Figure 2 - uploaded by Fatma Yalcinkaya
Content may be subject to copyright.
Droplets of oil under a microscope.

Droplets of oil under a microscope.

Source publication
Article
Full-text available
Preparing easily scaled up, cost-effective, and recyclable membranes for separation technology is challenging. In the present study, a unique and new type of modified polyvinylidene fluoride (PVDF) nanofibrous membrane was prepared for the separation of oil-water emulsions. Surface modification was done in two steps. In the first step, dehydrofluor...

Context in source publication

Context 1
... digital microscope (Levenhuk Digital Microscope, Prague, Czech Republic) was used for the determination of oil droplet size (Figure 2). The emulsion was kept for one week without any stirring. ...

Similar publications

Article
Full-text available
The effect of a N,N-dimethylformamide (DMF)/acetone solvent system (3:7, 4:6, 5:5, 6:4, 7:3) and spinning medium (air and water) on the membrane morphology and the structure-property relationship were investigated. A facile method was optimized to generate a porous, polymer-fiber membrane via the combinative effect of electrospinning and thermally...

Citations

... Pristine PVDF is naturally hydrophobic. PVDF may be converted into a hydrophilic membrane by modifying its surface using alkaline treatment [23,24]. It was found that PVDF membranes can be attacked and degraded upon exposure, even to a low concentration of NaOH (0.01 M) solution [25]. ...
Article
Full-text available
Membrane fouling is one of the most significant issues to overcome in membrane-based technologies as it causes a decrease in the membrane flux and increases operational costs. This study investigates the effect of common chemical cleaning agents on polymeric nanofibrous membranes (PNM) prepared by polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polyamide 6 (PA6) nanofibers. Common alkaline and acid membrane cleaners were selected as the chemical cleaning agents. Membrane surface morphology was investigated. The PAN PNM were selected and fouled by engine oil and then cleaned by the different chemical cleaning agents at various ratios. The SEM results indicated that the use of chemical agents had some effects on the surface of the nanofibrous membranes. Moreover, alkaline cleaning of the fouled membrane using the Triton X 100 surfactant showed a two to five times higher flux recovery than without using a surfactant. Among the tested chemical agents, the highest flux recovery rate was obtained by a binary solution of 5% sodium hydroxide + Triton for alkaline cleaning, and an individual solution of 1% citric acid for acidic cleaning. The results presented here provide one of the first investigations into the chemical cleaning of nanofiber membranes.
... Chemical grafting of titanium oxide onto the surface of PVDF membranes was carried out in [96]. The order of operations for modifying PVDF membranes is shown in Scheme 2. At the first stage, the hollow fiber PVDF membrane was treated with an alkali solution to replace fluorine ions with hydroxide ions-the dehydrofluorination process. ...
... As a result, hollow fiber membranes with a superhydrophilic surface were obtained, capable of separating oil-water emulsions with almost 100% selectivity. Scheme 2. Scheme of the modification of a hollow fiber membrane from PVDF [96] and PVDF + PAN [97]. ...
... Polyvinylidene fluoride has a large number of -F groups, thanks to which it is possible to carry out chemical grafting-for example, by aminosilanes [101], alkylamines [99], and, through the defluorination stage, titanium oxide [96]. In addition, PVDF membranes are modified by applying hydrophilic layers, dopamine [105], cellulose [103], and polymer mixing [107]. ...
Article
Full-text available
This review is devoted to the application of bulk synthetic polymers such as polysulfone (PSf), polyethersulfone (PES), polyacrylonitrile (PAN), and polyvinylidene fluoride (PVDF) for the separation of oil-water emulsions. Due to the high hydrophobicity of the presented polymers and their tendency to be contaminated with water-oil emulsions, methods for the hydrophilization of membranes based on them were analyzed: the mixing of polymers, the introduction of inorganic additives, and surface modification. In addition, membranes based on natural hydrophilic materials (cellulose and its derivatives) are given as a comparison.
... The production of nanofibers and mats by electrospinning technology allows the easy production of nanofiber mats from biobased, man-made polymers or polymer blends and by adding particles of ceramics, metals or metal oxides etc. [2][3][4][5]. New materials are promising for use in filtration, energy, biomedicine, electromagnetic shielding, neuromorphic computing, spintronics or energy storage [6][7][8][9][10]. Nanofibers with magnetic properties (MNFs) produced with electrospinning technology are currently attracting great interest from both academia and industry due to the development of new materials with magnetic and conducting properties [11]. ...
