Pristine Membrane Research Articles

Holistic approach for fabrication of superhydrophobic MXene-based membrane for enhanced membrane distillation

There is growing interest in membrane distillation (MD) as a means of desalinating seawater with 100 % theoretical salt rejection which has the capacity to address freshwater scarcity. MD has huge potential for commercial applications owing to its low operating temperature and pressure requirements. However, wetting polymeric membranes inhibits water permeance and lowers salt rejection. MXene nanosheet-incorporated polyvinylidene (PVDF) membranes have been constructed for enhanced vapor transport with high water repellence and antiwetting properties. MXene nanosheets in PVDF polymeric matrices are responsible for their high super-hydrophobicity, which can mitigate membrane fouling and wetting during the MD process. As far as experimental outcomes are concerned, the pristine PVDF membrane exhibited severe wetting with salt leakage. Ti3C2Tx MXene nanosheets allow the formation of hierarchical polymeric micro/nanostructures, changing the intrinsic hydrophilicity to super-hydrophobicity. Surface engineering of a PVDF membrane with MXene nanosheets enables efficient saline desalination during the MD process. The surface-engineered MXene/PVDF membrane demonstrated a high-water contact angle of 143° with extremely high self-cleaning characteristics as compared to that of pristine PVDF membrane. As far as the performance of the membrane is concerned, the water flux of the pristine PVDF membrane decreased from 6.5 LMH to 6 LMH after the 14th hour which can be attributed to partial pores wetting during MD operation. Eventually, the pristine PVDF membrane exhibited a continuous salt flux (SF) increase. However, MXene/PVDF membrane showed stable water flux (8 LMH) and negligible SF. The study therefore demonstrates a facile and holistic approach for constructing MXene-based PVDF membranes that exhibit superior antiwetting performance during MD operation.

A novel ZIF-L/PEI thin film nanocomposite membrane for removing perfluoroalkyl substances (PFASs) from water: Enhanced retention and high flux

Membrane separation technology is widely recognized as an effective method for removing perfluoroalkyl substances (PFASs) in water treatment. ZIF-L, a metal-organic framework (MOF) family characterized by its mat-like cavities and leaf-like morphology, has garnered considerable interest and has been extensively employed in fabricating thin-film nanocomposite (TFN) membranes. In this study, a robust, high-performance TFN membrane to remove PFASs in a nanofiltration (NF) process was created through an interfacial polymerization approach on the surface of polysulfone (PSF), incorporating ZIF-L within the selective layer. The TFN membrane modified by adding 5 wt% ZIF-L (relative to the weight of ethylene imine polymer (PEI)) exhibits 2.3 times higher water flux (up to 47.56 L·m−2·h−1·bar−1) than the pristine thin film composite membrane (20.46 L·m−2·h−1·bar−1), and the rejection for typical PFASs were above 95 % (98.47 % for perfluorooctanesulfonic acid (PFOS) and 95.85 % for perfluorooctanoic acid (PFOA)). The effectiveness of the ZIF-L/PEI TFN membrane in retaining representative PFASs was examined under various conditions, including different pressures, feed concentrations, aqueous environments, and salt ions. Notably, the experiments demonstrated that even after contamination with humic acid (HA), >88 % of the water flux could be restored by washing. Additionally, density functional theory (DFT) calculations were employed to predict the distinct intermolecular interactions between PFASs and ZIF-L as well as PEI. These calculations provide additional insights into the interception mechanism of TFN membranes towards PFASs. Based on this study, TFN membranes incorporating MOF as nanofillers show great potential as an effective method for purifying PFASs from aqueous environments and possess superior environmental sustainability and cost-effectiveness.

Sulfonated Cobalt Metal-Organic Framework Embedded Mixed Matrix Membrane towards Fuel-Cell Applications.

