Membrane Material Research Articles

Stabilizing Bicontinuous Emulsions with Sub-Micrometer Domains Solely by Nanoparticles.

Nanoparticle-stabilized, bicontinuous interfacially jammed emulsion gels (bijels) find potential applications as battery, separation membrane, and chemical reactor materials. Decreasing the liquid domain sizes of bijels to sub-micrometer dimensions requires surfactants, complicating bijel synthesis and postprocessing into functional nanomaterials. This work introduces surfactant-free bijels with sub-micrometer domains, solely stabilized by nanoparticles. To this end, the covalent surface functionalization of silica nanoparticles is characterized by thermogravimetric analysis, mass spectrometry, Fourier-transform infrared spectroscopy, and contact angle measurements. Bijels are generated with the functionalized nanoparticles via solvent transfer induced phase separation (STrIPS), enabling the optimization of nanoparticle functionalization and surface ionization. Nanoparticles of intermediate functionalization and controlled negative surface charge stabilize bijels with sub-micrometer liquid domains. This remarkable control over bijel synthesis provides urgently needed progress to facilitate the widespread implementation of bijels as nanomaterials in research and applications.

Fabrication of high-performance pervaporation desalination composite membranes with study of its acid-base stability

In the process of industrial production will produce a lot of acid and alkaline waste liquid, how to effectively treat acid and alkali waste liquid is an important topic at present. At present, there are some problems about the treatment of acid and alkali waste liquid, such as large investment, complicated process and low efficiency. Pervaporation has the characteristics of mild operating conditions and no influence of osmotic pressure threshold, so it has great application potential in the concentration, reuse and reduction of acid and alkali waste liquid. However, at present, conventional pervaporation dense membrane materials cannot maintain long-term stability in strong acid and alkali environment, in order to achieve this performance, we use perfluorosulfonic acid resin with good acid and alkali resistance as the dense layer substrate. PFSA/PTFE/PP composite membrane was prepared by spraying process, and the final prepared composite membrane had a pure water flux of 45 ± 1.2 kg/(m2∙h) at 70 ℃. The acid and alkali resistance of the intrinsic membrane and the composite membrane was evaluated, and it was found that the feed liquid was concentrated to 20 wt% after 19 h long concentration operation at 70℃ and starting liquid was 5 wt% H2SO4 and 5 wt% NaOH. The retention rate of acid and alkali can be maintained above 99.9 %. During the concentration of H2SO4 solution, the dense layer structure is affected, and the pure water flux of the composite membrane is reduced, eventually maintaining around 32 kg/(m2∙h). In the process of concentrating NaOH solution, the pure water flux of the composite membrane increased first and then decreased, and the final pure water flux of the membrane remained near 40 kg/(m2∙h).

Thin-film composite (TFC) membranes incorporated with hydrophilic additives and layered double hydroxides (LDHs) for effective brackish water (BW) desalination

To overcome the limited water permeability of thin-film nanocomposite (TFN) membranes for brackish water reverse osmosis (BWRO) processes, we have incorporated a few amine or hydroxyl group terminated hydrophilic additives during interfacial polymerization when fabricating RO membranes and found that the membrane comprising 1 wt% 2-(2-hydroxyethyl)pyridine (2-(2-pyridyl)ethylahydroxide, PEH) has the best BWRO performance. The membrane was subsequently infiltrated with layered double hydroxide (LDH) nanoparticles by a post ethanol activation and could deliver a water permeability of 4.18 LMH bar−1 which is 100 % more than the control membrane without much compromising the salt rejection. The newly developed process not only incorporates nanofillers with the advantages of simplicity and decoupling from the interfacial polymerization process, but also endows the TFN membranes with enhanced separation performance. The study may provide useful insights to incorporate nanofillers by the solvent activation approach for the fabrication of TFN membranes.

