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The safety concern on the uncontrollable growth of lithium dendrites in liquid electrolytes is the main challenge for high performance lithium-metal batteries. The traditional ex situ solid electrolytes can solve these issues to a great extent but are still plagued by low ionic conductivity , low Li + transference number, and high interfacial impedance. Herein, a solid polymer electrolyte (SPE) with highly concentrated (3.5 M) lithium bis(fluorosulfonyl)imide (LiFSI) in 1,3-dioxolane (DOL) is developed via a simple in situ initiator-free gelation route at room temperature. This simple and ingeniously designed in situ SPE integrates a high ionic conductivity (7.9 mS cm −1 at room temperature), high Li+ transference number (0.82), and low interface impedance. As a result, the in situ 3.5 M LiFSI-DOL SPE demonstrates a superior lithium dendrite-free behavior, which enables the Li|Li symmetric battery to be stably stripped/plated for more than 1000 cycles with a low overpotential of 45 mV at 5 mA cm−2 and 5 mAh cm−2. Moreover, the Li|Cu battery with the in situ 3.5 M LiFSI-DOL SPE also exhibits a high coulombic efficiency (CE) up to 98.0% at 5 mA cm−2. In addition, the in situ 3.5 M LiFSI-DOL SPE used in the Li|LiFePO4 battery leads to superior cycle life (500 cycles), CE (98.8%), rate performance, and good mechanical flexibility. Remarkably, the Li-S batteries with the in situ 3.5 M LiFSI-DOL SPE also show good compatibility and stability. This work shows tremendous prospect toward high performance solid-state lithium-metal batteries by combining the in situ polymerization and high concentration electrolyte.

This study reports on the preparation of a novel sulfonated polyether sulfone nanofiltration membrane via a manual coating method. The as-prepared membrane was modified by changing the drying temperature and utilizing additives. As the drying temperature was increased, the rejection performance of the as-prepared nanofiltration membrane increased, while flux decreased. The nanofiltration membrane dried at 40°C had relatively high permeation flux and good rejection performance for divalent ions and dyes; therefore, it is suitable for dye wastewater treatment. The nanofiltration membrane dried at 50°C had relatively low permeation flux and relatively good rejection performance for inorganic salts. The pore size of the skin layer was reduced as the drying temperature was increased. The average diameters of the as-prepared nanofiltration membranes dried at 40 and 50°C were 5.08 and 1.51 nm, respectively. Due to excellent hydrophilicity and relatively low roughness, the as-prepared nanofiltration membranes dried at 40 and 50°C had superior antipollution characteristics.

Nanofiltration membranes are the core elements for nanofiltration process. The chemical structures and physical properties of nanofiltration membranes determine water permeability, solute selectivity, mechanical/thermal stability, and antifouling properties, which greatly influence the separation efficiency and operation cost in nanofiltration applications. In recent years, a great progress has been made in the development of high performance nanofiltration membranes based on nanomaterials. Considering the increasing interest in this field, this paper reviews the recent studies on the nanofiltration membranes comprising various nanomaterials, including the metal and metal oxide nanoparticles, carbon-based nanomaterials, metal–organic frameworks (MOFs), water channel proteins, and organic micro/nanoparticles. Finally, a perspective is given on the further exploitation of advanced nanomaterials and novel strategy for fabricating nano-based nanofiltration membranes. Moreover, the development of precision instruments and simulation techniques is necessary for the characterization of membrane microstructure and investigation of the separation and antifouling mechanism of nanofiltration membranes prepared with nanomaterials.

Freeze casting liquid dispersions of solid particles is an effective method for preparing porous composites, thus creating strong and lightweight materials with “designed” microstructures for various applications. This work illuminates that tert-butyl alcohol (TBA)/water (H2O) mutually miscible system can be used as template to prepare aligned porous silicate cement supports with unique pore structures via directional freezing. The resulting pore morphology of porous cement substrates changes from prismatic to needle-like, dendritic, coralline, graininess and lamellar structure with the increasing of TBA-H2O ratio in cement slurry. Pore size distributions (macropores and mesopores) demonstrate the hierarchical pore structure of porous cement. The BET surface area (SBET) of porous cement support increases with the decreasing TBA content in cement slurry, until the pore forming agent was pure water. Porous cement that are fabricated from mixed slurries with relatively high TBA-H2O ratio show better mechanical strength. Porous cement support prepared from cement slurry with 90 wt% TBA exhibits the best permeation performance due to its well-distributed and oriented pore structure. These findings demonstrate how an aligned and hierarchical porous inorganic support with desirable properties can be prepared, under mild conditions, with the combination of advanced casting technique and most ancient construction material on earth.

Anion exchange membranes (AEMs) with a high ion exchange capacity, striking water uptake and excellent dimensional stability were prepared via an internal crosslinking networks strategy. Internal crosslinking networks were formed by reacting 4,4′-bipyridine with brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). 4,4′-bipyridine not only provides a functional group but also comprises a cross-linking agent without requirements of post-functionalization. The variation of the 4,4′-bipyridine amount into the casting polymer solution was explored to regulate the performance of the anion exchange membranes, and the membrane properties were evaluated by AFM, ion exchange capacity (IEC), water uptake, the linear expansion ratio, tensile strength, thermal stability, membrane area resistance and electrodialysis experiments, etc. The results showed that the cross-linked membrane with the IEC of 1.98 mmol/g has much more outstanding dimensional stability (water uptake: 11.68%; swelling ratio: 3.8%) than non-cross-linked BPPO-Tri membrane (water uptake: 53.26%; swelling ratio: 7.71%) and commercial Neosepta AMX membrane (water uptake: 60.29%; swelling ratio: 5.08%), at the high temperature (50 °C). When being applied in ED application, the cross-linked BPPO-20 membrane (NaCl remove: 59.7%; energy consumption: 5.97 kWh/kg NaCl) exhibits slightly higher desalination efficiency and lower energy consumption than commercial Neosepta AMX membrane (NaCl remove: 58.3%; energy consumption: 6.51 kWh/kg NaCl), suggesting its promising application in ED.