New strategies for enhancement of the fuel-cell performance of a poly(2,5-benzimidazole) (ABPBI) membrane loaded with a functionalized cobalt-based metal-organic framework (MOF) for H2-O2 fuel cells. ABPBI was prepared using the polycondensation method, and various proportions of sulfonated cobalt MOF (sCo-MOF) were incorporated into ABPBI to fabricate a proton-exchange membrane (PEM). Later, the fabricated membranes were soaked in 1 M sulfuric acid to produce sulfonated PEMs. The developed composite membranes had increased proton conductivity, tensile strength, physicochemical properties, and fuel-cell performance compared to the sulfonated ABPBI (sABPBI) membrane. A membrane embedded with 4 wt % sCo-MOF shows higher water uptake and ion-exchange capacity values of 23.25% and 2.89 mequiv g-1, respectively. The membrane electrode assemblies were fabricated to perform unit-cell tests for both sABPBI and 4 wt % sCo-MOF/sABPBI membranes. The 4 wt % sCo-MOF-loaded sABPBI membrane demonstrated good unit-cell performance in the fuel-cell test, with a power density of 415.8 mW cm-2 at 80 °C, superior to the pristine sABPBI membrane's power density of 178.6 mW cm-2.

Controlled architecture of multi-defense anti-fouling forward osmosis membrane for efficient shale gas wastewater treatment

Forward osmosis (FO) membrane process facilitates effective treatment of shale gas wastewater (SGW) due to its tolerance to high salinity and exceptional separation performance. However, serious membrane fouling remains a challenge regarding the complexity of realistic SGW. To address the fouling issues, controlled block copolymer architecture was constructed on the FO membrane surface to achieve combined effect of oil-resistance, self-regenerating, and fouling mitigation. In the modification process, zwitterionic polymer with strong hydrophilicity and fluoropolymers with low surface energy were successively grafted to the membrane active layer by atom transfer radical polymerization. The outermost fluoropolymer layer with low surface energy imparts the membrane with anti-oil and self-regenerating capabilities. Meanwhile, the strong hydration effect of the zwitterionic polymer ensures that nonspecific foulants breaking through the outermost defense are kept away from the membrane surface. According to the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the modified FO membrane exhibited a significantly higher total interaction energy (ΔGTOT) compared to the pristine membrane when exposed to various types of model foulants (bovine serum albumin, humic acid, sodium alginate, mineral oil). Furthermore, the advantage of having multiple defense mechanisms was further substantiated through dynamic filtration tests with realistic SGW. In comparison to the pristine TFC membrane, the modified membrane not only experienced a much smaller decrease in water flux (reduced by 52%) during fouling but also an exceptional flux recovery after cleaning (∼97%). These findings underscore that the modified FO membranes greatly mitigated membrane fouling associated with SGW through the synergistic interplay between a zwitterionic polymer and a low surface energy material, highlighting its promising potential in SGW treatment via membrane technology.

Cerium based metal-organic framework as the efficient radical quencher for proton exchange membrane fuel cells

Durability is one of the most key problems for the widespread commercialization of proton exchange membrane fuel cells (PEMFCs). Proton exchange membranes (PEMs) are pivotal components of the PEMFCs and their chemical stability is thus an important for the PEMFCs reliability. The incorporation of Ce-based radical quenchers such as ceria in PEMs can obviously alleviate the chemical deterioration of PEMs. Nevertheless, cell performance may decrease due to the presence of Ce-based radical quenchers. Therefore, a trade-off between cell performance and chemical stability of Ce-based radical quenchers containing PEM appears. To solve this issue, we developed a Ce-based metal organic framework Ce-BTC MOF with high radical trapping and proton-conducting properties. The Ce-BTC MOFs are introduced into the PFSA membrane to enhance the chemical stability and proton conductivity of the PFSA membrane. The PFSA/Ce-BTC membrane showed a maximum power density of 1.71 W/cm2 at 75 °C under 80％RH. After OCV test, PFSA/Ce-BTC membrane exhibited a decay of 0.56 mV/h after 120 h; pristine PFSA and Nafion membrane exhibited accelerated decay (for pristine PFSA, 1.72 mV/h; for Nafion membrane, 2.36 mV/h). Therefore, introduction of Ce-BTC MOFs offers an active defence approach to enhance the chemical stability of PEMFCs without sacrificing their cell performance.

