Electrospun fibrous membranes for efficient heavy metal removal

Heavy metal pollution is a growing environmental problem in recent decades, which requires immediate and urgent action. In this article, we provide an overview of the works published in the last decade concerning the development of electrospinning‐based micro‐ and nano‐porous membranes for efficient heavy metal removal. Apart from their super‐high surface‐to‐volume ratio, electrospun nanofibers possess a variety of surface groups which enable their further functionalization and functional nanoparticle incorporation. Compared to typical adsorbents, electrospun fibrous membranes are superior in many ways like higher permeation flux, lower pressure drop, flexible component adjustment, and even multi‐target adsorption. Therefore, electrospun‐based fibrous membranes hold great potential on the treatment of heavy metal contaminants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40864.     

Electrospun Nanofibers Membranes for Effective Air Filtration

In modern society, traffic and transportation and the manufacturing industry and construction industries continuously release large amounts of dust and particles into the atmosphere, which can cause heavy air pollution, leading to health hazards. The haze disaster, a serious problem in developing countries such as China and India, has become one of the main issues of global environmental pollution in recent decades. Many air filtration technologies have been developed. Air filtration using electrospun fibers that intercept fine particles/volatile organic gases/bacterium is a relatively new, but highly promising, technique. Due to their interconnected nanoscale pore structures, highly specific surface areas, fine diameters, and porous structure as well as their ability to incorporate active chemistry on a nanoscale surface, electrospun fibers are becoming a promising versatile platform for air filtration. In this review, following a short introduction concerning the need for air filtration and filtration theory and mechanism, electrospun nanofibers membranes for air filtration have been highlighted, including the preparation (electrospinning process) and the parameters relevant to filtration efficacy. Additionally, various types (function) of the electrospun air filtration membranes have been classified in detail. Furthermore, their potential in the filtration of fine particles and chemical pollutants has been discussed. Finally, the challenges of their practical application and the future prospects have been summarized. Given that some advanced electrospun air filtration nanofibrous membranes exist for treating different contaminants from various types of polluted atmosphere, it is believed that they should make a significant contribution in protection against air pollution.

     

Thrombin‐Loaded Poly(butylene succinate)‐Based Electrospun Membranes for Rapid Hemostatic Application

Poly(butylene succinate) (PBS) and gelatin‐coated PBS electrospun membranes are evaluated for use as support materials to immobilize thrombin, an effective hemostat for topical injury, and three methods differing in whether and when gelatin is included are envisaged to prepare thrombin‐loaded PBS‐based electrospun membranes for use as rapid hemostatic materials. Both PBS and gelatin‐coated PBS membranes have high porosity, excellent wettability, rapid water penetration rate, and high water uptake, and thus are suitable support materials for thrombin. The thrombin immobilized onto gelatin‐coated PBS membrane has both high initial enzyme activity and high storage stability ascribed to the stabilizing effect of gelatin on thrombin activity. The hemostasis performance of thrombin‐immobilized membrane is evaluated in a rat liver model, showing shorter hemostasis time and less blood loss than clinically used gelatin sponge. The hemostasis mechanism is attributed to combined effects of thrombin and porous structure of electrospun membrane.     

Electrospun Membranes Designed for Burst Release of New Gold-Complexes Inducing Apoptosis of Melanoma Cells

