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Membrane distillation technology has been studied thoroughly in China and since the beginning of the 1980s it has developed quickly. This article provides an introduction to the basic concept of membrane distillation and includes details of its application in the metallurgical industry. Membrane processes related to membrane distillation are also briefly discussed, as is the future development of this technology. [Copyright &y& Elsevier]

Abstract: The effects of pH, feed concentration and operation pressure on the recovery of vanadium from acid leach solution of stone coal using nanofiltration membrane technology were investigated. The rejection and permeate flux of vanadium with two kinds of membranes in nanofiltration process were also studied. After pre-treatment of leach solution to remove calcium by the addition of sodium carbonate, the vanadium in the final concentrated solution can be up to 30g/L from 1.429g/L in the feed under the optimum conditions of pH6–6.5 and operation pressure of 2069kPa at room temperature during nanofiltration process with the rejection of vanadium more than 95%. The final concentrated solution can be directly used to produce the V2O5 by traditional method, and the permeate stream can be recycled to leaching. The conceptual flow sheet for the extraction of vanadium from acid leach solution using nanofiltration membrane has been developed. [Copyright &y& Elsevier]

Abstract: N,O-carboxymethyl chitosan (NOCC) composite nanofiltration membranes crosslinked by ECH were developed using a method of coating and crosslinking, where an epichlorohydrin/ethanol 96.7% (0.067 M KOH) solution was used as the crosslinking agent. The structure and the morphology of the resulting membrane were characterized by attenuated total reflection infrared spectroscopy (ATR-IR) and environmental scanning electron microscopy (ESEM). The effects of preparation conditions on the rejection performance of the resulting composite membrane were also investigated. At 20°C and 0.40 MPa the rejections of the resulting membrane to Na2SO4 and NaCl solutions (1000 mg L−1) were 90.4% and 27.4%, respectively, and the permeate fluxes were 7.9, and 10.8 kg m−2h−1, respectively. The rejections of this kind of NOCC/PSF composite NF membrane to the inorganic electrolyte solutions decreased in the order of Na2SO4, NaCl, MgSO4, and MgCl2. [Copyright &y& Elsevier]

Abstract: N,O-carboxymethyl chitosan (NOCC) composite nanofiltration membranes having a polysulfone (PS) UF membrane as the substrate were prepared using a method of coating and cross-linking, in which a glutaraldehyde (GA) aqueous solution was used as the cross-linking agent. Attenuated total reflection infrared spectroscopy (ATR-IR) was employed to characterize the resulting membrane. The effects of the composition of the casting solution of the active layer, the concentration of the cross-linking agent, and the membrane preparation techniques on the performance of the composite membrane were investigated. At 13–15°C and 0.40MPa the rejections of the resulting membrane to Na2SO4 and NaCl solutions (1000mgL−1) were 92.7 and 30.2%, respectively, and the permeate fluxes were 3.0 and 5.1kgm−2 h−1, respectively. The rejection of this kind of membrane to the electrolyte solutions decreased in the order of Na2SO4, NaCl, MgSO4, and MgCl2. This suggests that the membrane active layer acquires a negative surface charge distribution by the adsorption of anions from the electrolyte solution and this charge distribution mainly determines the membrane performance. [Copyright &y& Elsevier]

Membrane separation technology is one of the cost effective and most efficient technologies for treatment of wastewater from textile industry. However, development of membranes with better performance and thermal stability is still a highly challenging task. In this study, successful preparation of a novel thermally stable polyimide (PI) polymer was demonstrated using 2,4,6-trimethyl-1,3-phenylenediamine, 4,4′-diaminodiphenylmethane and 1,2,4,5-benzenetetracarboxylic dianhydride components. PI was selected as representative candidate because of its excellent thermal stability (decomposition temperature of 529 °C), as revealed by thermogravimetric analysis. Furthermore, PI polymer was used to fabricate ultrafiltration (UF) membrane by phase inversion process. This UF membrane is especially interesting as it allowed for almost complete penetration of monovalent (NaCl) and divalent (Na 2 SO 4) inorganic salts because of its molecular weight cut off of 9320 Da. Moreover, the membrane exhibited very good surface hydrophilicity with the water contact angle of 67.6°. This PI-based UF membrane was found to be substantially effective as it showed high pure-water and dye-permeation fluxes of 345.10 and 305.58 L m−2 h−1 at 0.1 MPa, respectively. Besides, the membrane exhibited a rejection of 98.65% toward the direct red 23 dye (100 ppm) at 0.1 MPa. Thus, this PI-based UF membrane is highly beneficial and acts as a potential candidate for dye removal from wastewater produced by textile industry. [ABSTRACT FROM AUTHOR]

Highlights • TFC membrane with an asymmetric separation layer was fabricated for nanofiltration. • The membrane was fabricated via IP process followed by secondary interface reaction. • High efficient nanofiltration of anionic dye aqueous solution was achieved. • Steady-state water flux was improved by at least 36.0%. • Steady-state flux decline was lowered by more than 23.5%. Abstract The development of high performance membrane is crucial for enhanced separation efficiency of nanofiltration process in treating wastewaters from dye and textile industries. In this work, a novel thin-film composite nanofiltration membrane with an asymmetric separation layer composed of relatively compact skin and loose body was designed and fabricated for improved perm-selectivity and antifouling property. Nascent composite membrane with loose poly(piperazine amide) (PA) separation layer was interfacially synthesized and performed with secondary surface reaction using an aqueous tannic acid (TA) solution. Membrane characterizations verified the formation of compact TA skin on top of the loose PA layer through forming covalent bonds via esterification reaction. Compared with the composite nanofiltration membrane with PA symmetric separation layer having the same glucose rejection of about 82.0%, the permeability to pure water of the composite membrane with PA/TA asymmetric separation layer was higher by 28.0%, the water fluxes to aqueous solutions dissolved with model anionic dyes of alizarin yellow R, sunset yellow and Congo red under steady state were higher by 50.3, 43.9 and 36.1%, and the steady-state flux declines were lowered by 27.8, 43.4 and 23.5%, respectively. Furthermore, the PA/TA-based membrane also exhibited better antifouling property and rejection ability to alizarin yellow R. [ABSTRACT FROM AUTHOR]

