA NF membranes could also be tuned. • Divalent transitional metal cations increased both pore size and surface area. • Divalent main group metal cations increased water flux without changing selectivity. • Anions Cl- may act as a ligand to impeach the action of divalent transitional cations. [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: This work describes the covalently binding of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate(DMAEMA) brushes onto the poly(vinylidene fluoride) (PVDF) membrane surfaces via surface-initiated atom transfer radical polymerization (ATRP). Prior to ATRP, PVDF was coated with 3,4-dihydroxyphenylalanine (DOPA). The hydroxyl groups on the polyDOPA-coated PVDF membrane surface and pore surface were used for the immobilization of alkyl halide ATRP initiator. The grafting yield of poly(hydroxyethyl methacrylate) (PHEMA) and poly((dimethylamino)ethyl methacrylate) (PDMAEMA) was determined by weight gain which was linearly increased with the polymerization time. Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscope (AFM) were used to characterize the chemical composition and surface morphology of PVDF membrane and modified membrane, respectively. Water contact angles and water intake measurements indicated that the introduction of PHEMA graft chains promoted remarkably the surface hydrophilicity of PVDF membranes. It was also found that PHEMA graft chains provided higher pure water flux and better anti-protein absorption ability to PVDF membranes. Water flux decreased with increasing polymerization times, while the BSA rejection curves shifted to lower molecular weight cutoff values. The quaternized PVDF-g-PDMAEMA, PVDF-g-PDMAEMA-b-PHEMA membranes exhibited excellent antibacterial properties against Staphylococcus aureus. This study not only introduces a modification approach to obtain a PVDF membrane grafting hydrophilic PHEMA, but also provides the antibacterial properties for PVDF membrane with PDMAEMA. [Copyright &y& Elsevier]

Abstract: This study focus on the preparation and nanofiltration properties of a novel thin-film composite polyamide membrane formed by the interfacial polymerization of polyvinylamine (PVAm) and trimesoyl chloride (TMC) on a porous polysulfone supporting membrane. The fabrication of the PVAm–TMC composite membrane was conducted by studying preparation parameters including reaction time, pH of the aqueous phase solution, reactant concentration, as well as curing temperature and time. The properties of the resultant membrane were characterized in terms of morphological structure, surface zeta potential, pure water flux, molecular weight cut-off (MWCO) and rejections to different solutes including electrolytes and organic dyes. The results showed that the optimized composite membrane had a smooth and amphoteric surface with an isoelectric point at pH about 6.5, a MWCO of around 650Da, a pure water permeability of about 8.5l/m2 hbar and good long-term stability. The rejection order of the membrane to inorganic salts changed from MgCl2

Abstract: A novel thin-film composite polyamide nanofiltration membrane was prepared through interfacial polymerization of polymeric polyamine polyvinylamine (PVAm) with isophthaloyl chloride (IPC) on a polysulfone supporting film. The composite membranes were prepared under different conditions and characterized in terms of chemical and morphological structures, surface zeta potential, pure water permeability, and rejection to different solutes including electrolytes and sucrose. The results showed that the membrane performance was significantly affected by the content of amine units of PVAm and the concentrations of PVAm and IPC. The increase of the content of amine units of PVAm and the concentration of IPC resulted in an augment in salt rejection and a decrease in permeability, while the increase of PVAm concentration led to enhancement in both the salt rejection and water flux. The obtained membranes were positively charged at pHs lower than 6.5 and negatively charged at pHs higher than 7.0. The rejection order of the membrane changed from MgCl2 >MgSO4 >NaCl>Na2SO4 at pH 3.0 to MgSO4 >Na2SO4 >MgCl2 >NaCl at pH 7.5. The decrease of feed pH from 7.5 to 3.0 resulted in an over 35.0% augment in permeability. Furthermore, the novel nanofiltration membrane is of good performance stability and particularly suitable for treating acidic feed. [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 enhance the performance of thin-film composite (TFC) polyamide-urethane seawater reverse osmosis membrane prepared by interfacial polymerization of m-phenylenediamine (MPD) and 5-chloroformyloxyisophthaloyl chloride (CFIC). Attempts were made, such as using mixed cross-linking agents, selecting organic solvents of different MPD solubility and/or diffusivity, varying CFIC-organic temperature, modifying curing conditions as well as post-treatment. Water flux and salt rejection of the resulting membrane were evaluated through permeation experiment with synthetic seawater; chemical composition and hydrophilicity of the skin layer were characterized by XPS and contact angle measurement, respectively. The results show that the permeability of the TFC membrane is enhanced in an effective way while the selectivity remains stable or increases by adding diacyl chloride, or selecting organic solvent of high amine diffusivity, or preparing membrane at a relatively high temperature, or adopting the modified two-stage curing process, or soaking the membrane in an aqueous solution containing hypochlorite. The water flux of the improved membrane increases from about 35l/m2 h to around 42l/m2 h for seawater desalination, while the salt rejection is always above 99.4%. Additionally, polyamide-urethane seawater reverse osmosis membrane with optimal reverse osmosis performance appears to comprise a selective skin layer of certain cross-linking and a relatively hydrophobic surface. [Copyright &y& Elsevier]