A novel BiOI nanosheets modified TiO2/chitosan photocatalytic membrane for enhanced-performance removal of tetracycline

BiOI/TiO2/CS composite membrane materials were prepared by a simple room-temperature stirring-casting method. The BiOI/TiO2 grafted chitosan (CS) membranes exhibited enhanced visible light absorption, and their charge separation and interfacial transport were significantly improved. CS as the membrane substrate supported BiOI/TiO2/CS facilitates the recycling of the materials. The BiOI/TiO2/CS composites demonstrated enhanced photocatalytic performance for the degradation of tetracycline (TC) under UV–vis light. The composite BiOI/TiO2/CS-2 (BTC-2) was the best photocatalytic performance, completely degrading 10 ppm of tetracycline within 120 min and have good reusability. Besides, the mechanism of the enhanced photocatalytic activity of BiOI/TiO2/CS was explored.

Zero-dimensional quantum dot-modified membrane materials for the effective treatment of industrial wastewater: A comprehensive review

The efficient treatment and recycling of industrial wastewater is an important way to improve water resource utilization. Membrane separation technology has been widely used in the field of industrial wastewater treatment due to its high separation efficiency, low energy consumption, good scalability, and other advantages. A recent breakthrough in membrane technologies is the emergence of various nanocomposite membranes, which not only breaks the trade-off between membrane selectivity and permeability, but also enhances the anti-fouling ability and multi-scale separation effects of membranes. Among the nanomaterials used for membrane fabrication, zero-dimensional quantum dots (QDs) with size-dependent optical properties and excellent photocatalytic potential have become promising candidates for novel nanocomposite membrane construction. Significant improvements in membrane surface hydrophilicity, anti-fouling property, and permeability can be achieved by incorporating QDs during the membrane formation process or through membrane post-modification. This review focuses on recent advances in QD-modified membranes for industrial wastewater treatment. The synthesis methods of QDs were summarized firstly, especially for carbon-based and semiconductor QDs. Based on the blending modification and surface modification, the research progress in the modification strategies of QD-modified membranes is presented. Subsequently, the state-of-the-art studies of QD-modified membranes in the application of industrial wastewater treatment are reviewed. Finally, the current challenges and opportunities in QD-modified membranes are discussed.

Facile infiltration of polyethyleneimine as a strong CO2 retardant in scalable dual-polymer membranes for H2/CO2 separation

Successful pre-combustion CO2 capture from synthetic gas for H2 production requires effective membrane separation technology. While polymer-based membrane materials offer promising industrial scalability, they generally lack a sufficiently high H2/CO2 selectivity to make this process energy-efficient. In this work, we have designed a scalable dual-polymer blend membrane consisting of sulfonated polyphenylsulfone (sPPSU) and polybenzimidazole (PBI), and then being infiltrated with amine-rich poly(ethyleneimine) (PEI) molecules as effective CO2 retardants to substantially elevate the H2/CO2 selectivity. PEI molecules were infiltrated into the dual-polymer matrix via solution-treatment to crosslink the polymer network and retard CO2 transport using its amine-rich nature. The PEI infiltration dramatically increased the H2/CO2 selectivity of the dual-polymer matrix from 4.6 to up to 59.3 while maintaining a minimum H2 permeability of 2.49 Barrer at a low temperature of 35 °C, which not only surpasses the Robeson upper bound but also places the newly developed membrane among the best-performing polymer-based membranes. More importantly, the solution infiltration of PEI incurs no phase segregation, maintaining the polymer mechanical robustness, which is crucial for industrial scaling. This study offers promising opportunities to develop three-polymer membrane systems for H2/CO2 separation using synergistic polymer blends and CO2-retarding molecules.