Abstract Performance enhancement of the TFC membrane depends on the fine design of the functional layer. In this study, a gradient cross-linking strategy has been successfully applied to fabricate an ultra-thin gradient cross-linked PVA (GC-PVA) functional layer with the aid of surfactant on a polysulfone (PSF) support membrane. Such a strategy was accomplished by impregnating the crosslinker (Trimesic acid) on the porous support membrane prior to PVA coating. As confirmed by XPS and EDX studies, the GC-PVA membrane features a gradient cross-linked structure, where the bottom surface is densely cross-linked while the top is only slightly cross-linked. Overall, the lowest thickness achieved by the gradient-crosslinked ultrathin functional layer was 75.4 nm. This strategy significantly improved water flux compared with the conventional fully cross-linked PVA membranes while similar salt rejections can be maintained. In addition, the impact of key fabrication parameters, such as the concentration of PVA, surfactant, crosslinker, and the post-treatment temperature has been systematically studied. The optimized membrane had a significantly high water flux of 72.9 L m−2 h−1 at 0.2 MPa and showed rejection rates of 38.2% and 90.7% towards NaCl, Na 2 SO 4 aqueous solution (500 mg/L), respectively. Highlights • Preparation of bottom dense and top crisp gradient cross-linked structures by diffusion of cross linker. • Gradient cross-linking to prepare ultra-thin functional layer, improve water flux at low pressure, and showed good distinguishability for NaCl and Na 2 SO 4. • The surfactant (SDS) enhances the wettability of the PSF membrane and the dispersibility of the cross-linker. [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]

Membrane desalination has become an important solution to global water problems. Graphene-based materials have excellent advantages in the desalination process due to their intriguing features, including single atomic layer structure, large specific surface area, hydrophobic property, rich modification approaches, etc. After an introduction of membrane, graphene and graphene oxide (GO), this review systematically summarizes the current progress and gives an insight into the graphene-based separation membranes (GBSMs). The applications of the pressure-driven graphene-based membranes are introduced and their performances are listed and analyzed. By molecular dynamics simulation (MDS), the researchers predict the excellent performances of GBSMs, including high water flux, good salt rejection, etc. which have been verified in subsequent experiments. We believe that the application of graphene-based materials in pressure-driven membrane is worthy of further exploration. Several researchers have prepared electric-driven membranes with graphene-based materials, since their good stabilities and water-retention. However, graphene is not efficient in forward osmosis membrane area for now. In spite of the shortcomings like weak mechanical strength of single layer graphene, difficult to prepare nanopores on graphene film and hard to integrate with polymer, we hold the opinion that graphene-based films still have great research value especially in the membrane separation technology. [ABSTRACT FROM AUTHOR]

Based on the fact that when inlet bulk solution with low or medium concentration was involved, scaling was apt to appear on nanofiltration (NF) membrane surface in retentate side. Therefore, study on its surface charge performance under threshold concentration condition is necessary. Two polyamide composite NF membranes (DL and DK) were characterized with streaming potential ( E s ), zeta ( ξ ) potential and other measurements encountering with a wide ionic strength range (1.5–108 mol·m −3 ). Then, the interactional relations between membrane surface charge and concentration polarization ( CP ) degree, along with the relevant constituting factors were investigated. The results showed that even when the sparingly soluble salt concentration for CaSO 4 exceeded its threshold point, both NF membranes at pressure drop of 180 kPa still exhibited low and medium-intensity surface electrokinetic phenomena (−5.94 ≤  E s  ≤ −3.41 mV; −38.82 ≤  ξ -potential ≤ −36.34 mV). It turned out that solvent flux decreased almost linearly, but measured concentrations of the scalant ions in NF retentate streams increased slightly at first and then rapidly with the enlargement of ξ -potential, respectively. Meanwhile, mass transfer coefficient and boundary layer thickness had a negligible change in the scope of testing ξ -potential. Therefore, CP SO4 2− and CP Ca 2+ decreased apparently with ξ -potential becoming less negative for the adopted NF membranes. [ABSTRACT FROM AUTHOR]

Hierarchical porous silicate cements with lamellar/dendritic morphology were prepared by combination of ice-templating and hydration reaction routes. The macropores with multimodal pore distributions are found to be interconnected through intrinsic mesopores resulting from ice crystals growth and hydration products generation. As the slurry concentration increased from 40 to 60 wt%, the BET surface area decreased from 86.744 m 2  g −1 to 70.707 m 2  g −1 , the porosity decreased from 61.8% to 47.62%, whilst the compressive strength increased from 10.76 Mpa to 16.67 Mpa. Low-cost starting material and eco-friendly technique probably endow ordered porous cement with potential in a variety of applications including membrane separation and adsorption process. [ABSTRACT FROM AUTHOR]

