Progress in the production and modification of PVDF membranes

Development of inorganic and mixed matrix membranes for application in toxic dyes-contaminated industrial effluents with in-situ treatments

Dyes are the most ubiquitous organic pollutants in industrial effluents. They are highly toxic to both plants and animals; thus, their removal is paramount to the sustainability of ecosystem. However, they have shown resistance to photolysis and various biological, physical, and chemical wastewater remediation processes. Membrane removal technology has been vital for the filtration/separation of the dyes. In comparison to polymeric membranes, inorganic and mixed matrix (MM) membranes have shown potentials to the removal of dyes. The inorganic and MM membranes are particularly effective due to their high porosity, enhanced stability, improved permeability, higher enhanced selectivity and good stability and resistance to harsh chemical and thermal conditions. They have shown prospects in filtration/separation, adsorption, and catalytic degradation of the dyes. This review highlighted the advantages of the inorganic and MM membranes for the various removal techniques for the treatments of the dyes. Methods for the membranes production have been reviewed. Their application for the filtration/separation and adsorption have been critically analyzed. Their application as support for advanced oxidation processes such as persulfate, photo-Fenton and photocatalytic degradations have been highlighted. The mechanisms underscoring the efficiency of the processes have been cited. Lastly, comments were given on the prospects and challenges of both inorganic and MM membranes towards removal of the dyes from industrial effluents.

Reactive layered hydroxide membrane for advanced water treatment: Micropollutant degradation and antifouling potential

The effective removal of micropollutants by water treatment technologies remains a significant challenge. Herein, we develop a CoFe layered double hydroxide (CoFeLDH) catalytic membrane for peroxymonosulfate (PMS) activation to achieve efficient micropollutant removal with improved mass transfer rate and reaction kinetics. This study found that the CoFeLDH membrane/PMS system achieved an impressive above 98% degradation of the probe chemical ranitidine at 0.1 mM of PMS including five more micropollutants (Sulfamethoxazole, Ciprofloxacin, Carbamazepine, Acetaminophen and Bisphenol A) at satisfactory level (above 80%). Moreover, significant improvements in water flux and antifouling properties were observed, marking the membrane as a specific advancement in the removal of membrane fouling in water purification technology. The membrane demonstrated consistent degradation efficiency for several micropollutants and across a range of pH (4-9) as well as different anionic environments, thereby showing it suitability for scale-up application. The key role of reactive species such as SO4•-, and O2• - radicals in the degradation process was elucidated. This is followed by the confirmation of the occurrence of redox cycling between Co and Fe, and the presence of CoOH+ that promotes PMS activation. Over the ten cycles, the membrane could be operated with a flux recovery of up to 99.8% and maintained efficient performance over 24 h continuous operation. Finally, the efficiency in degrading micropollutants, coupled with reduced metal leaching, makes the CoFeLDH membrane as a promising technology for application in water treatment.

Cellulose acetate, a source from discarded cigarette butts for the development of mixed matrix loose nanofiltration membranes for selective separation

This study presents an environmentally friendly method for extracting cellulose acetate (CA) from discarded cigarette filters, which is then utilized in the fabrication of cellulose-based membranes designed for high flux and rejection rates. CA membranes are likeable to separate dyes and ions, but their separation efficiency is exposed when the contaminant concentration is very low. So, we have integrated graphene oxide (GO) and carboxylated titanium dioxide (COOH-TiO2) in CA to develop mixed matrix membranes (MMMs) and studied them against dyes and most used salts. The CA has been extracted from these butts and added GO and COOH-TiO2 nanoparticles to develop MMMs. The present work administers the effective separation of five dyes (methyl orange, methyl violet, methylene blue, cresol red, and malachite green) and salts (NaCl and Na2SO4) along with the high efficiency of water flux by prepared CA membranes. The prepared membranes rejected up to 94.94 % methyl violet, 91.28 % methyl orange, 88.28 % methylene blue, 89.91 % cresol red, and 91.70 % malachite green dye. Along with the dyes, the membranes showed ∼40.40 % and ∼ 42.97 % rejection of NaCl and Na2SO4 salts, respectively. Additionally, these membranes have tensile strength up to 1.54 MPa. Various characterization techniques were performed on all prepared CA membranes to comprehend their behaviour. The antibacterial activity of MMMs was investigated using the Muller-Hinton-Disk diffusion method against the gram-positive bacterium Staphylococcus aureus (S. aureus) and the gram-negative bacterium Escherichia coli (E. coli). We believe the present work is an approach to utilizing waste materials into valuable products for environmental care.

Recovery of Ag(I) from Wastewater by Adsorption: Status and Challenges

Untreated or inadequately treated silver-containing wastewater may pose adverse effects on hu-man health and the ecological environment. Currently, significant progress has been made in the treatment of Ag(I) in wastewater using adsorption methods, with adsorbents playing a pivotal role in this process. This paper provides a systematic review of various adsorbents for the recovery and treatment of Ag(I) in wastewater, including MOFs, COFs, transition metal sulfides, metal oxides, biomass materials, and other polymeric materials. The adsorption mechanisms of these materials for Ag(I) are elaborated upon, along with the challenges currently faced. Furthermore, insights into optimizing adsorbents and developing novel adsorbents are proposed in this study.

Flexible Aerogel Materials: A Review on Revolutionary Flexibility Strategies and the Multifunctional Applications

The design and preparation of flexible aerogel materials with high deformability and versatility have become an emerging research topic in the aerogel fields, as the brittle nature of traditional aerogels severely affects their safety and reliability in use. Herein, we review the preparation methods and properties of flexible aerogels and summarize the various controlling and design methods of aerogels to overcome the fragility caused by high porosity and nanoporous network structure. The mechanical flexibility of aerogels can be revolutionarily improved by monomer regulation, nanofiber assembly, structural design and controlling, and constructing of aerogel composites, which can greatly broaden the multifunctionality and practical application prospects. The design and construction criterion of aerogel flexibility is summarized: constructing a flexible and deformable microstructure in an aerogel matrix. Besides, the derived multifunctional applications in the fields of flexible thermal insulation (flexible thermal protection at extreme temperatures), flexible wearable electronics (flexible sensors, flexible electrodes, electromagnetic shielding, and wave absorption), and environmental protection (oil/water separation and air filtration) are summarized. Furthermore, the future development prospects and challenges of flexible aerogel materials are also summarized. This review will provide a comprehensive research basis and guidance for the structural design, fabrication methods, and potential applications of flexible aerogels.

Temperature Dependence of the Number of Defect-Structures in Poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) is predominantly characterized by alternating CH2 and CF2 units in a polymer backbone, originating from the head-to-tail addition of monomers or regular propagation. Due, to a small extent, to inverse monomer addition, so-called defect structures occur which influence the macroscopic properties of PVDF significantly. The amount of defect structures in the material is determined by the polymerization conditions. Here, the temperature dependence of the fraction of defect structures in PVDF obtained from polymerizations between 45 and 90 °C is reported. We utilized 19F-NMR spectroscopy to determine the fraction of defect structures as a function of temperature. To derive kinetic data, the polymerization of VDF is considered a quasi-copolymerization described by the Terminal Model involving four different propagation reactions. Based on the experimentally determined temperature-dependent fractions of defect structures, the known overall propagation rate coefficient, and taking into account the self-healing behavior of the macroradical, the Arrhenius parameters of the individual propagation rate coefficients were determined using the Monte Carlo methods.

PVDF-Based Piezo-Catalytic Membranes-A Net-Zero Emission Approach towards Textile Wastewater Purification

Among the various water purification techniques, advancements in membrane technology, with better fabrication and analysis, are receiving the most research attention. The piezo-catalytic degradation of water pollutants is an emerging area of research in water purification technology. This review article focuses on piezoelectric polyvinylidene difluoride (PVDF) polymer-based membranes and their nanocomposites for textile wastewater remediation. At the beginning of this article, the classification of piezoelectric materials is discussed. Among the various membrane-forming polymers, PVDF is a piezoelectric polymer discussed in detail due to its exceptional piezoelectric properties. Polyvinylidene difluoride can show excellent piezoelectric properties in the beta phase. Therefore, various methods of β-phase enhancement within the PVDF polymer and various factors that have a critical impact on its piezo-catalytic activity are briefly explained. This review article also highlights the major aspects of piezoelectric membranes in the context of dye degradation and a net-zero approach. The β-phase of the PVDF piezoelectric material generates an electron-hole pair through external vibrations. The possibility of piezo-catalytic dye degradation via mechanical vibrations and the subsequent capture of the resulting CO2 and H2 gases open up the possibility of achieving the net-zero goal.