Zeta potential characterization of the effects of fouling and cleaning of hollow fibre forwards osmosis membrane modules

Commercial Aquaporin Inside® hollow fibre forward osmosis (HFFO) membranes embedded in lab-scale filtration modules were employed to study their fouling propensity during forward osmosis (FO) up-concentration of a fermentation broth resulting from vaccine production. The fouling and subsequent cleaning processes were analysed in terms of the lumen side active layer zeta potential of the HFFO membranes. The zeta potential indicated significant adsorption of contaminants from the feed solution on the membrane's active surface. Various cleaning conditions: alkaline, alkaline + surfactant, complexation and acidic (hydrochloric and citric), were used to investigate the potential enhancement of contaminant removal compared to a simple rinse with deionized water. Despite a full recovery of the membrane performance after cleaning, the zeta potential measurements indicated contaminants remaining on the membrane surface. The extent of this residual contamination depends strongly on the applied cleaning conditions. Rinsing with deionized water and alkaline cleaning (with or without surfactant) results in a shift in the fouled membrane isoelectric point (IEP) with a concomitant shift of the zeta potential towards the IEP and zeta potential of the pristine membrane. However, cleaning with either the complexation agent or under acidic conditions exhibits a more negative zeta potential of the fouled HFFO membranes compared to the pristine membrane, indicating an additional effect superimposed on the removal of organic contaminants.

A homogeneous carbon nitride nanomodifier for promoting the water permeation of polyamide desalination membranes

Nanomaterial modification provides an effective way to enhance the separation performance of nanofiltration membranes, but the limited hydrophilicity of conventional nanostructures causes their poor solubility in solvents, affecting the quality of polyamide membranes for performance enhancement. Herein, we explored quasi-water soluble carbon nitride as a homogeneous modifier to improve the nanofiltration performance of polyamide membranes. With sufficient hydroxyl, amino, and cyano groups, the introduced quasi-water soluble carbon nitride significantly enhanced the surface hydrophilicity of the support membrane, resulting in the formation of an ultrathin functional layer for high-efficiency desalination. The high permeation flux of 108.64 L m-2h−1 (4 bar) was even twice and three times higher than those of the pristine polyamide membrane and commercial nanofiltration membranes, with a high Na2SO4 barrier rate of 98.84 % and a Cl-/SO42- selectivity of 76. This work provides an effective way to precisely regulate the structure of nanofiltration membranes for high-performance water purification.

Energy system for evaluation of modification methods on energy transfer efficiency and optimization of membranes

Saving energy is crucial for utilizing membrane technology, but there is no energy parameter for understanding the relationships among membrane performance and energy. Here, φ is defined as the energy transfer efficiency of the membrane, and its numerical expression of membrane performance is poor (e.g., in the range of 10−23). The method of modifying membranes is a crucial determinant for developing membrane science, but researchers using current parameters to evaluate modification methods might lead to erroneous conclusions. Hence, the newly established system θ is used to analyze the influence of different modification methods on energy consumption, which not only establish the relationship between different modification methods but also provide the research routes for future optimization methods. The main conclusions are as follows: (1) The current modification methods influence on the energy transfer efficiency of the pristine membrane by about 0.4902–3.278 × 104 times; (2) Using scientific data certifies that the modified support layer of the membranes is a more effective method for reducing the energy consumption than the modified activity layer of the membranes; (3) The establishment of this system provides data support for analyzing the advantages and disadvantages of modification methods, and provides guidance for how to optimize the modification methods of membranes. Therefore, this study not only fills key knowledge gaps in membrane science, but also provides theoretical support for how to optimize membrane modification methods.

