Production of Highly Porous Electrospun α-Fe2O3 Nanofibers For Environmental Applications

Production of Highly Porous Electrospun α-Fe2O3 Nanofibers For Environmental Applications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Production of Highly Porous Electrospun α-Fe 2 O 3 Nanofibers For Environmental Applications Emre ALP, İsmail BORAZAN This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2202218/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The electrospun α-Fe 2 O 3 nanofibers with mesoporous were fabricated by annealing electrospun Poly(acrylonitrile-co-vinyl acetate) (PAN)/Iron(III)chloride and Poly(acrylonitrile-co-vinyl acetate) (PAN)/Iron(III)chloride hexahydrate composite nanofibers. The used precursor for the iron source drastically affected the final morphologies of the electrospun α-Fe 2 O 3 nanofibers depending on whether it was hydrated. As a result of that, the photocatalytic performances of electrospun α-Fe 2 O 3 nanofibers exhibited significant differences from each other. It was observed that the electrospun α-Fe 2 O 3 nanofibers with highly porous, derived from a hydrated iron salt source, exhibited excellent photocatalytic activity against synthetic dye with anionic and cationic. The results here suggest that the electrospun α- Fe 2 O 3 nanofibers with highly porous were fabricated in the study, which exhibited excellent photocatalytic activity, can provide promising activities to remove organic contaminants from wastewater. Likewise, these nanofibers with highly porous can show high performances in solar-related applications such as water splitting and photovoltaics. Materials Engineering Hematite Porous Nanofibers Electrospinning Heterogeneous Photocatalysis Water Remediation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Now, society faces two serious challenges; environmental issues and energy problems. These issues determine the world's future and also, shape our society in the 21st century. With this perspective, the new technologies are surveyed to suggest new solutions in almost every aspect of climate, energy, and environment for Sustainable Development Goals (UN SDGs) [ 1 ] set out by the United Nations. The environment and climate are globally aggressively attacked by the way of various forms of environmental pollution, mainly air and water pollution. As a result of rapid industrialization and urbanization, as well as the increasing population, clean water supplies are polluted and parallelly, the need for clean water has increased all over the World [referans]. The wastewater infrastructure in the developed world faces increasing demands to generate higher quality clean water using less energy and with lower proceeding costs. [ 2 ]. Solar-driven semiconductors present significant opportunities to solve growing energy problems and environmental crises [ 3 ]. Dyes widely used in textiles, plastics, and paper industries, some of which are either carcinogenic, mutagenic or toxic, have led to severe environmental contamination and, consequently, seriously affect the nature of water [ 4 ]. Heterogeneous photocatalysts have numerous potentials in the different application fields, including degradation of dyes and organics, antibacterial, CO 2 reduction, and water splitting [ 5 ]. Heterogeneous photocatalysis has been considered one of the most attractive methods for wastewater treatment to degrade pollutants, from textile dyes and personal care products to harmful bacteria, with a solid photocatalyst using sunlight. [ 6 , 7 ]. The heterogeneous photocatalysis in the water remediation process has several benefits and opportunities. These advantages are that there is no harmful intermediate production (particularly for organic pollutants), allowing continuous re-use, the reactions taking place at room temperature, and photocatalysts are inexpensive [ 8 ]. Hematite (α-Fe 2 O 3 ) has attracted much attention as a promising material for solar-related applications due to its desirable properties, such as visible-driven optical band gap, high physicochemical stability (especially in aquatic media), an earth-abundant material, associatively low-cost, and eco-friendly [ 9 , 10 ]. Hematite has a band gap of 2.1 eV and is semiconducting material with an n-type band structure. Among all iron oxide phases, α-Fe 2 O 3 is one of the most thermodynamically stable phases; thus, this characteristic makes it suitable for heterogenous photocatalysis in aqueous media [ 11 ]. Based upon their unique physical, chemical and optical properties mentioned, hematite has numerous applications in emerging fields such as biomedical for cancer treatment, Li-ion batteries [ 12 ], sodium ion batteries (SIBs) and potassium ion batteries (PIBs) [ 13 ], air purification [ 14 ], gas sensor [ 15 ], photoelectrochemical (PEC) water splitting for hydrogen generation [ 16 , 17 ], biosensors [ 18 ], medical treatment and diagnosis [ 19 , 20 ], photocatalysis in wastewater treatment [ 21 , 22 ], pigments for energy saving [ 23 ] and etc. Although it has these unique features mentioned in the literature, it suffers from some insufficients such as short hole diffusion length [ 24 ], poor electrical conductivity [ 25 ], electron-hole recombination rate [ 26 ], absorptivity [ 27 ], and; thus, these poor properties limit its application fields and solar-related application performance. With the optimization of the structural properties of hematite at the nanometer level by utilizing engineering strategies such as morphology regulation, shape control, metallic supported architecture, doping, and creating a heterojunction, it is possible to overcome these limitations [ 28 , 29 , 30 , 31 , 32 , 33 ]. In recent years, the shape controllable synthesizes of nanoparticle materials have attracted the focus of research due to the size-dependent and shape-dependent remarkable properties of nanostructured materials [ 34 ]. Up to now, The well-defined hematite forms with countless morphology and dimensionalities, including nanotube [ 35 ], hollow spheres [ 36 ], rods [ 37 ], ellipsoids [ 38 ], wires [ 39 ], cubic [ 40 , 41 ], hexagonal platelets [ 42 ], bipyramid [ ], double