Asymmetric Membrane Structure Research Articles

Structure of symmetric and asymmetric lipid membranes from joint SAXS/SANS.

Small-angle X-ray and neutron scattering (SAXS/SANS) techniques excel in unveiling intricate details of the internal structure of lipid membranes under physiologically relevant temperature and buffer conditions, all without the need to resort to bulky labels. By concurrently conducting and analyzing neutron and X-ray data, these methods harness the complete spectrum of contrast and resolution from various components constituting lipid membranes. Despite this, the literature exhibits only a sparse presence of applications compared to other techniques in membrane biophysics. This chapter serves as a primer for conducting joint SAXS/SANS analyses on symmetric and asymmetric large unilamellar vesicles, elucidating fundamental elements of the analysis process. Specifically, we introduce the basics of interactions of X-rays and neutrons with matter that lead to the scattering contrast and a description of membrane structure in terms of scattering length density profiles. These profiles allow fitting of the experimentally observed scattering intensity. We further integrate practical insights, unveiling strategies for successful data acquisition and providing a comprehensive assessment of the technique's advantages and drawbacks. By amalgamating theoretical underpinnings with practical considerations, this chapter aims to dismantle barriers hindering the adoption of joint SAXS/SANS approaches, thereby encouraging an influx of studies in this domain.

Dynamics of Janus vesicles passing through a narrow pore

Janus vesicles have garnered significant attention due to their versatility and potential applications. Investigating the perforation dynamics of Janus vesicles represents a fundamental physical inquiry in this distinctive structure and helps to understand their promising applications in drug delivery, biomedicine, and others. However, the perforation kinetic behavior of Janus vesicles has yet to be elaborated. Here, we employ the finite element method to explore the dynamics of Janus vesicles passing through a narrow pore in a microchannel. Results demonstrate that Janus vesicles, characterized by their asymmetric membrane structure, have a non-negligible effect on vesicle deformation while crossing the pore. Specifically, the Janus property strengthens membrane deformation on the low modulus side while weakening it on the high modulus side. Additionally, Janus vesicles exhibit an increased perforation speed. Results further determine that the non-axially positioned Janus vesicles experience a bigger rotation angle than uniform modulus vesicles by constructing the rotation angle θ. This research provides valuable insight into the movement and deformation of Janus vesicles during their passage through a pore, which can guide optimization and design of Janus vesicles for drug carriers, catalysis, and more.

Large Scalable High Ion Conductive and Selective Double Layer Membrane Achieved through Dual Ion Conducting Mechanisms

As the share of sustainable energy sources in the electricity supply rises, large-scale energy storage becomes increasingly important. All vanadium flow batteries, as one of the most promising large-scale energy storage methods, have reached the commercialization stage because of their unique feature of uncoupling power and energy, as well as the advantages of long life, high safety, and low cost. The ion-selective membrane is an essential part of flow batteries, which allows specific ions to pass through to maintain a neutral charge and prevents the crossover of active species to maintain the capacity. However, the high cost and low ion-selectivity of the commercialized ion-selective membranes (i.e., Nafion membranes) hindered the further promotion of the flow batteries. Herein, we developed a large scalable double-layer ion selectivity membrane with a unique bifunctional nanoporous boron nitride (PBN) ion selective layer and a low-cost porous polyetherimide (PEI) ion conductivity and support layer. PBN was synthesized by a large scalable template-free method, which was further decorated with Nafion resin. The nano-sized and tortuous pores of the PBN can effectively block the crossover of vanadium ions and provide excellent ion selectivity based on the pore size exclusion mechanism. Furthermore, the super-acidic sulfonic acid groups of Nafion decorated on the nanoporous structure of PBN provide high-speed proton transfer channels that increase proton conductivity through both Grotthuss and vehicle mechanisms. The low-cost porous PEI ion conductivity and support layer was prepared by the phase separation method. The well-aligned asymmetric finger-like porous structure of the PEI membrane provides excellent ion conductivity. The addition of a hydrophilic polymer additive, polyvinylpyrrolidone, further increased its ion conductivity. The PBN–PEI double layer membrane, prepared by a simple spray coating method, demonstrated an excellent ion selectivity (1.49×108 mS cm−3 min), which is almost 15 times higher than that of the pristine PEI membrane (6.71×106 mS cm−3 min) while maintaining high ion conductivity (64 mS cm−1). The PBN–PEI membrane achieved superior performance (97% of coulombic efficiency, 94% of voltage efficiency, and 91% of energy efficiency at 40 mA cm−2) than the Nafion 115 membrane in the all-vanadium flow battery with higher discharge capacity at all current densities and high stability with a lower capacity fading rate (0.17% per cycle vs. 0.74% per cycle at 100 mA cm−2). The PBN–PEI membrane also demonstrated a stable operation in the all-vanadium flow battery at a current density of 100 mA cm−2 over 700 cycles. The work presented the remarkable performance of the ultra-thin PBN bifunctional layer in terms of ion conductivity and selectivity; the combination with the low-cost high ion-conductive porous PEI membrane and a simple fabrication process demonstrated a great potential for commercialization of the PBN-PEI double-layer membrane.