Article
Full-text available
Electrospun magnetic nanofibers are promising for a variety of applications in biomedicine, energy storage, filtration or spintronics. The surface morphology of nanofiber mats plays an important role for defined application areas. In addition, the distribution of magnetic particles in nanofibers exerts an influence on the final properties of nanofiber mats. A simple method for the production of magnetic nanofiber mats by the addition of magnetic nanoparticles in an electrospinning polymer solution was used in this study. In this work, magnetic nanofibers (MNFs) were prepared by needle-free electrospinning technique from poly(acrylonitrile) (PAN) in the low-toxic solvent dimethy lsulfoxide (DMSO) and 20 wt% Fe3O4 at different parameter conditions such as PAN concentration, voltage and ultrasonic bath. The distribution of nanoparticles in the fiber matrix was investigated as well as the chemical and morphological properties of the resulting magnetic nanofibers. In addition, the surface morphology of magnetic nanofiber mats was studied by confocal laser scanning microscope (CLSM), scanning electron microscope (SEM), Fourier transform infrared microscope (FTIR) and ImageJ software, and distribution of Fe3O4 particles in the matrix was investigated by energy dispersive X-ray spectroscopy (EDX).
... Even functionalization with molecules is possible [7,8]. Depending on the material composition, such nanofiber mats can be used for various applications, such as biotechnology, biomedicine and tissue engineering [9][10][11], filters for fluids and gases [12][13][14], and energy harvesting and storage [15][16][17]. Most recent applications can be found in water purification, H 2 production, environmental protection [18][19][20][21], or as catalysts [22][23][24]. ...
Article
Full-text available
Electrospinning can be used to produce nanofiber mats containing diverse nanoparticles for various purposes. Magnetic nanoparticles, such as magnetite (Fe3O4), can be introduced to produce magnetic nanofiber mats, e.g., for hyperthermia applications, but also for basic research of diluted magnetic systems. As the number of nanoparticles increases, however, the morphology and the mechanical properties of the nanofiber mats decrease, so that freestanding composite nanofiber mats with a high content of nanoparticles are hard to produce. Here we report on poly (acrylonitrile) (PAN) composite nanofiber mats, electrospun by a needle-based system, containing 50 wt% magnetite nanoparticles overall or in the shell of core–shell fibers, collected on a flat or a rotating collector. While the first nanofiber mats show an irregular morphology, the latter are quite regular and contain straight fibers without many beads or agglomerations. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) reveal agglomerations around the pure composite nanofibers and even, round core–shell fibers, the latter showing slightly increased fiber diameters. Energy dispersive X-ray spectroscopy (EDS) shows a regular distribution of the embedded magnetic nanoparticles. Dynamic mechanical analysis (DMA) reveals that mechanical properties are reduced as compared to nanofiber mats with smaller amounts of magnetic nanoparticles, but mats with 50 wt% magnetite are still freestanding.
... Electrospinning can be used to prepare fibers with diameters in a typical range of some ten to some hundred nanometers, sometimes up to the range of a few micrometers [1][2][3]. Due to their small diameter and the corresponding large surfaceto-volume ratio, there are diverse applications of such nanofibers or nanofiber mats, for example, in the biomedical or biotechnological area [4][5][6], in filters [7][8][9], batteries, solar cells, and supercapacitors [10][11][12]. ...
Chapter
Electrospinning is a versatile method to produce nanofibers or nanofiber mats from diverse polymers or polymer blends. Including ceramic or metallic nanoparticles can even be used to create purely inorganic nanofibers for diverse applications. On the other hand, biocompatible and biodegradable polymers are of high interest especially for biomedical applications. Biodegradable nanofiber mats as scaffolds can be used in tissue engineering, especially when degradation times are in the same order of magnitude as cell proliferation on these substrates. Biodegradation, however, involves more aspects than the pure time profile. Especially for utilization in vitro and in vivo, byproducts of degradation processes may lead to undesired reactions with the surrounding tissue, and vice versa. Here, we give an overview of the production techniques of biodegradable nanofibers and nanofiber mats by different electrospinning techniques. In addition, we report on biotechnological and biomedical applications of such fully or partly biodegradable nanofibers and show the chances and challenges in interaction with living tissue and organisms.