Effective oil/water separation is urgently demanded but still remains a global challenge. Membranes with super-wettability have been rapidly developed, but most of the membranes are suffered from the complicated fabrication procedures and inability of separating different types of emulsions. In this work, super-amphiphilic PVDF composite membranes were developed via synchronous in-situ growth and immobilization of Ag nanoparticles during phase inversion. This method allowed the membrane formation and nanoparticle immobilization at the same time. The impact of silver growth time on the surface morphology and wettability was comprehensively investigated. The introduction of Ag nanoparticles endowed the membranes with micro/nano-structures and super-wetting property, which made the membrane possess reversible under-liquid superamphiphobicity. The PVDF composite membranes exhibited high permeate flux and outstanding separation efficiency for different surfactant-stabilized oil/water emulsions. Moreover, the prepared membranes could be regenerated through a facile method of rinsing and drying and the high separation performance could be maintained after repeated cycles, indicating the outstanding anti-fouling performance of the membranes. Furthermore, the PVDF composite membranes exhibited superior antibacterial performance. This work made progress in fabricating super-wetting membranes with excellent emulsion separation performance and the membranes can be prospective candidate for oily-mixture separation in practical applications. [Display omitted] • Under-liquid superlyophobic PVDF membrane was successfully fabricated. • A novel synchronous in-situ growth and immobilization of Ag NPs was adopted. • The impact of Ag growth time on morphology and wettability was investigated. • The membrane could effectively separate various surfactant-stabilized emulsions. • The membrane exhibited excellent durability and anti-fouling performance. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO), prepared using Hummers method, is used to fabricate nanofiltration membranes by pressure-assisted self-assembly method. The reasons for the formation of wrinkles on the surface of GO membranes are analyzed in this paper. GO membranes have serious flux attenuation and obvious changes in surface morphology due to hydraulic pressure. At 1.0 MPa, the water flux of GO membranes decreases about 75%, while at 1.5 MPa, sodium sulfate rejection increases from 21.32% to 85.84%. GO membranes were compacted and wrinkles became narrower under the influence of hydraulic pressure. By comparing flux decline between support membranes and GO membranes and analyzing the structure of GO laminate, we concluded that flux decline is due to the changes in the support membrane and GO laminate synergistically. This study reveals a defect of GO membranes and provides a profound analysis of water permeation through GO membranes. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA) has the advantages of excellent hydrophilicity, good film-forming properties and competitive prices, thus it is an ideal membrane material. However, rare reports about PVA membrane for monovalent/divalent salt separation, which is widespread in chemical industry can be found. Herein, we developed a novel boric acid (BA)-loosened PVA/glutaraldehyde (GA) membrane with high flux and selectivity for monovalent/divalent salt separation. Our idea is based on the fact that BA and PVA can form a complex due to some special interactions (including chemical bonding and H-bonding). In general, PVA membrane needs to crosslink with GA for obtaining a high salt rejection. However, PVA/GA membrane is usually too compact, leading to a low membrane water flux. The formation of PVA/BA complex reduced PVA/GA membrane crystallinity and increased its pore size, thereby improving the membrane flux obviously (by 16 times). PVA/GA/BA membrane flux is high: under 7.5 bar, its pure water flux was 20.20 L/m2·h. Besides, a high monovalent/divalent salt selectivity (64.21) was also achieved since the rejection of monovalent salt (NaCl) declined sharply and meanwhile the high rejection of divalent salt (Na 2 SO 4) was maintained. Moreover, the developed PVA/GA/BA membrane exhibited a good alkali resistance, antifouling performance and stability of permselectivity, which has a bright application prospect. This work may pave a novel avenue to develop high-performance PVA monovalent/divalent salt separation membranes. [Display omitted] • The introduction of boric acid greatly improves the PVA NF membrane permeability. • PVA/GA/BA membrane has high selectivity for monovalent/divalent salt separation. • The membrane exhibited a good alkali resistance, antifouling performance. [ABSTRACT FROM AUTHOR]

This tutorial review suggests promising potential approaches for design, fabrication, and application of electro-driven membranes in target ion selective separation for resource sustainability. [Display omitted] The conversion of industrial wastewater, salt-lakes and seawater into the valuable ionic resources is a critical challenge for sustainable global development. Electro-driven membranes are a remarkable class of separation materials established as a viable solution for this challenge. In the past few years, the design and development of ionic transfer materials in electro-driven membranes with target ion selectivity for diverse resources and environment-related applications has attracted a huge surge of interest in material science and engineering disciplines. This tutorial review aims to analyses and summarize the latest advances in the key principles and experimental procedures for designing target ion-selective separation in electro-driven membranes. Particular attention is given to the fabrication process of target ion-selective electro-driven membranes, in view of obtaining a controllable membrane structure, cross-linking and assembly. Moreover, the current evaluation metrics for the selective separation efficiency of electro-driven membranes are critically analyzed. In addition, the state-of-the-art applications of the membranes are summarized, including the selective separation of lithium, fluoride, heavy metal ions, and nutrient ions (e.g., NH 4 +, PO 4 3−). Overall, this tutorial review suggests promising potential approaches for designing, fabricating, testing, and applying electro-driven membranes in target ion-selective separation for resource sustainability. [ABSTRACT FROM AUTHOR]