Cellulose Acetate Hollow Fiber Membranes for Forward Osmosis Using the Green Solvent Agnique AMD 3 L

A set of cellulose acetate (CA) hollow fiber membranes is manufactured by using a variation of CA (20–25 wt %) and different weight ratios of acetone and the green solvent Agnique AMD 3 L (3:2, 1:1, 2:3) in dope solutions (DS). The DSs are spun combining an evaporation and non-solvent-induced phase separation (EIPS–NIPS) process. The obtained hollow fibers (HF) annealed in either water (95 °C) or humid air (95 °C, 98% relative humidity) reveal an asymmetric membrane structure with a dense layer on the shell side and a molecular weight cutoff down to 100 g mol–1. Regarding the use of forward osmosis (FO), the hollow fibers are tested with aqueous NaCl (1 M) as draw solution in the lumen of the fibers and ultra-pure water as feed at the shell side. With a decreasing amount of acetone in the DSs, an increase in water flux from 2.0 L m–2 h–1 (LMH) to 6.2 LMH and a reverse salt flux from 0.5 g m–2 h–1 (GMH) to 13.3 GMH of the HF annealed in water are found. When annealing in humid air, the water flux of the HF increases from 2.0 to 4.5 LMH and a reverse salt flux from 0.5 to 4.1 GMH occurs, compared to annealing in water. Decreasing the NaCl concentration to 0.5 M, an increase in the performance ratio up to 17.9% is given, which is in the same range of commercially available cellulose ester-based HFs for FO.

Multilevel hierarchical super-hydrophobic ceramic membrane for water-in-oil emulsion separation

Hierarchical silicon nitride (Si3N4) membranes were fabricated by catalytic growth of α-Si3N4 nanowires onto the rod-like β-Si3N4 grains. Compared to the bare asymmetric structure of β-Si3N4 membranes, the average pore size reduced from 0.9 µm to 0.67 µm, while the porosity decreased slightly from 47 ± 0.6% to 45.3 ± 1.1%. Inorganic nanoparticles derived from organosilane were used to further modify the membranes. The membranes displayed super-hydrophobic characteristics with a water contact angle of 155 ± 1° due to the multilevel hierarchical structure and the -Si-CH3 low energy terminal groups. The super-hydrophobic membranes were successfully applied for the water-in-oil emulsion separation process. At various driving pressures, the water rejection of the water-in-oil emulsion was higher than 95%. This work's durable super-hydrophobic ceramic membrane has promise for the purification of a variety of oil products.

Chemical cleaning and membrane aging of poly(vinylidene fluoride) (PVDF) membranes fabricated via non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS)

Poly(vinylidene fluoride) (PVDF) is one of the most used membrane materials in the water industries, and the PVDF membrane can be fabricated majorly through non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS). The differences in membrane aging of NIPS-PVDF and TIPS-PVDF remain unclear. In this study, the agings of commercially available NIPS-PVDF and TIPS-PVDF membranes were investigated in the pilot-scale MBRs experiment as well as in the batch soaking tests. The raw PVDF powders in different crystalline polymorphs were also subjected to aging tests to examine the relation between PVDF polymorphous structure and aging. The results showed that the NIPS-PVDF membrane experienced more severe aging in the pilot-scale MBR experiment in comparison with the TIPS-PVDF membrane. Acid aging dislodged and eliminated the additives in the membrane, but did not attack the PVDF. NIPS-PVDF membrane was the dominant β PVDF phase, which was more susceptible to dehydrochlorination in alkaline oxide aging. The thin top layer in the asymmetric structure of the NIPS-PVDF membrane resulted in its vulnerability against alkaline oxide aging. The α PVDF phase and the symmetric structure of the TIPS-PVDF membrane contributed to its greater stability in alkaline oxide aging. Overall, the results can provide a basis for selecting a chemical cleaning strategy for PVDF membranes, and for improving the anti-aging characteristics of the PVDF in the membrane fabrication.