Preparation of mixed matrix self-cleaning membrane incorporated by Z-scheme heterostructure via robust engineering in terms of dimension for decreasing cake fouling in a cross-flow reactor

Reducing irreversible fouling in polymer membranes by integrating photocatalytic and membrane processes as the self-cleaning photocatalytic membrane is a promising candidate for improving membrane filtration performance. In this study, mixed matrix photocatalytic membranes were prepared from the combination of different morphologies ZnO-g-C3N4 heterostructure in the polymer matrix by the phase-separation method. To investigate the self-cleaning and performance properties of mixed matrix photocatalytic membranes prepared from different morphologies heterostructures, the photocatalytic membrane reactor with a visible-light source was applied. Nanoflower/nanosheet (NF/NS) ZnO-g-C3N4 photocatalytic membrane showed good self-cleaning performance owing to the high photocatalytic performance of NF/NS ZnO-g-C3N4 heterostructure by the reduction of irreversible membrane fouling, thus improving the antifouling and filtration performance of the membrane. Also, the morphology and the uniform distribution of the NF/NS ZnO-g-C3N4 heterostructure in the membrane matrix caused good hydrophilic properties, high porosity, and a more symmetrical structure in the (NF/NS) ZnO-g-C3N4 photocatalytic membrane (F4). For the F4 membrane, the permeability and rejection values increased from 40.35 L m-2 h-1 and 90.9% in the dark environment to 84.37 L m-2 h-1 and 97.4% under visible-light for dye pollutants. Accordingly, F4 had the best filtration and self-cleaning performance, which can be used as a promising visible-light photocatalytic membrane in wastewater treatment processes.

PDOL-Based Solid Electrolyte Toward Practical Application: Opportunities and Challenges

Polymer solid-state lithium batteries (SSLB) are regarded as a promising energy storage technology to meet growing demand due to their high energy density and safety. Ion conductivity, interface stability and battery assembly process are still the main challenges to hurdle the commercialization of SSLB. As the main component of SSLB, poly(1,3-dioxolane) (PDOL)-based solid polymer electrolytes polymerized in-situ are becoming a promising candidate solid electrolyte, for their high ion conductivity at room temperature, good battery electrochemical performances, and simple assembly process. This review analyzes opportunities and challenges of PDOL electrolytes toward practical application for polymer SSLB. The focuses include exploring the polymerization mechanism of DOL, the performance of PDOL composite electrolytes, and the application of PDOL. Furthermore, we provide a perspective on future research directions that need to be emphasized for commercialization of PDOL-based electrolytes in SSLB. The exploration of these schemes facilitates a comprehensive and profound understanding of PDOL-based polymer electrolyte and provides new research ideas to boost them toward practical application in solid-state batteries.

A PEGylated PVDF Antifouling Membrane Prepared by Grafting of Methoxypolyethylene Glycol Acrylate in Gama-Irradiated Homogeneous Solution

In this study, methoxypolyethylene glycol acrylate (mPEGA) served as a PEGylated monomer and was grafted onto polyvinylidene fluoride (PVDF) through homogeneous solution gamma irradiation. The grafting process was confirmed using several techniques, including infrared spectroscopy (FTIR), thermodynamic stability assessments, and rotational viscosity measurements. The degree of grafting (DG) was determined via the gravimetric method. By varying the monomer concentration, a range of DGs was achieved in the PVDF-g-mPEGA copolymers. Investigations into water contact angles and scanning electron microscopy (SEM) images indicated a direct correlation between increased hydrophilicity, membrane porosity, and higher DG levels in the PVDF-g-mPEGA membrane. Filtration tests demonstrated that enhanced DGs resulted in more permeable PVDF-g-mPEGA membranes, eliminating the need for pore-forming agents. Antifouling tests revealed that membranes with a lower DG maintained a high flux recovery rate, indicating that the innate properties of PVDF could be largely preserved.

Preparation of heterogeneous cation exchange membrane and its contributions in enhancing the removal of Ni2+ by capacitive deionization system

Capacitive deionization (CDI), an emerging method to eliminate ions from water at a low cost, has garnered significant interest in recent years. This study evaluates the implication of cation exchange resin loading on the membrane via the nonsolvent-induced phase inversion method. After determining the quantity of resins efficiently loaded on the membrane, it was subsequently utilized as a cation exchange membrane in the membrane capacitive deionization (MCDI) unit to examine the performance removal of Ni2+. The results show that the amount of resins influenced the membrane structure and significantly improved the efficiency of Ni2+ removal. The sulfonic acid group show a strong intensity directly proportional to the quantity of resins based on the FTIR measurement. In conjunction with the enhanced resin amount, ion exchange capacity and water content were increased. Simultaneously, there was an observed elevation in the water contact angle and the roughness of the membrane surface with increased resin amount. In the MCDI unit, membrane M20 (20% by weight resin) was employed to elucidate its roles in the CDI unit, encompassing an examination of various concentrations and flow rates, with Ni2+ utilized as a test contaminant. The results demonstrated that using membrane M20 in the MCDI (MCDI-M20) unit consistently exhibited higher adsorption levels than the CDI unit, reaching 19.80 mg g-1 ACC in the MCDI-M20 unit, while CDI unit achieved 10.27 mg g-1 ACC at 200 mg L-1 Ni2+ concentration and a flow rate of 10 mL min-1 at 1.2 V. Additionally, Ni2+ concentrations and flow rates in CDI system had an evident impact on the duration of adsorption due to the mechanisms of ions transport on the membrane. This study suggests that employing the prepared membrane in the MCDI unit enhanced the removal of Ni2+ from the solution, contributing to sustainable development goals.

The Integration of Two-Dimensional Materials and Ferroelectrics for Device Applications

In recent years, there has been growing interest in functional devices based on two-dimensional (2D) materials, which possess exotic physical properties. With an ultrathin thickness, the optoelectrical and electrical properties of 2D materials can be effectively tuned by an external field, which has stimulated considerable scientific activities. Ferroelectric fields with a nonvolatile and electrically switchable feature have exhibited enormous potential in controlling the electronic and optoelectronic properties of 2D materials, leading to an extremely fertile area of research. Here, we review the 2D materials and relevant devices integrated with ferroelectricity. This review starts to introduce the background about the concerned themes, namely 2D materials and ferroelectrics, and then presents the fundamental mechanisms, tuning strategies, as well as recent progress of the ferroelectric effect on the optical and electrical properties of 2D materials. Subsequently, the latest developments of 2D material-based electronic and optoelectronic devices integrated with ferroelectricity are summarized. Finally, the future outlook and challenges of this exciting field are suggested.

Structural Characterization and Physicochemical Properties of Functionally Porous Proton-Exchange Membrane Based on PVDF-SPA Graft Copolymers

Fluorinated proton-exchange membranes (PEMs) based on graft copolymers of dehydrofluorinated polyvinylidene fluoride (D-PVDF), 3-sulfopropyl acrylate (SPA), and 1H, 1H, 2H-perfluoro-1-hexene (PFH) were prepared via free radical copolymerization and characterized for fuel cell application. The membrane morphology and physical properties were studied via small-(SAXS) and wide-angle X-ray scattering (WAXS), SEM, and DSC. It was found that the crystallinity degree is 17% for PEM-RCF (co-polymer with SPA) and 16% for PEM-RCF-2 (copolymer with SPA and PFH). The designed membranes possess crystallite grains of 5-6 nm in diameter. SEM images reveal a structure with open pores on the surface of diameters from 20 to 140 nm. Their transport and electrochemical characterization shows that the lowest membrane area resistance (0.9 Ωcm2) is comparable to perfluorosulfonic acid PEMs (such as Nafion®) and polyvinylidene fluoride (PVDF) based CJMC cation-exchange membranes (ChemJoy Polymer Materials, China). Key transport and physicochemical properties of new and commercial membranes were compared. The PEM-RCF permeability to NaCl diffusion is rather high, which is due to a relatively low concentration of fixed sulfonate groups. Voltammetry confers that the electrochemical behavior of new PEM correlates to that of commercial cation-exchange membranes, while the ionic conductivity reveals an impact of the extended pores, as in track-etched membranes.

