Fabricate Polyvinylidene Fluoride Research Articles

Contact-electro-catalysis for degradation of trace antibiotics in wastewater

Antibiotic contamination of water bodies is a major concern in environmental management. Despite their superior efficacy in antibiotic removal, advanced oxidation processes (AOPs) have yet to be widely adopted owing to their substantial cost associated with the large amounts of chemicals required. In this study, a novel contact-electro-catalysis (CEC) process with reusable polytetrafluoroethylene (PTFE) particles as a trigger catalyst was applied to replace traditional AOPs, and it was able to degrade three typical antibiotics (sulfamethoxazole [SMX], ciprofloxacin [CIP], and tetracycline [TET]) in the secondary effluent of a wastewater treatment plant for the first time. The PTFE particles at a concentration of 0.8 g/L were introduced into antibiotic solutions with an antibiotic concentration of 1 mg/L, and the removal rates of SMX, CIP, and TET after a 90-min operation time reached 50 %, 80 %, and 90 %, respectively. Our findings revealed that the CEC reaction generated ●OH and 1O2, contributing substantially to antibiotic degradation. Thus, new reactive oxygen species generation mechanisms during the CEC process were proposed. Furthermore, we fabricated polyvinylidene fluoride nanofiber membranes using electrospinning to recycle PTFE particles, where a nearly 100 % recovery rate through dead-end filtration was realized with a high water flux of 7.5 m3/(m2∙h). The results of this study provide a promising approach for antibiotic removal from wastewater.

Visible-light-driven photocatalytic PVDF-TiO2/CNT/BiVO4 hybrid nanocomposite ultrafiltration membrane for dairy wastewater treatment

Enhancing the performance of polymeric membranes by nanomaterials has become of great interest in the field of membrane technology. The present work aimed to fabricate polyvinylidene fluoride (PVDF)–hybrid nanocomposite membranes and modify them with TiO2 and/or BiVO4 nanoparticles and/or carbon nanotubes (CNTs) in various ratios. Their photocatalytic performance under visible light was also investigated. All modified PVDF membranes exhibited higher hydrophilicity (lower contact angle of water droplets) than that of the neat membrane used as a reference. The membranes were characterized by using bovine serum albumin (BSA) as model dairy wastewater. The hybrid membranes had better antifouling properties as they had lower irreversible filtration resistance than that of the neat membrane. Hybrid PVDF membranes containing TiO2/CNT/BiVO4 showed the highest flux and lowest irreversible resistance during the filtration of the BSA solution. PVDF-TiO2/BiVO4 had the highest flux recovery ratio under visible light (70% for the PVDF mixed with 0.5% TiO2 and 0.5% BiVO4). The hydrophilicity of membrane surfaces increased with the incorporation of nanoparticles, preventing BSA to bind to the surface. This resulted in a slight decrease in BSA and chemical oxygen demand rejections, which were still above 97% in all cases.

Dehydrofluorination and One‐Pot Hydrothermal Process for Polyvinylidene fluoride/Polytetrafluoroethylene@TiO2 Membranes with Durable Superhydrophobicity toward Repeatable Separating and Photodegrading Oily Dyes in Water‐in‐Oil Emulsions

AbstractThe photocatalytic and inherently hydrophilic characteristic of titanium dioxide (TiO2) make it very suitable for separating oil‐in‐water emulsion and aqueous pollutants removal. However, the removal of the oily dyes in water‐in‐oil emulsion usually needs superhydrophobic/superoleophilic membranes. Although surface modification of TiO2 with fluorinated organic compounds can bring hydrophobicity, the hydrophobic surface would change back to a hydrophilic surface again after light illumination as fluorinated organic molecules are easily photodegraded too. To date, very few reports have successfully fabricated TiO2 photocatalysts keeping long‐term superhydrophobicity after repeatable photodegradation. Herein, an approach to fabricate polyvinylidene fluoride (PVDF)/polytetrafluoroethylene (PTFE) @TiO2 nanofibrous membranes through dehydrofluorination and one‐pot hydrothermal process, which possess stable superhydrophobicity in various harsh environments, is reported. For the first time, PTFE is bonded with PVDF through dehydrofluorination which induces crosslinking between PTFE and PVDF chains. Owing to the existence of PTFE, extensive hydrophobic TiO2 can be in situ grown on the rough surface of PVDF/PTFE nanofibers through one‐pot hydrothermal process. These features ensure that the membranes possess durable and high‐efficient water‐in‐oil emulsion separation and photodegradation performance. The photodegradation efficiency of the PVDF/PTFE@TiO2 membranes for oil‐soluble dyes remains above 95% even after ten cycles.