In this study, a high-flux organic solvent nanofiltration (OSN) membrane with the permeance of 66.7 Lm–2 h–1 bar–1 in methanol and 38.0 Lm–2 h–1 bar–1 in ethanol was successfully prepared from nanoporous PAN by phase inversion and hydrolyzation in sodium hydroxide solution. The polymer concentration and hydrolysis time were varied to control the final morphology and performance. The ternary phase diagram and viscosity measurements were used to describe precipitation thermodynamics and kinetics of the phase inversion process. The prepared membranes had a typical asymmetric structure, which could be observed from images of the cross section, comprising a dense skin layer and a porous substructure in the sublayer. It was found that the polymer concentration has an apparent influence on the morphology, selectivity and permeability of the prepared membranes. FTIR analysis, ζ-potential and water contact angle measurements confirm a molecular chain rearrangement as hydrogen bonds were formed between CONH2 and CO...

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/m2/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/m2/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/m2/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.

Surface modification by generating a dense anionic layer on the surface of a substrate membrane is the main method for preparing monovalent selective anion exchange membranes. However, this method has a trade-off between the permselectivity and the stability of the surface layer. To overcome this problem, a simple preparative pathway is devised to covalently immobilize the polyethyleneimine (PEI) onto the surface of an anion exchange membrane (partly quaternized poly (phenylene oxide) (QPPO)). Firstly, a brominated poly (2,6-dimethyl-1, 4-phenylene oxide) (BPPO) based anion membrane was prepared by quaternization. Then, this membrane was modified by electro-deposition of a PEI solution. The composition and structure of the membrane were observed by infrared spectroscopy and scanning electron microscopy. The permselectivity was evaluated by electrodialysis in a Cl - /SO 4 2- system. The experimental results prove that the PEI modification method is an effective, simple, feasible and well-controlled strategy to fabricate mono-valent selective anion membranes.

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).

In this paper, one brackish groundwater quality, which represented typically the water quality in the Huanghuai region of China, was simulated and used to run a bench-scale ultrafiltration (UF)–nanofiltration (NF) system. The influences of feed pH (3.0–10.0), feed total dissolved solids (TDS) (1182–5319 mg L−1) and feed dissolved organic carbon (DOC) (0.54–2.43 mg L−1) on the separating efficiencies of two different NF membranes (Thin-Film Composite (DL) and Polyamide (DK)) were investigated. In addition, long-term operation for 580 h was also conducted by the superior NF membrane to evaluate the performance stability and fouling potential after a number of subsequent cleaning cycles. Within the scope of the test, NF separating performance in terms of salt rejection showed different changing tendencies: V-shaped curve for pH, inverted V-shaped curve for TDS and linear curve for DOC. While in general, specific permeate flux was reduced in different degrees except for DK membrane with feed pH variation. The observed separating performance decline with operating time was mainly due to the scale formation on the NF membrane surface, which was rinsed effectively (FR1 = 97.80% and RR1 = 61.63%; FR2 = 95.40% and RR2 = 49.35%) by chemical cleaning, as certified by FESEM−EDX and AFM images.

Modified three-compartment electrodialysis (MTED), a novel process containing intermediate compartment with fluorinated ion exchange membrane, has been applied to the recovery of petroleum sulfonate from petrochemical dispersion. The fluorinated ion exchange membrane has higher degree of crosslinking than heterogeneous ion exchange membrane. The petroleum sulfonate is separated from the petrochemical dispersion during anion migration by the different steric effect of ion exchange membranes. In order to reduce the membrane fouling and increase the current efficiency, the 50 nm ceramic membrane was utilized as the pretreatment of MTED. The result indicated that in total of 99.4 wt% of petroleum sulfonate in the petrochemical dispersion could be recovered at the applied voltage 25 V, flux rate 30 L/h, temperature 40 °C and initial concentration 7.5 wt% (NH 4 ) 2 SO 4 . Simultaneously, the (NH 4 ) 2 SO 4 solution without petroleum sulfonate was received in concentrate compartment of MTED. The results verified the feasibility of MTED on separating the petroleum sulfonate and inorganic salt in petrochemical dispersion, and provided important technical basis for a large-scale procedure of MTED in petrochemical dispersion treatment.

Surface modification of anion exchange membranes (AEMs) by attaching a negatively charged layer is the main method for preparing monovalent anion selective membranes. However, tremendous increase of membrane resistance and poor long term stability of the modified membranes face great challenges. In this work, a photosensitive molecule (4,4-diazostilbene-2,2-disulfonic acid disodium salt (DAS)) was infiltrated into the membrane surface and immobilized in the structure by cross-linking under UV irradiation. This method introduced negative charge to the surface layer of the AEMs without increasing membrane thickness, leading to high performance membrane with high monovalent anion selectivity. The optimized membrane (D-5) shows the highest perm-selectivity of 11.21, which is superior to the commercial selective membrane Selemion® ASV and previously reported monovalent anion selective AEMs. Furthermore, the newly developed membrane exhibits excellent long-term stability, which can maintain constant selectivity during the 80 h ED experiment. This article is protected by copyright. All rights reserved.

Bipolar membrane electrodialysis (BMED) has already been described for the preparation of quaternary ammonium hydroxide. However, compared to quaternary ammonium hydroxide, di-quaternary ammonium hydroxide has raised great interest due to its high thermal stability and good oriented performance. In order to synthesize N , N -hexamethylenebis(trimethyl ammonium hydroxide) (HM(OH) 2 ) by EDBM, experiments designed by response surface methodology were carried out on the basis of single-factor experiments. The factors include current density, feed concentration and flow ratio of each compartment (feed compartment: base compartment: acid compartment: buffer compartment). The relationship between current efficiency and the above-mentioned three factors was quantitatively described by a multivariate regression model. According to the results, the feed concentration was the most significant factor and the optimum conditions were as follows: the current efficiency was up to 76.2% (the hydroxide conversion was over 98.6%), with a current density of 13.15 mA·cm − 2 , a feed concentration of 0.27 mol·L − 1 and a flow ratio of 20 L·h − 1 :26 L·h − 1 :20 L·h − 1 :20 L·h − 1 for feed compartment, base compartment, acid compartment, and intermediate compartment, respectively. This study demonstrates the optimized parameters of manufacturing HM(OH) 2 by direct splitting its halide for industrial application.