Nanocelluloses fine-tuned polyvinylidene fluoride (PVDF) membrane for enhanced separation and antifouling

To mitigate membrane fouling and address the trade-off between permeability and selectivity, we fabricated nanocellulose (NC) fine-tuned polyvinylidene fluoride (PVDF) porous membranes (NC-PVDFs) using phase inversion method through blending NCs with varied aspect ratios, surface charges and grafted functional groups. NC-PVDF presented rougher surface (increased by at least 18.3 %), higher porosity and crystallinity compared to PVDF membrane. Moreover, cellulose nanocrystals incorporated PVDF (CNC-PVDF) elevated membrane surface charge and hydrophilicity (from 74.3° to 71.7°), while 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized cellulose nanofibers modified PVDF (TCNF-PVDF) enhanced the porosity (from 25.0 % to 40.3 %) and tensile strength (63.6 % higher than PVDF). For separation performance, NC improved flux, rejection and fouling resistance due to facilitation of phase transition thermokinetics as pore-forming agent and increased hydrophilicity at both interface and pore wall. For water flux, NC-PVDFs (139-228 L·m-2·h-1) resulted in increased permeability compared to bare PVDF. CNC-PVDF membrane exhibited the highest water flux because of improved porosity, roughness and hydrophilicity. For bovine serum albumin (BSA) rejection, the removal rates of all NC-PVDFs were all above 90 %. Notably, TCNF-PVDF exhibited the most remarkable elevation of BSA rejection (95.1 %) owing to size exclusion and charge repulsion in comparison with PVDF.

Porous polyvinyl fluoride coated cellulose beads for efficient removal of Cd(II) from phosphoric acid

In order to enhance the removal of cadmium from phosphoric acid, it is imperative to explore novel resources that may be utilized for the development of highly effective and environmentally sustainable adsorbents. Cellulose beads are composed of naturally occurring polysaccharide fibers and find extensive utilization across several industrial sectors and applications. Within this framework, this research paper presents a green and simple method for producing porous cellulose beads using date palm fibers as the preferred raw material. The innovation lies in immersing the obtained cellulose beads in a Polyvinyl fluoride (PVDF)/N,N-dimethylformamide (DMF) suspension as a coating polymer with different concentrations (2.5, 5, 10 %) to maintain their stability in an acidic environment. The surface of cellulose/PVDF beads were subjected to multiple characterizations like Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), size distribution then pH stability confirming that the coating has been perfectly achieved and conserved well the shape of the beads. The coated cellulose/PVDF-2.5 % underwent evaluation by the process of batch adsorption experiments while different parameters were varied including contact time (5, 10, 20, 30, 60, 90 min), temperature (25, 35, 45 and 55 °C), and adsorbent mass (20, 40, 60, 80 and 100 mg). The obtained ICP data showed that the adsorption rate of Cd (II) from phosphoric acid medium decreased while increasing both temperature from 25 to 55 °C and contact time from 5 to 90 min while adding more adsorbent dosage from 20 to 100 mg enhanced the removal percentage. The cellulose/PVDF-2.5 % was more effective with an adsorption capacity equal to 3.4998 mg/g at optimal conditions including 25 °C as the temperature after 5 min as contact time and by adding a mass 100 mg of the biosorbent while the pH = 2 of the solution is maintained the same. The examined material's adsorption processes proved to be exothermic and non-spontaneous, and it proved that the pseudo-second-order model provided the best match for the cellulose/PVDF-2.5 % beads kinetics data. Furthermore, the cellulose beads exhibited exceptional reusability for up to four repeated cycles without undergoing desorption. The present study offers a viable approach for producing environmentally sustainable biomass-derived adsorbents. Additionally, the study validates the potential of cellulose/PVDF beads as an intriguing material for phosphoric acid decadmiation.

Charged Fibrous Dressing to Promote Diabetic Chronic Wound Healing

Diabetic chronic wounds cause a significant amount of pain to patients because of their low cure rates and high recurrence rates. Traditional approaches to treating diabetic chronic wounds often involve the delivery of drugs or cytokines that regulate the microenvironment and eliminate bacterial infection in the wound area, but they are passive in controlling cell behaviors and may lead to drug resistance. Emerging drug-free wound treatments are important for convenient, effective, and safe treatment strategies. However, the current approaches cannot fully promote tissue regeneration or prevent bacterial infections. Here, the efficacy of a negatively charged fiber dressing in promoting diabetic chronic wound healing is investigated. The negatively charged fiber dressing can generate reactive oxygen species to inhibit bacterial reproduction with the assistance of ultrasound during the inflammatory phase. Furthermore, the dressing provides an electrostatic field that regulates cellular behavior during the inflammatory and proliferative phases. In particular, the dressing can promote fibroblast migration and induce macrophage polarization and neovascularization without any additional drugs. It is demonstrated that this strategy enables the healing of diabetic chronic wounds in a mouse model, achieving effective wound closure over a 12-day treatment cycle and providing a drug-free therapeutic strategy for diabetic chronic wound care.

Array Study of VLF Thin-Film Magnetoelectric Antenna with a Microbridge Structure

Recently, magnetoelectric (ME) antennas have become a hot topic in the field of antenna miniaturization in the very-low-frequency (VLF) band because their size can be reduced to one-ten-thousandth of the size of conventional electric antennas. However, they still suffer from narrow transmission/reception bandwidth and weak radiation intensity. To address these issues, VLF thin-film ME antennas with a microbridge structure are designed, and the method of array connection is used. Test results show that the detection limit of the ME antenna unit is 636 pT/√Hz at 23 kHz and the radiant magnetic field intensity at 0.12 m is 0.87 nT (input power of 10 mW). By series-connecting three ME antenna units with the same resonance frequency, the output response has been increased to 1.72 times and the EM wave radiation intensity is increased to 1.9 times compared to a single unit. By parallel-connecting two ME antenna units with different resonance frequencies, the output response bandwidth has been expanded to 1.56 times compared to a single unit, and the signal radiation bandwidth has been expanded to 1.47 times. This work provides a valuable reference for the future larger-scale arraying of ME antennas.

Highly Biocompatible Polyester-Based Piezoelectric Elastomer with Antitumor and Antibacterial Activity for Ultrasound-Enhanced Piezoelectric Therapy

Currently, the use of piezoelectric materials to provide sustainable and noninvasive bioelectric stimulation to eradicate tumor cells and accelerate wound healing has raised wide attention. The development of a multifunctional piezoelectric elastomer with the ability to perform in situ tumor therapy as well as wound repair is of paramount importance. However, current piezoelectric materials have a large elastic modulus and limited stretchability, making it difficult to match with the dynamic curvature changes of the wound. Therefore, by copolymerizing lactic acid, butanediol, sebacic acid, and itaconic acid to develop a piezoelectric elastomer (PLBSIE), we construct a new ultrasound-activated PLBSIE-based tumor/wound unified therapeutic platform. Excitedly, it showed outstanding piezoelectric performance and high stretchability, and the separated carrier could react with water to generate highly cytotoxic reactive oxygen species (ROS), contributing to effectively killing tumor cells and eliminating bacteria through piezoelectric therapy. In addition, ultrasound-triggered piezoelectric effects could promote the migration and differentiation of wound-healing-related cells, thus accelerating wound healing. Herein, such a piezoelectric elastomer exerted a critical role in postoperative tumor-induced wound therapy and healing with the merits of possessing multifunctional abilities. Taken together, the developed ultrasound-activated PLBSIE will offer a comprehensive treatment for postoperative osteosarcoma therapy.