Biomass-based mixed matrix membrane adsorbers for removal of creatinine in dialysate fluid

Dialysate fluid is a vital component in hemodialysis therapy. Processing and reusing spent dialysate in hemodialysis significantly reduces costs and produces environmentally friendly hemodialysis. In this research, mixed matrix membrane adsorbers (MMMAs), which have the potential to recycle spent dialysate, have been developed. MMMA is composed of cellulose acetate (CA)-based polymers synthesized from cellulose isolated from oil palm empty fruit bunches (OPEFB) and integrated with silica (Si) bio-adsorbent from rice husk ash waste. The membrane was cast using the phase inversion method to form MMMAs CA-Si. The MMMAs CA-Si has a porous structure with evenly distributed silica particles. The pristine CA membranes had swelling and porosity degrees of 38.89 % and 21.23 %, while the MMMAs CA-Si had swelling and porosity degrees of 41.43 % and 27.81 %, respectively. The pristine CA membrane had a clean water flux of 86.86 L/m2h, while the MMMAs CA-Si membrane had a 96.25 L/m2h clean water flux. The MMMAs CA-Si has a tensile strength of 15.89 (Kgf/mm2) and an elongation of 14.01 %. The pristine CA membrane had a creatinine adsorption capacity of 2.8 mg/g, while the CA-Si MMMAs membrane had a maximum adsorption capacity of 9.98 mg/g. The maximum adsorption capacity (qm) is 9.98 mg/g MMMAs, equivalent to 24.95 mg creatinine/g silica in MMMAs and the dissociation constant (Kd) value is 1.91 mg/L. Creatinine can be removed from the dialysate through a continuous flow dialysis process using MMMAs CA-Si with a total removal of 10.48 mg/g or above 66.45 %. Creatinine can also be filtered by cross-flow circulation, and the total creatinine removal is above 81.0 %. MMMAs CA-Si can be an alternative separation medium to remove creatinine in the dialysate.

Nanofiltration membrane with surface nanostructure induced by interfacial modification for heavy metal ions removal, salt selection and antibacterial

Positively charged nanofiltration membranes offer promising options for the removal of heavy metal ions. However, their electrical properties often lead to serious drawbacks such as impaired filtration performance and poor fouling resistance, thus further modification of these positively charged membranes are imperative. Herein, we report the interfacial manipulation of nanofiltration membranes using a hydroxyl monomer (β-cyclodextrin) in concert with the typical positively charged ammonia monomer (polyethyleneimine) to achieve efficient removal of heavy metals, improved perm-selectivity and fouling resistance. The results indicated that water flux of the modified membrane was increased by over 2-folds owing to structural modification compared with pristine membrane. The charge effects and enhanced cross-linking improve the rejection of salts ions, especially divalent ions. The topological and Turing-structured membranes reached 99.9% removal of heavy metal ions due to the combination of adsorption, complexation, Donnan and site resistance effects, and has excellent stability. Additionally, the functionalized membranes exhibited reduced adhesion and survival of bacteria on the surface based on the excellent bacteriostatic and hydrophilicity properties. These findings revealed the mechanism of interfacial modification induction on the nanostructure and properties of membranes and provided an efficient solution for the synthesis of multifunctional membranes.

Improving dye removal ability and fouling resistance of thin‐film nanocomposite nanofiltration membranes using a new citric acid functionalized FSM‐16 mesoporous

AbstractThe development of superior thin‐film nanocomposite (TFN) membranes with good separation performance and anti‐fouling capacity is required to address the larger‐scale freshwater need. In this study, a new citric acid‐functionalized FSM‐16 (CA‐FSM‐16) mesoporous was successfully synthesized and characterized. Subsequently, it was introduced on the surface of the sodium hydroxide/cyanuric chloride‐activated PES membrane to fabricate the CA‐FSM‐16 TFN membrane. It was investigated how various CA‐FSM‐16 loadings affected the overall physicochemical characteristics and performance of the membrane. The SEM analysis confirmed the TFN structure of the fabricated membranes. All manufactured membranes displayed improved hydrophilicity and flux. For the pristine membrane, the salt (Na2SO4) rejection was measured 73.20 ± 2.10%, whereas for the TFN‐0.08 membrane, it was measured 91.40 ± 1.80%. The dye rejection experiment in cross‐flow filtration showed that the TFN‐0.08 membrane had the maximum licorice retention among the membranes (99.10 ± 2.00%). In addition, the CA‐FSM‐16 TFN membranes demonstrated superior antifouling performance, especially the optimum membrane (TFN‐0.08), which showed a high flux recovery ratio (FRR) of 97.10 ± 1.90% and a low irreversible fouling ratio (DRir) of 2.90%. The introduction of CA‐FSM‐16 on the surface of the PES membrane via the surface modification method was a potentially useful technology to fabricate a high‐performing TFN membrane for water treatment applications.