Effects of electrode materials on solution-processed polyvinylidene fluoride-based piezoelectric nanogenerators: Do they matter?

Numbers of energy harvesting studies have reported that using the appropriate electrode materials could enhance the electrical output performance of the energy harvesters. In this work, we fabricated polyvinylidene fluoride (PVDF)-based piezoelectric nanogenerators (PENGs) using the solution-process method. Different combinations of silver nanowires, indium-tin-oxide (ITO), and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate were used as top and bottom electrodes to investigate the effect of electrode materials on the electrical output performance. The open-circuit voltage (VOC), short-circuit current (ISC), the charge generated, instantaneous areal power measured, and internal impedance were measured. The obtained data reveal no significant difference between the different electrode combinations, with a mean absolute deviation of 0.21 V, and 0.03 μA for VOC and ISC, respectively. Thereby, an equivalent circuit for a real capacitor is adopted to analyze further and identify the impedance manifestation attributed to the PVDF layer and electrode materials. Overall, the electrode materials have an insignificant impact on the electrical output performance of PVDF-based PENGs in this study. Nevertheless, the obtained data inciting that tuning the PVDF impedance by introducing the 2D MXene nanofillers approach could be useful information to improve the performance of solution-processed PVDF-based PENGs.

Production of spherical polymeric composite powder for selective laser sintering via plasma assisted solid state shear milling: From theory to piezoelectric application

With the advent of digital industry, intelligent manufacturing is becoming a pillar industry guiding the rapid development of modern industry and daily life of human kind. Nevertheless, the lack of advanced functional materials severely restricts the technological updates and product upgrades. Herein, we developed a facile method to fabricate polyvinylidene fluoride (PVDF)/barium titanate (BaTiO3) spherical piezoelectric powder for SLS processing by combining solid state shear milling (S3M) and plasma technology. With assistance of simulation of heat transfers and molecular dynamics, the transformation of irregular powder to spherical one was successfully clarified by melt surface tension. As a proof-of-concept, the as-prepared spherical powder endowed SLS parts with advanced mechanical properties and piezoelectric properties derived from the excellent accumulation characteristics. The improved piezoelectric properties could reach an open-circuit voltage of 4.7 V and a short-circuit current of 106.5 nA, which exhibited better output performance than those of most reported piezoelectric 3D parts. This work not only contributed a high quality piezoelectric material for SLS processing, but also provided a new route for efficient and clean preparation of polymer-based spherical powder for all chemical engineering fields.

Achieving UV and X-ray Dual Photochromism in a Metal-Organic Hybrid via Structural Modulation.

Rational design and synthesis of new photochromic sensors have been active research areas of inquiry, particularly on how to predict and tailor their properties and functionalities. Herein, two thulium 2,2':6',2''-terpyridine-4'-carboxylate (TPC)-functionalized metal-organic hybrids, Tm(TPC)2(HCOO)(H2O) (TmTPC-1) and Tm(TPC)(HCOO)2 (TmTPC-2) with different photochromic response behaviors, have been successfully prepared, allowing for straightforward investigations of the structure-property correlation. Single-crystal X-ray diffraction and electron paramagnetic resonance analyses revealed that the incorporation of a unique dangling decorating TPC unit in TmTPC-1 offers a shorter and more accessible π-π interaction pathway between the adjacent TPC moieties than that in TmTPC-2. Such a structural feature leads to the production of radical species via a photoinduced intermolecular electron-transfer (IeMCT) process upon UV or X-ray irradiation, which ultimately endows TmTPC-1 with a rather unusual UV and X-ray dual photochromism. A linear relationship between the change of UV-vis absorbance intensity and X-ray dose was established, making TmTPC-1 a promising dosimeter for X-ray radiation with an extremely high energy threshold (30 kGy). To advance the development for real-world application, we have fabricated polyvinylidene fluoride (PVDF) membranes incorporating TmTPC-1 for functioning either as a UV imager or as an X-ray radiation indicator. Lastly, TmTPC-1 exhibits high thermal stability (up to 400 °C) and radioresistance (at least 900 kGy), and also excellent reversibility of photochromic transformation (at least 5 cycles).