Effect of basic and basic/acid modifications on the surface of PVDF membranes for the insertion of TiO2 and its use in environmental applications

Supporting titanium oxide (TiO2) on polymeric membrane surfaces is a strategy to increase the photocatalytic activity of this material as well as to modify membrane surface with antifouling properties or to develop hybrid processes of water treatment. The chemical characteristics of the polymeric membrane surfaces are a determining factor in the correct impregnation of TiO2 particles. In this work, the titanium oxide was immobilized on polyvinylidene fluoride (PVDF) membrane surface by direct impregnation during the synthesis of the inorganic particles by sol-gel route. The PVDF membranes were previously modified by treatments based on an alkaline attack followed by acid treatment. The final TiO2-modified membranes were characterized by infrared and Raman spectroscopy, as well as by scanning electron microscopy. In addition, the changes on the surface characteristics were determined by contact angle measurements. Finally, the membranes were tested on the photocatalytic degradation of methyl orange (MO). The results obtained indicate that the basic/acid pretreatment allows the generation of active sites in the membrane and that when carrying out the synthesis of TiO2 on the membrane, it can be anchored stably on its surface and through the pores. The microscopies indicate that the structure of the membrane is not compromised by the pretreatment. The amount of TiO2 deposited on the membrane was of 0.1580 ± 0.01773 mg TiO2/cm2 membrane. With this amount of TiO2, a degradation percentage of 98.2% is achieved after 450 min; when the membrane is used for a second cycle, a degradation percentage of 82.0% is obtained, which remains constant for 3 subsequent cycles. This method, which uses the PVDF membrane as a support for TiO2 particles, represents a low-cost and easy-to-prepare insertion procedure, with good degradation percentages, which means that the membrane can be used for subsequent studies in filtration systems in the treatment of effluents from the textile industry.

Quantifying interfacial interactions for improved membrane antifouling: A novel approach using triangulation and surface element integration method

To gain a thorough understanding of interfacial behaviors such as adhesion and flocculation controlling membrane fouling, it is necessary to simulate the actual membrane surface morphology and quantify interfacial interactions. In this work, a new method integrating the rough membrane morphology reconstruction technology (atomic force microscopy (AFM) combining with triangulation technique), the surface element integration (SEI) method, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the compound Simpson's approach, and the computer programming was proposed. This new method can exactly mimic the real membrane surface in terms of roughness and shape, breaking the limitation of previous fractal theory and Gaussian method where the simulated membrane surface is only statistically similar to the real rough surface, thus achieving a precise description of the interfacial interactions between sludge foulants and the real membrane surface. This method was then applied to assess the antifouling propensity of a polyvinylidene fluoride (PVDF) membrane modified with Ni-ZnO particles (NZPs). The simulated results showed that the interfacial interactions between sludge foulants in a membrane bioreactor (MBR) and the modified PVDF-NZPs membrane transformed from an attractive force to a repulsive force. The phenomenon confirmed the significant antifouling propensity of the PVDF-NZPs membrane, which is highly consistent with the experimental findings and the interfacial interactions described in previous literature, suggesting the high feasibility and reliability of the proposed method. Meanwhile, the original programming code of the quantification was also developed, which further facilitates the widespread use of this method and enhances the value of this work.

TiO2-PAA-SiO2 pearl chain blend modified polyvinylidene fluoride ultrafiltration membrane with excellent oil-water separation, anti fouling performance and durability

In this work, a new type of composite nanoparticles, 'pearl chain', was developed by linking titanium dioxide and silicon dioxide by polyacrylic acid polymer chains, and the prepared TiO2-PAA-SiO2 composite nanoparticles were analysed by SEM, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and thermogravimetric analysis, zeta potential, x-ray diffraction, etc. The success of this work was verified by the successful linking of TiO2-PAA-SiO2 composite nanoparticles.TiO2-PAA-SiO2 composite nanoparticles were analysed to verify the successful attachment of pearl chains. The obtained TiO2-PAA-SiO2 were subsequently blended in different ratios to prepare polyvinylidene fluoride (PVDF) ultrafiltration membranes. The membrane performance was tested by porosity and water contact angle measurements, scanning electron microscopy, as well as experiments using bovine serum proteins and MTBE interception. The results showed that when a certain amount of TiO2-PAA-SiO2 was added, the surface wettability, porosity and permeability of the prepared modified composite membranes were significantly improved, and the BSA adsorption rate was increased from 71.59% to 80.86%, and the retention rate of MTBE was increased by 77%, in addition to showing a better anti-pollution effect (FRR: 91.07%). It was finally concluded that the prepared membranes embedded with 1.0 wt.% TiO2-PAA-SiO2 nanofillers showed good overall filtration performance, better contamination resistance and remarkable durability. The present work successfully demonstrated the feasibility of using polyacrylic acid chemical chains to connect nanoparticles with different functions to prevent particle loss and substantially enhance membrane performance, which is valuable for bridging connection of composite nanoparticles and exploring the development of high-performance ultrafiltration membranes.

Statistical Modeling and Optimization of Electrospinning for Improved Morphology and Enhanced β-Phase in Polyvinylidene Fluoride Nanofibers

The fabrication of PVDF-based nanofiber mats with enhanced β-phase using electrospinning and post processing was optimized using Taguchi design methodology. The parameters studied include the concentration of PVDF in the DMF (Dimethylformamide) solvent, applied voltage, flow rate, and drum speed. A reliable statistical model was obtained for the fabrication of bead-free PVDF nanofibers with a high fraction of β-phase (F(β)%). The validity of this model was verified through comprehensive regression analysis. The optimized electrospinning parameters were determined to be a 23 wt% PVDF solution, 20 kV voltage, a flow rate of 1 mL/h, and a drum speed of 1200 revolutions per minute.

Mechanism of PVDF Membrane Formation by NIPS Revisited: Effect of Precipitation Bath Nature and Polymer-Solvent Affinity

A new interpretation of the mechanism of the polyvinylidene fluoride (PVDF) membrane formation using the nonsolvent-induced phase separation (NIPS) method based on an analysis of the complete experimental phase diagram for the three-component mixture PVDF-dimethyl acetamide (DMAc)-water is proposed. The effects of the precipitation bath's harshness and thermodynamic affinity of the polymer's solvent on the morphology, crystalline structure, transport and physical-mechanical properties of the membranes are investigated. These characteristics were studied via scanning electron microscopy, wide-angle X-ray scattering, liquid-liquid porosimetry and standard methods of physico-mechanical analysis. It is established that an increase in DMAc concentration in the precipitation bath results in the growth of mean pore size from ~60 to ~150 nm and an increase in permeance from ~2.8 to ~8 L m-2 h-1 bar-1. It was observed that pore size transformations are accompanied by changes in the tensile strength of membranes from ~9 to ~11 and to 6 MPa, which were explained by the degeneration of finger-like pores and appearance of spherulitic structures in the samples. The addition of water to the dope solution decreased both the transport (mean pore size changed from ~55 to ~25 nm and permeance reduced from ~2.8 to ~0.5 L m-2 h-1 bar-1) and mechanical properties of the membranes (tensile strength decreased from ~9 to ~6 MPa). It is possible to conclude that the best membrane quality may be reached using pure DMAc as a solvent and a precipitation bath containing 10-30% wt. of DMAc, in addition to water.

Nanodiamond embedded polyaniline/polyvinylidene fluoride nanocomposites as microfiltration membranes for removal of industrial pollution

Membrane fouling remains a challenge to the membrane technology. Herein, we report the fabrication of composite membranes of polyaniline/polyvinylidene fluoride (PANI/PVDF) blended with nanodiamond (ND) with improved antifouling properties. The designed membranes were characterized by XRD, FTIR and SEM techniques. Characterization analysis revealed that addition of ND has maintained the structural integrity and porosity of composite membranes. The membrane permeation and antifouling performances were tested for hydrophilicity, porosity, pure water flux, shrinkage ratio, salt rejection of zinc acetate and copper acetate, and their fouling recovery ratio (FRR) measurements. A high solvent content ratio of 0.55 and a low shrinkage ratio of <12% due to enhanced hydrophilicity and porosity of the composite membrane with fouling-recovery of membranes to 88% were achieved. Separation of copper and zinc ions from aqueous solution was achieved. These findings imply that ND-based PANI/PVDF composite membranes can effectively serve as microfiltration membranes in industrial and municipal wastewater treatment.