Enhanced proton conductivity of sulfonated poly(ether ether ketone) membranes by constructing cation‐π through doping ammonium ionic liquid and graphene oxide

AbstractIn this paper, sulfonic acid functionalized benzothiazole ionic liquid ([(CH2)3SO3HBth] [H2PO4]) and graphene oxide were combined together through the cation‐π. The sulfonated poly (ether ether ketone) was doped with ionic liquid‐modified GO (IL‐GO) to prepare the SPEEK/IL‐GO composite membrane through the solution casting method. The SO3H and benzothiazole rings act as both proton acceptors and proton donors during proton transport and can replace the role of water in medium‐ and high‐temperature environments, increasing the proton transport sites to a certain extent and increasing the proton conductivity of the SPEEK/IL‐GO composite membrane. The proton conductivity of the SPEEK/IL‐GO‐2 composite membrane achieved an 18.02 mS/cm at 120°C, which is 2.43 times higher than that of the pristine SPEEK membrane. This paper provided a method for increasing proton conductivity and limiting IL loss of the SPEEK membrane.Highlights [(CH2)3SO3HBth][H2PO4] and graphene oxide were combined through cation‐π. The benzothiazole ring and SO3H form acid–base pairs. The proton conductivity of SPEEK/IL‐GO‐2 membrane achieved 18.02 mS/cm.

From environmental issue to purification aid: Novel positively charged functionalized algal biochar as robust modifier of composite nanofiltration membranes

Robust membrane modifiers were achieved for the first time by functionalizing the algal biochar of unique porous structure. The biochar was prepared through the pyrolysis of Cladophora glomerata, the most widespread freshwater macroalga, functionalized by diethylenetriamine and dendrimer poly(amidoamine), and employed to fabricate positively charged composite nanofiltration membranes. The presence of hydrophilic functionalizers of positive charge on the membrane was verified through Fourier transform infrared and energy dispersive X-ray analyses and atomic force microscopy and zeta potential measurements were performed to determine surface roughness and confirm positive charge of the modified membranes. Dispersion of modifiers on the surface and morphology of the were also revealed through field-emission scanning electron microscopy images. It has shown that, compared to the pristine membrane, pure water fluxes were increased by 214% and 185%, and water contact angles were reduced from 66.1° to 39.5° and 43.3° in those modified by biochar functionalized with dendrimer poly(amidoamine) and diethylenetriamine, respectively. More than 90% dye rejections and salt and heavy metals removals were recorded for the membranes possessed 0.6 wt% of modifiers. Finally, a comparative study conducted between the novel modifier introduced in this study and those reported in the literature, indicated that C. glomerata biochar decorated with amine functional groups could be considered as a robust and practical alternative to the common modifiers used to manipulate nanocomposite membranes characteristics.

Metal-organic framework-intercalated graphene oxide nanofiltration membranes for enhanced treatment of wastewater effluents

Graphene oxide membranes (GO) hold immense potential in the field of water purification. However, when applied directly to real wastewater effluents, pure GO membranes suffer from drawbacks such as fouling sensitivity and limited stability. To address these challenges and unlock the full potential of GO membranes, novel nanocomposite membranes have been developed by the intercalation of GO with nanoparticles of ZIF-8 (a type of zeolitic imidazolate framework). The prepared GO/ZIF-8 (GZ) nanocomposite membranes have exhibited enhanced hydrophilicity and exceptional water purification capabilities. Specifically, the GZ membranes have demonstrated a permeance enhancement of over two-fold when compared to the pristine GO reference membrane. This enhancement is coupled with anti-fouling performance and competitive rejection rates for both salts and organic pollutants. GZ membranes have been effectively employed for the purification by cross-flow filtration of 3 industrial wastewater effluents. They have shown improved separation performance compared to the pristine GO reference membrane, and high stability under cross-flow conditions. The origin of the high performances of the GZ membrane has been clarified using structural and morphological analyses. This work highlights the significant progress made in the field of water treatment using graphene-based membranes.