Titania and zirconia ceramic nanofiltration membrane fabrication by coating method on mullite and mullite-alumina microfiltration supports for industrial wastewater treatment

Industrial wastewater treatment increasingly relies on membrane separation, with ceramic membranes offering many advantages such as thermal stability and pH resistance. The resistance of ceramic membranes to extreme pH conditions indicates their ability to maintain structure and performance when exposed to highly acidic or alkaline environments. A high-permeability ceramic nanofiltration membrane was developed, boasting excellent rejection rates through a multilayer asymmetric design. Initially, two tubular porous supports, mullite and mullite-alumina, with a weight percent of 50, were fabricated using the extrusion method. Subsequently, a colloidal sol of titania (TiO2) and titania-zirconia (TiO2- ZrO2) was prepared via the sol–gel method and coated on the ceramic supports using the dip-coating method. After analyzing the membrane microstructure using SEM, XRD, and BET, the efficiency of the membranes in treating synthetic oily wastewater was evaluated. The results underscore the significant impact of the Donnan exclusion mechanism on the rejection of nanofiltration (NF) membranes. An increase in pressure led to a rise in rejection rates up to 7 bars. The Chemical Oxygen Demand (COD) rejection for mullite-titania zirconia (MTZ) and mullite-alumina-titania zirconia (MATZ) membranes was 98.65 % and 98 %, respectively. The pure water permeability test results for mullite and mullite-alumina supports, as well as MTZ and MATZ membranes, were recorded as 254, 382, 70, and 89 L bar-1m-2h−1, respectively.

Fabrication of mixed matrix membranes based on PVDF matrix and ZrT-1-NH2 filler for efficient adsorptive removal of Orange G

Adsorption membranes have become a hot spot for wastewater treatment in recent years. Due to the lack of active sites in traditional inert materials such as polyvinylidene fluoride (PVDF) membranes, it is difficult to bind pollutants in water with high affinity. Therefore, in this study, ZrT-1-NH2/PVDF mixed matrix membranes (MMMs) were prepared by combining an amino-functionalized Zr-based metal–organic cage (ZrT-1-NH2) with a polymer substrate via non-solvent-induced phase separation method for the efficient removal of Orange G (OG) from water. This method has many advantages such as simplicity in operation, high applicability, controllable MOFs loading. The structural characteristics and adsorption properties and of MMMs were also investigated through a series of characterizations and experiments. The result shows that in a 100 mL OG solution with an initial concentration of 50 mg/L and pH=3, M60 exhibited significant adsorption capacity, the removal efficiency reached 97.23 %, with an adsorption capacity of 64.18 mg/g, which is much higher than the pristine PVDF membrane. It is mainly attributed to electrostatic interactions and hydrogen bonding interactions between ZrT-1-NH2 and OG molecules. This is consistent with the DFT calculations. The introduction of ZrT-1-NH2 filler improves the performance of PVDF membranes and expands their potential applications.

Effect of the main properties of membrane materials on denitrification of hydrogen-based membrane biofilm reactors (H2-MBfRs)

Hydrogen-based membrane biofilm reactors using hollow-fiber membrane modules as their functional cores can play an important role in treating oxidizing pollutants. However, most studies have focused on pollutant removal, and few have investigated how membrane material properties affect reactor's operation. Here, we selected polyvinyl chloride (PVC) and polyvinylidene fluoride (PVDF) hollow fiber membrane materials with large differences in membrane surface properties to assemble the reactor, and investigated how the membrane properties affected nitrate removal and EPS secretion in MBfRs. The results showed that the membrane surface zeta potential and membrane contact angle had a certain positive impact on the NO3−-N removal rate and total EPS secretion in the MBfRs. When the contact angle (74.51–85.51°) and zeta potential (−12.5–4.5) increased, the biofilm on the membrane surface secreted more binding proteins (90.81–113.54 mg/gVSS), facilitating reactor biofilm growth, pollutant removal, and impact loads. Moreover, the properties of the experimentally selected PVC membrane material are more suitable for MBfR operation and are in line with the fundamental need for energy saving and emission reduction in modern society. This study provides a theoretical basis for the selection of membrane materials to enhance denitrification in H2-MBfRs, and an engineering foundation for reactors applications.