Two non-commercial metallic Au-based complexes were tested against one of the most aggressive malignant melanomas of the skin (MeWo cells), through cell viability and time-lapse live-cell imaging system assays. The tests with the complexes were carried out both in the form of free metallic complexes, directly in contact with the MeWo cell line culture, and embedded in fibers of Polycaprolactone (PCL) membranes produced by the electrospinning technique. Membranes functionalized with complexes were prepared to evaluate the efficiency of the membranes against the melanoma cells and therefore their feasibility in the application as an antitumoral patch for topical use. Both series of tests highlighted a very effective antitumoral activity, manifesting a very relevant cell viability inhibition after both 24 h and 48 h. In the case of the AuM1 complex at the concentration of 20 mM, melanoma cells completely died in this short period of time. A mortality of around 70% was detected from the tests performed using the membranes functionalized with AuM1 complex at a very low concentration (3 wt.%), even after 24 h of the contact period. The synthesized complexes also manifest high selectivity with respect to the MeWo cells. The peculiar structural and morphological organization of the nanofibers constituting the membranes allows for a very effective antitumoral activity in the first 3 h of treatment. Experimental points of the release profiles were perfectly fitted with theoretical curves, which easily allow interpretation of the kinetic phenomena occurring in the release of the synthesized complexes in the chosen medium.     

多形貌聚醚砜纤维毡吸附双酚A的特性

以四氢呋喃和N,N–二甲基甲酰胺作溶剂,将一定浓度的聚醚砜(PES)通过静电纺丝获得具有串珠结构的纳米纤维毡,并且发现通过提高制备过程中空气相对湿度可进一步获得形貌均一且无串珠结构的纳米纤维。采用比表面积与孔隙度分析仪,扫描电镜与水接触角测量仪等对PES纤维毡的形貌和物理特性进行了系统表征。在相对湿度(RH)为0.20 g/mL时获得串珠状PES纳米纤维,其具有不同的珠长径比。当RH值增加到60%时,获得均匀的无珠子纳米纤维毡。此外,在此条件下,随着PES浓度的增加,纤维的平均直径,比表面积和累积孔容均逐渐增加。通过紫外分光光度计测定了不同PES纤维毡样品对双酚A(BPA)的吸附量及吸附速率,发现具有更大比表面积和更好亲水性能的PES纳米纤维毡能够吸附更多的BPA,在RH=60%时,PES浓度为0.22 g/mL的比表面积为31.33 m^2/g,水接触角为108°,对BPA的吸附量可达8.28 mg/g,且吸附过程均符合准二级动力学模型。     

Assessing the Suitability of Electrospun Poly(Ethylene Terephthalate) and Polystyrene as Cell Carrier Substrates for Potential Subsequent Implantation as a Synthetic Bruch's Membrane

Electrospun poly(ethylene terephthalate) (PET) and polystyrene (PS) were tested for suitability as cell carrier substrates. Membranes were UV/ozone treated, which improved protein adsorption, with aminolysis observed on PET. PET demonstrated greater handling and durability compared to PS. Treated and untreated PET supported cell proliferation, with cells exhibiting the desired monolayer morphology. Untreated PS did not support cell proliferation and although treated PS did, the resultant RPE cell morphology was undesirable. Preliminary tests investigating thickness of mats were also undertaken, with PET exhibiting better results. Electrospun PET exhibited cytocompatibility, and could prove to be a suitable candidate for potential subsequent implantation.     

Electrical Detection of Vibrations of Electrospun PVDF Membranes

We prepared electroactive PVDF membranes, which were subjected to mechanical as well as dual electro–mechanical signals and their responses were detected by the evoked electrical pulses. The aim was to obtain primarily electric energy that could be used for light signalling, sensing of the membrane properties and membrane motion detection. The obtained data showed the unique as well as usable properties of PVDF membranes. From this point of view, the gain and analysis of the electrical responses to combined electro–mechanical loads of PVDF membranes have been important in terms of identifying the mechanism. The detected electrical response of the PVDF membrane to their electro–mechanical pulses also indicated the possibility of using this phenomenon. Among others, it suggests monitoring of membrane fouling and use for a self-cleaning mechanism.     