Effect of Surfactants’ Tail Number on the PVDF/GO/TiO2-Based Nanofiltration Membrane for Dye Rejection and Antifouling Performance Improvement

In this work, the novel utilisation of customised double- and triple-tail sodium bis(3,5,5-trimethyl-1-hexyl) sulphosuccinate (AOT4) and sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-silphonate (TC14) surfactants to assist the direct graphene oxide (GO) synthesis via electrochemical exfoliation utilising dimethylacetamide (DMAc) as a solvent were investigated. The synthesised DMAc-based GO and titanium dioxide (TiO2) nanoparticles were then used to fabricate polyvinylidene fluoride (PVDF)-based nanofiltration (NF) membranes by the non-solvent-induced phase separation method. The incorporation of GO and TiO2 as hydrophilic nanoparticles were to enhance membrane hydrophilicity. The utilisation of higher surfactants’ tail number obviously alters the fabricated membrane’s morphology which further affects its performance for dye rejection and antifouling ability. Higher surfactants’ tail number resulted in higher oxidation process which then provided more interaction between the GO and PVDF. Based on the dead-end cell measurement, PVDF/TC14-GO/TiO2 presented a slightly higher dye rejection efficiency of 92.61% as compared to PVDF/AOT4-GO/TiO2 membrane (92.39%). However, PVDF/TC14-GO/TiO2 possessed three times higher water permeability (48.968 L/m2 h MPa) than PVDF/AOT4-GO/TiO2 (16.533 L/m2 h MPa) and also higher hydrophilicity as presented by lower contact angle (65.4 ± 0.17°). This confirmed that higher surfactants’ tail number improved the fabricated membrane’s performance. Both fabricated membranes also exhibited high flux recovery ratio (FRR) ( $$>$$ 100%) which indicated better antifouling properties.

Effect of Pore Characteristics in Polyvinylidene Fluoride/Fumed Silica Membranes on Mass Flux in Solar-Assisted Evaporation Applications

Although important, very little has been demonstrated in the literature to experimentally demonstrate the effects of porosities and pore size on the evaporation flux in polymeric membranes. Additionally, we suspect that a batch-mode setup, i.e., stagnant water, could cause a build-up of heat in the system, influencing the evaporation mass-flux mechanism, and jeopardizing the ability to attain a real correlation between evaporation and effects of pore characteristics. Herein, we fabricate polyvinylidene fluoride membranes containing variable amounts of a Fumed Silica additive to achieve membranes with variable properties, and we investigate the change in the performance of the solar-assisted thin-film evaporation utilizing an in-house built continuous flow evaporation setup (to avoid heat build-up effects in the bulk of the water and demonstrate a continuous flow system). Our membrane design approach had two important advantages: (1) the achievement of similar heat transfer and solar absorbance properties and (2) the achievement of variable pore sizes and volume porosities. We show that the mass flux increased as the mean pore size decreased, indicating that the mode of mass transfer occurred due to the thin-film region of the meniscus from the small fluid velocities near the interface, and we attribute the results to the increase in the capillary pumping effects through the mesoporous channels as they get thinner.

Synergistic effects of polyaniline and pulsed electromagnetic field to stem cells osteogenic differentiation on polyvinylidene fluoride scaffold

Repairing the lost or damaged mandible is very difficult and time-consuming, so there is a great hope for tissue engineering to accelerate it. At the present study, electrospinning was applied to fabricate polyvinylidene fluoride (PVDF) and PVDF-polyaniline (PANI) composite scaffolds. In addition, extremely low frequency pulsed electromagnetic field (PEMF) was applied for treating the stem cells derived from dental pulp (DPSCs) when cultured on the nanofibrous scaffolds. Osteoinductive property of the fabricated PVDF, PVDF-PANI scaffold at the presence and absence of the PEMF was investigated by evaluating the common osteogenic differentiation markers in seeded-DPSCs on the scaffold. Results demonstrated that cell attachment, protein adsorption and cells viability were increased when PEMF was applied. In addition, ALP activity, calcium content, osteogenic genes and protein evaluations confirmed that PEMF could significantly increase osteoinductivity of the PVDF while composite with PANI. According to the results, the use of polymers with piezoelectricity and conductivity features plus PEMF exposure has a promising potential to improve the current treatment methods in bone and mandibular defects.