ellipsoid [ 43 ] and, plate [ 44 ], belts [ 45 ] have been fabricated. The formation of these nanoparticles with diverse shapes and dimensionalities has been adjusted by controlling so many kinetic (e.g., diffusion of reactants, surface adhesion of surfactants) and thermodynamic (e.g., the relative stability of crystal polymorphs) complicated factors associated with each other [ 46 ]. Nanotechnology plays a substantial role in water purification through synthesizing nanoparticles of different morphologies and shapes with unique physicochemical properties. [ 47 ]. Electrospinning is a simple technique by which one can easily fabricate one-dimensional (1D) nanomaterials on an industrial scale and with controllable features such as morphologies, diameters, and compositions [ 48 ]. From the perspective of structure advantages which are ideally suited for heterogenous photocatalytic reactions, the electrospun one-dimensional (1D) semiconductor nanofibers exhibit countless unique characteristics such as extraordinary length, a large ratio of length to diameter, hierarchically porous structure, high surface area, small grain sizes, and high porosity [ 49 , 50 ]. As it is known, polyacrylonitrile (PAN) is one of the most popular polymers used in fabricating nanofiber by electrospinning [ 51 ] and are frequently used for the production of composite nanofiber [ 52 ]. We used polyacrylonitrile (PAN) as a polymeric matrix to fabricate polymer/metal composite nanofiber. In the light of the unique characteristics of electrospinning production mentioned, firstly, we wondered how a precursor used as an iron source, depending on whether it includes hydrate, would affect fibres' final morphologies. With this perspective, we fabricated electrospun nanofibres using iron chloride with hydrate and without hydrate. Besides, we wondered how their photocatalytic performances would change based on their final morphological characteristics. The electrospun α-Fe 2 O 3 nanofibers were characterized and their photocatalytic activities were examined against two organic synthetic dyes showing different characteristics relative to each other. It was observed that using precursors, depending on whether it includes hydrate forms, for producing electrospun hematite nanofibers strongly affected their final morphologies, associatively resulting in different photocatalytic activities. The electrospun hematite nanofibers fabricated by iron(III) chloride hexahydrate were smaller in diameter and highly porous in structure according to those fabricated by iron(III) chloride. These highly porous and smaller diameters electrospun nanofibers also exhibited higher photocatalytic performances against both model dye molecules. The results here propose that the electrospun α-Fe 2 O 3 nanofibers with highly porous would provide suitable photocatalytic activities to remove organic contaminants from wastewater. 2. Experimental 2.1. Production of Electrospun α-Fe 2 O 3 Nanofibers Poly(acrylonitrile-co-vinyl acetate) (PAN) with a density of 1.18 g/cm3 is supplied courtesy of AKSA Corporation. 10% (w:w) PAN(co-polymer) is solved in DMF and stirred for 24 hours. Iron(III) chloride and iron(III) chloride hexahydrate was purchased from Sigma-Aldrich. 1% (weight ratio) of iron compounds were separately dispersed in DMF in an ultrasonic bath for 15 min; afterwards, 10% (weight ratio) PAN was added into the iron solution and stirred overnight to dissolve properly. Iron-added PAN solutions were filled into a syringe, then loaded in the NanoYarn Spinner (Inovenso Co. Ltd.), and high voltage (30 kV) was applied to the tip of a needle that connected to the syringe. The syringe was pumped with a constant rate of 1 ml/hour, and the polymer was collected as a nanofibers mat on an aluminium foil placed on the grounded and rotating collector. The distance between the needle and collector was 10 cm. The rotation of the collector was 500 rpm during the fabrication. The electrospinning device and its elements are shown in Fig. 1 . Afterwards, heat treatment was applied to as-synthesized PAN/Metal composite fibres. They were heated up to 500°C with a heating rate of 2°C/min and maintained at that temperature for 2 hours. Then, they were naturally cooled down to room temperature in the furnace. The schematic representation of producing the electrospun α-Fe 2 O 3 nanofibers is presented in Fig. 1 . The electrospun α-Fe 2 O 3 nanofibers produced by using iron(III) chloride as an iron source are named AnHyd-Fe 2 O 3 and The electrospun α-Fe 2 O 3 nanofibers produced by using iron(III) chloride hexahydrate as an iron source are named Hyd- Fe 2 O 3 . 2.2. Characterization The produced PAN/metal composite structure’s morphological and microstructural features were conducted using a field emission gun TESCAN™ MAIA XMU scanning electron microscope (FESEM). The Powder X-ray diffraction (XRD) pattern of produced electrospun α-Fe 2 O 3 nanofibers was carried out by using a RIGAKU SmartLab™ X-ray diffractometer operated at 40 mA current and 40 kV voltage with Cu-Kα radiation (λ = 1.5406 Å ). The UV-vis spectra for determining the optical properties (such as band gap and absorption characteristics) of produced electrospun α-Fe2O3 nanofibers and photocatalytic performances of photocatalysts against dye pollutants were measured via Shimadzu UV- 3600 UV-Vis-NIR spectrophotometers. 2.3. Photocatalytic Activity Experiments The photocatalytic activities of electrospun α-Fe 2 O 3 nanofibers with porous against two pollutant dyes with different kind characteristics exhibiting anionic and cationic, respectively called methyl orange (MO), rhodamine B (RhB) dyes, were executed. The specific test solution used for photocatalytic performances of produced electrospun α-Fe 2 O 3 nanofibers has an identical concentration of 10 mg/L for both dye molecules. The solution was prepared by adding electrospun α-Fe 2 O 3 nanofibers photocatalysts (0.5 g/L) into dye solution (10 mg/L). Before solar irradiation, the solution was magnetically stirred in the dark for 60 minutes to provide an adsorption-desorption equilibrium on the surface of photocatalyst powders. Afterwards, the dispersion was put under an AM 1.5 solar simulator and irradiated by a 500 W xenon lamp under continuously magnetic stirring conditions. The samples were taken from the solution to identify the adsorption characteristic at indicated intervals. Before estimating absorption characteristics, all samples from the aqueous solution were centrifuged to separate the catalysts from the aqueous media. The UV/vis/NIR absorption spectra of samples from the aqueous solution were characterized to monitor photocatalytic performances of the produced electrospun α-Fe 2 O 3 nanofibers photocatalysts against dye molecules via a UV/vis spectrophotometer. 