Super-wetting membranes have recently attracted widespread attention for their promising application in oil/water separation. Generally, the preparation procedures of the super-wetting membranes are quite arduous, and it remains challenging to design a reasonable fabrication method. In this work, we present a facile method to prepare polyvinylidene fluoride (PVDF) based super-wetting membranes from direct immobilization of nanoparticles by in-situ polymerization and ionic cross-linking during phase inversion. The as-prepared membranes exhibited excellent amphiphilic properties, and had switchable wettability between super-oleophobic underwater and super-hydrophobic under oil. The modified PVDF membranes with such switchable wettability had high separating performance towards both surfactant-stabilized water-in-oil and oil-in-water emulsions under gravity and exhibited good durability and recyclability. This research not only provides a simple preparation method of amphiphilic super-wetting membranes, but also the unique performance of the membrane in water treatment. [Display omitted] • Amphiphilic super-wetting membranes was successfully fabricated. • A novel in situ surface decoration during phase inversion method was adopted. • The wettability of membrane could be reversibly switched. • The membrane could effectively separate emulsions under gravity. • The membrane demonstrated excellent durability and recyclability. [ABSTRACT FROM AUTHOR]

The structure of the polyamide (PA) nanofilm formed via interfacial polymerization (IP) is vital to the permeance-selectivity of composite membranes. However, it is challenging to control the morphology (e.g., nodules, ridge-and-valley) of the PA nanofilm due to the fast IP kinetics. Herein, we deconstructed the kinetic pathways of IP to probe the structure of the PA nanofilm and demonstrated that (I) the main skeleton of the nanofilm was composed of sub-10 nm nanoclusters; (II) the growth and assembly of nanoclusters shaped the nanofilm structure. Furthermore, we controlled PA nanofilm structure via adjusting the monomers' stoichiometric ratio at the new reaction interface, and the resulted nodules with controlled size and surface characteristics endowed tunable water-salt transport properties. This work offered a detailed understanding of the formation and structure of IP PA nanofilm; these insights can potentially guide the production of high-performance polyamide-based thin-film composite membranes. [Display omitted] • A new insight was provided into the structural evolution of PA nanofilm. • The main skeleton of the nanofilm was composed of nanoclusters. • The nodular structure originated from the growth and assembly of nanoclusters. • The "structure-performance" relationship of PA nanofilms was established. [ABSTRACT FROM AUTHOR]

Pore size distribution is crucial for the application of nanofiltration membrane in size-selective separation of industrial fluids. In this work, a novel combined interfacial polymerization (IP) and in-situ sol-gel strategy was proposed to fabricate composite nanofiltration membrane with narrow pore size distribution. Aqueous solution of piperazine and polyvinyl alcohol (PVA) was employed to perform interfacial polymerization with organic solution of trimesoyl chloride and tetraethyl orthosilicate (TEOS) on porous support. The non-reactive additive TEOS within the interfacially synthesized selective separation layer was then employed to perform sol-gel. The space-limited hydrolysis and condensation of TEOS molecules and their chemical bonding with PVA molecules were confirmed by analyzing membrane physico-chemical property and were found to be effective in tuning mean pore diameter, narrowing the pore size distribution and thus enhancing membrane perm-selectivity. Compared to those of membrane PA1 with similar mean pore size fabricated by only IP technique, the water permeability and rejection ratio of PEG1000 to raffinose (R PEG1000 /R raffinose) of membrane PA-TEOS0.5 fabricated by combined IP and sol-gel technique were higher by 25.0 and 20.1%, respectively. Moreover, static adsorption and dynamic deposition tests using aqueous bovine serum albumin solution proved that in-situ sol-gel process could endow the membrane with better protein fouling resistance. Image 1 • A combined interfacial polymerization and in-situ sol-gel technique was proposed. • Structure of interfacailly synthesized barrier layer was tuned via in-situ sol-gel. • In-situ sol-gel led to decreased mean pore size and narrowed pore size distribution. • Membrane fabricated by the combined technique exhibited improved perm-selectivity. • In-situ sol-gel endowed the membrane with improved anti-protein-fouling property. [ABSTRACT FROM AUTHOR]

Interfacial matching optimization between polyamide (PA) layer and porous substrate is crucial for an efficient thin-film-composite (TFC) membrane for desalination. In this study, TFC membranes were prepared via interfacial polymerization, and a series of single-walled carbon nanotubes (SWCNTs) interlayers with single-side dopamine-polyethyleneimine (DA-PEI) post-modification was constructed to regulate the interfacial matching. Interlayer robustness was enhanced by the synergic interactions of π−π stacking among CNTs and packing effect of DA-PEI deposition. The effects of interlayer on the microstructure and separation performance of PA layers were systematically investigated. It indicated that compared to the membrane without interlayers, a more hydrophilic interlayer facilitated to form a more uniform, more robust, thinner and denser PA layer. The resulting TFC membrane exhibited a superior performance in both RO test and FO test, compared to the most available commercially and reported membranes in literature. A high H 2 O/NaCl selectivity (permeance ratio, A / B) of 44.0 bar−1 was achieved in RO test. A high water flux of 51.3 L m−2 h−1 with a relatively superior H 2 O/NaCl selectivity (reverse salt flux/water flux, J s / J v of 0.16 g L−1) was achieved in FO mode. This work paved a way to understand the crucial roles of interfacial regulation between PA layer and substrate. Unlabelled Image • SWCNTs interlayers with single-side DA-PEI modification were constructed. • Interfacial matching and microstructure of PA layer were regulated. • Hydrophilic interlayer can form a more uniform, more robust, thinner and denser PA layer. • Membranes exhibited a superior desalination performance in both RO and FO applications. [ABSTRACT FROM AUTHOR]