To improve the dimensional stability of electrodialysis membranes, a series of crosslinked sulphonated polysulfone cation exchange membranes with different degrees of sulfonation were prepared by a simple and low energy consumption method, namely UV-crosslinking. The crosslinking reaction was performed by UV irradiation and using 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) as photoinitiator and trimethylolpropane tri-acrylate (TMPTA) as crosslinker. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that crosslinking leads to a denser and smoother surface. Compared with the swelling and water uptake results of pristine membranes, the crosslinked membranes exhibited an enhanced dimensional stability, especially at higher temperature (40–70 °C). The thermogravimetric analysis and measurement of mechanical properties indicated that the crosslinked membrane has better mechanical and thermal properties. The electrochemical properties were analyzed, and the membrane after crosslinking showed a better ion permselectivity. When applied in electrodialysis and compared to the commercial membrane with a NaCl removal ratio of 75.6%, the crosslinked membranes showed a more efficient performance (NaCl removal ratio = 89.1% for SPSU-60). These improvements showed that the crosslinked membranes can be promising candidates for high-temperature and industrial application.

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.

Antifouling is important for RO membranes. Taking advantage of the reaction between hydroxyl groups on zwitterionic colloid nanoparticles (ZCPs) and acyl chloride group, ZCPs with tuned chemical structures were added into m -phenylenediamine aqueous solution to prepare thin-film nanocomposite membranes (ZPMs) via interfacial polymerization in this study. The incorporation of ZCPs tailored the membrane surface morphology and chemical properties, which were characterized by SEM, AFM, WCA, FTIR and XPS. Meanwhile, the effect on RO membranes separation and antifouling performances were systematically evaluated. In comparison with pristine membranes, the values of WCA decreased which means the hydrophilicity of membranes surface enhanced due to the existence of ZCPs, endowing the membrane with advanced water flux (37.3 L·m − 2 ·h − 1 ) when operate with 2000 ppm NaCl aqueous solution at 25 °C under 1.5 MPa. In order to evaluate the antifouling properties, the filtration with different types of model foulants were operated. When feed solution containing tannic acid, sodium alginate or sodium dodecyl sulfonate respectively as model foulants, ZPMs exhibited low water flux reduction and high water flux recovery after cleaning due to increased hydrophilicity and surface smoothness. Therefore, the ZPMs with improved separation and antifouling performances are promising candidates for practical application in brackish water desalination.

Conventional methods for the synthesis of aldonic acids are typically expensive and complex, generate contaminated water, and generally yield a low purity of the products. In this work, the bipolar membrane electrodialysis (BMED) process was used as an environmentally friendly and efficient method to produce aldonic acids (lactobionic acid and gluconic acid as examples). The influence of cell configuration and current efficiency was investigated. The BMED process was further evaluated on the basis of energy consumption and current efficiency. The experimental results show that the two studied cell configurations (two compartment cell configuration and multichamber cell configuration) were viable to increase the concentration of aldonic acids to a satisfactory level. The multichamber cell configuration stack, consisting of two cation exchange membranes in conjunction with a bipolar membrane, was found more suitable to produce gluconic acid due to lower energy consumption, higher current efficiency, and hig...

In this study, a process design consisting of chemical precipitation, electrodialysis with monovalent-selective membranes, and bipolar membrane electrodialysis (BMED) is proposed to valorize seawater concentrate discharged from an RO (reverse osmosis) plant for the production of acid/base and coarse salt with high purity. After pre-precipitation and electrodialysis with monovalent-selective membranes, a high purity of coarse salt (∼92%) was obtained. Furthermore, the effect of current density and feed concentration of the BMED process on the production of acid/base with high purity was investigated. It is acceptable to attain acid/base with a purity of ∼95%/∼85% when operating at a current density of 10 mA/cm2 and a feed conductivity of 100 mS/cm by applying the screened BMED stack. Finally, the total process cost for the acid/base production was estimated at $0.50/kg at the current density of 10 mA/cm2, which is appropriate and competitive for industrial application.

In this study, an electrodialysis (ED) system which was divided into three-stage operation was designed to treat seawater concentrate. The experiment was carried using a laboratory ED-cell with an effective area of 189 cm2. Two types of monovalent selective ion-exchange membranes were investigated: CIMS/ACS and CSO/ASV. The effect of applied current density during ED process was also studied. The experimental results indicate that the separation performance for divalent ions (i.e., Ca2 +, Mg2 +) with CIMS/ACS membranes stack was superior to CSO/ASV membranes stack; furthermore, a lower current density can increase the selectivity in monovalent ions to divalent ions with either the CIMS membrane or the CSO membrane. The current efficiency and energy consumption were optimal at a current density of 4 mA/cm2 by using CIMS/ACS membranes stack as the first stage of system in this experiment. Furthermore, the desalination rate (70%) was chosen as the experimental operation endpoint of the first-stage ED operation based on the experimental results. Moreover, the latter two-stage operation was used to concentrate brine to produce coarse salt after evaporation process. Finally, the repeated batch experiments confirmed the system feasibility for treating seawater concentrate to produce coarse salt with the purity of ~ 85% under continuous operation.

High strength polyelectrolyte complex (PEC) nanocomposite membranes were prepared via synergistic ionic complexation between graphene oxide/carbon nanotubes nanofillers (GO/CNT) and oppositely charged polyelectrolytes of sodium carboxymethyl cellulose (CMC) and poly(2-methacryloyloxy ethyl trimethylammonium chloride) (PDMC). Ultraviolet-visible, Raman spectroscopy and microscopies results demonstrated that the combination of one-dimensional CNTs and two-dimensional GO nanosheets lead to an integrated three-dimensional network through π-π interaction with GO distributed parallel to the surface of PEC membranes. Besides, CNTs and GO nanosheets are tightly encapsulated by PEC matrix through electrostatic interactions. The tensile strength of PEC/GO-CNT nanocomposite membrane containing 3 wt% GO-CNT (1:1, w/w) was 155.4 MPa, showing 2.3 and 1.6 times as high as that of PEC/CNT and PEC/GO membranes, respectively. Moreover, PEC/GO-CNT membranes showed improved separation performance and operation stability with introduction of the three-dimensional network constructed by GO and CNT. Keywords: Synergistic effect, Polyelectrolyte complex, GO, CNT, Mechanical strength, Pervaporation