Macromolecular Architecture-Dependent Polymorphous Crystallization Behavior of PVDF in the PVDF/γ-BL System via Thermally Induced Phase Separation

This study investigates the effect of the macromolecular architecture of poly(vinylidene fluoride) (PVDF) on its thermally induced phase separation (TIPS) behavior and polymorphic crystallization in the PVDF/γ-butyrolactone (PVDF/γ-BL) system. Preparative PVDF fractions with specific macromolecular architecture and phase constitution are generated. The results show that PVDF's macromolecular architecture, particularly the degree of branching and regio-defects, plays a significant role in its temperature-dependent crystallization and resulting polymorphic phases. While regio-defects dominate crystallization in the temperature range between 30 and 25 °C, the degree of branching becomes decisive in the 25-20 °C interval. The developed fractions of PVDF are further analyzed in terms of their molecular weight distribution, revealing that the PVDF fractions crystallized out of solution have similar molecular weight distributions with lower dispersity compared with the feed polymer. These findings are crucial for macromolecular separation and adjustment of PVDF polymorphic properties and hence for the development of tailor-made PVDF matrix materials for composites and membranes. The findings suggest the possibility of polymorphous phase tailoring of PVDF based on macromolecular architecture due to temperature-controlled crystallization out of solution and strongly motivate further research to reveal deeper knowledge of regio-defect and branching influence of PVDF solution crystallization.

A workflow for the development of template-assisted membrane crystallization downstream processing for monoclonal antibody purification

Monoclonal antibodies (mAbs) are commonly used biologic drugs for the treatment of diseases such as rheumatoid arthritis, multiple sclerosis, COVID-19 and various cancers. They are produced in Chinese hamster ovary cell lines and are purified via a number of complex and expensive chromatography-based steps, operated in batch mode, that rely heavily on protein A resin. The major drawback of conventional procedures is the high cost of the adsorption media and the extensive use of chemicals for the regeneration of the chromatographic columns, with an environmental cost. We have shown that conventional protein A chromatography can be replaced with a single crystallization step and gram-scale production can be achieved in continuous flow using the template-assisted membrane crystallization process. The templates are embedded in a membrane (e.g., porous polyvinylidene fluoride with a layer of polymerized polyvinyl alcohol) and serve as nucleants for crystallization. mAbs are flexible proteins that are difficult to crystallize, so it can be challenging to determine the optimal conditions for crystallization. The objective of this protocol is to establish a systematic and flexible approach for the design of a robust, economic and sustainable mAb purification platform to replace at least the protein A affinity stage in traditional chromatography-based purification platforms. The procedure provides details on how to establish the optimal parameters for separation (crystallization conditions, choice of templates, choice of membrane) and advice on analytical and characterization methods.

Effectiveness of different CuO morphologies nanomaterials on the permeability, antifouling, and mechanical properties of PVDF/PVP/CuO ultrafiltration membrane for water treatment

The hydrophobic nature of Poly (vinylidene fluoride) (PVDF) is a significant barrier to use in ultrafiltration, resulting in fouling, flux decline, and reduced lifespan in water treatment. This study examines the effectiveness of different morphologies of CuO nanomaterials (NMs) (spherical, rod, plate, and flower), synthesized by the facile hydrothermal method, to modify PVDF membrane with PVP additive for improving the performance of water permeability and antifouling. Such membrane configurations with different morphologies of CuO NMs improved hydrophilicity with a maximum water flux of 222-263 L m-2h-1 compared to 195 L m-2h-1 for the bare membrane and exhibited excellent thermal and mechanical strengths. The characterization results exhibited that plate-like CuO NMs were dispersed uniformly in the membrane matrix, and their incorporation as a composite improved the membrane properties. From the antifouling test with the bovine serum albumin (BSA) solution, the membrane with plate-like CuO NMs had the highest flux recovery ratio (FRR) (∼91%) and the lowest irreversible fouling ratio (∼10%). The antifouling enhancement was due to less interaction between modified membranes and foulant. Further, the nanocomposite membrane showed excellent stability and negligible Cu2+ ion leaching. Overall, our findings provide a new strategy for developing inorganic nanocomposite PVDF membranes for water treatment.

Biodegradable Piezoelectric Polymers: Recent Advancements in Materials and Applications

Recent materials, microfabrication, and biotechnology improvements have introduced numerous exciting bioelectronic devices based on piezoelectric materials. There is an intriguing evolution from conventional unrecyclable materials to biodegradable, green, and biocompatible functional materials. As a fundamental electromechanical coupling material in numerous applications, novel piezoelectric materials with a feature of degradability and desired electrical and mechanical properties are being developed for future wearable and implantable bioelectronics. These bioelectronics can be easily integrated with biological systems for applications, including sensing physiological signals, diagnosing medical problems, opening the blood-brain barrier, and stimulating healing or tissue growth. Therefore, the generation of piezoelectricity from natural and synthetic bioresorbable polymers has drawn great attention in the research field. Herein, the significant and recent advancements in biodegradable piezoelectric materials, including natural and synthetic polymers, their principles, advanced applications, and challenges for medical uses, are reviewed thoroughly. The degradation methods of these piezoelectric materials through in vitro and in vivo studies are also investigated. These improvements in biodegradable piezoelectric materials and microsystems could enable new applications in the biomedical field. In the end, potential research opportunities regarding the practical applications are pointed out that might be significant for new materials research.

Development of Support Layers and Their Impact on the Performance of Thin Film Composite Membranes (TFC) for Water Treatment

Thin-film composite (TFC) membranes have gained significant attention as an appealing membrane technology due to their reversible fouling and potential cost-effectiveness. Previous studies have predominantly focused on improving the selective layers to enhance membrane performance. However, the importance of improving the support layers has been increasingly recognized. Therefore, in this review, preparation methods for the support layer, including the traditional phase inversion method and the electrospinning (ES) method, as well as the construction methods for the support layer with a polyamide (PA) layer, are analyzed. Furthermore, the effect of the support layers on the performance of the TFC membrane is presented. This review aims to encourage the exploration of suitable support membranes to enhance the performance of TFC membranes and extend their future applications.

Robust self-cleaning membrane with superhydrophilicity and underwater superoleophobicity for oil-in-water separation

The discharge of oily wastewater has increased dramatically and will bring serious environmental problems. In this work, a self-cleaning and anti-fouling g-C₃N₄/TiO₂/PVDF composite membrane was fabricated via the layer-by-layer approach. The surface of as-prepared composite membrane displayed a superhydrophilic and underwater superoleophobic behavior under irradiation with visible light. Also, upon irradiation with visible light, the fabricated g-C₃N₄/TiO₂/PVDF composite membrane displayed enhanced permeation flux and improved oil removal efficiency as a result of the generation of hydroxyl free radicals during the photocatalytic filtration process. Significantly, irradiation with visible light remarkably improved reusability of the composite membrane by initiating photocatalytic decomposition of deposited oil foulants, which enabled removal of over 99.75% of oils, thus reaching a nearly 100% flux recovery ratio. Furthermore, the g-C₃N₄/TiO₂/PVDF composite membrane exhibited great anti-fouling behavior in photocatalysis-assisted filtration. The mechanistic study revealed that underwater superhydrophobicity and the generation of free hydroxyl radicals jointly contributed to membrane anti-fouling. The greatest advantages of this g-C₃N₄/TiO₂/PVDF composite membrane are that not only does it degrades the oil pollutants, but it also makes the membrane less vulnerable to fouling.

Facile preparation of high performance GO/Mn3O4/PVDF composite membranes with intercalation of manganese oxide nanowires

Polyvinylidene fluoride (PVDF) has been widely studied and applied in separation membranes due to its high thermal and chemical stability and mechanical strength. However, PVDF has strong hydrophobicity, resulting in easy contamination of the membrane surface and fast flux attenuation, so it is necessary to modify the membrane surface to improve its separation selectivity and service life. In this paper, PVDF microporous membrane was used as the matrix material and graphene oxide (GO) as the separation layer material. The GO/Mn₃O₄/PVDF composite membrane was prepared by layer self-assembly of GO nanosheets, and the functional layer spacing was adjusted by nanometer Mn₃O₄ intercalation. The prepared composite membrane showed high flux and separation selectivity in the filtration of organic compounds. The results showed that the rejection of methylene blue increased from 34% to 99.5%, and the flux decreased from 3000 L m^-2 h^-1 to 95 L m^-2 h^-1 when GO nanosheets covered the PVDF supporting membrane. After the introduction of Mn₃O₄ nanowires in the GO interlayer, the dye rejection reached 99.9% and the flux reached 612 L m^-2 h^-1. Compared with the unintercalated composite membranes, the flux of the prepared composite membranes showed good stability in the treatment of methylene blue, and the rejection remained unchanged.