In this study, heterostructured MOF/lamellar talc composites was successfully synthesized by in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles on acidified black talc (ABT) and introduced into polydimethylsiloxane (PDMS) matrix to prepare high-performance mixed matrix membranes (MMMs) via spin coating and thermal cross-linking. The submicron-size natural lamellar black talc (BT) was first explored as stable carrier to synthesize laminated composite with continuous MOF phase. Owing to its silica-oxygen tetrahedral structure, the resultant laminated composite presented good compatibility with PDMS matrix, avoiding the formation of interfacial defect between polymer and nanoparticles. Moreover, well-dispersed and continuous ZIF-8 nanoparticles on lamellar nanosheets had preferential adsorption effect for alcohol, enhancing the selectivity of membranes. The coupling effects of graphene-like lamellar structure from talc and sequential transport channels from ZIF-8 attributed to greatly enhance permeation flux. Various techniques such as FESEM, TEM, FTIR, XRD and EDS were applied to investigate the morphology and structure of composites and membranes, and pervaporation experiments were applied to probe the behavior of polymer-based composite membranes. High performance defect-free ZIF-8@ABT/PDMS MMMs exhibited excellent total permeate flux of 1711 g m−2 h−1 with very competitive separation factor of 41 for low concentration n-butanol recovery. [Display omitted] • Heterostructured composite was first achieved by in-situ growth of MOF on talc nanosheet. • MMMs were obtained by introducing lamellar composites into PDMS matrix via spin-coating. • Interfacial defect was avoided by good compatibility between ZIF-8@ABT and PDMS matrix. • Preferential adsorption and unobstructed pathway were achieved by MOFs and lamellar ABT. • Stable ZIF-8@ABT/PDMS membranes exhibited excellent performance for butanol recovery. [ABSTRACT FROM AUTHOR]

A pilot-scale ultrafiltration (UF)–nanofiltration (NF) integrated membrane system (IMS) which included a self-cleaning crossflow UF filtration process and a dual-stage NF process with a capacity of 100 m 3 ·d − 1 NF permeation water was established for seawater softening investigation. The separation performance of the dual-stage NF process under different conditions, such as operating pressure, recovery rate, and inlet flowrate, was extensively investigated; long-term performance and energy consumption of the dual-stage NF process were analyzed as well. The results showed that during the long-term operation, UF could provide qualified filtrate for NF. The dual-stage NF process achieved high separation performance with good permeate quality, especially high rejection of Ca 2 + and Mg 2 + (> 90%). In addition, the dual-stage NF process showed good anti-fouling characteristics, with the normalized NF permeate flux maintaining at an essential constant value of about 14 L·m − 2 ·h − 1 at 3.5 MPa, and DOC rejection around 90% during the long-term experiment. Energy consumption of the dual-stage NF process increased with the increase of the operating pressure and the decrease of the raw seawater temperature, which was about 1.8 kWh·m − 3 at 3.5 MPa and 25 °C. [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]

Membrane fouling is the main problem during the nanofiltration (NF) process of brackish water desalination due to the existence of natural organic matter, especially humic acid (HA). Moreover, the conventional membrane cleaning method would do great harm to the environment because large amount of chemicals were employed. In order to control organic fouling, a novel cleaning method via direct osmosis backwash (DOBW) by injecting high salinity (HS) solution was developed. Different operating conditions for HS-DOBW technology in the actual process were systematically investigated. The results demonstrated that there was a strong driving force to lift and sweep the foulants from the membrane surface which would be carried over to the brine. The optimal conditions in terms of HS (150 kg/m 3 NaCl solution) flow rate of 0.121 L/min were selected for the subsequent experiments. The results showed that the fouling could be almost fully reversible (more than 99.78% permeate water flux recovery), and the membrane needed to be cleaned for about 10 min because of the appearance of HA on membrane surface at the fouling time of 24 h. Most importantly, the HS-DOBW technology is very effective in keeping the membrane continuously clean and ensuring stable permeate production. [ABSTRACT FROM AUTHOR]

Highlights: [•] Regenerating spent acid produced by HZSM-5 zeolite preparation is proved feasible by BMED. [•] The pure sodium hydroxide in the base chamber can be recycled. [•] The recycled acid solution can replace the pure acid solution completely. [Copyright &y& Elsevier]

Abstract: In this study, asymmetric polysulfone (PSf) membranes with capsaicin-mimic groups were prepared from PSf/P(H-M)/DMAc system via phase inversion induced by immersion precipitation. Effects of coagulation bath temperature and composition on morphology, wettability, pure water permeability (L p), separation performance and anti-fouling property of the prepared membranes were systematically studied by scanning electron microscopy, contact angle measurement and fouling–filtration experiments. The results demonstrated that the elevation in the coagulation bath temperature resulted in greater formation of macrovoids and lower surface hydrophilicity, which attributed to higher both pure water permeability and permeation flux for filtration of HA solution, yet lower both HA rejection and anti-fouling capacity. Either ethanol or glacial acetic acid with different concentrations was used as non-solvent coagulation bath in this study. It was shown that pores on the membrane surface changed larger in size and then obviously shrank with an increase in either ethanol or GAA concentration in the testing range, while the surface hydrophilicity of the membranes was gradually enhanced. When 25% ethanol solution was used in coagulation bath, the membranes exhibited the excellent permeability, separation performance as well as anti-fouling capacity. Moreover, ethanol has several advantages over GAA on the fabrication of the membranes with higher hydrophilicity, permeability, permeation flux and anti-fouling capacity, while GAA favors the improvement in HA rejection of the membranes. On the whole, adjusting coagulation bath condition is an effective approach to tailor the separation performance and anti-fouling capacity of the formed P(H-M)-containing PSf membranes. [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: Using molecular dynamics simulations, we study the transport of Li+ and Mg2+ through membranes formed from armchair type (8,8) to (11,11) single wall carbon nanotubes (SWNTs) under hydrostatic pressure, and investigate the potential of mean force(PMF), conductance and axial density distributions of ions in the carbon nanotubes, the results show that under 100MPa, (9,9) and (10,10) SWNT are capable of extracting Li+; when adjusting pressure to 200MPa, (8,8), (9,9) and (10,10) tubes can separate Li+ and Mg2+ with higher ion fluxes which also augment with increasing tube diameters. By calculating the potential mean force for ion translocation, we show that Mg2+ face greater energy barrier than Li+ when passing the carbon nanotube with same diameter, and free energy difference of ∼8kJ/mol seem to be the threshold to effectively separate Li+ and Mg2+. Membrane incorporating narrow carbon nanotubes is found to be promising in Li+ and Mg2+ separation. [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]