In this study, on a basis of the single additive optimization experiments of the cellulose triacetate (CTA) forward osmosis (FO) membranes, the CTA FO membranes with binary mixed pore-forming additives were designed and fabricated to retrofit the membrane structure and separation performance for FO desalination. The binary mixed additives such as acetic acid-lactic acid (AA-LA), acetic acid-maleic acid (AA-MA) as well as zinc chloride-lactic acid (ZnCl2-LA) were selected via combining a single additive with the capacity to improve the salt rejection with another single additive with the capacity to improve the water flux. The effectiveness of the binary mixed additives on the FO performance was extensively evaluated and confirmed. For example, with the ZnCl2-LA as binary additive, the resulting CTA membrane exhibited a much improved water flux of ~ 11.5 L/m2 h and an excellent salt rejection of ~ 98.3% under the fixed FO operating condition (0.1 M NaCl solution as feed, 2 M glucose solution as draw solution, FO mode, 2 h), which were increased by approximately 51.3% and 8.1% compared to the commercial CTA membrane from HTI, respectively. Compared to the single additives, the binary mixed additives could significantly enhance the water flux for the CTA membranes with an insignificant reduction in salt rejection, which might depend on the interaction between two additives as well as the interaction between additives and solvent during the phase inversion. It indicated that the trade-off effect between the selectivity and permeability of a polymer membrane was partially broken for our membranes with binary mixed additives. This study helps us to pave the way to design highly efficient additives for high-performance FO membranes.

A novel amidoxime (AO) functionalized SBA-15 (AO@SBA-15) with platelet shape and short channels, was prepared by the amidoximation reaction of hydroxylamine with cyanoethyl (CN) functionalized SBA-15 (CN@SBA-15) under N 2 atmosphere. The precursor CN@SBA-15 was initially synthesized by co-condensation of tetraethoxysilane with 2-cyanoethyltriethoxysilane (CTES) using a triblock copolymer (P123) as a structural directing agent in acid medium or via the post-grafting of CTES onto SBA-15 with short channels. The AO@SBA-15 with platelet shape and short channels was employed as an adsorbent to remove U(VI) from an aqueous solution. The g-AO@SBA-15 (precursor prepared by post-grafting method) has higher adsorption capacity (625 mg g −1 ) than that of c-AO@SBA-15 (precursor prepared by co-condensation method) (516 mg g −1 ) at an optimum pH of 6, but with one more preparation step. Results indicated that both the adsorbents showed fast adsorption rate, high selectivity to Na + , K + , Mg 2+ , and Ca 2+ , and reusability for uranium extraction. Therefore, AO-functionalized SBA-15 with short channels is a promising adsorbent to remove uranium ion from an aqueous solution.

The desalting performance of graphene oxide (GO) membranes was further optimized using one-step carboxylation via nucleophilic substitution reactions between epoxy groups of graphene oxide (GO) and amino groups of glycine. GO and GO-COOH membranes with highly ordered structure were prepared by pressure-assisted self-assembly technique. The performance of GO and GO-COOH membranes was investigated and compared. The results showed that GO-COOH membranes exhibited not only higher permeability but also better salt rejections compared with pristine GO membranes. The surface physicochemical properties of GO-COOH membrane including negativity and hydrophilicity were improved as well. The transport mechanism revealed that the improvement of desalting properties was attributed to enhanced electrostatic repulsion by inducing effective negative charge. The higher permeability of GO-COOH membranes resulted from increased water nanochannels and improved surface hydrophilicity. Overall, GO-COOH membranes show great potential in the separation field due to prominent permeation performance and desirable separation property.

Reverse electro-dialysis (RED) is a potentially available technology to harvest salinity gradient power, which can be extracted from high-salinity wastewater in industrial processes. This study proposes a hybrid RED/ED system to simultaneous osmotic energy recovery and complete desalination in the phenol-containing wastewater treatment process. Experimental investigation on standalone ED system reveals that the high stack resistance, resulting from the salinity difference between both feed streams, accounts for the inefficient desalination performance in early stages, which implies potential implication of RED as a pre-desalination process with natural driving force to reduce the salinity difference. Pre-desalination rate is related to power generation in RED stage and energy saving in ED stage under optimal operation conditions. Compared with artificial seawater, greater power generation is produced by using phenol-containing wastewater as the high-salinity stream. Economic analysis suggests that average power generation and limiting wastewater treatment capacity can provide insightful guidelines for the design and improvement of the hybrid system. Control conditions are listed as a fundamental criterion to search for potentially applicable wastewater systems in the hybrid system. Therefore, hybrid RED/ED system can realize triplex advantages of salinity energy usage, high-valued resource reclamation, and low-energy desalination in high-salinity wastewater treatment processes.

Pure organic nature and nanoporous structure make covalent organic frameworks (COFs) a promisingly potential candidate in mixed matrix membranes (MMMs). However, COFs-based MMMs have hardly ever been applied in water purification due to their hydrolytic nature. In this study, we elaborately selected TpPa-2 with extensive stability in complicated water-environments as nanofiller to prepare MMMs for water treatment for the first time. Microwave synthetic technique was employed and optimized to construct the TpPa-2(MW) with a much higher BET surface area, smaller particle size, less agglomeration tendency and excellent stability. TpPa-2 was also synthesized mechanochemically (MC) for comparison to indicate how the synthetic technique influences the TpPa-2 and TpPa-2-incorporated MMMs. Membrane structure and property, water transport capacity and separation performance of both TpPa-2(MW)- and TpPa-2(MC)-incorporated MMMs were comprehensively investigated. It proved that our MMMs with an ultralow amount (0.2 wt%) of TpPa-2(MW) featured both improved water flux and rejection, breaking the trade-off between permeability and selectivity for polymer membrane. A membrane forming mechanism was further proposed to understand the effectiveness of TpPa-2(MW) in MMMs. This new generation COFs-based MMMs would be highly efficient, resource saving and cost-effective, which promise a great potential application in practical water purification.