... Such applications concern diverse polymers, polymer blends or polymers with embedded nanoparticles [1][2][3][4][5]. Such nanofiber mats can be used in a broad range of possible applications, from filters [6,7] and catalyzers [8,9] to tissue engineering and cell growth [10][11][12][13]. ...
Article
Full-text available
Two-dimensional structures, either periodic or random, can be classified by diverse mathematical methods. Quantitative descriptions of such surfaces, however, are scarce since bijec-tive definitions must be found to measure unique dependency between described structures and the chosen quantitative parameters. To solve this problem, we use statistical analysis of periodic fibrous structures by Hurst exponent distributions. Although such a Hurst exponent approach was suggested some years ago, the quantitative analysis of atomic force microscopy (AFM) images of nanofiber mats in such a way was described only recently. In this paper, we discuss the influence of typical AFM image post-processing steps on the gray-scale-resolved Hurst exponent distribution. Examples of these steps are polynomial background subtraction, aligning rows, deleting horizontal errors and sharpening. Our results show that while characteristic features of these false-color images may be shifted in terms of gray-channel and Hurst exponent, they can still be used to identify AFM images and, in the next step, to quantitatively describe AFM images of nanofibrous surfaces. Such a gray-channel approach can be regarded as a simple way to include some information about the 3D structure of the image.
... The alkaline solutions were prepared by dissolving 36 g NaOH in 30 mL of distilled water and 2 g KOH in 20 mL of isopropyl alcohol (Penta s.r.o., Prague, Czech Republic). Both alkaline solutions were mixed for three hours at room temperature, following which, membranes were submerged in the NaOH solution for 48 h and the KOH solution for 1 h (previous experience has shown that the KOH treatment works faster than NaOH [18]). The membranes were then washed with distilled water. ...
... SEM images indicated that TiO2 particles were not well distributed on the treated membranes, with clear aggregation on the fibre's surface (Figures 8; S4 and S6), suggesting that PAN hydrolysis following alkaline treatment was irregular. In a previous study [18], a more regular distribution of TiO2 nanoparticles was observed on the surface of polyvinylidene fluoride (PVDF) nanofibres following alkaline treatment as dehydrofluorination of the PVDF surface was more regular, allowing improved attachment of TiO2 nanoparticles to hydrophilic -OH groups on the fibres. ...
... 189. 33 As observed in previous studies [18,26], a higher web density generally results in increased fibre compaction, which reduces air permeability. As such, we undertook an air permeability test following the lamination process in order to assess to what degree the melted adhesive web clogged the nanofibre pores. ...
Article
Full-text available
In order to protect the environment, it is important that oily industrial wastewater is de-greased before discharging. Membrane filtration is generally preferred for separation of oily wastewater as it does not require any specialised chemical knowledge, and also for its ease of processing, energy efficiency and low maintenance costs. In the present work, hybrid polyacrylo-nitrile (PAN) nanofibrous membranes were developed for oily wastewater filtration. Membrane surface modification changed nitrile groups on the surface into carboxylic groups, which improve membrane wettability. Subsequently, TiO2 nanoparticles were grafted onto the modified membranes to increase flux and permeability. Following alkaline treatment (NaOH, KOH) of the hy-drolysed PAN nanofibres, membrane water permeability increased two-to eight-fold, while TiO2 grafted membrane permeability increase two-to thirteen-fold, compared to unmodified membranes. TiO2 grafted membranes also displayed amphiphilic properties and a decrease in water contact angle from 78.86° to 0°. Our results indicate that modified PAN nanofibrous membranes represent a promising alternative for oily wastewater filtration.
... Among all the electrospinning post-processes, one of the most widely studied when working with NPs is the surface treatment of electrospun mats. In particular, surface treatment consists in the immersion of electrospun mats into a NPs solution [55]. Thus, the surface of electrospun fibers is covered by NPs thanks to electrostatic forces, hydrogen bonding or interactions among functional groups. ...
Article
Full-text available