3. Results And Discussion We wondered how precursor used as an iron source, depending on whether it includes hydrate, would affect fibres' morphologies. With this viewpoint, we fabricated electrospun nanofibres using iron chloride with hydrate and without hydrate. Besides, we wondered how their photocatalytic performances would change based on morphological differences. Microstructural features of as-synthesized PAN/Metal composite nanofibers are presented in figure 2. SEM micrographs show that PAN/Metal composite nanofibers collected on the aluminium foil were randomly distributed to form a web of fibres. PAN/Metal composite nanofibers produced by iron(III) chloride hexahydrate salt as an iron source are presented in figures 2a-b. The average diameters of PAN/Metal composite nanofibers produced using hydrated iron salt are 340 nm, as seen in figure 2a-b. The average diameters of PAN/Metal composite nanofibers formed by using anhydrated iron salt, which is wider than those produced by hydrated iron salt, are 532 nm, as seen in figure 2c-d. The PAN/Metal composite nanofibers fabricated by electrospinning are subsequently calcined to transform into metal oxide nanofibers and remove polymer components at 500 °C temperature for 2 hours. The micrographs belonging to transformed nanofibers after annealing are given in figure 3, and drastic changes in nanofibers are seen in the images. After the heat treatment, the diameter of the electrospun nanofibers inherently decreases due to the evaporation of the solvent and polymer. The average diameter of fabricated α-Fe 2 O 3 nanofibers is approximately 150 nm and 240 nm for Hyd-α-Fe 2 O 3 and AnHyd-α-Fe 2 O 3 , respectively. Both nanofibers also have a shrinkage ratio of %55 relative to their uncalcined forms. It should be noted that the shrinkage ratio of nanofibers due to the loss of the polymer after heat treatment is identical to each other, but their morphological feature is not. Their morphological differences are obviously seen when looking at STEM images of related nanofibers presented in figure 4. The named AnHyd-Fe 2 O 3 nanofibers consist of smaller grain, low porosity, and strictly form, whereas named Hyd-Fe 2 O 3 nanofibers consist of bigger grain and higher porosity. It is important to note that the size of the grains and porosity ratio in the iron oxide nanofibers changes by using metal salts as an iron source. As a result, it is observed that the used iron source to fabricate porous α-Fe 2 O 3 nanofibers, concerning whether metal salt contains hydrate or not, has an important influence on the final morphological characteristics of α-Fe 2 O 3 nanofibers. Araujo and co-researchers reported the avarage fibres’ diameters of electrospun Fe2O3 was 360 nm and diameter distribution ranging from 200 to 900 nm calcinated at 800 °C by using Iron (III) nitrate nonahydrate and polyvinylpyrrolidone [ 53 ]. Another work executed by Petrovicovà and coworkers reported that the diameters of hematite fibres calcined for 2 hours at 600 °C varied between 120 and 500 nm using iron (II) acetate and polyacrylonitrile (PAN) as precursors [ 54 ]. In that study, the smaller average diameter of hematite fibres could be fabricated after a lower calcination temperature. Phase analysis of the produced electrospun α-Fe 2 O 3 nanofibers crystals with highly and slightly porous was carried out using an X-ray diffractometer (XRD) and obtained characteristic phase patterns of samples are shown in Fig 5. All of the observed diffraction peaks of produced porous nanofibres are well convenient with JCPDS file data (JCPDS card no. 33–0664), which is a trigonal hematite phase (α-Fe 2 O 3 , space group: R-3c) with lattice parameters of a = b = 0.503 nm and c = 1.373 nm. It was observed that there are no peaks belonging to another phase. On the other hand, It was observed that the (110) reflections created from electrospun Hyd-Fe 2 O 3 nanofibers are more intense than those created from electrospun AnHyd- Fe 2 O 3 nanofibers. The absorption/reflection characteristics and the calculated optical bandgap of produced electrospun α- Fe 2 O 3 nanofibers have been presented in figure 6a-d. The absorption spectrum curve of electrospun α- Fe 2 O 3 nanofibers as a function of wavelength are given in Figure 6b, derived from transforming the diffused reflectance of nanofiber powders into the absorbance by utilizing the Kubelka-Munk (K-M) Reflectance Theory [ 55 , 56 ]. To determine the optical band gap values of electrospun α- Fe 2 O 3 nanofibers, the Tauc relation below is used [ 57 , 58 ]. αhν = A(hν-E g ) n (1) In the equation given above, α is the extinction coefficient and corresponds to F(R) in the Kubelka-Munk Reflectance Theory. The other variables of h, ν, A, and E g in the equation are Planck constant (J.s), light frequency (s -1 ), proportionality constant, and optical bandgap of the material (eV), respectively. Some recent studies [ 59 , 60 ] report that the band type of the hematite has a direct allowed transition band. The bandgap values of produced electrospun α-Fe 2 O 3 nanofibers were determined from the plot of (F(R)hν) 2 vs hν via extrapolating the straight portion to the energy axis at α=0 for allowed direct transition as shown in figure 6c and 6d. The band gap value of AnHyd-Fe 2 O 3 nanofibers was calculated to be 1.90 eV. For Hyd-Fe 2 O 3 nanofibers, that value was found to be 2.02 eV, which was slightly wider than that belonging to AnHyd-Fe 2 O 3 nanofibers. The valence and conduction band positions of the