Enhanced photogenic self-cleaning of superhydrophilic Al2O3@GO-TiO2 ceramic membranes for efficient separation of oil-in-water emulsions

In the emulsion separation process, the adhesion of oil-contamination severely hampers the long-term operation of ceramic membranes, and photocatalytic membranes present a promising approach to mitigate membrane fouling and enhance membrane performance. The present study describes the fabrication of a novel Al2O3@GO-TiO2 composite photocatalytic membrane through a two-step dip-coating method. TiO2 particles were uniformly deposited onto the surface of the pristine membrane via a thermal coating method, while the pleated graphene oxide (GO) formed a laminar-flow-like coating through stirring-ultrasonication, ultimately being stably anchored to the composite membrane's surface by co-built connections with TiO2. Due to the successful coating of hydrophilic groups, the composite membrane exhibited super hydrophilic-underwater superoleophobic properties to separate stable water-in-diesel emulsions with excellent permeation flux (4347.17 L∙m−2∙h−1) and oil removal rate (94.98 %). The composite membrane showed excellent oil resistance stability and durability in severe environment hydrodynamic washout and cycling tests. In addition, the combined modification of GO-TiO2 endowed the composite membranes with strong photocatalytic ability, which made the membranes exhibit a good recovery of membrane performance in the separation of oilfield-produced water (OPW). The thick oil layer was completely removed by •OH, •O2– and 1O2 generated by UV irradiation excitation. After 6 h of operation, the flux and oil removal rate of the Al2O3@GO-TiO2 membrane were 31.91 % and 2.1 % higher than those of the Al2O3@TiO2 membrane, demonstrating enhanced light self-cleaning performance. The exceptional oil–water separation capability coupled with its efficient photocatalytic degradation potential positions the ceramic membrane as a promising solution for treating actual OPW.

Rejection of malathion by nanofiltration and reverse osmosis membranes exposed to foulant and two clean-in-place procedures

ABSTRACT This research tested the treatment efficacy of an Energy Savings Nanofiltration 1 Low Fouling (ESNA 1-LF) nanofiltration (NF) and an Energy Saving Polyamide 2 (ESPA2) reverse osmosis (RO) membrane for removing malathion from water. Both membranes are of composite polyamide construction. The study included measuring malathion rejection using both pristine membranes and membranes exposed to a simulated secondary wastewater effluent foulant before and after two types of clean-in-place procedures. Across all conditions studied, malathion rejection ranged from 84 to 95% for the ESNA1-LF NF membrane and 77 to 94% for the ESPA2 RO membrane. Contact angle measurements were also collected for each membrane exposure condition. While the contact angle measurements indicated changes to the hydrophobicity of the selective layer of the membranes, they did not correlate to changes in the performance of malathion rejection. As expected, it was observed that malathion rejection improved with the introduction of foulant. Also, the clean-in-place procedures helped restore flux while maintaining malathion rejection.

Incorporation of multilayered double hydroxides/sepiolite augments proton conductivity performance in low sulfonated polyether sulfone octyl sulfonamide

AbstractLow-sulfonation-level polyether sulfone octyl sulfonamide (LSPSO) was blended with a layered double hydroxides (LDHs, Mg2AlCl)/sepiolite nanostructure clay as a filler to create an electrolyte membrane for fuel cell applications. Comprehensive characterization of the composite membranes was conducted, encompassing Fourier-transform infrared spectroscopy, X-ray diffraction, mechanical stability assessment, thermal gravimetric analysis, ion exchange capability, swelling characteristics, water uptake performance, and electrochemical impedance spectroscopy analysis. In comparison to the pristine LSPSO membrane, the presence of LDHs/sepiolite nanoarchitecture material within LSPSO exhibited superior water retention and proton conductivity values, especially at elevated temperatures. The proton conductivity of the composite membranes reached approximately 250 mS/cm, while the unmodified LSPSO membrane only achieved 35 mS/cm at 100 °C. Moreover, LSPSO composite membranes demonstrated enhanced chemical and thermal stability along with higher proton conductivity when compared to pristine LSPSO membranes. These findings highlight the potential of developing tailored LSPSO composite membranes to advance the prospects of commercial applications in proton exchange membrane fuel cells.