Antimony Nanobelt Asymmetric Membranes for High Capacity Sodium Ion Battery Anodes

The standard lithium-ion battery (LIB) using graphite electrodes has become exceedingly important in today’s world. Everything from electric cars to solar energy storage systems need these batteries, and the capabilities and progress of these devices rely on the steady advancement of battery technology. However, lithium is a scarce resource and is projected to run out with the ever-increasing demand we are placing on it. For this reason, we are investigating sodium ion batteries (SIB) as an alternative to LIB.While many methods have been studied to improve SIB capacities and lifespans, our method stands out by using antimony nanobelts incorporated into an asymmetric membrane structure as a high performance anode material for SIB due to its theoretical capacity of 660 mAh g-1 compared to hard carbon-based SIB (300 mAh g-1). In addition to the asymmetric membrane structure, we use a carbon coating around the membrane which can further improve performance and stability. Embedding these group V nanomaterials within an asymmetric membrane structure coated in carbon will accommodate the large volume expansion of Sb-based SIB anode, enhance mechanical strength, and prevent rapid capacity loss due to leaching of cracked materials.Herein, we demonstrate that the capacity and the cycling performance of SIB can be significantly improved over not only current SIB but also LIB. Preliminary results indicate that Sb nanobelts incorporated into an asymmetric membrane exhibit increased performance as a sodium-ion battery anode compared to Sb nanoparticle membranes, furthermore, dip coating the asymmetric membranes with a carbon based solution increases both capacity and cycling performance compared to membranes with no extra carbon coating. The batteries made using the dip coated Sb nanobelt asymmetric membranes show a specific capacity between 630 and 650 mAh g-1 with a capacity retention of 99.4 percent over 45 cycles and an initial capacity loss of only 14 percent. In addition to electrochemical tests, we have also characterized the samples using scanning electron microscopy, energy dispersive x-ray spectroscopy, thermal gravimetric analysis, powder x-ray diffraction spectroscopy, and RAMAN spectroscopy to identify and quantify the materials in the membranes and starting materials. Using these characterizations, we were able to confirm the chemical composition and morphology of the Sb and C in our membranes. Thereby a scalable and cost-effective method of increasing capacity of NIB, while maintaining relatively good life cycle longevity has been developed by our research laboratory.

Influence of NIPS on the structure and gas separation performance of asymmetric carbon molecular sieve membranes

Influence of NIPS on the structure and gas separation performance of asymmetric carbon molecular sieve membranes

Pattern Recognition and Modeling of Asymmetric Microporous Polymer Membrane Structure for the Bio-Separation of Viruses from Blood Cells

Pattern Recognition and Modeling of Asymmetric Microporous Polymer Membrane Structure for the Bio-Separation of Viruses from Blood Cells

Pattern Recognition and 3d Modeling of Asymmetric Microporous Polymer Membrane Structure for the Bio-Separation of Viruses from Blood Cells

Pattern Recognition and 3d Modeling of Asymmetric Microporous Polymer Membrane Structure for the Bio-Separation of Viruses from Blood Cells

A unified thermodynamic fouling mechanism based on forward osmosis membrane unique properties: An asymmetric structure and reverse solute diffusion