多级结构静电纺纳米纤维膜在空气过滤领域研究进展

静电纺纳米纤维膜具有纤维直径小、比表面积大、孔隙率高等优势,使其在空气过滤领域具有广阔的应用前景。相比特殊结构的纳米纤维膜,常规的静电纺纤维膜堆积密度大、过滤阻力高,增加了在实际使用中的能源消耗。从静电纺纤维膜结构和过滤性能的角度探讨了高效低阻空气过滤纳米纤维膜的构筑,介绍了珠粒、突起和多孔结构纤维膜在空气过滤领域的研究进展,指出了多级结构静电纺纳米纤维膜是高效低阻空气过滤膜的重点研究方向。     

Electrospun melamine-blended activated carbon nanofibers for enhanced control of indoor CO2

Electrospun carbon nanofibers were activated with melamine–polyacrylonitrile [melamine-blended carbon nanofibers (MACNFs)] for use as a fibrous adsorbent for indoor CO₂ removal. Although, melamine doping was intended solely to incorporate basic nitrogen functionalities on the nanofibers, it also shortened fabrication time, conserving time, and energy cost. The specific surface area and microporosity of the fibers were enhanced from 412 m² g⁻¹ and 0.1646 cm³ g⁻¹ to 547 m² g⁻¹ and 0.220 cm³ g⁻¹, respectively, upon final CO₂ activation of the nanofibers. With the chemical properties, we observed significant tethering of pyridine functionality. The sample, MACNF-7 (10 mL of polymer solution doped with 0.7 g of melamine), provided the optimum melamine doping condition to achieve the highest CO₂ adsorption capacity of 3.15 mmol g⁻¹. The adsorption performance was based on simultaneous improvement in microporosity (physical) and surface basicity (chemical) properties of the adsorbent. However, in a binary mixture with nitrogen, the selective adsorption of CO₂ showed the predominance of the improved surface basicity over microporosity. The highest CO₂ selective capture (1.22 mmol g⁻¹) was occurred for a CO₂:N₂ ratio of 0.15:0.85, with a selectivity of 58.19 at 273 K. In a regeneration test, stable and robust performance was achieved more than five cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47747.     

Electrospun Differential Wetting Membranes for Efficient Oil–Water Separation

Separation of low viscous oil from water has attracted immense attention in recent times due to the ever‐increasing amount of oily industrial wastewater discharge and frequent oil spill accidents. Hence, there is a persistent demand for the fabrication of robust oil–water separation membranes. Herein, robust oil–water separation membranes are successfully fabricated by direct electrospinning of poly(vinylidene fluoride‐co‐hexafluoropropylene) and fluorinated polyhedral oligomeric silsesquioxane composite mixture. These hybrid membranes exhibit differential wetting (highly hydrophobic/superoleophilic) behavior for water and oil. The contact angle made by water and low viscous oil (hexane) with the membrane are measured to be 145 and 0° respectively. The nanofiber membranes efficiently separate low viscous oil from water in a single‐step with separation efficiency of nearly 100%. Furthermore, the results demonstrate that the membranes are robust and durable exhibiting differential wettability even after several oil–water separation cycles. The results reveal the potential of their use for real‐time industrial wastewater treatment applications.

     

Preparation of Mineralized Electrospun Fibers as a Biomimetic Nanocomposite

Mineralization of gelatin electrospun nano and micro fiber was investigated in order to prepare a biomimetic bone nanocomposite. For this aim, at first, calcium containing gelatin nanofibers were electrospun by a novel ethanol/water/salt solution. Fibers with mean diameters varying from 300 to 3000 nm were acquired. Then, fiber mats were exposed to phosphate ions by soaking them in phosphate solution or laminating them between phosphate containing gelatin films. SEM micrographs demonstrated the presence of nano to micro sized minerals on gelatin fibers. FTIR and XRD results illustrated that the calcium phosphates in all samples are combinations of brushite and hydroxyapatite.     