A New Approach to the Development of Hollow Fiber Membrane Modules for Water Treatment: Mixed Polymer Matrices

In this study, mixed matrix hollow fiber polymeric membranes were prepared using polyethersulfone (PES) and polyvinylidene fluoride (PVDF) as polymers in their composition. N-methyl-2-pyrrolidone (NMP) was used as a solvent and demineralized water with an electrical conductivity below 3 μS·cm^-1 was used as a non-solvent. A new approach to producing enhanced polymeric hollow fiber membranes based on the preparation of a simple blend PVDF/PES solution, and on the conformation of the composite membranes through the extrusion technique followed by the phase inversion process in a non-solvent bath, was applied. The investigation focused on the preparation of polymeric membranes with different polymer ratios and further assessment of the effects of these proportions on the membrane performance and in specific physical properties. The amount of PVDF ranged from 10 to 90% with 10% steps. The presence of PVDF, although it increased the membranes' plasticity, had a negative effect on the overall mechanical properties of the composite membranes. Scanning electron microscopy (SEM) results showed good dispersion of both polymers in the polymeric matrix. Furthermore, the membrane permeability showed a slight negative correlation with contact angle, suggesting that membrane hydrophilicity played an important role in membrane permeability. Finally, it was found that membranes with low ratios of PVDF/PES may have potential for water treatment applications, due to the combined advantageous properties of PES and PVDF.

Preparation of PVDF-PVP Composite Membranes for Oily Wastewater Treatment

The oil and gas industry and related applications generate large quantities of oily wastewater, which can adversely affect the environment and human health if not properly handled. This study aims to prepare polyvinylidene fluoride (PVDF) membranes incorporated with polyvinylpyrrolidone (PVP) additives and utilize them to treat oily wastewater through the ultrafiltration (UF) process. Flat sheet membranes were prepared using PVDF dissolved in N,N-dimethylacetamide, followed by the addition of PVP ranging from 0.5 to 35 g. Characterization by scanning electron microscopy (SEM), water contact angle, Fourier transform infrared spectroscopy (FTIR), and mechanical strength tests were performed on the flat PVDF/PVP membranes to understand and compare the changes in the physical and chemical properties of the membranes. Prior to the UF process, oily wastewater was treated by a coagulation-flocculation process through a jar tester using polyaluminum chloride (PAC) as a coagulant. Based on the characterization of the membrane, the addition of PVP improves the physical and chemical properties of the membrane. The membrane's pore size becomes larger, which can increase its permeability and flux. In general, the addition of PVP to the PVDF membrane can increase the porosity and decrease the water contact angle, thereby increasing the membrane's hydrophilicity. With respect to filtration performance, the wastewater flux of the resultant membrane increases with increasing PVP content, but the rejections for TSS, turbidity, TDS, and COD are reduced.

Effect of High-Entropy Spinel Ferrite (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4 Doping Concentration on the Ferroelectric Properties of PVDF-Based Polymers

Polyvinylidene fluoride (PVDF)-based dielectric energy storage materials have the advantages of environmental friendliness, high power density, high operating voltage, flexibility, and being light weight, and have enormous research value in the energy, aerospace, environmental protection, and medical fields. To investigate the magnetic field and the effect of high-entropy spinel ferrite (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ nanofibers (NFs) on the structural, dielectric, and energy storage properties of PVDF-based polymers, (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ NFs were prepared via the use of electrostatic spinning methods, and (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄/PVDF composite films were prepared via the use of the coating method. The effects of a 0.8 T parallel magnetic field, induced for 3 min, and the content of high-entropy spinel ferrite on the relevant electrical properties of the composite films are discussed. The experimental results show that, structurally, the magnetic field treatment causes the originally agglomerated nanofibers in the PVDF polymer matrix to form a linear fiber chain with different fiber chains parallel to each other along the magnetic field direction. Electrically, the introduction of the magnetic field enhanced the interfacial polarization, and the (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄/PVDF composite film with a doping concentration of 10 vol% had a maximum dielectric constant of 13.9, as well as a low energy loss of 0.068. The high-entropy spinel ferrite (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ NFs and the magnetic field influenced the phase composition of the PVDF-based polymer. The α-phase and γ-phase of the cohybrid-phase B1 vol% composite films had a maximum discharge energy density of 4.85 J/cm³ and a charge/discharge efficiency of 43%.

Design and characterization of molecular, crystal and interfacial structures of PVDF-based dielectric nanocomposites for electric energy storage

PVDF-based polymers with polar covalent bonds are next-generation dielectric materials for electric energy storage applications. Several types of PVDF-based polymers, such as homopolymers, copolymers, terpolymers and tetrapolymers, were synthesized by radical addition reactions, controlled radical polymerizations, chemical modifications or reduction with the monomers of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), hexafluoropropylene (HFP) and chlorotrifluoroethylene (CTFE). Owing to rich molecular structures and complicated crystal structures, PVDF-based dielectric polymers can show versatile dielectric polarization properties, including normal ferroelectrics, relaxor ferroelectrics, anti-ferroelectrics and linear dielectrics, which are beneficial for designing polymer films with high capacity and high charge-discharge efficiency for capacitor applications. Furthermore, to satisfy the requirements of practical high-capacity capacitors, the polymer nanocomposite method is another promising strategy to achieve high-capacitance dielectric materials by the addition of high-dielectric ceramic nanoparticles, moderate-dielectric nanoparticles (MgO, and Al₂O₃), high-insulation nanosheets (BN), etc. It is concluded with the current problems and future perspectives of interfacial engineering, such as core-shell strategies and hierarchical interfaces in polymer-based composite dielectrics for high-energy-density capacitor applications. In addition, an in-depth understanding of the roles of interfaces on the dielectric properties of nanocomposites can be achieved by indirect analysis techniques (theoretical simulation) and direct analysis techniques (scanning probe microscopy). Our systematic discussions on molecular, crystal and interfacial structures provide guidance for designing fluoropolymer-based nanocomposites for high-performance capacitor applications.

PVDF/Clay Spheres Obtained through Phase Inversion for Cu Ion Removal

In this study, spheres of poly (vinylidene fluoride)/clay were synthesized using an easy dripping method (also known as phase inversion). The spheres were characterized by scanning electron microscopy, X-ray diffraction, and thermal analysis. Finally, application tests were carried out using commercial cachaça, a popular alcoholic beverage in Brazil. The SEM images revealed that during the solvent exchange process for sphere formation, PVDF tends to form a three-layered structure with a low-porosity intermediate layer. However, the inclusion of clay was observed to reduce this layer and also widen the pores in the surface layer. The results of the batch adsorption tests showed that the composite with 30% clay content in relation to the mass of PVDF was the most effective among those tested, with the removal of 32.4% and 46.8% of the total copper present in the aqueous and ethanolic media, respectively. The adsorption of copper from cachaça in columns containing cut spheres resulted in adsorption indexes above 50% for samples with different copper concentrations. Such removal indices fit the samples within the current Brazilian legislation. Adsorption isotherm tests indicate that the data fit better to the BET model.

Ultrathin g-C3N4 composite Bi2WO6 embedded in PVDF UF membrane with enhanced permeability, anti-fouling performance and durability for efficient removal of atrazine

A novel Bi₂WO₆-g-C₃N₄/polyvinylidene fluoride (PVDF) composite ultrafiltration (UF) membrane (BWO-CN/PVDF) was prepared by microwave hydrothermal and immersion precipitation phase transformation method. The BWO-CN/PVDF-0.10 exhibited an outstanding photocatalytic removal rate of atrazine (ATZ) (97.65 %) under the simulated sunlight and enhanced permeate flux (1356.09 L·m^-2·h^-1). The multiple optical and electrochemical detection confirmed that combining ultrathin g-C₃N₄ and Bi₂WO₆ can increase carrier separation rate and prolong its lifetime. The quenching test revealed that h⁺ and ¹O₂ were the prominent reactive species. Additionally, after a 10-cycle photocatalytic process, the BWO-CN/PVDF membrane presented remarkable reusability and durability. And it showed excellent anti-fouling performance by filtering BSA, HA, SA, and Songhua River under simulated solar irradiation. The molecular dynamic (MD) simulation showed that the combination of g-C₃N₄ and Bi₂WO₆ can enhance the interaction between BWO-CN and PVDF. This work opens up a new idea for designing and constructing a highly efficient photocatalytic membrane for water treatment.