Fouling mechanism of the forward osmosis membrane, which was peculiarly featured by the asymmetric membrane structure and reverse solute diffusion, was investigated at the molecular level and from the energy perspective. Two noteworthy fouling behaviors were observed in batch fouling tests conducted in AL-FS mode (active layer facing feed solution) and AL-DS mode (active layer facing draw solution) after filtering foulants with identical volume: 1) after filtering 100 mL of foulants, the flux decline rate in AL-DS mode was 1.78 times faster than that in AL-FS mode, but the flux decline behaviors of the two modes were similar in the subsequent filtration stages; 2) although the foulant layer weight of the same mode increased linearly in middle and late stages, the flux loss rate was distinctly different. Thermodynamic analysis indicated that the attractive interaction energy between the foulants and the support layer was about 5 times higher than that between the foulants and the active layer, well interpreting the higher flux decline rate of AL-DS mode in initial stage. Meanwhile, a non-invasive microscope observed that the structure of the fouling layer remarkably changed from loose to dense in the middle stage, and stabilized in the late stage. Furthermore, quantum chemistry calculation proved that the reverse diffusion of NaCl brought alginate molecular chains closer, whereas the distance between them tended to be constant as the continuous increase of NaCl. Based on these findings, the thermodynamic fouling mechanism proposed by combining the structure change process of the fouling layer with Flory-Huggins lattice theory satisfactorily interpreted the noteworthy fouling behaviors caused by reverse NaCl diffusion in middle and late stages. The revealed fouling mechanism unifies the adhesion and filtration behaviors related to the unique properties of FO membrane, deepening understanding of membrane fouling in the dynamic and complex ternary system of the FO process.

Fabrication and dialysis performance of functionalized multiwall carbon nanotubes integrated cellulose acetate/poly(vinylpyrrolidone) membranes

Mixed matrix membranes (MMMs) of cellulose acetate/poly(vinylpyrrolidone) (CA/PVP) infused with acid functionalized multiwall carbon nanotubes (f-MWCNTs) were fabricated by an immersion phase separation technique for hemodialysis application. Membranes were characterized using FTIR, water uptake, contact angle, TGA, DMA and SEM analysis. The FTIR was used to confirm the bonding interaction between CA/PVP membrane matrix and f-MWCNTs. Upon addition of f-MWCNTs, TGA thermograms and glass transition temperature indicated improved thermal stability of MMMs. The surface morphological analysis demonstrated revealed uniform distribution of f-MWCNTs and asymmetric membrane structure. The water uptake and contact angle confirmed that hydrophilicity was increased after incorporation of f-MWCNTs. The membranes demonstrated enhancement in water permeate flux, bovine serum albumin (BSA) rejection with the infusion of f-MWCNTs; whereas BSA based anti-fouling analysis using flux recovery ratio test shown up to 8.4% improvement. The urea and creatinine clearance performance of MMMs were evaluated by dialysis experiment. It has been found that f-MWCNTs integrated membranes demonstrated the higher urea and creatinine clearance with increase of 12.6% and 10.5% in comparison to the neat CA/PVP membrane. Thus, the prepared CA/PVP membranes embedded with f-MWCNTs can be employed for wide range of dialysis applications.

New Express Method of Non-Destructive Controlling of the Porous Structure of Asymmetric Membranes

An important practical and fundamental problem in the production of porous polymer membranes is the study of the porous structure and the detection of "defects" or large pores in the area of ​​the membrane. Known porosimetry methods cannot solve this problem. This work proposes a new non-destructive express method for studying the porous structure of asymmetric polymer membranes in high-intensity electric fields. This method can be successfully implemented on both flat sheet and hollow fiber membranes with a known porous structure. On the example of hollow fiber membranes made of polyacrylonitrile and polysulfone an assessment of the chemical structure effect of the membrane material on the high-voltage discharge currents in a highly inhomogeneous electric field through hollow fiber membranes with a given pore size was made. Under normal conditions and an average intensity of an inhomogeneous electric field E = 5 kV/cm, the results obtained allow us to conclude about a certain practical potential of the developed express method.

Asymmetric Lipid Membranes under Shear Flows: A Dissipative Particle Dynamics Study.

We investigate the phase behavior of the asymmetric lipid membranes under shear flows, using the dissipative particle dynamics simulation. Two cases, the weak and strong shear flows, are considered for the asymmetric lipid microstructures. Three typical asymmetric structures, the membranes, tubes, and vesicle, are included in the phase diagrams, where the effect of two different types of lipid chain length on the formation of asymmetric membranes is evaluated. The dynamic processes are demonstrated for the asymmetric membranes by calculating the average radius of gyration and shape factor. The result indicates that different shear flows will affect the shape of the second type of lipid molecules; the shape of the first type of lipid molecules is more stable than that of the second type of lipid molecules. The mechanical properties are investigated for the asymmetric membranes by analyzing the interface tension. The results reveal an absolute pressure at the junctions of different types of particles under the weak shear flow; the other positions are almost in a state of no pressure; there is almost no pressure inside the asymmetric lipid membrane structure under the strong shear flow. The findings will help us to understand the potential applications of asymmetric lipid microstructures in the biological and medical fields.