Understanding the multiple functions of styrene-co-maleic anhydride in fabricating polyvinylidene fluoride hollow fiber membrane via coupled phase inversion process and its effect on surface infiltration behavior and membrane permeability

Polyvinylidene fluoride/styrene-co-maleic anhydride (SMA) hollow fiber membranes were prepared via coupled phase inversion (thermally induced phase separation-nonsolvent induced phase separation) process. The multiple functions of SMA, such as surface enrichment, non-diluent, dispersion, pore-former, hydrophilicity and surface infiltration behavior, were discussed. The membrane formation mechanisms about surface deposition of SMA for the outer surface and pore-former of micelle for the matrix were proposed. The membrane microstructure for the matrix changed from the spherulite to the interconnected cellular pores enclosed by the stackage of small size spherulite and the porosity of the membrane increased from 57.22% to 74.62% with the addition of SMA. Interestingly, the continuous SMA deposition layer as thin as 50~160 nm can be fabricated by this coupled phase separation process, which in turn not only decreased the thickness of outer skin-layer and the pore size, but also enriched the SMA content on outer surface markedly, improved the hydrophilicity, flux and the anti-fouling performance. Finally, based on the traditional hydration layer (HL) notion, the anti-fouling mechanism of the membrane was further developed from the point of “building-foundation” relationship via the surface infiltration of SMA. The purpose of this manuscript is to offer a simple and effective way to regulate the membrane microstructure, introduce functional group and propose a revised anti-fouling mechanism.

Performance enhancement of triboelectric nanogenerators based on polyvinylidene fluoride/graphene quantum dot composite nanofibers

Wearable mechanical energy harvesting technologies have been achieved much attention for the wireless sustainable power source applications. In this study, we have fabricated polyvinylidene fluoride (PVDF)/graphene quantum dot (GQD) composite nanofibers (NFs), which showed improved triboelectric nanogenerator (TENG) performance. PVDF/GQD composite NFs were fabricated by an electrospinning method. Structural and chemical investigations show that the GQDs were embedded in the PVDF NFs and promoted the formation of polar β-phase when an optimal amount of GQDs was incorporated. The PVDF/GQD NFs showed strong photoluminescence at a wavelength of 453 nm, which was attributed to the electronic transitions in the GQDs. As the GQD content increased from 0 to 5 vol%, the maximum output power from TENG devices increased from 35 to 97 μW but decreased with further additions of GQDs. The enhancement and degradation of the TENG performance with increasing the GQD contents were due to the enhanced formation of polar β-phase and the detrimental effect of conductive GQDs for charge trapping, respectively.

Effects of modified nano-silica on the microstructure of PVDF and its microporous membranes

In this study, effects of modified silica on the microstructure of polyvinylidene fluoride and its microporous membranes were investigated. The silica was modified by 3-Methacryloxypropyltrimethoxysilane to improve its compatibility with the polyvinylidene fluoride matrix. The relaxation time of polyvinylidene fluoride was markedly improved by modified nano-silica, especially at the loading of 0.1 wt‰. Effects of the modified silica on the nanocomposite microstructure, such as crystallization and orientation behavior, were studied in the manuscript. Furthermore, adding 3-Methacryloxypropyltrimethoxysilane modified silica could effectively handicap the relaxation of orientation structure in polyvinylidene fluoride and facilitate the formation of uniform lamellar structures which could be described by two-dimensional small-angle X-ray scattering testing. Finally, casting films with more uniform lamellar structure was also in favor of fabricating polyvinylidene fluoride microporous membranes by melt-stretching method.

A modified, mussel-inspired method to fabricate polyvinylidene fluoride membranes filled with halloysite nanotubes modified with dopamine, iron oxide, and silane for oil–water separation

Polyvinylidene fluoride is an excellent membrane separation material, but its hydrophilicity is weak, which makes the membrane susceptible to contamination during use. In this study, a novel compos...