Protein-folding-inspired approach for UF fouling mitigation using elevated membrane cleaning temperature and residual hydrophobic-modified flocculant after flocculation-sedimentation pre-treatment

Hydrophobic-modified flocculants have demonstrated considerable promise in the removal of emerging contaminants by flocculation. However, there is a lack of information about the impacts of dosing such flocculants on the performance of subsequent treatment unit(s) in the overall water treatment process. In this work, inspired by the ubiquitous protein folding phenomenon, an innovative approach using an elevated membrane cleaning temperature as the means to induce residual hydrophobic-modified chitosan flocculant (TRC), after flocculation-sedimentation, to reduce membrane fouling in a subsequent ultrafiltration was proposed; this was evaluated in a continuous flocculation-sedimentation-ultrafiltration (FSUF) process treating samples of the Yangtze River. The hydrophobic chains of TRC had similar temperature-dependent hydrophobicity to those of natural proteins. In the 40-day operation of the FSUF system with combined dosing of alum and TRC, a moderately elevated cleaning water temperature (45 °C) of both backwash with air-bubbling and soaking with sponge-scrubbing cleaning, significantly reduced reversible and irreversible fouling resistance by 49.8%∼61.3% and 73.9%∼83.3%, respectively, compared to the system using cleaning water at 25 °C. Material flow analysis, statistical analysis, instrumental characterizations, and computational simulations, showed that the enhanced fouling mitigation originated from three factors: the reduced contaminant accumulation onto membranes, the strengthened membrane-surface-modification role of TRC, and the weakened structure of the fouling material containing TRC, at the elevated cleaning temperature. Other measures of the performance, these being water purification, membrane stability and economic aspects, also confirmed the potential and feasibility of the proposed approach. This work has provided new insights into the role of hydrophobic-modified flocculants in membrane fouling control, in addition to emerging contaminant removal, in a FSUF surface water treatment process.

Removal of polyvinylidene fluoride binder and other organics for enhancing the leaching efficiency of lithium and cobalt from black mass

The agglomeration and encapsulation of recoverable materials of interest (e.g. metals and graphite) as a result of the presence of polyvinylidene fluoride (PVDF) in spent lithium-ion batteries (LIBs) with mixed chemistries (black mass) lower the extraction efficiency of metals. In this study, organic solvents and alkaline solutions were used as non-toxic reagents to investigate the removal of a PVDF binder from a black mass. The results demonstrated that 33.1%, 31.4%, and 31.4% of the PVDF were removed using dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO) at 150, 160, and 180 °C, respectively. Under these conditions, the peel-off efficiencies for DMF, DMAc, and DMSO were 92.9%, 85.3%, and approximately 92.9%, respectively. Using tetrabutylammonium bromide (TBAB) as a catalyst and 5 M sodium hydroxide (NaOH) at room temperature (RT- 21 °C-23 °C), 50.3% of PVDF and other organic compounds were eliminated. The removal efficiency was enhanced to approximately 60.5% when the temperature was raised to 80 °C using NaOH. Using 5 M potassium hydroxide at RT in a TBAB-containing solution, ca. 32.8% removal efficiency was obtained; raising the temperature to 80 °C further enhanced the removal efficiency to almost 52.7%. The peel-off efficiency was 100% for both alkaline solutions. Lithium extraction increased from 47.2% to 78.7% following treatment with DMSO and to 90.1% following treatment with NaOH via leaching black mass (2 M sulfuric acid, solid-to-liquid ratio (S/L): 100 g L-1 at 50 °C, for 1 h without a reducing agent) before and after removal of the PVDF binder. Cobalt's recovery went from 28.5% to 61.3% with DMSO treatment to 74.4% with NaOH treatment.

Enhancing quorum quenching media with 3D robust electrospinning coating: A novel biofouling control strategy for membrane bioreactors

Bacterial quorum quenching (QQ) is an effective strategy for controlling biofouling in membrane bioreactor (MBR) by interfering the releasing and degradation of signal molecules during quorum sensing (QS) process. However, due to the framework feature of QQ media, the maintenance of QQ activity and the restriction of mass transfer threshold, it has been difficult to design a more stable and better performing structure in a long period of time. In this research, electrospun fiber coated hydrogel QQ beads (QQ-ECHB) were fabricated by using electrospun nanofiber coated hydrogel to strengthen layers of QQ carriers for the first time. The robust porous PVDF 3D nanofiber membrane was coated on the surface of millimeter-scale QQ hydrogel beads. Biocompatible hydrogel entrapping quorum quenching bacteria (sp.BH4) was employed as the core of the QQ-ECHB. In MBR with the addition of QQ-ECHB, the time to reach transmembrane pressure (TMP) of 40 kPa was 4 times longer than conventional MBR. The robust coating and porous microstructure of QQ-ECHB contributed to keeping a lasting QQ activity and stable physical washing effect at a very low dosage (10g beads/5L MBR). Physical stability and environmental-tolerance tests also verified that the carrier can maintain the structural strength and keep the core bacteria stable when suffering long-term cyclic compression and great fluctuations in sewage quality.

Fabrication and Evaluation of Filtration Membranes from Industrial Polymer Waste

Polyvinylidene fluoride (PVDF) polymers are known for their diverse range of industrial applications and are considered important raw materials for membrane manufacturing. In view of circularity and resource efficiency, the present work mainly deals with the reusability of waste polymer 'gels' produced during the manufacturing of PVDF membranes. Herein, solidified PVDF gels were first prepared from polymer solutions as model waste gels, which were then subsequently used to prepare membranes via the phase inversion process. The structural analysis of fabricated membranes confirmed the retention of molecular integrity even after reprocessing, whereas the morphological analysis showed a symmetric bi-continuous porous structure. The filtration performance of membranes fabricated from waste gels was studied in a crossflow assembly. The results demonstrate the feasibility of gel-derived membranes as potential microfiltration membranes exhibiting a pure water flux of 478 LMH with a mean pore size of ~0.2 µm. To further evaluate industrial applicability, the performance of the membranes was tested in the clarification of industrial wastewater, and the membranes showed good recyclability with about 52% flux recovery. The performance of gel-derived membranes thus demonstrates the recycling of waste polymer gels for improving the sustainability of membrane fabrication processes.

Facile, green and scalable preparation of low-cost PET-PVDF felts for oil absorption and oil/water separation

3D felt materials with pore structures have the advantages of high absorption performance and recyclability in oily wastewater treatment and chemical leakage. However, most of them were fabricated using either toxic organic solvents or complicated procedures. Herein, we report a facile, green, and scalable route for the fabrication of 3D composite felts with large pore structures by sequentially stirring and heating polyethylene terephthalate (PET) fibers and polyvinylidene fluoride (PVDF). The resulting PET-PVDF felt exhibits high oil absorption capacity to a variety of oil and organic solvents with a maximum saturated absorption capacity of 32 g/g. Additionally, it can be used to separate oil/water mixtures with a separation efficiency of 99.9% and separation flux of 89570 L m^-2 h^-1. Moreover, this felt shows excellent mechanical durability and chemical stability under acid, base, salt solution, and other harsh environments. The current study provides a promising approach for large-scale industrial oily wastewater separation.

Optimization of PVDF-TrFE Based Electro-Conductive Nanofibers: Morphology and In Vitro Response

In this study, morphology and in vitro response of electroconductive composite nanofibers were explored for biomedical use. The composite nanofibers were prepared by blending the piezoelectric polymer poly(vinylidene fluoride-trifluorethylene) (PVDF-TrFE) and electroconductive materials with different physical and chemical properties such as copper oxide (CuO), poly(3-hexylthiophene) (P3HT), copper phthalocyanine (CuPc), and methylene blue (MB) resulting in unique combinations of electrical conductivity, biocompatibility, and other desirable properties. Morphological investigation via SEM analysis has remarked some differences in fiber size as a function of the electroconductive phase used, with a reduction of fiber diameters for the composite fibers of 12.43% for CuO, 32.87% for CuPc, 36.46% for P3HT, and 63% for MB. This effect is related to the peculiar electroconductive behavior of fibers: measurements of electrical properties showed the highest ability to transport charges of methylene blue, in accordance with the lowest fibers diameters, while P3HT poorly conducts in air but improves charge transfer during the fiber formation. In vitro assays showed a tunable response of fibers in terms of viability, underlining a preferential interaction of fibroblast cells to P3HT-loaded fibers that can be considered the most suitable for use in biomedical applications. These results provide valuable information for future studies to be addressed at optimizing the properties of composite nanofibers for potential applications in bioengineering and bioelectronics.