Development of a P84/ZCC Composite Carbon Membrane for Gas Separation of H2/CO2 and H2/CH4.

Hydrogen (H2) has become one of the promising alternative clean energy resources. Membrane technology is a potential method for hydrogen separation or production. This study aims to develop a new carbon membrane for hydrogen separation or production. Moreover, the permeation behavior of H2, CO2, and CH4 through a hollow fiber composite carbon membrane derived from P84 co-polyimide and with incorporation of zeolite composite carbon (ZCC) was also examined. ZCC was synthesized via the impregnation method of sucrose into zeolite-Y pores, followed by carbonization at 800 °C. Thus, this filler has a high surface area, high microporosity, ordered pore structure, and low hydrophilicity. The presence of zeolites in ZCC is predicted to increase certain gases’ affinity for the membrane. Various heating rates (1–5 °C/min) were applied during pyrolysis to understand the effect of the heating rate on the pore structure and H2/CO2 and H2/CH4 gas separation performance. Moreover, gas permeation was evaluated at various temperatures (298–373 K) to study the thermodynamic aspect of the process. A characteristic graphite peak was detected at 2θ ∼ 44° in all carbon samples. Scanning electron microscopy (SEM) observations revealed the void-free surface and the asymmetric structure of the carbon membranes. During the permeation test, it was found that gas permeation through the membrane was significantly affected by the temperature of the separation process. The highest permeability of H2, CO2, and CH4 was detected on the composite carbon membrane at a 3 °C/min heating rate with a permeation temperature of 373 K. The thermodynamic study shows that CO2 and H2 have lower activation energies compared to CH4. The transport mechanism of the membrane involved adsorption and activated surface diffusion. The permeation temperature has a large impact on the transport of small penetrants in the carbon matrix.

Effect of Asymmetric Membrane Structure on Hydrogen Transport Resistance and Performance of a Catalytic Membrane Reactor for Ethanol Steam Reforming.

The performance of catalytic membrane reactors (CMRs) depends on the specific details of interactions at different levels between catalytic and separation parts. A clear understanding of decisive factors affecting their operational parameters can be provided via mathematical simulations. In the present paper, main results of numerical studies of ethanol steam reforming, followed by downstream hydrogen permeation through an asymmetric supported membrane, are reported. The membrane module consists of a thin selective layer supported on a substrate with graded porous structure. One-dimensional isothermal reaction–transport model for the CMR has been developed, and its validation has been carried out by using performance data from a lab-scale reactor with a disk-shaped membrane. Simulations demonstrate the model’s capabilities to analyze local concentrations gradients, as required to provide accurate estimates of the relationship between structure–property–performance. It was shown that transport properties of multilayer asymmetric membranes are highly related to the structural properties of each single layer.

Tailoring the asymmetric structure of polyamide reverse osmosis membrane with self-assembled aromatic nanoparticles for high-efficient removal of organic micropollutants

Abstract The widespread occurrence of organic micropollutants (OMPs) in water has serious effects on the environment and human health. Recently, reverse osmosis (RO) membrane technology has been used for resolving this emerging concern, and the state-of-the-art polyamide RO membranes are normally fabricated by the interfacial polymerization method. Further reducing the energy consumption and operation cost, developing high-performance polyamide RO membranes will be the key for resolving the issue of effective removal of OMPs. Herein, a new strategy is proposed for fabricating robust and high-efficient polyamide RO membranes via the self-assembled aromatic nanoparticles (SANs) controlled interfacial polymerization (SANCIP) method. The membrane surface characteristics and interior microstructures of polyamide layer could be conveniently manipulated by regulating the SAN nanoparticles size and content. The SANs tuned polyamide membrane (PAM-SAN) with asymmetric structure, e.g., much looser and crumpled front surface and much denser and smooth rear surface, exhibits ultra-high water flux ~ 67.8 L∙m−2∙h−1 and satisfactory NaCl rejection (>98.3%), as well as very high OMPs rejection (>99.4%). Moreover, the PAM-SAN membrane has good stability and anti-fouling performance in long-term RO running process. This facile and cost-effective strategy provides a useful guideline in designing high-performance polyamide membranes with a vast potential in the removal of OMPs for advanced water treatment.