Preparation of ultra-high permeability dual-layer Al2O3 hollow fiber supports for zeolite membrane fabrication

Four-channel dual-layer Al2O3 hollow fiber with ultra-high permeability and mechanical strength was prepared by co-extrusion and co-sintering technique for the first time and used as support for NaA zeolite membranes fabrication. The macroporous inner layer of the Al2O3 hollow fiber, composed by large Al2O3 particle, gives supports the high permeability and mechanical strength, while the thin out layer, composed by small particles, provides an even and smooth surface for zeolite membrane growth. By using SiO2 as the sintering aid, the sintering temperature of the inner layer was reduced and match with that of the outer layer. The effects of SiO2 adding amount, sintering temperature, Al2O3 particle size and their content on the structure and properties of the prepared hollow fiber were investigated systematically. At a sintering temperature of 1520 °C, a dual-layer hollow fiber with surface pore size of 0.38 μm and fracture load of 24.52 N, exhibits pure water flux as high as 22.23 m3 m 2 h−1 bar−1. The NaA membrane prepared on this support achieved a flux of 14.14 kg m−2 h−1 and a separation factor >10,000 in pervaporation separation of EtOH/H2O solution (90 wt%, 75 °C). This work provides an efficient and low-cost way to prepare ceramic hollow fiber support for high-performance zeolite membrane fabrication.

Advanced photocatalytic membrane GO-NiFe@SiO2/PVDF for efficient decontamination of synthetic dyes in batik wastewater with superior antifouling features

A novel composite membrane, GO-NiFe@SiO2/polyvinylidene fluoride (PVDF), was prepared via the sol-gel method for nanocomposite synthesis and phase inversion method for membrane fabrication. The investigation encompassed the structural features and properties of the nanocomposite membranes, including photocatalytic activity under UV type C, antifouling capability, and self-cleaning behavior. The degradation of dyes in real Batik wastewater followed pseudo-first-order kinetics, with the GO-NiFe@SiO2/PVDF 1 wt% nanocomposite membranes exhibiting a highest dyes removal efficiency up to 90.50 % within 8 h, compared to the pristine PVDF membrane (60.95 %). The XRD pattern analysis indicates that the incorporation of GO-NiFe@SiO2 into the PVDF membrane induced a transformation in the semi-crystalline phase of PVDF, shifting from the alpha-phase to the beta-phase, consequently facilitating the development of electrostatic charge on the membrane surface. The pore-size distribution analysis revealed that all prepared membranes fall within the range of nanofiltration and tight ultrafiltration (NF-TUF). Additionally, the photocatalytic membrane demonstrated enhanced permeation flux of 30.46 L.m−2.h−1 and flux recovery rate up to 92.57 % under simulated UV light irradiation, showcasing improved antifouling capability. Moreover, the membrane exhibited outstanding cycle test with 6 consecutive cleaning every 3 h, self-cleaning efficiency, with 61.32 % cleaning efficiency under UV irradiation. The incorporation of GO-NiFe@SiO2 enhanced the physicochemical properties of the photocatalytic membrane, including hydrophilicity, surface topologies, and mechanical strength, thereby improving photocatalytic anti-fouling performance and expanding the potential applications of membrane filtration technology.

Advancing drinking water safety: Facile fabrication of nanofiltration membrane for enhanced antibiotics removal and efficient water softening

Long-term water consumption with contaminated antibiotics and high levels of hardness threatens the health of humans and animals. In this study, a novel positively charged nanofiltration membrane was designed for the dual purpose of efficiently removing antibiotics and softening hard water. The membrane was fabricated by casting P84 polymer solution onto non-woven fabrics, followed by immersion in the polyethyleneimine (PEI) solution for phase inversion and cross-linking, and finalized interfacial polymerization with trimesoyl chloride. Notably, the rapid immersion of the P84 substrate into PEI drastically reduces preparation time by 95 % compared to the regular method while maximizing PEI storage, resulting in uniform pore sizes and a positively charged surface. The optimal membrane showed a high water permeance of 11.3 L m−2 h−1 bar−1 and exceptional antibiotic rejection, i.e., 99.6 % for enrofloxacin, 99.2 % for ciprofloxacin, and 96.3 % for sulfamethoxazole, as well as a highly effective removal in water hardness (over 96 % of Ca2+ and Mg2+) at 4 bar. Simulated water separation tests showed that the optimal membrane effectively controls hard water salinity within optimum drinking water ranges (Ca2+ ≤ 80 mg/L; Mg2+ ≤ 30 mg/L), providing efficient water softening and antibiotic capture ability. Additionally, the optimal membrane demonstrated a superior anti-bacterial and long-term stability performance. This study has significant potential for improving drinking water supply safety and addressing pressing public health and environmental concerns.