[Display omitted] • Separation efficiency of PA NF membrane was improved by modification with APTES. • Modification was fulfilled via surface cross-linking and in-situ condensation. • Homogenized pore size and reduced mean pore diameter were achieved by modification. • Removal efficiency to both cationic and anionic dye aqueous solutions was improved. • Anti-fouling resistances to model foulants CTAB, HA and BSA were enhanced. Surface modification has been adopted to tune surface property of nanofiltration membrane for improved separation performance. However, it has rarely been explored to modulate membrane pore size distribution. Here, we reported a novel modification strategy combined with surface cross-linking and in-situ condensation for fabricating composite nanofiltration membrane with reduced and homogenized pore size. The strategy was fulfilled by soaking the surface of nascent polyamide-based membrane with an aqueous solution of 3-aminopropyltriethoxysilane (APTES). Membrane physico-chemical property analyses demonstrated that the hydrolyzed APTES molecules bonded onto membrane surface through amidation and esterification reactions with the residual acyl chloride groups, and chemically combined with each other through condensation reaction. Modification was found to hydrophilize membrane surface, homogenize pore size and reduce mean pore diameter. The modification under desired conditions led to an improvement in pure water permeance from 12.2 to 14.0 l/m2 h bar, a decrease in geometric mean pore diameter from 0.71 nm to 0.63 nm, and a decline in geometric standard deviation from 1.32 to 1.23. Permeation test results showed that the APTES-modified membrane also exhibited improved removal performance to methylene blue and cresol red removal and enhanced antifouling resistances to model foulants cetyltrimethylammonium bromide, humic acid and bovine serum albumin. [ABSTRACT FROM AUTHOR]

Abstract: In this study, several anti-fouling approaches including coagulation conditions (FeCl3 dosage and feed pH), air-enhanced backwash (AEB) conditions (backwash interval and AEB duration) and chemical cleaning conditions (reagents, soak time and temperature) were evaluated to enhance the feasibility of a commercial ultrafiltration (UF) membrane as a pretreatment of RO seawater desalination. A tubular commercial ceramic UF membrane with a surface layer of zirconium dioxide (ZrO2) and a supporting layer of α-alumina oxide (α-Al2O3) was employed in this study. The results showed that ferric coagulation was functional to enhance the performance of ceramic UF for seawater treatment, especially on COD removal. The trial of cleaning demonstrated that the performance of NaClO was much better than that of HNO3 under various evaluated pH values. The relevant additional experiments showed that the cleaning efficiency increased with NaClO concentration, soak time and soak temperature but decreases when soak temperature was up to 60°C. An important finding of this study is that the fouled membrane from coagulation-filtration trial can be easily and quickly recovered by acid cleaning regents followed by NaClO solution. Furthermore, short backwash interval performed more efficiently. However, it is certain that both backwash interval and AEB duration enhanced less than other approaches on the permeate quality. This study finally summarized the operating condition of each anti-fouling approach for the further potential application of UF ceramic membrane as a pretreatment of RO seawater desalination. [Copyright &y& Elsevier]

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: Flat sheet asymmetric PSf/clay nanocomposite membranes with different clay dosage were prepared by phase inversion method. Dimethyl acetamide was used as a solvent and water was used as a coagulant. PEG 400 was used as a pore forming additive in the casting solution. The morphology and structure of membranes were analyzed by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The performance of membranes was evaluated in terms of pure water flux (PWF), protein rejection, porosity, contact angle, tensile strength and elongation at break respectively. Results showed that clay had a good dispersion in the PSf matrix. The addition of clay additive increased the ratio of large pore in the skin layer and weakened the tensile strength. PWF and porosity of membranes increased with the increase of clay dosage. With increase in clay dosage from 0wt.% to 6wt.%, the PWF increased from 342Lm−2 h−1 to 382Lm−2 h−1. [Copyright &y& Elsevier]