Studying the surfaces of bacteria using neutron scattering: finding new openings for antibiotics.

The use of neutrons as a scattering probe to investigate biological membranes has steadily grown in the past three decades, shedding light on the structure and behaviour of this ubiquitous and fundamental biological barrier. Meanwhile, the rise of antibiotic resistance has catalysed a renewed interest in understanding the mechanisms underlying the dynamics of antibiotics interaction with the bacterial cell envelope. It is widely recognised that the key reason behind the remarkable success of Gram-negative pathogens in developing antibiotic resistance lies in the effectiveness of their outer membrane (OM) in defending the cell from antibacterial compounds. Critical to its function, the highly asymmetric lipid distribution between the inner and outer bilayer leaflets of the OM, adds an extra level of complexity to the study of this crucial defence barrier. Here we review the opportunities offered by neutron scattering techniques, in particular reflectometry, to provide structural information on the interactions of antimicrobials with in vitro models of the OM. The differential sensitivity of neutrons towards hydrogen and deuterium makes them a unique probe to study the structure and behaviour of asymmetric membranes. Molecular-level understanding of the interactions between antimicrobials and the Gram-negative OM provides valuable insights that can aid drug development and broaden our knowledge of this critically important biological barrier.

Enlargement of oil droplets by using asymmetric structure of polyvinylidene fluoride membranes

This work demonstrates a study for enlarging the oil droplets by using the asymmetric polyvinylidene fluoride (PVDF) membranes in a cross-flow membrane filtration system. The membranes were fabricated from PVDF/DMA/LiCl: 10/88/2% wt. and coagulated in the ethanol solutions at concentrations of 0, 10, 20, and 30% v/v. The alkaline-surfactant-polymer (ASP) produced water was simulated and tested as the feed solutions. Results indicate that the variation of the ethanol concentrations did not affect the membrane porosity and thickness remarkably while control the membrane surface pore size significantly. The water permeation flux increased with the average membrane surface pore size when increasing the ethanol concentrations in the coagulation baths from 10 to 30% v/v. However, the membrane surface pore sizes have no notable effect on the enlargement of the oil droplets because at least 50% of the membrane pores were larger than the oil droplets in the feed solutions. Coalescence of the oil droplets did occur due to the tortuous pore structures of the asymmetric membranes especially when the filtration process was pressurized. At least 65% of the coalesced oil droplets in permeate having the diameters exceeding 1.0 μm. The resistance to the permeation increased with the transmembrane pressure due to more oil droplets accumulated on the membrane pores.

Development of Janus membrane with controllable asymmetric wettability for highly-efficient oil/water emulsions separation

Due to the given complexity and diversity of practical oily wastewater, developing highly-efficient separation materials with multifunctional and switchable separation property is urgently needed. To advance this emerging field, a functionalized surface silicification layer based Janus membrane with asymmetric wetting selectivity was developed onto the polyvinylidene fluoride (PVDF) substrate, via the hydrophobic 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFTS) modification (F–SiO2/PVDF) followed by a unilateral plasma-etching treatment (P–SiO2/PVDF). By precisely tuning the surface hierarchical nanosphere-like architecture of the silicification layer, a robust superhydrophobicity/superoleophilicity, and underwater superoleophobicity/superhydrophilicity of F–SiO2/PVDF and P–SiO2/PVDF surfaces were obtained, reaching an extremely opposing surface wettability with a high water/underwater oil contact angle (CA) difference up to 150°. Based on the exceptionally asymmetric wetting selectivity incorporated with the ultrathin silicification layer (with the thickness of 15 nm), the as-developed Janus membrane achieved a remarkable separation property with the surfactant-stabilized oil-in-water (O/W), and water-in-oil (W/O) emulsion permeances up to 7200 and 9300 Lm−2h−1bar−1, by accompanying with their high separation efficiencies up to 99.8% and 99.0%, respectively, which shows an overall oil/water separation property superior to the state-of-the-art Janus membranes reported so far. Moreover, it should be noted that the reusability of the Janus membrane also performed excellently, where a nearly 100% recovery ratio of permeating flux was obtained after several cycles of O/W and W/O emulsion filtration tests. Overall, this work provides a perspective to explore an asymmetric Janus membrane structure with promoted separation property for highly efficient oily wastewater treatment.