Global View and Trends in Electrospun Nanofiber Membranes for Particulate Matter Filtration: A Review

Numerous experimental works for particulate matter (PM) filtration by electrospun nanofiber membranes (ESNFMs) are published in the last 10 years (2010–2021). Organizing and comparing the large amount of the available information to identify the best trends constitutes a big challenge. This review classifies all kinds of ESNFMs considering their physical, chemical, or electrical characteristics. All of them are obtained by modifying several parameters during a specific stage associated to the electrospinning process (ES). In this review, each of these stages is considered a "moment” as a particular instant in time. According to that, three modifications are made: Moment 1—before ES, which refers to changes in polymeric solution composition; moment 2—during ES, which refers to modifying parameters while ES is performed; and moment 3—after ES, which involves applying post-treatments directly on the membrane. After classifying all kinds of filters by moments, a detailed comparison of ESNFMs with the highest quality factors for PM_0.3 is presented, finding out the best trends and comparing their main filtration parameters as well, where the most promising ones correspond to charged and nanofiber/nets membranes, due to their high capture efficiencies (>95%) while maintaining low pressure drops (<100 Pa).     

Electrospun polymeric coatings on aluminum alloy as a straightforward approach for corrosion protection

Several metals and alloys are susceptible to corrosion attack and this usually implies the accurate selection of a specific material depending on the working conditions and the characteristics of the environment to which it will be exposed to. However, it could represent a restriction at the same time because a limited range of materials can be practically considered. In addition, they could be also characterized by unsuitable properties for the intended application and high costs. To address this issue, polymeric coatings exhibit high potentiality to be a valid alternative to toxic chromates, allowing to deal with the most appropriate metallic materials and affordable deposition procedures. In this work, polyvinyl alcohol (PVA) fibrous coating was successfully collected onto aluminum alloy‐6082 by means of electrospinning technique. The anticorrosion performance of the final system has been evaluated in 3 wt % NaCl solution by means of electrochemical impedance spectroscopy (EIS). To avoid PVA disintegration in aqueous environment, several crosslinking procedures were assessed using glyoxal. The two most promising ones (120°C for 60 min and 150°C for 15 min) were then considered for a further investigation. Crosslinked PVA mats showed improved properties as compared to the as‐spun case, as demonstrated by mechanical and thermal analyses. Electrochemical tests revealed that crosslinked coatings can protect aluminum substrates against corrosion, especially for the electrospun PVA coating treated at 120°C. In this case, after 270 h, a significant corrosion resistance of about 26 kΩ was recorded with respect to the blank alloy (about 3.8 kΩ). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41250.     

静电纺PPEK/SiO2锂离子电池隔膜的制备及性能

为制备吸液率高、热尺寸稳定性良好的隔膜,以聚芳醚酮(PPEK)和SiO_2为原料,采用静电纺丝技术制备了PPEK/SiO_2复合纤维膜。通过SEM、电化学工作站、蓝电电池测试系统等对电纺纤维膜及组装的电池进行了结构表征和性能测试,讨论了SiO_2质量分数对电纺纤维膜结构和性能的变化规律,并考察了其作为锂离子电池隔膜用时的电化学和电池性能。结果表明:随着SiO_2质量分数的增加,电纺纤维膜的孔隙率、吸液率和离子电导率逐渐增加。电纺纤维膜在200℃下热处理1 h的热收缩率为0,具有良好的热尺寸稳定性。当SiO_2质量分数为6%(以PPEK质量为基准)时,孔隙率和吸液率分别达到179%、1031%,离子电导率为2.63×10~(–3) S/cm;将该电纺纤维膜组装成石墨/Li电池,1 C下放电比容量为332～350 mA·h/g,具有良好的循环和倍率性能。     

Porous Electrospun PES/PEG Ultrafine Fibers for the Removal of Endocrine Disruptors

In this work, porous polyethersulfone (PES)/polyethylene glycol (PEG) ultrafine fibers were prepared via electrospinning technique, and then were used to removing endocrine disrupters from their aqueous solutions. The surface and the internal structures of PES/PEG ultrafine fibers were characterized by scanning electron microscopy (SEM) and the result showed that they were both porous. The porous electrospun PES/PEG ultrafine fibers can remove endocrine disrupters such as biphenyl A (BPA) and biphenyl (BP) effectively. Compared with pure PES ultrafine fibers, PES/PEG ultrafine fibers showed larger adsorption capacity and faster kinetics of uptaking target species. The hydrophilic properties and the porosity of porous PES/PEG ultrafine fibers can be controlled by adding hydrophilic materials such as polyethylene glycol (PEG), which can improve the adsorption properties of porous PES/PEG ultrafine fibers significantly. The results showed that porous electrospun PES/PEG ultrafine fibers had the potential to be used in environmental application and water treatment.     