produced electrospun α-Fe 2 O 3 nanofibers can be calculated using the following empirical relation. [ 61 ]: E CB = χ – E e – ½ E g (2) E VB = E CB + E g (3) where χ is the absolute electronegativity of the semiconductor, which is related to the first ionization energy and atomic electron affinity for constituent atoms of the semiconductor. The details of the empirical relation above could be found in the literature to determine absolute electronegativity [ 62 , 63 ]. The value of absolute electronegativity for hematite (Fe 2 O 3 ) is 5.88 eV [ 64 ]. E e is the energy of free electrons on the hydrogen scale (4.5 eV). E CB , E VB , and E g conduction band potential, valence band potential, and semiconductor bandgap, respectively. Hence, E CB and E VB were calculated to be 0.37 eV and 2.39 eV, respectively, for electrospun Hyd-Fe 2 O 3 nanofibers, whose optical bandgap value was found to be 2.02 eV via Tauc approximation, and the results are depicted in figure 6. It is well known that the degradation of chemical pollutants in aqueous solutions are emanated from highly reactive free radicals. The reactive oxygen species (ROS) [ 65 ], such as superoxide anion radical ( • O 2 - ), singlet oxygen ( 1 O 2 ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radical ( • OH), are produced in an aqueous media by induced reactions for decontamination of wastewater [ 66 ]. In the heterogeneous photocatalytic process, the reactive oxygen species are produced by photoinduced electrons (e - )-holes (h + ) pairs in the presence of a photocatalyst. [ 67 , 68 ]. In that work, photogenerated electron-hole pairs are generated by electrospun α-Fe 2 O 3 nanofibers utilising the visible region of the solar spectrum. The following factors specify the destiny of photogenerated electrons [ 69 ]: a) The photogenerated electrons are trapped to produce OH radicals by H 2 O 2 added because it acts as an electron acceptor: Fe 2 O 3 → Fe 2 O 3 (e cb - , h vb + ) (4) H 2 O 2 + e cb - → OH - + OH • (5) b) The photogenerated electrons are trapped to create Fe 2+ by the surface Fe 3+ in the following reactions: Fe 3+ + e cb - → Fe 2+ (6) Fe 2+ + H 2 O 2 → Fe 3+ + OH - + OH • (7) The generated reactive oxygen species cause the degradation of organic dye molecules by transforming them into less harmful or harmless products via photocatalytic α- Fe 2 O 3 nanofibers in the presence of H 2 O 2 , which takes place by the two factors above. Additionally, it is important to consider that the •OH radicals can be generated by the photolysis of H 2 O 2 under light irradiation. Fig. 7 shows a schematic illustration of the simplified free radical generation (•OH) mechanism and photocatalytic degradation of the MO and RhB dyes. The degradation rate of pollutants in aquatic media is assigned through monitoring changes in their absorption characteristics as a function of time. Briefly, the light absorption changes by a species in solution are dependent on its absorptivity and concentration according to the Beer-Lambert Law. It is said that the absorbance's maximum values should gradually decrease depending on the undegraded dye concentration remaining in the solution because of the degradation of organic molecules during photocatalytic reactions. With this perspective, the degradation rate of dye as a function of time in any photocatalytic process can easily be calculated by Beer-Lambert Law, given by the following equation [ 70 ] : A= ε l c (8) where A is absorbance, ε is molar absorption coefficient (M -1 cm -1 ), l is the optical path length (cm) of light in the medium, and c is the molar concentration of the absorbing species in the medium. We examined photocatalysis of electrospun nanofibers fabricated by two different iron salts of precursors against rhodamine B (RhB) and methyl orange (MO), respectively, exhibiting different ionic characteristics. The absorption spectrum changes (in a and b) obtained from heterogeneous photocatalysis and their related transformed concentration vs time graphics (c) are represented in figures 8 and 9. When looking at the absorptivity of electrospun nanofibers after stirring for 1 hour in the dark, electrospun Hyd-Fe 2 O 3 nanofibers showed higher adsorption towards different characteristics of dyes relative to the AnHyd- Fe 2 O 3 nanofibers. In the case of the photocatalysis of RhB, AnHyd-Fe 2 O 3 nanofibers degraded %56 of the dye in 2 hours while Hyd-Fe 2 O 3 nanofibers degraded all of the dye molecules in the aquatic media. In the photocatalytic degradation experiment of methyl orange (MO), electrospun Hyd-Fe 2 O 3 nanofibers with highly porous destroyed all MO dye molecules in 90 minutes, whereas Hyd- Fe 2 O 3 nanofibers could degrade as low as %13 of dye in 120 minutes. The electrospun Hyd- Fe 2 O 3 nanofibers, which were smaller in diameter and highly porous, exhibited higher photocatalytic performances against both dyes according to electrospun AnHyd-Fe 2 O 3 nanofibers. Also, the electrospun Hyd-Fe 2 O 3 nanofibers were better for degrading MO than for degrading RhB. The efficient removal of model dyes (RhB and MO) through heterogeneous photocatalytic processes in this work could have resulted from several incorporated sophisticated effects. First, the morphology of the fibres owns orientated nanograins with a few ten nanometers in size and is highly porous, which could enhance the charge transfer mechanism and facilitate electron-hole pair separation. The shorter charge transfer pathway causes faster e − -h + charge transfer towards the surface before their recombination happens, leading to an enhanced photodegradation rate [ 71 ]. The observed enhancement in the photocatalytic activity of the electrospun Hyd-Fe 2 O 3 nanofibers might be due to its multiple light scattering processes leading to reduced e − -h + recombination rate in the porous architecture. The highly porous architecture can increase light-harvesting efficiency by scattering enhancement and trapping [ 72 ]. 