Fabrication of PVDF nanofibrous hydrophobic composite membranes reinforced with fabric substrates via electrospinning for membrane distillation desalination

To improve the mechanical properties of the electrospun nanofibrous membrane, the nonwoven fabrics and spacer fabrics were employed as support substrates to fabricate polyvinylidene fluoride (PVDF) nanofibrous composite membranes. The influences of the substrate on membrane morphology, hydrophobicity, pore size and pore size distribution, porosity, mechanical strength and permeability were comprehensive evaluated. The electrospun composite membranes had a three dimension bead-fiber interconnected open structure and a rough membrane surface. The membrane surface presented a multilevel re-entrant structure and all the water contact angles were above 140°. In contrast with the pure PVDF nanofibrous membrane, the stress at break and the elastic modulus of the composite membranes increased by 4.5–16 times and 17.5–37 times, respectively. Since the spacer fabrics had less resistance to mass transfer, the membranes composited with spacer fabrics exhibited greater permeate fluxes compared with the composite membranes with the nonwoven fabrics as substrates. During the membrane distillation test, the highest permeate flux was up to 49.3kg/m2/hr at the feed temperature of 80°C. The long-time and repeat operation of membrane distillation desalination indicated the fabricated membrane with a good resistance to scaling and wetting. The results suggested the potential of the electrospun composite membrane for membrane distillation application.

Geothermal Membrane Distillation in Industrial Greenhouse Applications: Membrane Fabrication and Characterization

Abstract Membrane distillation is reported for the first time in the literature being used to desalinate geothermal brackish groundwater for industrial greenhouse applications. Asymmetric hollow fiber membranes were fabricated and characterized for their direct contact membrane distillation (DCMD) application to provide irrigation water at Masson Greenhouse, New Mexico. Membranes exhibited an asymmetric configuration with an external sponge layer and an internal macrovoid layer. The intention was to prevent pore wetting from the hot saline fluid with the sponge layer, while using the macrovoid layer to increase the water flux and thermal efficiency of the membrane. A water flux of 55 liters/m2-h (LMH) with a salt rejection greater than 99.99% was observed for the fabricated polyvinylidene fluoride (PVDF) hollow fiber membranes at a water vapor pressure gradient of 3.2 MPa/cm (shell-side inlet temperature of 80°C). Further investigation, however, revealed that pore wetting existed in the macrovoid layer at...

Using green solvent, triethyl phosphate (TEP), to fabricate highly porous PVDF hollow fiber membranes for membrane distillation

While membrane technology continues to thrive in seawater desalination, it would defeat the very purpose of saving the environment if toxic solvents are involved in membrane manufacture. As a paradigm of green chemistry, a non-toxic solvent, triethyl phosphate (TEP), was used for the first time to fabricate polyvinylidene fluoride (PVDF) hollow fiber membranes for direct contact membrane distillation (DCMD). The phase inversion kinetics of the PVDF/TEP system was closely investigated and compared with the conventional N-Methyl-2-pyrrolidone (NMP)/PVDF system. The former showed a less abrupt phase inversion rate and produced a more porous sponge-like structure than the latter. The 12/88wt% PVDF/TEP binary solution produced fibers with promising performance. They not only possessed robust mechanical properties and a liquid entry pressure up to 2.0bar but also exhibited an average flux of 20kg/m2·h at 60°C and a NaCl rejection of 99.99%. In addition, hollow fiber membranes spun from this PVDF/TEP system had porosity of greater than 83% for all conditions studied. Since there were no additives or non-solvents in the dope solutions and no post-treatments involved, the use of TEP as a green solvent could significantly reduce the complexity of membrane fabrication, scale up and commercialization. Clearly, the much safer solvent TEP is able to replace toxic solvents commonly used in membrane manufacture and to produce membranes with highly competitive performance.