Electrospun Biopolyesters as Drug Screening Platforms for Corneal Keratocytes

In vitro drug screening techniques provide rapid and easy to analyze data, while saving a lot of animals from being sacrificed. An important part of any in vitro drug screening platform is a biomaterial which promotes cell growth and proliferation. The potential of electrospun scaffolds made of polyhydroxybutyrate (PHB), poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV), and polycaprolactone (PCL) were studied to serve as drug screening platform for corneal keratocyte tissues. The results showed that the proliferation rate was slightly higher for PCL and PHBV on day 7. Gene expression results showed that PCL was the best in maintaining keratocyte genes.     

Preparation of Composite Electrospun Membranes Containing Strontium‐Substituted Bioactive Glasses for Bone Tissue Regeneration

Barrier membranes used for the treatment of bone tissue defects caused by periodontitis lack the ability to promote new bone tissue regeneration. However, the addition of an osteogenic component to membranes may enhance their regenerative potential. Here the manufacturing of composite membranes made of poly(caprolactone) and strontium‐substituted bioactive glass is described using the solution‐electrospinning technique, with particles located both inside and on the surface of the fibers. All membranes are characterized using scanning electron microscopy and energy dispersive X‐ray spectroscopy, and glass dissolution from within the fibers is investigated in water. In vitro material cytotoxicity is determined using a rat osteosarcoma cell line. Electrospun fibers exhibit porous surfaces and regions of increased diameter where the particles are accumulated. The glass dissolves after immersion in water, releasing dissolution products that are associated with increased pH. Further evidence suggests accelerated polymer degradation due to interactions between both components, which may provide the additional benefit of reducing the pH changes associated with glass dissolution. All compositions are biocompatible in vitro, with the exception of membranes with >50 μg of glass on their surface. In conclusion, these membranes show great potential for bone healing applications, including guided bone regeneration and scaffolds for musculoskeletal tissue engineering.

     

Electrospun cellulose acetate/P(DMDAAC-AM) nanofibrous membranes for dye adsorption

In recent years, organic nanofibrous membranes have received more attention because of their excellent performance in wastewater treatment. In this study, the soluble poly(dimethyldiallylammonium chloride-acrylamide) (P(DMDAAC-AM)) was first synthesized by aqueous copolymerization. Afterward, cellulose acetate (CA)/P(DMDAAC-AM) composite nanofibrous membranes were electrospun and utilized to remove acid black 172 from simulated wastewater. When the proportion of P(DMDAAC-AM) to CA was 20, 30, and 40 wt %, the equilibrium adsorption capacities were 116, 159, and 192 mg g⁻¹, respectively. The adsorption capacity of CA/P(DMDAAC-AM) composite nanofibrous membrane showed a well linear relationship with the average fiber diameter. When the average fiber diameter was 185 nm, the adsorption capacity of 231 mg g⁻¹ was achieved. The adsorption kinetics of CA/P(DMDAAC-AM) membranes with various fiber diameters was all consistent with the pseudo-second-order model. The rate-limiting step was primarily controlled by chemisorption. The adsorption isothermal data fitted well with the Langmuir isotherm model. The prepared CA/P(DMDAAC-AM) nanofibrous membrane was effective to remove the acid black 172 in the environmental interested pH range of 4.0–10.0. As an effective dye adsorbent, CA/P(DMDAAC-AM) nanofibrous membrane shows wide application prospect with its excellent adsorption performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48565.