4. Conclusions The visible-driven α-Fe 2 O 3 nanofibers with highly porous were fabricated by electrospinning the PAN/Metal composite nanofibers, followed by calcination at 500°C temperature for 2 hours. We observed that a precursor used as an iron source, depending on whether it includes hydrate, played an important role in fibres' final morphologies and size in diameter. The electrospun α-Fe 2 O 3 nanofiber synthesized from an iron source with a hydrated were smaller in fibre diameter and showed higher porous morphology than those synthesized under similar conditions. In the heterogeneous photocatalysis of the electrospun α-Fe 2 O 3 nanofibers against two model dyes representing anionic (MO) and cationic (RhB) characteristics, both electrospun α-Fe 2 O 3 nanofibers showed good photocatalytic activity against used model pollutants. The α- α-Fe 2 O 3 nanofibers produced using iron(III) chloride hexahydrate exhibited a higher photocatalytic degradation rate against both dye pollutants relative to the α- α-Fe 2 O 3 nanofibers produced using iron(III) chloride. Furthermore, the highest degradation rate was observed against anionic dye (MO) by the electrospun α-Fe 2 O 3 nanofibers with highly porous. Depending on the used iron sources and associatively their final morphological characteristics, it was observed that their photocatalytic degradation performances were seriously affected. It is suggested that electrospun α- Fe 2 O 3 nanofibers, especially those with highly porous and smaller diameters, are suitable candidates as a visible-light-driven semiconductor material to use in advanced oxidation processes for removing pollutants from wastewater. Declarations Acknowledgements We would like to gratefully acknowledge Inovenso Co. Ltd. for the electrospinning device as a courtesy and Aksa Co. Ltd. for polymer supply. 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The effect of dispersion technique, silver particle loading, and reduction method on the properties of polyacrylonitrile–silver composite nanofiber. Journal of Industrial Textiles, 45(6), pp.1173-1187. [ ] Araujo, R.N., Nascimento, E.P., Firmino, H.C.T., Macedo, D.A., Neves, G.A., Morales, M.A. and Menezes, R.R., 2021. α-Fe2O3 fibers: an efficient photocatalyst for dye degradation under visible light. Journal of Alloys and Compounds, 882, p.160683. [ ] Petrovičovà, B., Ferrara, C., Brugnetti, G., Ritter, C., Fracchia, M., Ghigna, P., Pollastri, S., Triolo, C., Spadaro, L., Ruffo, R. and Santangelo, S., 2021. Effect of germanium incorporation on the electrochemical performance of electrospun Fe2O3 nanofibers-based anodes in sodium-ion batteries. Applied Sciences, 11(4), p.1483. [ ] P. Kubelka, New contributions to the optics of intensely light-scattering materials. Part I, Josa 38 (5) (1948) 448e457. [ ] Kubelka, P., 1931. 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Electronegativity: the density functional viewpoint. The Journal of Chemical Physics, 68(8), pp.3801-3807. [ ] Pearson, R.G., 1988. Absolute electronegativity and hardness: application to inorganic chemistry. Inorganic chemistry, 27(4), pp.734-740. [ ] Xu, Y. and Schoonen, M.A., 2000. The absolute energy positions of conduction and valence bands of selected semiconducting minerals. American Mineralogist, 85(3-4), pp.543-556. [ ] Nosaka, Y. and Nosaka, A.Y., 2017. Generation and detection of reactive oxygen species in photocatalysis. Chemical reviews, 117(17), pp.11302-11336. [ ] Glaze, W. H., Kang, J. W., and Chapin, D. H. (1987). The chemistry of water treatment processes involving ozone, hydrogen peroxide and ultraviolet radiation. Ozone Sci. Eng., 9(4), 335–352. [ ] Poyatos, J.M., Muñio, M.M., Almecija, M.C., Torres, J.C., Hontoria, E. and Osorio, F., 2010. Advanced oxidation processes for wastewater treatment: state of the art. Water, Air, and Soil Pollution, 205(1-4), p.187. [ ] Rauf, M.A. and Ashraf, S.S., 2009. Fundamental principles and application of heterogeneous photocatalytic degradation of dyes in solution. Chemical engineering journal, 151(1-3), pp.10-18. [ ] Bandara, J., Klehm, U. and Kiwi, J., 2007. Raschig rings-Fe2O3 composite photocatalyst activate in the degradation of 4-chlorophenol and Orange II under daylight irradiation. Applied Catalysis B: Environmental, 76(1-2), pp.73-81. [ ] D.F. Swinehart, The beer-lambert Law, J. Chem. Educ. 39 (7) (1962) 333. [ ] Ebrahimi, M., Yousefzadeh, S., Samadi, M., Dong, C., Zhang, J. and Moshfegh, A.Z., 2018. Facile preparation of branched hierarchical ZnO nanowire arrays with enhanced photocatalytic activity: a photodegradation kinetic model. Applied Surface Science, 435, pp.108-116. [ ] Ko, S.H., Lee, D., Kang, H.W., Nam, K.H., Yeo, J.Y., Hong, S.J., Grigoropoulos, C.P. and Sung, H.J., 2011. Nanoforest of hydrothermally grown hierarchical ZnO nanowires for a high efficiency dye-sensitized solar cell. Nano letters, 11(2), pp.666-671. Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-2202218","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":146894803,"identity":"d1822921-10cf-4618-bcae-602b5921b5a4","order_by":0,"name":"Emre 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University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"İsmail","middleName":"","lastName":"BORAZAN","suffix":""}],"badges":[],"createdAt":"2022-10-25 11:52:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2202218/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2202218/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":28288904,"identity":"7697d35c-c2e9-4c4f-a095-7ce084968bbc","added_by":"auto","created_at":"2022-10-26 17:04:21","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":445020,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic representation of producing the electrospun α-Fe\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanofibers with porous.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/9c1e1fe111e2ddf39f38f0ed.png"},{"id":28288907,"identity":"a03323bb-5a97-4002-8e60-4cad633cb379","added_by":"auto","created_at":"2022-10-26 17:04:21","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1674284,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMicrostructural features of as-synthesized PAN/Metal composite structure. \u003c/strong\u003e\u0026nbsp;low and high magnification FESEM images of as-synthesized PAN/Metal composite by hydrous iron salt are represented in a) and b); and of as-synthesized PAN/Metal composite by anhydrous iron salt are represented in c) and d).