Nanocomposite polyphenyleneoxide with amino-functionalized silica: structural characterization based on thermal analysis

AbstractA polymer nanocomposite based on sulfonated polyphenylene oxide with amino-functionalized mesoporous silica was designed, synthesized, and tested as a new material for proton exchange membrane (PEM preparation. Characterization of the intermediate and final products of synthesis was realized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and thermal analysis. Broadband Dielectric Spectroscopy (BDS) was used to determine dielectric properties including ionic conductivity. Thermogravimetric analysis has provided important information regarding the composition and thermal stability of the three compounds, subject to thermal degradation: 1) the amino-silica with cetyltrimethylammonium bromide (CTAB) template inside the pores (MS-NH2I), 2) the mesoporous amino-silica after removing the template (MS-NH2II) and 3) the polymer nanocomposite (sPPO-MS-NH2). The thermal decomposition of the composite samples occurs in three stages: in the first, up to 150 °C, water and organic solvents were lost; the second stage, between 200-300 °C, was due to breaking the organic functionalities (-NH2, amino and -SO3H, sulfonic acid), and the third stage, above 400 °C was due to polymer chain degradation. The final residue at 700 °C reflects the contribution of inorganic silica. The proton conductivity, for polymeric (sPPO) and composite (sPPO-MS-NH2) membranes was determined from BDS dates, both in dry and hydrated states. For dried samples, the higher values of proton conductivities were: 0.16 mS cm−1 (sPPO, 70 °C) and 0.03 mS cm−1 (sPPO-MS-NH2, 120 °C), and the higher values of proton conductivity increased for the hydrated samples with two orders of magnitude: 36.5 mS cm−1 (sPPO, 40 °C) and 22.4 mS cm−1 (sPPO-MS-NH2, 50 °C). However, the proton conductivity is still dependent on the hydration state, even for the composite membrane.

Enhanced removal of hazardous organic contaminants with advanced visible light-active F-doped TiO2/rGO/PVDF photocatalytic membranes

Polyvinylidene fluoride (PVDF) membranes and composite variants with x% FGT/PVDF photocatalytic membranes were prepared at different concentrations (x = 1 %, 5 %, and 10 %) using the phase inversion technique. The synthesized photocatalysts and the membrane materials were thoroughly characterized using different analytical methods. The focus was on determining the photocatalytic efficiency of these materials in degrading two important harmful dyes, namely methylene blue (MB) and crystal violet (CV), under visible light irradiation. High degradation percentages of MB (96 %) and CV (92 %) at 90 minutes were observed with 5 % F-TiO2/rGO (named as 5 %FGT). Similarly, the 5 % F-TiO2/rGO/PVDF (5 %FGT/PVDF) photocatalytic membranes showed 98 % and 93 % degradation of MB and CV, respectively. Kinetic studies revealed that the photocatalytic degradation reaction followed a pseudo-first-order mechanism. The total organic carbon (TOC) analysis of the treated MB and CV dyes showed a degradation of 78 % and 71 %, respectively. Recycling of the most active 5 % FGT/PVDF composite membrane exhibited very high stability of 800 min. The composite material utilizes the photocatalytic properties of TiO2 and the stimulating transport properties of rGO. Additionally, fluorine doping enhances charge carrier separation, tunes the bandgap for visible light response, and increases surface activity, thereby improving the overall degradation of organic pollutants. These properties make the composite material promising for various applications in environmental remediation and wastewater treatment.