In this paper, a simple and feasible prepressing method in spacer-filled channels was applied to improve the membrane performance for commercial TFC-FO membranes. Deformation-induced water flux increase rate reached up to 65.41%, meanwhile reverse solute flux had just increased by 24.90%. Such results showed that the membrane performance was effectively improved without complex chemical modification. Stability experiments also demonstrated that the viscous forces in the water permeation process had exerted slight adverse effect on the permeability–selectivity performance of deformed membranes compared to hydraulic pressure. As such, repeated prepressing operation turned out to be effective in terms of stable water flux in long-term filtration process. Therefore, the prepressing operation in spacer-filled channels can be an alternative method to enhance the initial membrane performance and, more significantly, improve the process efficiency in FO.

In this study, two types of forward osmosis (FO) membranes (CTA-HM membranes prepared in this work and commercial CTA membranes from HTI) were used in FO concentration (FOC) for actual oily wastewater (serving as feed solution, FS) treatment using 2 M NaCl as draw solution (DS). Concentration performance, fouling behavior and cleaning efficiency were extensively evaluated. Results demonstrated that the concentration factors of salt and organic matter were lower than that obtained by FS weight, attributing to the salt diffusion from FS to DS and the organic accumulation on the membrane surface. An increasing FS salinity and obvious membrane fouling led to a decreasing permeation flux. Such a membrane fouling, mainly composed of alkane (rather than inorganic or colloid fouling) was not efficiently removed by simple hydraulic washing even at a high-flow-rate. Therefore, five cleaning protocols (osmotic backwash, oxidant, acid, surfactant and complexant cleaning) were performed to improve cleaning efficiency. Results indicated that the osmotic backwash performed best to enhance flux recovery to 95% without an obvious impact on the salt rejection. Furthermore, compared to CTA-HTI membranes, CTA-HM membranes exhibited several advantages over the higher concentration efficiency, permeation flux recovery and the lower reverse salt flux.

High energy consumption and membrane fouling are the two major obstacles that limit the extensive application of nanofiltration technology in treatment of textile and dyeing wastewaters. In this work, traditional polyamide (PA) thin-film composite (TFC) nanofiltration membrane was modified with diethanolamine (DEA) for improved water permeability and antifouling property in the removal of dyes from aqueous solution. The DEA-modified PA-TFC membrane was fabricated by a facile approach of pouring the DEA-aqueous solution on the surface of the nascent polyamide membrane prepared via interfacial polymerization between trimesoyl chloride and piperazine. The covalent attachment of DEA molecules was found to make membrane surface more hydrophilic and less negatively charged while having no influence on the morphological structure and compactness of the active layer. Compared with the traditional PA-TFC membrane, the steady-state water fluxes of the DEA-modified PA-TFC membrane to dye aqueous solutions of Congo red, methyl blue, sunset yellow and neutral red were higher by more than 37.0%, the flux decline ratios due to membrane fouling were lower by at least 35.0%, while the dye removal remained constant, and furthermore, the dye molecules adsorbed and deposited on membrane surface could be more readily washed off by simple hydraulic washing.

This study focuses on the fabrication of flat-sheet thin-film composite poly(piperazine-amide)-based nanofiltration membrane with enhanced both perm-selectivity and fouling resistance. Sericin was used as the co-reactant of piperazine (PIP) to form the selective skin layer through the interfacial reaction with trimesoyl chloride (TMC) on the surface of polysulfone porous support. Membranes prepared with different contents of sericin were rigorously characterized to investigate the effects of the incorporation of sericin on membrane physico-chemical and permeation properties. ATR-FTIR and EDX analyses confirmed the incorporation of sericin in the formed active layer, which was found to significantly enhance membrane water flux through enlarging membrane pore size and increasing surface hydrophilicity while maintaining Na2SO4 rejection through intensifying electrostatic repulsion effect. Membranes with both enhanced water permeability and solute selectivity could be prepared through controlling the content of sericin. For instance, by adding 0.06%(w/v) of sericin into the PIP-aqueous solution, the pure water permeability was enhanced by 36.7%, the Na2SO4 rejection was remained as high as 97.5% of the PIP-TMC membrane, and the selectivity to mixed NaCl/Na2SO4 solution was increased from 21.2 to 25.2. Moreover, the incorporation of sericin was also found to endow the membrane with improved fouling resistance to bovine serum albumin.

CO2 separation membranes prepared by green, simple, and efficient methods have faced great challenges. In this work, a facilitated transport membrane with high CO2 permeance and CO2/N2 selectivity was prepared by an aqueous self-assembly method using commercially available polyethylenimine (PEI) and reverse osmosis (RO) membranes as the assembled molecule and substrate, respectively. When the PEI concentration was 50 mg L−1, the prepared membranes showed excellent permeability and selectivity. The effects of PEI concentration, pH of electrostatic-assembly and operating conditions on the membrane performance were systemically studied. The prepared membrane was also analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements to determine the adsorption and assembly kinetics of PEI. For CO2, the facilitated transport mechanism was dominant because of the presence of amine groups from PEI molecules, while N2 transport was accomplished by a simple solution-diffusion mechanism.

We report a promising strategy for the preparation of nano-aggregation suppressed thin film nanocomposite (TFN) membranes via an in situ method. Tetra-butyl ortho-titanate (TBOT) was added to the organic phase to prepare the new TFN membranes (in situ TFN). The in situ addition of TBOT produced TiO2 nanoparticles in the polyamide layer during interfacial polymerization. In comparison with TFN membranes fabricated by the conventional method (ex situ TFN preparation), the nanoparticles in the in situ synthesized TFN membranes exhibited better dispersion, and more TiO2 nanoparticles were observed on the membrane surface. Surprisingly, at a rather low concentration of TBOT (250 mg L−1), the water flux of the in situ TFN membranes was increased by more than 50% in comparison with that of a pure polyamide membrane with negligible rejection loss, which was close to the performance of the sate-of-the art TFN membranes. The surface properties of the membranes were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and contact angle analysis. Our results demonstrate that in situ generation of nano-additives can effectively suppress nano-agglomeration and improve the performance and surface features of TFN membranes.