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/67300e5c1009adc6a98b8eee.png"},{"id":28290396,"identity":"f30ddaf2-15d9-456a-a143-f0e5b10b3b9b","added_by":"auto","created_at":"2022-10-26 17:19:21","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1904459,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMicrostructural features\u0026nbsp;of metal oxide nanofibers after the heat treatment process. a-b) \u003c/strong\u003eFESEM images of Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers\u003csub\u003e \u003c/sub\u003eare represented, and \u003cstrong\u003ec-d) \u003c/strong\u003e\u0026nbsp;FESEM images of AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers\u003csub\u003e \u003c/sub\u003eare represented.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/901810e8cd43cafc1067c3bd.png"},{"id":28289238,"identity":"f4adbec8-5d00-40e7-85f3-dd80c5244b01","added_by":"auto","created_at":"2022-10-26 17:09:21","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":982397,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMicrostructural features\u0026nbsp;of metal oxide Nanofibers. a-b) \u003c/strong\u003eBright-field STEM micrographs of Hyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers with highly porous \u003cstrong\u003ec-d)\u003c/strong\u003e Bright-field STEM micrographs of AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with slightly porous.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/b5c4c15150082cbd0fdb4b7e.png"},{"id":28289237,"identity":"b6e084dc-41dd-4fc2-b0c4-dc59b0e67071","added_by":"auto","created_at":"2022-10-26 17:09:21","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":153888,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eXRD diffraction patterns of the produced electrospun α-Fe\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanofibers.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/89c0896be6d3c24ff387d773.png"},{"id":28289952,"identity":"ff99de49-77d6-4820-a74d-6edbc3527399","added_by":"auto","created_at":"2022-10-26 17:14:21","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":315722,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOptical properties of the produced electrospun α-Fe\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanofibers. a) \u003c/strong\u003eDiffused reflectance spectra of the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003cstrong\u003e \u003c/strong\u003enanofibers\u003cstrong\u003e b) \u003c/strong\u003eabsorption spectra of the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers (derived by the Kubelka-Munk (K-M) Reflectance function) c) determination of optical band gap by Tauc’plots c) for AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers d) for Hyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/0c363aabe70c05655f2f16d2.png"},{"id":28289241,"identity":"fd368e0a-376d-4da9-a57a-0d21ec039598","added_by":"auto","created_at":"2022-10-26 17:09:21","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":300754,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic drawing of redox potentials of the produced electrospun α-Fe\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanofibers and mechanisms of photocatalysis under solar irradiation.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/dee8a05449b3c2a99fdf0746.png"},{"id":28289239,"identity":"e5d791f2-bf0a-47ff-a891-f1d159851698","added_by":"auto","created_at":"2022-10-26 17:09:21","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":222262,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhotocatalytic remediation process results against rhodamine B (RhB) under \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003esolar simulator irradiated\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e. \u003c/em\u003ea) After photocatalysis at indicated time intervals, the UV–vis absorption spectrum of RhB solutions executed by electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers with highly Porous, b) executed by electrospun AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with slightly porous and c) Photodegradation ratio of RhB vs irradiation times for electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers along with the photolysis of RhB (with the time of light on set as 0, C\u003csub\u003e0 \u003c/sub\u003edenotes the initial concentration of RhB and C\u003csub\u003et \u003c/sub\u003edenotes concentration of RhB at indicated irradiation time).\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/84066e29aa321426dfa4f79f.png"},{"id":28288909,"identity":"9e399bf4-b53c-4d9d-bbe9-dda58c937c2b","added_by":"auto","created_at":"2022-10-26 17:04:21","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":207077,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhotocatalytic remediation process results against methyl orange (MO) under solar simulator irradiated\u003c/strong\u003e\u003cem\u003e. \u003c/em\u003ea) After photocatalysis at indicated time intervals, the UV–vis absorption spectrum of MO solutions executed by electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers with highly porous, b) executed by electrospun AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with slightly porous and c) Photodegradation ratio of MO vs irradiation times for electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3 \u003c/sub\u003enanofibers along with the photolysis of MO (with the time of light on set as 0, C\u003csub\u003e0 \u003c/sub\u003edenotes the initial concentration of MO and C\u003csub\u003et \u003c/sub\u003edenotes concentration of MO at indicated irradiation time).