Poly(vinylidene fluoride) membrane with immobilized TiO2 for degradation of steroid hormone micropollutants in a photocatalytic membrane reactor

The lack of effective technologies to remove steroid hormones (SHs) from aquatic systems is a critical issue for both environment and public health. The performance of a flow-through photocatalytic membrane reactor (PMR) with TiO₂ immobilized on a photostable poly(vinylidene fluoride) membrane (PVDF-TiO₂) was evaluated in the context of SHs degradation at concentrations from 0.05 to 1000 µg/L under UV exposure (365 nm). A comprehensive investigation into the membrane preparation approach, including varying the surface Ti content and distribution, and membrane pore size, was conducted to gain insights on the rate-limiting steps for the SHs degradation. Increasing surface Ti content from 4 % to 6.5 % enhanced the 17β-estradiol (E2) degradation from 46 ± 12-81 ± 6 %. Apparent degradation kinetics were independent of both TiO₂ homogeneity and membrane pore size (0.1-0.45 µm). With optimized conditions, E2 removal was higher than 96 % at environmentally relevant feed concentration (100 ng/L), a flux of 60 L/m²h, 25 mW/cm², and 6.5 % Ti. These results indicated that the E2 degradation on the PVDF-TiO₂ membrane was limited by the catalyst content and light penetration depth. Further exploration of novel TiO₂ immobilization approach that can offer a larger catalyst content and light penetration is required to improve the micropollutant removal efficiency in PMR.

Tuning PVDF Membrane Porosity and Wettability Resistance via Varying Substrate Morphology for the Desalination of Highly Saline Water

Here, we report the fabrication of a series of highly efficient polyvinylidene fluoride (PVDF) membranes via substrate morphology variations. A wide range of sandpaper grit sizes (150-1200) were utilized as casting substrates. The effect of the penetration of abrasive particles present on the sandpapers on the casted polymer solution was tuned, and the impact of these particles on porosity, surface wettability, liquid entry pressure and morphology were investigated. The membrane distillation performance of the developed membrane on sandpapers was evaluated for the desalination of highly saline water (70,000 ppm). Interestingly, the utilization of cheap and widely available sandpapers as a substrate for casting can not only help in tuning the MD performance, but also in producing highly efficient membranes with stable salt rejection (up to 100%) and a 210% increase in the permeate flux over 24 h. The findings in this study will help in delineating the role of substrate nature in controlling the produced membrane characteristics and performance.

Rationalizing the Dependence of Poly (Vinylidene Difluoride) (PVDF) Rheological Performance on the Nano-Silica

Research on the rheological performance and mechanism of polymer nanocomposites (PNCs), mainly focuses on non-polar polymer matrices, but rarely on strongly polar ones. To fill this gap, this paper explores the influence of nanofillers on the rheological properties of poly (vinylidene difluoride) (PVDF). The effects of particle diameter and content on the microstructure, rheology, crystallization, and mechanical properties of PVDF/SiO₂ were analyzed, by TEM, DLS, DMA, and DSC. The results show that nanoparticles can greatly reduce the entanglement degree and viscosity of PVDF (up to 76%), without affecting the hydrogen bonds of the matrix, which can be explained by selective adsorption theory. Moreover, uniformly dispersed nanoparticles can promote the crystallization and mechanical properties of PVDF. In summary, the viscosity regulation mechanism of nanoparticles for non-polar polymers, is also applicable to PVDF, with strong polarity, which is of great value for exploring the rheological behavior of PNCs and guiding the process of polymers.

Preparation and Characterization of PVDF-TiO2 Mixed-Matrix Membrane with PVP and PEG as Pore-Forming Agents for BSA Rejection

Polymeric membranes offer straightforward modification methods that make industry scaling affordable and easy; however, these materials are hydrophobic, prone to fouling, and vulnerable to extreme operating conditions. Various attempts were made in this study to fix the challenges in using polymeric membranes and create mixed-matrix membrane (MMMs) with improved properties and hydrophilicity by adding titanium dioxide (TiO₂) and pore-forming agents to hydrophobic polyvinylidene fluoride (PVDF). The PVDF mixed-matrix ultrafiltration membranes in this study were made using the non-solvent phase inversion approach which is a simple and effective method for increasing the hydrophilic nature of membranes. Polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) as pore-forming chemicals were created. Pure water flux, BSA flux, and BSA rejection were calculated to evaluate the mixed-matrix membrane's efficiency. Bovine serum albumin (BSA) solution was employed in this study to examine the protein rejection ability. Increases in hydrophilicity, viscosity, and flux in pure water and BSA solution were achieved using PVP and PEG additives. The PVDF membrane's hydrophilicity was raised with the addition of TiO₂, showing an increased contact angle to 71°. The results show that the PVDF-PVP-TiO₂ membrane achieved its optimum water flux of 97 L/(m²h) while the PVDF-PEG-TiO₂ membrane rejected BSA at a rate greater than 97%. The findings demonstrate that use of a support or additive improved filtration performance compared to a pristine polymeric membrane by increasing its hydrophilicity.

Stability of Superhydrophobicity and Structure of PVDF Membranes Treated by Vacuum Oxygen Plasma and Organofluorosilanisation

Superhydrophobic poly(vinylidene fluoride) (PVDF) membranes were obtained by a surface treatment consisting of oxygen plasma activation followed by functionalisation with a mixture of silica precursor (SiP) (tetraethyl-orthosilicate [TEOS] or 3-(triethoxysilyl)-propylamine [APTES]) and a fluoroalkylsilane (1H,1H,2H,2H-perfluorooctyltriethoxysilane), and were benchmarked with coated membranes without plasma activation. The modifications acted mainly on the surface, and the bulk properties remained stable. From a statistical design of experiments on surface hydrophobicity, the type of SiP was the most relevant factor, achieving the highest water contact angles (WCA) with the use of APTES, with a maximum WCA higher than 155° for membranes activated at a plasma power discharge of 15 W during 15 min, without membrane degradation. Morphological changes were observed on the membrane surfaces treated under these plasma conditions, showing a pillar-like structure with higher surface porosity. In long-term stability tests under moderate water flux conditions, the WCA of coated membranes which were not activated by oxygen plasma decreased to approximately 120° after the first 24 h (similar to the pristine membrane), whilst the WCA of plasma-treated membranes was maintained around 130° after 160 h. Thus, plasma pre-treatment led to membranes with a superhydrophobic performance and kept a higher hydrophobicity after long-term operations.

Formation of Porous Structures and Crystalline Phases in Poly(vinylidene fluoride) Membranes Prepared with Nonsolvent-Induced Phase Separation-Roles of Solvent Polarity

PVDF membranes were prepared with nonsolvent-induced phase separation, using solvents with various dipole moments, including HMPA, NMP, DMAc and TEP. Both the fraction of the polar crystalline phase and the water permeability of the prepared membrane increased monotonously with an increasing solvent dipole moment. FTIR/ATR analyses were conducted at the surfaces of the cast films during membrane formation to provide information on if the solvents were present as the PVDF crystallized. The results reveal that, with HMPA, NMP or DMAc being used to dissolve PVDF, a solvent with a higher dipole moment resulted in a lower solvent removal rate from the cast film, because the viscosity of the casting solution was higher. The lower solvent removal rate allowed a higher solvent concentration on the surface of the cast film, leading to a more porous surface and longer solvent-governed crystallization. Because of its low polarity, TEP induced non-polar crystals and had a low affinity for water, accounting for the low water permeability and the low fraction of polar crystals with TEP as the solvent. The results provide insight into how the membrane structure on a molecular scale (related to the crystalline phase) and nanoscale (related to water permeability) was related to and influenced by solvent polarity and its removal rate during membrane formation.