Polysaccharide nanofiltration (NF) membrane with traditional modification normally suffers from poor water permeability as a result of its tight packing of polymeric chains. In this work, a novel membrane building block, polyelectrolyte complex (PEC) nanoparticles (NPs) armed with adjustable content of sulfated groups was developed using chitosan and dextran sulfate sodium. The sulfated polyelectrolyte complex membranes (SPECMs) were first prepared by solution-casting and glutaraldehyde crosslinking process, and their structural characteristics and surface properties were systematically investigated. Intrinsic aggregation structure combined with numerous sulfate groups attenuates packing density of polymeric chains and promotes hydrophilicity, endowing SPECMs with high flux and perm-selectivity. SPECMs achieved a water permeability of 6.71 L m−2 h−1 bar−1, which was ∼2.3 times higher than pristine sulfated chitosan membrane. The selectivity for NaCl/Na2SO4 separation and NaCl/methyl blue dye separation were as high as 13.1 and 850.0, respectively. Moreover, SPECMs featured efficient dye antifouling property with low flux decline ratio (6.8%) and high recovery ratio (96.8%), which was primarily attributed to its hydrophilicity and smooth surface. The prominent perm-selectivity associated with antifouling property suitably position SPECMs for practical small organic molecule/inorganic salt mixture separation in a long-term process.

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

Novel thin-film composite (TFC) membranes were elaborately designed and fabricated via the incorporation of mussel-inspired dopamine (DA) into an m-phenylendiamine (MPD) aqueous solution followed by interfacial polymerization with trimesoyl chloride (TMC) on a macroporous substrate. This DA-incorporation strategy was distinct from the previous DA layer serving as a hydrophilicity–promoter or reactive intermedia. The elastic structure of the polyamide (PA) layer and the hydrophilicity of both the PA layer and substrate were in situ flexibly manipulated by regulating the DA/MPD mass ratio and solution pH. The optimized TMC/MPD–DA TFC membranes achieved a significantly enhanced water flux (50 L m−2 h−1, improved 3-fold compared to the conventional TMC/MPD membrane) and a comparable reverse salt flux of 8.19 g m−2 h−1 for forward osmosis (FO) using deionized water as the feed along with 1 M NaCl draw solution in the FO mode. It also yielded a superior water permeability (A) of 1.8 L per m2 per h per bar compared to the TMC/MPD membrane (1.0 L per m2 per h per bar) while maintaining a NaCl rejection of over 92% at 2 bar. The proposed synergistic interaction between DA and MPD in aqueous solution responding to the solution pH played a crucial role in controlling the interfacial polymerization process. Michael addition and Schiff base reaction between PDA and MPD at a proper pH (8.5) could weaken both the residual DA monomer and the PDA aggregate generation, facilitating the establishment of a defect-free and uniform PA layer with a proper cross-linking degree to enhance the water transport. This DA-incorporation strategy for the TFC membrane demonstrated here sheds light on the exploration of high water transport for highly efficient FO and other desalination processes.

In this work, a novel semi-aromatic polyamide RO membrane was fabricated by using a new self-made dendritic molecule trimesoylamidoamine (TMAAM) as a key functional amine monomer that combined 1,3-diamino-2-propanol (DAP) to react with trimesoyl chloride (TMC) through interfacial polymerization technology. By adjusting the TMAAM concentration and amine-immersion mode, this new TMAAM-based semi-aromatic polyamide RO membrane exhibits simultaneously improved water permeability, antifouling and chlorine-tolerant properties. The introduced TMAAM units in polyamide chains can enhance the TMAAM-based membrane's water flux due to its dendritic structure as well as rich hydrophilic groups, and the DAP–TMAAM–TMC membrane prepared via the new two-step amine-immersion mode has 1.9 times more water flux without loss of salt rejection than the pristine DAP–TMC membrane and also shows higher water flux than the hand-cast conventional aromatic polyamide MPD–TMC membrane, respectively. At the same time, the regularly distributed hydroxyl groups and aliphatic amide bonds in TMAAM units contribute to the improved hydrophilicity and chlorine-tolerant property of the resultant DAP–TMAAM–TMC membrane, respectively. It is also demonstrated that the new two-step amine-immersion mode leads to a much smoother surface which endows the resultant DAP–TMAAM–TMC membrane with a favorable antifouling ability. This research provides us with a promising functional amine monomer and a new membrane formation method to fabricate a high performance RO membrane.

Both reverse osmosis (RO) and nanofiltration (NF) membranes have been increasingly used for water purification and desalination. However, the salt rejection of NF membranes is quite different from that of RO membranes, which makes a significant distinction in their process designs. This work started from the performance investigation of a single NF membrane element and then focused on the process design of the NF system for surface water treatment. In experimental tests, it was found that the observed rejection of the NF element becomes nearly constant when the concentrate flow is large enough, while the membrane flux of the NF element is quite stable regardless of the water flow across the membrane surface. These findings can be used to instruct the process design of the NF system for surface water treatment. In process design, a two-stage arrangement is sufficient for the NF system to reach the highest water recovery, while the RO system requires a three-stage arrangement.

In this paper, one brackish water quality, which typically represented the water quality in the Huanghuai region of China, was simulated and used as feedwater to run an ultrafiltration (UF)–nanofiltration (NF) integrated membrane system. Laboratory-scale experiments were carried out to evaluate NF softening performance. The influences of transmembrane pressure (0.6–2.2 MPa), inlet tangential flow velocity (0.087–0.384 m·s − 1 ) and feedwater temperature (7–35 °C) on the softening efficiencies of two NF membranes denoted as DK (termed as NF1) and DL (termed as NF2) were investigated. The experimental results revealed that the calculated total hardness and the bivalent ion (SO 4 2 − , CO 3 2 − , Mg 2 + and Ca 2 + ) concentrations in NF2 product water on the same operation were all slightly lower than those in NF1 permeate in two schemes. Additionally, pH value of NF permeate decreased prominently than those in feedwater with increasing of transmembrane pressure, inlet tangential flow velocity or decreasing of feedwater temperature within the testing scope.