\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/7baa3147a5955f618e07415c.png"},{"id":28290699,"identity":"2641293f-addc-4805-b4a3-f3230d0156ea","added_by":"auto","created_at":"2022-10-26 17:24:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5281296,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2202218/v1/6c6e4c2a-03bb-46e7-9303-922d9c049ccb.pdf"}],"financialInterests":"\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e","formattedTitle":"\u003cp\u003eProduction of Highly Porous Electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e Nanofibers For Environmental Applications\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eNow, society faces two serious challenges; environmental issues and energy problems. These issues determine the world\u0026apos;s future and also, shape our society in the 21st century. With this perspective, the new technologies are surveyed to suggest new solutions in almost every aspect of climate, energy, and environment for Sustainable Development Goals (UN SDGs) [\u003csup\u003e1\u003c/sup\u003e] set out by the United Nations. The environment and climate are globally aggressively attacked by the way of various forms of environmental pollution, mainly air and water pollution. As a result of rapid industrialization and urbanization, as well as the increasing population, clean water supplies are polluted and parallelly, the need for clean water has increased all over the World [referans]. The wastewater infrastructure in the developed world faces increasing demands to generate higher quality clean water using less energy and with lower proceeding costs. [\u003csup\u003e2\u003c/sup\u003e]. Solar-driven semiconductors present significant opportunities to solve growing energy problems and environmental crises [\u003csup\u003e3\u003c/sup\u003e].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDyes widely used in textiles, plastics, and paper industries, some of which are either carcinogenic, mutagenic or toxic, have led to severe environmental contamination and, consequently, seriously affect the nature of water [\u003csup\u003e4\u003c/sup\u003e]. Heterogeneous photocatalysts have numerous potentials in the different application fields, including degradation of dyes and organics, antibacterial, \u0026nbsp;CO\u003csub\u003e2\u003c/sub\u003e reduction, and water splitting [\u003csup\u003e5\u003c/sup\u003e]. Heterogeneous photocatalysis has been considered one of the most attractive methods for wastewater treatment to degrade pollutants, from textile dyes and personal care products to harmful bacteria, with a solid photocatalyst using sunlight. [\u003csup\u003e6\u003c/sup\u003e, \u003csup\u003e7\u003c/sup\u003e]. The heterogeneous photocatalysis in the water remediation process has several benefits and opportunities. These advantages are that there is no harmful intermediate production (particularly for organic pollutants), allowing continuous re-use, the reactions taking place at room temperature, and photocatalysts are inexpensive [\u003csup\u003e8\u003c/sup\u003e].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHematite (\u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) has attracted much attention as a promising material for solar-related applications due to its desirable properties, such as visible-driven optical band gap, high physicochemical stability (especially in aquatic media), an earth-abundant material, associatively low-cost, and eco-friendly [\u003csup\u003e9\u003c/sup\u003e, \u003csup\u003e10\u003c/sup\u003e]. Hematite has a band gap of 2.1 eV and is semiconducting material with an n-type band structure. \u0026nbsp;Among all iron oxide phases, \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is one of the most thermodynamically stable phases; thus, this characteristic makes it suitable for heterogenous photocatalysis in aqueous media [\u003csup\u003e11\u003c/sup\u003e]. Based upon their unique physical, chemical and optical properties mentioned, hematite has numerous applications in emerging fields such as biomedical for cancer treatment, Li-ion batteries [\u003csup\u003e12\u003c/sup\u003e], sodium ion batteries (SIBs) and potassium ion batteries (PIBs) [\u003csup\u003e13\u003c/sup\u003e], air purification [\u003csup\u003e14\u003c/sup\u003e], gas sensor [\u003csup\u003e15\u003c/sup\u003e], photoelectrochemical (PEC) water splitting for hydrogen generation [\u003csup\u003e16\u003c/sup\u003e, \u003csup\u003e17\u003c/sup\u003e], biosensors [\u003csup\u003e18\u003c/sup\u003e], medical treatment and diagnosis [\u003csup\u003e19\u003c/sup\u003e, \u003csup\u003e20\u003c/sup\u003e], photocatalysis in wastewater treatment [\u003csup\u003e21\u003c/sup\u003e, \u003csup\u003e22\u003c/sup\u003e], pigments for energy saving [\u003csup\u003e23\u003c/sup\u003e] and etc. Although it has these unique features mentioned in the literature, it suffers from some insufficients such as short hole diffusion length [\u003csup\u003e24\u003c/sup\u003e], poor electrical conductivity [\u003csup\u003e25\u003c/sup\u003e], electron-hole recombination rate [\u003csup\u003e26\u003c/sup\u003e], absorptivity [\u003csup\u003e27\u003c/sup\u003e], and; thus, these poor properties limit its application fields and solar-related application performance. With the optimization of the structural properties of hematite at the nanometer level by utilizing engineering strategies such as morphology regulation, shape control, metallic supported architecture, doping, and creating a heterojunction, it is possible to overcome these limitations [\u003csup\u003e28\u003c/sup\u003e, \u003csup\u003e29\u003c/sup\u003e, \u003csup\u003e30\u003c/sup\u003e, \u003csup\u003e31\u003c/sup\u003e, \u003csup\u003e32\u003c/sup\u003e, \u003csup\u003e33\u003c/sup\u003e].\u003c/p\u003e\n\u003cp\u003eIn recent years, the shape controllable synthesizes of nanoparticle materials have attracted the focus of research due to the size-dependent and shape-dependent remarkable properties of nanostructured materials [\u003csup\u003e34\u003c/sup\u003e]. Up to now, The well-defined hematite forms with countless morphology and dimensionalities, including nanotube [\u003csup\u003e35\u003c/sup\u003e], \u0026nbsp;hollow spheres [ \u003csup\u003e36\u003c/sup\u003e], rods [\u003csup\u003e37\u003c/sup\u003e], ellipsoids [ \u003csup\u003e38\u003c/sup\u003e], wires [ \u003csup\u003e39\u003c/sup\u003e], cubic [\u003csup\u003e40\u003c/sup\u003e, \u003csup\u003e41\u003c/sup\u003e ], hexagonal platelets [\u003csup\u003e42\u003c/sup\u003e], bipyramid [ ], double ellipsoid [\u003csup\u003e43\u003c/sup\u003e ] and, plate [\u003csup\u003e44\u003c/sup\u003e], belts [\u003csup\u003e45\u003c/sup\u003e ] have been fabricated. The formation of these nanoparticles with diverse shapes and dimensionalities has been adjusted by controlling so many kinetic (e.g., diffusion of reactants, surface adhesion of surfactants) and thermodynamic (e.g., the relative stability of crystal polymorphs) complicated factors associated with each other [\u003csup\u003e46\u003c/sup\u003e].