Unraveling the nanostructures and self-assembly behavior of perfluorosulfonic acid in water/ethanol solvent: Effect of EW and side-chain chemistry

The perfluorosulfonic acid (PFSA) ionomers are key materials for proton exchange membranes (PEMs) and catalyst layers (CLs). Their morphology is profoundly influenced by the chain assembly behavior of PFSA in dispersions. Hence, we combine the characterization techniques of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (Cryo-TEM) to study the nanostructures of PFSA dispersions, and provide a structure model for diverse PFSA ionomers in water/ethanol solvent. It is seen that PFSA ionomers self-assembly into a rod-like particle in dilute dispersion. As the concentration increases, the primary rod aggregates gradually assemble into a swollen- or Gaussian-network structure. Beyond this feature, we see that different PFSA ionomers show different nanostructures in dispersion. For the long-side-chain (LSC) PFSA ionomers, the 800-LSC PFSA tends to form monodisperse rod-like aggregates that is in a highly ordered arrangement with a rod diameter of 3.16 nm and a length of 28.72 nm. As the equivalent weight (EW) increases to 960, the poor solubility of the main chains in water/ethanol solvents leads to the “end-to-end” assemblies of the primary rod particles and dendritic secondary aggregates. The short-side-chain (SSC) PFSA ionomer that shares the same backbone with 960-LSC PFSA exhibit remarkable mono-dispersity and ordered arrangement of rod-like aggregates in water/ethanol solvents due to the strong electrostatic repulsion.

The Key to MOF Membrane Fabrication and Application: the Trade-off between Crystallization and Film Formation.

Metal-organic frameworks (MOFs), owing the merits of ordered and tailored channel structures in the burgeoning crystalline porous materials, have demonstrated significant promise in construction of high-performance separation membranes. However, precisely because this crystal structure with strong molecular interaction in their lattice provides robust structural integrity and resistance to chemical and thermal degradation, crystalline MOFs typically exhibit insolubility, infusibility, stiffness and brittleness, and therefore their membrane-processing properties are far inferior to the flexible amorphous polymers and hinder their subsequent storage, transportation, and utilization. Hence, focusing on film-formation and crystallization is the foundation for exploring the fabrication and application of MOF membranes. In this review, the film-forming properties of crystalline MOFs are fundamentally analyzed from their inherent characteristics and compared with those of amorphous polymers, influencing factors of polycrystalline MOF membrane formation are summarized, the trade-off relationship between crystallization and membrane formation is discussed, and the strategy solving the film formation of crystalline MOFs in recent years are systematically reviewed, in anticipation of realizing the goal of preparing crystalline membranes with optimized processability and excellent performance.

Light-Driven Ionic and Molecular Transport through Atomically Thin Single Nanopores in MoS2/WS2 Heterobilayers.

Nanofluidic ionic and molecular transport through atomically thin nanopore membranes attracts broad research interest from both scientific and industrial communities for environmental, healthcare, and energy-related technologies. To mimic the biological ion pumping functions, recently, light-induced and quantum effect-facilitated charge separation in heterogeneous 2D-material assemblies is proposed as the fourth type of driving force to achieve active and noninvasive transport of ionic species through synthetic membrane materials. However, to date, engineering versatile van der Waals heterostructures into 2D nanopore membranes remains largely unexplored. Herein, we fabricate single nanopores in heterobilayer transition metal dichalcogenide membranes with helium ion beam irradiation and demonstrate the light-driven ionic transport and molecular translocation phenomena through the atomically thin nanopores. Experimental and simulation results further elucidate the driving mechanism as the photoinduced near-pore electric potential difference due to type II band alignment of the semiconducting WS2 and MoS2 monolayers. The strength of the photoinduced localized electric field near the pore region can be approximately 1.5 times stronger than that of its counterpart under the conventional voltage-driven mode. Consequently, the light-driven mode offers better spatial resolution for single-molecule detection. Light-driven ionic and molecular transport through nanopores in van der Waals heterojunction membranes anticipates transformative working principles for next-generation biomolecular sequencing and gives rise to fascinating opportunities for light-to-chemical energy harvesting nanosystems.