A novel anion exchange membrane (AEM) is developed through poly (sodium 4-styrene sulfonate) (PSS) and hydroxypropyltrimethyl ammonium chloride chitosan (HACC) alternate electro-deposition to enhance the monovalent selectivity. Compared to the commercial original AEM, coating of the (PSS/HACC)N alternate electro-deposition multilayer on the membrane surface dramatically enhance the selectivity of anions. In addition, the permselectivity for monovalent anions of the membranes was investigated by electrodialysis experiments. For comparison, the corresponding Cl−/SO42− were chosen and the average values of permselectivity and separation efficiency of commercial AEM are 0.66 and −0.19 respectively. As result of alternate electro-deposition of PSS/HACC layers, the permselectivity raised up to 2.90 and the separation efficiency also increased up to 0.28 for nine PSS/HACC bilayers needed. Under the optimal fabricating conditions, the area resistance of membrane arrived at 4.52 Ω cm2 with nine PSS/HACC bilayers. Meanwhile, the polarization current-voltage curves and ζ-potential of membranes were also tested to characterize the electrochemical behavior of the modified membrane. The high selectivities of these membranes may enable electrodialysis applications in separation of monovalent and divalent anions.

Although multiple methods and materials have been developed to fabricate pH-responsive membranes, separating organics/inorganic salts mixtures and divalent/monovalent ions systems with these membranes still remains a challenging task. In this study, pH-responsive nanofiltration membranes (PCHMs) with tunable ion selectivity were first prepared with poly(carboxybetaine methacrylamide (CBMA) -co-N-(Hydroxymethyl) acrylamide) (PCHs) through surface coating and glutaraldehyde cross-linking method. The membrane ion selectivity towards divalent ions and monovalent ions can be well tuned by adjusting the pH of feeding solution. At pH 3.0, the retention of PCHM3 (CBMA content in PCHs is 48.8 mol%) to MgCl 2 (92.9%) is much higher than that to NaCl (3.4%). And by adjusting the feed pH value to pH 10.0, the retention to Na 2 SO 4 (91.8%) is much higher than that to NaCl (3.8%). While at neutral environment, PCHM3 allows the transport of the inorganic salts but blocks the transport of PEG800. It indicates that PCHMs could be a kind of high performance membranes for divalent/monovalent ions separation and organics/inorganic salts separation. Furthermore, the PCHMs possess a reversible and stable pH-responsive property, which is essential for practical charge-based separations. The responsiveness and adaptiveness of the PCHMs to the feeding solution make it being a versatile material for custom-designed membrane separations.

The application of electrochemical energy storage materials to capacitive deionization (CDI), a low-cost and energy-efficient technology for brackish water desalination, has recently been proven effective in solving problems of traditional CDI electrodes, i.e., low desalination capacity and incompatibility in high salinity water. However, Faradaic electrode materials suffer from slow salt removal rate and short lifetime, which restrict their practical usage. Herein, a simple strategy is demonstrated for a novel tubular-structured electrode, i.e., polyaniline (PANI)-tube-decorated with Prussian blue (PB) nanocrystals (PB/PANI composite). This composite successfully combines characteristics of two traditional Faradaic materials, and achieves high performance for CDI. Benefiting from unique structure and rationally designed composition, the obtained PB/PANI exhibits superior performance with a large desalination capacity (133.3 mg g-1 at 100 mA g-1 ), and ultrahigh salt-removal rate (0.49 mg g-1 s-1 at 2 A g-1 ). The synergistic effect, interfacial enhancement, and desalination mechanism of PB/PANI are also revealed through in situ characterization and theoretical calculations. Particularly, a concept for recovery of the energy applied to CDI process is demonstrated. This work provides a facile strategy for design of PB-based composites, which motivates the development of advanced materials toward high-performance CDI applications.

Recently, the fine-grained geolocalization of User-Generated Short Text (UGST) has become increasingly important. Existing methods can not make full use of the location information in the UGSTs. Besides, existing works only consider the importance of terms for all locations, but do not distinguish the importance of the same term in different locations. To solve these problems, we propose a fine-grained geolocalization method based on a weight probability model (FGST-WP). The method mainly includes three parts: 1) Using the reverse maximum match algorithm to filter out UGSTs that do not contain any location indicative information. 2) Building coupling of terms and locations and adopting a mixed weight strategy to assign weights to terms. 3) Calculating the probability of non-geotagged UGST posted from each location and selecting k locations according to the top-k probabilities. Experiments on ground-truth datasets prove the superior performance of FGST-WP.

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 (Na2SO4) 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.

Biofouling is a critical issue in the membrane separation process as it can increase the operational cost by lower down membrane permeability. Covalent binding of an antibacterial agent on the membrane surface to kill microorganisms to hinder biofouling formation process draws great attention. In this study, we used three kinds of capsaicin derivatives, MBHBA, HMBA, and HMOBA, to fabricate antibiofouling membrane via UV-assisted photo grafting method. The influence of these capsaicin derivatives on membrane properties was investigated and compared. The results suggest that HMBA showed the best UV activity, followed by HMOBA and MBHBA successively. Due to the difference of functional groups among capsaicin derivatives, there is an increase in membrane wettability of HMBA and HMOBA-modified membranes, while there is a decrease for MBHBA-modified membrane. MBHBA-modified membrane showed enhanced irreversible fouling, which is in contrast to that of HMBA- and HMOBA-modified membranes. The modified membranes showed similar antibacterial activity against Escherichia coli. The practicability of the modified membranes was examined by dipping them into tap water and seawater for 30 days, and the results displayed the modified surfaces have the potential to relieve biofouling for separation membranes.

Carbon-based materials have attracted intensive attentions for a wide range of energy and environment-related applications. Energy storage/conversion devices with improved performance have been achieved by utilization of metal-organic-framework (MOF)-derived carbon structures as active materials in recent years. However, the effects of MOF precursors on the performance of derived carbon materials are rarely investigated. Here, we report that the incorporation of small amount of Fe or Ni in Co-based MOFs leads to a significant enhancement for the derived carbon nanotube-based frameworks (CNTFs) in Na+/Cl- ion electrosorption. Further investigation revealed the enhanced performance can be attributed to the improved specific surface area, electrical conductivity, and electrochemical activity. Notably, the CoFe-CNTF derived from bimetallic CoFe-MOFs achieves a high ion adsorption capacity of 37.0 mg g-1, superior to most of recently reported carbon-based materials. Furthermore, the CoFe-CNTF also demonstrates high catalytic activity toward oxygen evolution reaction (OER) with a Tafel slope of 87.7 mV dec-1. After combination with three-dimensional graphene foam (3DG), the resultant CoFe-CNTF-coated 3DG is used as air-cathode to fabricate a flexible all-solid-state Zn-air battery, which exhibits a high open circuit potential of 1.455 V. Importantly, the fabricated flexible battery can light a light-emitting diode (LED) even when it is bent. This work provides new insights into designs of high-performance and flexible electrode based on MOF-derived materials.