Utilization of cellulose-based carbon nanodots in sulfonated polysulfone based membrane for direct methanol fuel cell

Sulfonated polysulfone (SPS) composite membranes consisting of cellulose-based carbon nanodots (CNDs) were successfully prepared as a proton exchange membrane (PEM) for direct methanol fuel cell (DMFC) applications. The CNDs were prepared using the top-down hydrothermal method. The structure transformation from cellulose to CNDs was confirmed by the FTIR and XRD analysis. The particle size of CNDs was between 1 and 3 nm. The particles exhibited good optical properties. The incorporation of CND into matrix polymer increased the thermal stability of the membranes. Morphology analysis of the SPS/CND composite membranes revealed that CNDs had been successfully dispersed within the SPS polymer matrix. The cross-linking between SPS and CNDs enhanced the proton conductivity of the composite membranes compared to the pristine SPS membrane. The SPS/CND-1 (1 wt%) exhibited the highest selectivity with a proton conductivity of 35.5 mS.cm−1 and a methanol permeability of 3.50 × 10−6 cm2.s−1. The experimental results indicate that the incorporation of CNDs into the SPS membrane also decreased the amount of methanol that can pass through the membrane when used in DMFCs.

Preparation and Characterization of Electrospun EVOH/Ti3C2 Composite Fibers.

In this work, the EVOH/Ti3C2 composite fibers were prepared via electrospinning and the effect of added Ti3C2 on the structure and properties of electrospun EVOH fibrous membranes was further investigated. The morphology, crystal structure, thermal properties, wettability, tensile properties, as well as air permeability and water vapor permeability of as-prepared EVOH/Ti3C2 composite fibers were studied. The Ti3C2 is uniformly loaded onto the surface and inside the composite fiber and affects the fiber diameters. Furthermore, The Ti3C2 self-orients along the fiber axis and does not change the crystal structure of the electrospun EVOH fibers, improving the crystallinity and thermal stability of the electrospun EVOH/Ti3C2 fibrous membranes. With the increase in the Ti3C2 concentration in the electrospinning polymer solution, the addition of Ti3C2 not only rapidly improves the wettability of the fibrous membranes, but also enhances their air permeability, compared with the pristine electrospun EVOH fibrous membranes. The experimental results provide theoretical guidance for the preparation of Ti3C2 composite fibers, and also expand the application of electrospun EVOH and EVOH/Ti3C2 fibrous membranes.

Polyphenol-mediated defect patching of graphene oxide membranes for sulfonamide contaminants removal and fouling control

Graphene oxide (GO)-based laminar membranes are promising candidates for next-generation nanofiltration membranes because of their theoretically frictionless nanochannels. However, nonuniform stacking during the filtration process and the inherent swelling of GO nanosheets generate horizontal and vertical defects, leading to a low selectivity and susceptibility to pore blockage. Herein, both types of defects are simultaneously patching by utilizing tannic acid and FeⅢ. Tannic acid first partially reduced the upper GO framework, and then coordinated with FeⅢ to form a metal-polyphenol network covering horizontal defects. Due to the enhanced steric hindrance, the resulting membrane exhibited a two-fold increase in sulfonamide contaminants exclusion compared to the pristine GO membrane. A non-significant reduction in permeance was observed. In terms of fouling control, shielding defects significantly alleviated the irreversible pore blockage of the membrane. Additionally, the hydrophilic metal-polyphenol network weakened the adhesion force between the membrane and foulants, thereby improving the reversibility of fouling in the cleaning stage. This work opens up a new way to develop GO-based membranes with enhanced separation performance and antifouling ability.