Progress of persulfate-based advanced oxidation process (PS-AOPs) coupled with ultrafiltration membrane to alleviate membrane fouling: A review

Membrane fouling significantly hampers the extensive deployment of ultrafiltration membranes in treating drinking water. To mitigate fouling and improve filtration effectiveness, advanced oxidation processes (AOPs) have been considered as a potent approach, particularly the activation of AOPs by persulfate (PS-AOPs). Establishing a membrane system based on PS-AOPs is a promising approach to addressing membrane fouling. This article reviews the homogeneous and heterogeneous activation methods of PS. Recent research on the degradation of sulfamethoxazole by various activation methods are summarized, their mechanisms are discussed, and their advantages and disadvantages are compared. The integration of PS-AOPs with UF membranes to control fouling is highlighted, with evidence showing a significant reduction in membrane fouling. The article emphasizes the improvements and limitations of the PS-AOPs coupled with membrane system, especially in heterogeneous systems. Heterogeneous catalysts are doped into membrane materials to form catalytic membranes that can not only participate in membrane filtration but also undergo advanced oxidation upon PS introduction. Finally, the article looks ahead to future research paths and challenges for the PS-AOPs coupled UF membrane system. Based on metal-carbon catalytic membranes, the exploration of materials suitable for activating persulfate is discussed to promote further development of the technology.

Recent Advances for Wastewater Treatment on Polyvinylidene Fluoride-Based Membrane: A Review

The development of scalable membrane-based separation processes has attracted considerable interest on laboratory and industrial scales. Polyvinylidene fluoride (PVDF) is one of the most widely used fluoropolymer materials for membrane fabrication due to its excellent mechanical strength, good thermal stability and chemical resistance as well as aging resistance. However, the hydrophobic nature of PVDF has resulted in serious membrane fouling during the filtration process. From the past decade, the embedment of hydrophilic materials in/on PVDF-based membranes can significantly alter the membrane’s morphology and surface properties. Therefore, based on most articles retrieved from Web of Science, Scopus, Google Scholar, etc., this article provides the overview of the recent development of PVDF-based membranes during the recent several decades. The detailed information regarding PVDF as a polymer material as well as the main challenge in the development of PVDF-based membranes with better performance was summarised. Moreover, the factors influencing membrane fouling including surface hydrophilicity, roughness and charge are also addressed. Then, the PVDF-based membrane preparation and its recent modification via the blending method were discussed. Finally, the overview and future perspective of PVDF-based membrane development are reviewed. Overall, it can be concluded that PVDF-based membranes have great potential for further advances towards the development of membrane technologies for the future.

Polypyrrole-mediated construction of superhydrophobic photo/electro thermal composite fabric for efficient crude oil dehydration and recovery

During crude oil extraction, transportation, and oil spill recovery, rapid and effective removal of water from crude oil is a great challenge. Super-hydrophobic functional membranes with electrothermal/photothermal effects are considered to be an effective method. However, simply polymerizing photothermal/electrothermal nanomaterials on the membrane surface will lead to unstable thermal effects and easy shedding. Therefore, in this study we propose the synthesis of a novel superhydrophobic electrothermal/photothermal Nylon fabric (PSPPNF) by an innovative in situ polymerization method of Pyrrole (Py), to realize efficient viscosity reduction and dehydration of crude oil. In particular, by controlling FeCl3 solution from solid (−18 °C) to liquid state (0 °C), Py was polymerized on the fabric surface by slow oxidative process, which can effectively solve the problem of pore blocks to obtain a stable-conductive layer on the NF surface. The PSPPNF surface temperature can reach 80 °C under 1 kW m−2 sunlight intensity or by inputting 30 V, which brings a separation efficiency of 97 % for high-viscous crude oil/water mixture. We systematically analyzed the effects of PSPPNF with different pore sizes and oils with different viscosities on the separation flux, as well as the effects of the thermal properties of the membranes under different illumination conditions and voltages on crude oil permeation. Additionally, the PSPPNF combined with the roller can realize all-weather available crude oil spill recovery under solar and electrical energy. This work provides new insights into membrane materials that can realize the efficient dehydration and recovery of crude oil for day-night alternation and complex environments.