Surface modification has been proven to be an effective approach for ion exchange membranes to achieve separation of counterions with different valences by altering interfacial construction of membranes to improve ion transfer performance. In this work, we have fabricated a series of novel cation exchange membranes (CEMs) by modifying sulfonated polysulfone (SPSF) membranes via codeposition of mussel-inspired dopamine (DA) and 4'-aminobenzo-15-crown-5 (ACE), followed by glutaraldehyde cross-linking, aiming at achieving selective separation of specific cations. The as-prepared membranes before and after modification were systematically characterized in terms of their structural, physicochemical, electrochemical, and electrodialytic properties. In the electrodialysis process, the modified membranes exhibit distinct perm selectivity to K

The core of the organic solvent nanofiltration (OSN) technology is solvent-resistant nanofiltration (SRNF) membranes. Till now, relative poor performance of solvent resistance is still the bottleneck of industrial application of SRNF membranes. This work reports a novel polyimide (PI)-based thin-film nanocomposite (TFN) membrane which was embedded with graphene quantum dots (GQDs) and showed an improved solvent resistance for OSN application. This kind of SRNF membrane, termed (PI-GQDs/PI)XA, was synthesized via serial processes of interfacial polymerization (IP), imidization, cross-linking, and solvent activation. The IP process was performed between an aqueous m-phenylenediamine solution doped with GQDs, having an average size of 1.9 nm, and an 1,2,4,5-benzenetetracarboxylic acyl chloride n-hexane solution on the PI substrate surface. The prepared (PI-GQDs-50/PI)X SRNF membranes without organic solvent activation achieved an ethanol permeance of nearly 50% higher than those of the GQD-free membranes under the same preparation conditions, while no compromise of the dye rejection was observed. Further, after the solvent activation using N, N-dimethylformamide (DMF) at 80 °C for 30 min, the ethanol permeance achieved about an 8-folds increment, from 2.84 to 22.6 L m-2 h-1 MPa-1. Interestingly, the rejection of rhodamine B also increased from 97.8 to 98.6%. A long-term permeation test of more than 100 h using rose bengal (RB, 1017 Da)/DMF solution at room temperature demonstrated that the synthesized (PI-GQDs-50/PI)XA membranes could maintain the DMF permeance and the RB rejection as high as 18.3 L m-2 h-1 MPa-1 and 99.9%, respectively. Moreover, the immersion test of the prepared (PI-GQDs-50/PI)XA SRNF membranes in both DMF and ethanol at room temperature for about one year also demonstrated the long-term organic solvent stability, indicating their good potential for OSN application.

A thin and robust organic solvent cation exchange membrane (CEM) was successfully fabricated for the first time using dissolved Kevlar aramid nanofibers as the casting solution and 4-aminobenzenesulfonic acid (ABS) as the negatively charged functional group via an amide condensation reaction. The synthesized Kevlar CEMs inherited the advantages of Kevlar aramid nanofibers, achieving an excellent ion exchange capacity as high as 1.0 mmol g−1 (with 22.5% water content), a low swelling rate of ∼2.0%, a low membrane surface electrical resistance of 2.95 Ω cm2, a high mechanical strength of over 9.0 kPa of a water column (the membrane thickness was 5.0 μm) and a high membrane limiting current density of 45.0 mA cm−2 (in 0.1 M NaCl solution). In electrodialysis, the Kevlar CEMs demonstrated an exceptional cation/anion separation in dilute and concentrated cells. After 72 h of immersion in aqueous acetone solutions (25%, 50%, 75% and 100%, Vacetone/Vwater), the resulting membranes still exhibited a significant separation in ED. This work demonstrates the promising potential application of Kevlar aramid nanofibers in the preparation of organic solvent CEMs.

A novel nanofiltration membrane prepared by modification of a commercial membrane surface is fabricated using polydopamine (PDA) and hydroxyl propyl trimethyl ammonium chloride chitosan (HACC) mixed with chitosan (CN) and chelated silver (Ag) nanoparticles. The surface chemical composition, cross-sectional morphology, hydrophilicity and surface structure of the prepared membranes were examined by scanning electron microscopy, water contact angle measurements, and atomic force microscopy, respectively. The membrane performance was evaluated in terms of volumetric flux and protein rejection. In addition, the antifouling and antibacterial properties of the membranes were also explored. The results demonstrated that the prepared membranes exhibited an excellent antifouling property due to their three-layer architecture and it provided a special layer to promote the antibacterial property. According to the results, the modified membrane has a significantly improved flux recovery rate (over 96%). Besides, the antibacterial activity tests showed that the proposed three-layer architecture modification extensively prevented bacterial growth on the membrane surface.

Organic solvent nanofiltration (OSN) as a high-efficient membrane separation technology has play an important role in chemical industrial separation, clean energy production, and high-value resources recycling, etc. Inspired by the asymmetric biological structure of Desert beetle, herein a novel kind of polymeric OSN membranes with asymmetric structure have been fabricated via fluorinated polymeric networks (FPNs) regulated interfacial polymerization. The FPNs were formed with m-phenylenediamine (MPD), dopamine (DA) and 1H,1H,2H,2H-Perfluorodecane-thiol (PFDT) via the Michael addition and Schiff-base reaction. The FPNs tailored thin-film composite membrane (FPN-TFC) with biomimetic asymmetric structure, e.g., much hydrophilic looser front surface and much hydrophobic denser rear surface, exhibits an optimum ethanol permeance ~15.7 L m−2 h−1.MPa−1 and high rejection ~99.5% for Rose Bengal (RB) dye molecules (test with 0.05 g L−1 RB ethanol solution at 25 °C under 1.5 MPa), which is almost 6 times higher than that of the conventional TFC membranes. Moreover, there is a good stability for the FPN-TFC membrane tested with different polar solvents in long-term operation process. Therefore, this work provides a guidance for the development of advanced polymeric OSN membranes with both high solvent permeability and solute selectivity, as well as good stability in OSN process, which would have broad application prospects in chemical and other industrial fields.

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 (RPEG1000/Rraffinose) 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.