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: Nanofiltration (NF) membranes are playing a more and more important role in brackish and seawater softening process, wastewater reclamation and other industrial separation. In this study, ultrafiltation (UF) and NF (ESNA3, Hydranautics) were assembled to an integrated membrane system (IMS) as pretreatment prior to seawater reverse osmosis (SWRO) to evaluate the NF efficiency of seawater softening. The influences of NF feed property (the feed from UF1 with 100kDa MWCO and UF2 with 20kDa MWCO, respectively), operating pressure (0.5–3.0MPa), cross-flow velocity (0.028–0.048m/s) and feed temperature (5–17°C) on the softening efficiency in terms of the NF flux and ion rejection were investigated. The results showed that the high softening efficiency of NF membrane could be achieved using UF membrane with smaller MWCO (20kDa). NF system using UF2 as pretreatment process yielded a higher flux of 61.4L/(m2 h) with Ca2+, Mg2+, SO4 2− rejection of 44.37%, 73.26% and 99.82%, respectively, under the optimum operating conditions of operating pressure at 1.5MPa, cross-flow velocity at 0.035m/s and feed temperature at 12.5°C. And, the relatively excellent selectivity of divalent ions and univalent ions can be obtained by ESNA3 membrane compared to that of other NF membranes reported in the literature, indicating that the ESNA3 membrane seems to be appropriate for seawater softening process. [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: The zero shear viscosity of two kinds of polysulfone (PSF) casting solutions and the morphology and permeability of their membranes prepared via the phase-inversion process were investigated. The zero shear viscosities, dominated by changing the concentration of PSF and the molecular weight of poly(vinyl pyrrolidone) (PVP) additive for the PSF/N, N-Dimethylacetamide (DMAC) binary system and PSF/DMAC/PVP ternary system respectively, were measured by a falling sphere viscometer. The cloud point of solutions was investigated in the cloud point experiment, and the phase-inversion process was monitored by the light transmittance apparatus. The surface and cross-section morphology of the corresponding membranes were characterized by SEM, and the water flux of the membranes was performed in the permeation experiment. Increasing the viscosity of the casting solution leads to the less porous surface and thick-skinned top-layer of the membrane. These experimental results are attributed to the mutable thermodynamic property of the system and the poor diffusion between components during the phase-inversion process, and finally results in the low water flux of PSF membranes. It suggests that the zero shear viscosity of the casting solution is one of the most important parameters for the morphology and permeability of membranes prepared via the phase-inversion process with the same coagulation bath. [Copyright &y& Elsevier]

Abstract: A novel thin-film composite (TFC) seawater reverse osmosis membrane was developed by the interfacial polymerization of 5-chloroformyloxyisophthaloyl chloride (CFIC) and metaphenylenediamine (MPD) on the polysulphone supporting membrane. The performance of the TFC membrane was optimized by studying the preparation parameters, which included the reaction time, pH of the aqueous-MPD solution, monomer CFIC concentration, additive isopropyl alcohol content in aqueous solution, curing temperature and time. The reverse osmosis performance of the resulting membrane was evaluated through permeation experiment with synthetic seawater, and the structure of the novel membrane was characterized by using SEM, AFM and XPS. Furthermore, the separation properties of the TFC membrane were tested by examining the reverse osmosis performances of various conditions, the boron rejection performance and the long-term stability. The results show that the desired TFC seawater reverse osmosis membrane has a typical salt rejection of 99.4% and a flux of about 35L/m2 h for a feed aqueous solution containing 3.5wt.% NaCl at 5.5MPa, and an attractive boron rejection of more than 92% at natural pH of 7–8; that the novel seawater reverse osmosis membrane appears to comprise a thicker, smoother and less cross-linking film structure. Additionally, the TFC membrane exhibits good long-term stability. [Copyright &y& Elsevier]

Metal-organic frameworks (MOFs) are an increasingly popular class of porous materials due to their tailorable structure comprised of ordered porous cavities, high specific surface areas, and versatile functional organic ligands. Implementation of these porous materials into membrane separation technologies can create an energy-efficient alternative for ion-selective separation. However, their low stability in aqueous environments and other challenges has limited their industrial breakthrough. In the past five years, many developments have improved MOF-based membranes for the selective separation of target ions. Novel insight into MOF-based membranes' structure-property relationships improves dispersibility, stability, size-sieving, electrostatic repulsion, and ionic conductivity for ideal membrane performance. The latest design principles for MOF-based membrane use advanced confinement conversion, in situ self-assembly, layer-by-layer assembly, and interfacial polymerization methods for enhanced separation performance. Analysis of separation mechanisms in MOF-based membranes now extends applications to desalination, lithium extraction, removal of heavy metal ions, and separation of ions from organic solvents. Overall, further development of MOF-based membranes presents numerous opportunities and challenges in target ion separation. This review provides guidelines for the preparation methods and properties of MOF-based membranes for target ions separations. [Display omitted] • This review focused on the latest advancements in MOF-based membranes for selective separation of target ions. • The fundamental properties and novel design strategies for MOFs in ion separation were analyzed and concluded. • The theoretical simulations and separation mechanisms of ion transport in MOFs, were analyzed and concluded. • Applications in selective ion separation and future opportunities for MOF-based membranes were provided. [ABSTRACT FROM AUTHOR]

Abstract: A novel composite nanofiltration (NF) membrane was prepared by over-coating the PAN ultrafiltration (UF) membrane with a glycolchitin (GC) thin layer. The effects of the membrane preparation techniques and operating conditions on the rejection performance of the composite membranes were studied. The structure of the composite NF membrane was characterized by scanning electron microscopy (SEM) and infrared spectroscopy (IR). And the surface roughness of the composite membrane was also characterized by atomic force microscope (AFM). The pressure osmobic coefficient (β) was about −2mV/MPa and the molecular weight cut-off (MWCO) was obtained at 540Da or so. Rejections of the composite membrane of Na2SO4, K2SO4, MgSO4, NaCl, KCl, MgCl2 solutions (1.0g/L) were 95.2%, 91.5%, 41%, 31.1%, 31% and 20.1% at 25°C under 1.0MPa, and permeation fluxes are 10.0, 10.1, 19.2, 19.7, 20.8 and 13.0L/m2 h, respectively. The results suggest that rejection performance is governed by solute–membrane and solute–solute electrostatic interactions. This charge distribution mainly determined the performances of the membranes. [Copyright &y& Elsevier]