In the last few decades, the development of new electrospun materials with different morphologies and advanced multifunctional properties are strongly consolidated. There are several reviews that describe the processing, use and characterization of electrospun nanocomposites, however, based on our knowledge, no review on electrospun nanocomposites reinforced with nanoparticles (NPs) based on magnesium, Mg-based NPs, are reported. Therefore, in the present review, we focus attention on the fabrication of these promising electrospun materials and their potential applications. Firstly, the electrospinning technique and its main processing window-parameters are described, as well as some post-processing methods used to obtain Mg-based materials. Then, the applications of Mg-based electrospun nanocomposites in different fields are pointed out, thus taking into account the current trend in developing inorganic-organic nanocomposites to gradually satisfy the challenges that the industry generates. Mg-based electrospun nanocomposites are becoming an attractive field of research for environmental remediation (waste-water cleaning and air filtration) as well as for novel technical textiles. However, the mayor application of Mg-based electrospun materials is in the biomedical field, as pointed out. Therefore, this review aims to clarify the tendency in using electrospinning technique and Mg-based nanoparticles to huge development at industrial level in the near future.
... Electrospinning makes it possible to create nanofiber mats from diverse materials, such as pure polymers [1][2][3], polymers blends, composite fibers from polymers and ceramics or metals [4,5], and cyclodextrins [6]. These can be used in diverse applications such as filters [7][8][9], biotechnology and tissue engineering [10][11][12], for energy harvesting and storage [13,14], or other "smart" functions [15]. Recently, a strong focus of diverse research groups has been related to electrospinning magnetic nanofibers, either as composites [16][17][18] or, after calcination of the composites to remove polymers, as pure metal nanofibers [19][20][21]. ...
Article
Full-text available
Magnetic nanofibers are of great interest in basic research, as well as for possible applications in spintronics and neuromorphic computing. Here we report on the preparation of magnetic nanofiber mats by electrospinning polyacrylonitrile (PAN)/nanoparticle solutions, creating a network of arbitrarily oriented nanofibers with a high aspect ratio. Since PAN is a typical precursor for carbon, the magnetic nanofiber mats were stabilized and carbonized after electrospinning. The magnetic properties of nanofiber mats containing magnetite or nickel ferrite nanoparticles were found to depend on the nanoparticle diameters and the potential after-treatment, as compared with raw nanofiber mats. Micromagnetic simulations underlined the different properties of both magnetic materials. Atomic force microscopy and scanning electron microscopy images revealed nearly unchanged morphologies after stabilization without mechanical fixation, which is in strong contrast to pure PAN nanofiber mats. While carbonization at 500 °C left the morphology unaltered, as compared with the stabilized samples, stronger connections between adjacent fibers were formed during carbonization at 800 °C, which may be supportive of magnetic data transmission.
... A similar attempt has been made using PVDF nanofiber web. Differently, the plasma treatment has been eliminated [64]. PVDF membranes were defluorinated in alkaline solution, and then TiO2 nanoparticles were attached on the surface, as illustrated in Figure 3. Results indicated that after adding TiO2 nanoparticles, membranes exhibited outstanding antifouling and self-cleaning performance with high selectivity. ...
... Moreover, some of the membranes improve self-cleaning properties. Literature research shows that, for effective and high-performance oil separation, surface modification of membrane is needed [58][59][60][61][62][63][64][65][66]. Surface modified membranes not only offer superior flux but also antifouling performance. ...
... Schematic illustration of surface modification of PVDF nanofibrous membrane (inspired from[64]). ...
Article
Full-text available
Cleaning of wastewater for the environment is an emerging issue for the living organism. The separation of oily wastewater, especially emulsified mixtures, is quite challenged due to a large amount of wastewater produced in daily life. In this review, the membrane technology for oily wastewater treatment is presented. In the first part, the global membrane market, the oil spill accidents and their results are discussed. In the second and third parts, the source of oily wastewater and conventional treatment methods are represented. Among all methods, membrane technology is considered the most efficient method in terms of high separation performance and easy to operation process. In the fourth part, we provide an overview of membrane technology, fouling problem, and how to improve the self-cleaning surface using functional groups for effectively treating oily wastewater. The recent development of surface-modified membranes for oily wastewater separation is investigated. It is believed that this review will promote understanding of membrane technology and the development of surface modification strategies for anti-fouling membranes.