Versatile polyvinylidene fluoride hybrid ultrafiltration membranes with superior antifouling, antibacterial and self-cleaning properties for water treatment

Novel ultrafiltration membranes with both superior antibacterial and self-cleaning properties were fabricated. By using a non-solvent induced phase separation method (NIPS), N-halamine epoxide and siloxane were grafted onto the multi-walled carbon nanotubes (N-Si-MWNTs) to fabricate polyvinylidene fluoride (PVDF) hybrid membranes. The membrane morphology was observed under a field emission scanning electron microscopy. The results demonstrated that the PVDF hybrid membranes had an asymmetrical structure, and their hydraulic permeability was evidently enhanced with the addition of modified MWNTs. When compared with the primitive PVDF membrane, the hybrid membranes presented improved surface hydrophilicity. After three ultrafiltration–regeneration cycles with bovine serum albumin as model biofoulant and pure water as detergent, the PVDF hybrid membranes exhibited a high flux recovery ratio (FRR). Furthermore, when compared with other membranes, the membrane containing N-Si-MWNTs displayed the highest FRR value of above 96.5% after the entire fouling and cleaning experiment. The fabricated PVDF/N-Si-MWNTs hybrid membranes had excellent antibacterial efficacy, presenting maximum antibacterial efficacy of 98.0% and 95.6% against Staphylococcus aureus and Escherichia coli, respectively. Thus, the PVDF/N-Si-MWNTs membranes fabricated in this study are environment-friendly with both benign antibacterial and self-cleaning properties.

Preparation of Polyvinylidene Fluoride (PVDF) Triboelectric Nanogenerators with Different Polymer

Triboelectric nanogenerators have recently been used to harvest mechanical energy from surrounding environment which is of great significance in the field of energy conversion. Electrospinning provides a simple, low cost and versatile method for the generation of 1D nanostrucutures. Nanofiber membranes have many advantages over the commonly used dense film for designing the riboelectric nanogenerators, such as the low wear resistance caused from the internal and excellent external consistency of the electrospinning membranes. In this paper, we produce a variety of polymer films by electro-spinning, and fabricate Polyvinylidene Fluoride (PVDF) triboelectric nanogenerators with different polymer films afterwards. We except to explore the TEG power generation effect, and influencing factors, and then determine the best combination of the results of TEG (PVDF-PHBV). Such a flexible polymer TEG generates output voltage of up to 112 V at a power of 0.045W.

A novel approach to fabricate interconnected sponge-like and highly permeable polyvinylidene fluoride hollow fiber membranes for direct contact membrane distillation

A novel, environmental friendly approach was introduced to fabricate polyvinylidene fluoride hollow fiber membranes with interconnected sponge-like structure and high permeability for membrane distillation. The effect of different parameters on the morphologies and properties of the membranes were investigated. The pore size and porosity were in the range of 0.20–0.40μm and 61.07–79.36% respectively. The maximum tensile strength was 6.941MPa. The nitrogen flux under 0.2MPa and pure water flux were as high as 44L/(m2s) and 4290L/(m2atmh) respectively. The direct contact membrane distillation flux reached 77.6kg/(m2h). The membranes prepared by this method meet the requirements of direct contact membrane distillation.

Study on CO2 stripping from water through novel surface modified PVDF hollow fiber membrane contactor

Abstract Dry–wet phased inversion method was used to fabricate polyvinylidene fluoride (PVDF) hollow fiber membranes. Different concentration of surface modifying macromolecules (SMM) i.e., 2, 4 and 6 wt.% were used as additives in the spinning dope. In the phase inversion SMM migrates to the membrane surface and changes the surface morphology with chemical properties on the membrane surface. This modification results into larger pore size, higher gas permeance, effective surface porosity and water contact angle. The surface modified membrane was used in membrane contactor for CO 2 stripping from water by using self-fabricated gas–liquid membrane contactor module. The result of CO 2 stripping experiment shows that the performance of surface modified membrane is better than plain PVDF membrane. CO 2 desorption flux increased with respect to SMM concentration, considerably. The membrane fabricated with 6 wt.% SMM as additive showed higher CO 2 desorption flux and efficiency of 2.1 × 10 −3 (mol m −2 s −1 ) and 80%, respectively at 200 ml/min of liquid flow rate. For this membrane CO 2 stripping flux was investigated for different liquid phase temperature. It was found that desorption flux increased by increasing liquid temperature and the highest stripping flux was obtained in the temperature of 90 °C. The enhancement of the gas flow rate increased the CO 2 desorption flux but this change was negligible.