Abstract: A novel positively charged composite nanofiltration membrane is prepared by using PAN UF membrane as support layer, quaternized chitosan, i.e. called 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) as active layer and diisocyanate as cross-linking reagent, respectively. Effects of membrane forming and testing variables on membrane properties are reported. The results indicate that a membrane from 2.0wt% HACC casting solution, cured at 50°C for 2h, cross-linked at 50°C for 9h with hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI) (HDI/TDI (w/w)=0.3g/0.3g) in 50g ethanol, heat-treated at 50°C for 20min is found to have optimum performance. The membrane, called HACC/PAN composite NF membrane is positively charged, with a RMS roughness of 12.3±0.52×103 nm. And the molecular-weight cut-off (MWCO) is approximately 560Da (NF range) by measuring the rejections of glucose, sucrose and polyethylene glycols (PEG) (MW=600–1000Da) at a concentration of 1000mg/L at 1.0MPa, respectively. At 25°C, the pure water permeability of this membrane is 10.59kgh−1 m−2 MPa−1. The rejection to different salt solutions follows the decreasing order of MgCl2, CaCl2, NaCl, KCl, MgSO4, Na2SO4 and K2SO4, which is typical characteristics of positively charged NF membranes. Besides, the curve about the streaming potential illustrates the positively charged characteristics of this membrane, with a pressure osmotic coefficient of 7.73mVMPa−1. [Copyright &y& Elsevier]

Abstract: A novel composite nanofiltration (NF) membrane was prepared by over-coating the PAN ultrafiltration (UF) membrane with a GCTACC thin layer. The effects of membrane preparation techniques and operating conditions on the performance of the composite membrane were studied. The results indicate that a composite NF membrane from 1.0wt% GCTACC casting solution, vaporized for 2h at 50°C, cross-linked for 20h at 50°C and pH≈12 with ethanol/epichlorohydrin (50/0.45 wt/wt) had optimum performance. The resultant GCTACC/PAN composite membrane was positively charged. Scanning electron microscopy showed its asymmetric and composite features. At 25°C and 30L/h of cycling flow, the permeability of pure water through this membrane is 6.3L/hm2 MPa. At 25°C, 1.2MPa and 30L/h of cycling flow, the rejection of 1000mg/L MgCl2, CaCl2, MgSO4, Na2SO4, and NaCl solutions is 0.976, 0.972, 0.897, 0.65, and 0.407, respectively, with fluxes of 6.8, 6.12, 6.12, 5.57, and 5.51L/hm2, respectively. The order of rejection of different salts follows the decreasing order of MgCl2, CaCl2, MgSO4, NaCl, KCl, Na2SO4, and K2SO4, which reveals the characteristics of the positively charged NF membrane. In addition, the curve for the streaming potential also illustrates the positively charged characteristics of this membrane, with a pressure osmotic coefficient of 11.7mVMPa−1. [Copyright &y& Elsevier]

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]

High performance membrane is crucial for energy-efficient desalination of salty water and reclamation of wastewater. Commercially available reverse osmosis membranes manufactured by interfacial polymerization or phase inversion techniques usually face the obstacle of "trade-off" effect between water permeation ability and salt rejection capability. In this work, a novel approach of constructing selective separation layer of double-layer structure was proposed to break through the difficulty of fabrication of reverse osmosis membrane with both high water permeation and salt rejection capabilities. Selective separation layer comprising loose polyamide (PA) sub bulk and dense hydroxypropyl methylcellulose (HPMC)-modified polyvinyl alcohol (PVA) top skin was constructed by the technique of interfacial polymerization followed with surface coating and cross-linking. The double-layer selective separation layer was found to possess an enhanced balance in water and salt permeations and endow the composite membrane with both high water flux and salt rejection. The desired membrane with an optimized selective layer of PA2/PVA + HPMC0.2 achieved 99.4% salt rejection and 37.9 kg/m2 h MPa water permeance to brackish water, which were higher than those of commercial membrane BW30. Furthermore, the desired membrane also exhibited better separation and antifouling performances in reclamation of secondary industry effluent when compared with the state-of-the-art antifouling membrane BW30FR. Unlabelled Image • Selective separation layer of double-layer structure was successfully constructed. • 99.4% rejection and 37.9 kg/m2 h MPa water permeance to brackish water were achieved. • Desalination performance of desired membrane was better than BW30 and BW30FR. • Performance of desired membrane in treating textile effluent was better than BW30FR. • Durability of desired membrane was also better than commercial membrane BW30FR. [ABSTRACT FROM AUTHOR]

Ultrathin polyamide (PA) nanofilm based separation membranes have attracted drastically increasing attention recently. Typically, PA nanofilms with the thickness of around tens of nanometers are supported by a PSF substrate membrane which provides mechanical support. However, the low surface porosity of the PSF substrate membrane has required the transverse diffusion (parallel to the membrane plane) of water molecules in the nanofilm, which causes much longer mean diffusion paths compared to the thickness of the nanofilm. In this study, we address this problem by introducing a much looser polypiperazinamide (PPA) interlayer in between the PA nanofilm and the PSF support membrane, with the PPA nanofilm serving as a low resistance region for water molecules. A dual interfacial polymerization strategy was applied to create an asymmetrical ultrathin polyamide selective layer comprised of a high permeability loose PPA sublayer and a high selectivity dense PA top layer. Quartz crystal microbalance with dissipation (QCMD) techniques and Doppler broadening energy spectroscopy (DBES) were applied to study the asymmetry structure of the ultrathin polyamide nanofilms. Compared with the home-made traditional ultrathin polyamide (uPA) membrane, the asymmetrical ultrathin polyamide (A-uPA) membrane has 2–2.5 folds higher permeability while maintaining higher salt rejection. Our study demonstrates that the asymmetrical structure can significantly enhance the flux for ultrathin polyamide membranes. Further, the impact of the structure of the top layer and the sublayer on the membrane separation performance was explored by tuning the recipe of the PA top layer and the PPA sublayer. Image 1 • A novel strategy was proposed to enhance the permeance of ultrathin PA membranes. • The physiochemical asymmetry was realized by fabricating a PPA interlayer. • QCMD and DBES techniques confirm the physiochemical asymmetry of A-uPA nanofilm. • The compatibility between the PSU substrate and PA nanofilm was improved. [ABSTRACT FROM AUTHOR]

• Carbodiimide-assisted zwitterionic modification was performed with PA TFC membrane. • Irreversible depositions by dyes CR and VBB were lowered by 68.4 and 91.8 %. • Water permeabilities to CR and VBB aqueous solutions were enhanced by 62.3 and 95.2 %. • Permselectivity property was better than most of the reported zwitterionic membranes. • Separation performance to dye aqueous solutions was better than membrane NF270. In this work, a novel method of carbodiimide-assisted zwitterionic modification was proposed and implemented to incorporate zwitterionic moieties onto poly(piperazine amide) membrane for improved water permeability and anti-depositing property, which are crucial for highly efficient nanofiltration of dye-contained effluents. Carboxyl groups of polyamide layer were firstly transferred into N-acylurea using excess l-ethyl-3-(3-(dimethylamino)propyl)-carbodiimide. Zwitterions were then incorporated through ring-opening reaction between tertiary amine groups of N-acylurea and 1, 4-butanesultone. Carbodiimide-assisted zwitterionic modification was verified by ATR-IR and XPS analyses and was found to not affect membrane pore size but significantly enhance membrane's permeation and anti-dye-deposition performances. Compared with those of virgin membrane, water permeabilities of the desired zwitterionic membrane to pure water, Congo red aqueous solution and Victoria blue B aqueous solution were higher by 42.9, 62.3 and 95.2 %, respectively, hydraulic resistances from irreversible deposition of Congo red and Victoria blue B molecules were dramatically lowered by 68.4 and 91.8 %, respectively. Furthermore, the perm-selectivity performance of the desired zwitterionic membrane in terms of molecular weight cut-off and pure water permeability was better than most of the reported zwitterionic membranes, and the separation and anti-depositing performances to both anionic and cationic dye aqueous solutions were better than commercial membrane NF270. [ABSTRACT FROM AUTHOR]

Oil/water separation membranes with high flux efficiency and robust anti-oil-fouling property have attracted numerous attention, and superwetting carbon nanotube (CNT) membranes are promising candidates. The key challenges focus on the versatile integration of multiple materials/structures and the facile functionalization towards superhydrophilicity/underwater superoleophobicity. In this study, a polyzwitterion/titania functionalized carbon nanotube membrane for antifouling and high-flux oil/water emulsion separation is synthesized by a novel and simple dual-bioinspired strategy. The strategy involves the co-assembly of polyzwitterion and bioinspired-adhesive polydopamine (PDA) modified CNTs and the bioinspired mineralization of titania nanoparticles (TNPs). The as-prepared CNT membrane is evenly decorated with polyzwitterion and TNPs mediated by the comprehensive adhesive capability of PDA. The integration of the hydrophilic advantages of polyzwitterion and titania and the integration of the multiscale structures of CNTs and TNPs endow membranes with superhydrophilicity, underwater superoleophobicity and anti-oil-adhesion property. The nanoscale porous structures of CNT assembled network ensure the high permeability (about 3400 L m−2 h−1) and separation efficiency (over 99.5% for emulsified oils) of membranes. Furthermore, when applied to oil-in-water emulsion separation, the as-prepared CNT membrane exhibits good recycle performance throughout several filtration cycles and maintains high recovery ratio of 95% after several cycles, indicating excellent antifouling property. The dual-bioinspired strategy combining bioinspired adhesion and bioinspired mineralization provides new insights into the design and construction of nano-structured membranes for oil/water separation. Polyzwitterion/titania co-functionalized carbon nanotube membrane is fabricated via a novel dual-bioinspired strategy combining bioinspired adhesion and bioinspired mineralization for antifouling and high-flux oil/water emulsion separation. Image 1 • Bioinspired adhesion and mineralization combined dual-bioinspired strategy is developed. • The polyzwitterion and titania functionalized CNTM is prepared via dual-bioinspired strategy. • The CNTM shows both hierarchical organized structures and hydrophilic composite composition. • Superhydrophilicity, underwater superoleophobicity and anti-oil-adhesion are achieved. • The CNTM enables antifouling and high-flux oil/water emulsion separation. [ABSTRACT FROM AUTHOR]