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNanotechnology plays a substantial role in water purification through synthesizing nanoparticles of different morphologies and shapes with unique physicochemical properties. [\u003csup\u003e47\u003c/sup\u003e]. Electrospinning is a simple technique by which one can easily fabricate one-dimensional (1D) nanomaterials on an industrial scale and with controllable features such as morphologies, diameters, and compositions [\u003csup\u003e48\u003c/sup\u003e]. From the perspective of structure advantages which are ideally suited for heterogenous photocatalytic reactions, the electrospun one-dimensional (1D) semiconductor nanofibers exhibit countless unique characteristics such as extraordinary length, a large ratio of length to diameter, hierarchically porous structure, high surface area, small grain sizes, and high porosity \u0026nbsp;[\u003csup\u003e49\u003c/sup\u003e,\u003csup\u003e50\u003c/sup\u003e].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs it is known, polyacrylonitrile (PAN) is one of the most popular polymers used in fabricating nanofiber by electrospinning [\u003csup\u003e51\u003c/sup\u003e] and are frequently used for the production of composite nanofiber [\u003csup\u003e52\u003c/sup\u003e]. We used polyacrylonitrile (PAN) as a polymeric matrix to fabricate polymer/metal composite nanofiber. In the light of the unique characteristics of electrospinning production mentioned, firstly, we wondered how a precursor used as an iron source, depending on whether it includes hydrate, would affect fibres\u0026apos; final morphologies. With this perspective, we fabricated electrospun nanofibres using iron chloride with hydrate and without hydrate. Besides, we wondered how their photocatalytic performances would change based on their final morphological characteristics.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe electrospun \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers were characterized and their photocatalytic activities were examined against two organic synthetic dyes showing different characteristics relative to each other. It was observed that using precursors, depending on whether it includes hydrate forms, for producing electrospun hematite nanofibers strongly affected their final morphologies, associatively resulting in different photocatalytic activities. The electrospun hematite nanofibers fabricated by iron(III) chloride hexahydrate were smaller in diameter and highly porous in structure according to those fabricated by iron(III) chloride. These highly porous and smaller diameters electrospun nanofibers also exhibited higher photocatalytic performances against both model dye molecules. The results here propose that the electrospun \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with highly porous would provide suitable photocatalytic activities to remove organic contaminants from wastewater.\u0026nbsp;\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Production of Electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e Nanofibers\u003c/h2\u003e \u003cp\u003ePoly(acrylonitrile-co-vinyl acetate) (PAN) with a density of 1.18 g/cm3 is supplied courtesy of AKSA Corporation. 10% (w:w) PAN(co-polymer) is solved in DMF and stirred for 24 hours. Iron(III) chloride and iron(III) chloride hexahydrate was purchased from Sigma-Aldrich. 1% (weight ratio) of iron compounds were separately dispersed in DMF in an ultrasonic bath for 15 min; afterwards, 10% (weight ratio) PAN was added into the iron solution and stirred overnight to dissolve properly. Iron-added PAN solutions were filled into a syringe, then loaded in the NanoYarn Spinner (Inovenso Co. Ltd.), and high voltage (30 kV) was applied to the tip of a needle that connected to the syringe. The syringe was pumped with a constant rate of 1 ml/hour, and the polymer was collected as a nanofibers mat on an aluminium foil placed on the grounded and rotating collector. The distance between the needle and collector was 10 cm. The rotation of the collector was 500 rpm during the fabrication. The electrospinning device and its elements are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Afterwards, heat treatment was applied to as-synthesized PAN/Metal composite fibres. They were heated up to 500\u0026deg;C with a heating rate of 2\u0026deg;C/min and maintained at that temperature for 2 hours. Then, they were naturally cooled down to room temperature in the furnace. The schematic representation of producing the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers produced by using iron(III) chloride as an iron source are named AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and The electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers produced by using iron(III) chloride hexahydrate as an iron source are named Hyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Characterization\u003c/h2\u003e \u003cp\u003eThe produced PAN/metal composite structure\u0026rsquo;s morphological and microstructural features were conducted using a field emission gun TESCAN\u0026trade; MAIA XMU scanning electron microscope (FESEM). The Powder X-ray diffraction (XRD) pattern of produced electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers was carried out by using a RIGAKU SmartLab\u0026trade; X-ray diffractometer operated at 40 mA current and 40 kV voltage with Cu-Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring; ). The UV-vis spectra for determining the optical properties (such as band gap and absorption characteristics) of produced electrospun α-Fe2O3 nanofibers and photocatalytic performances of photocatalysts against dye pollutants were measured via Shimadzu UV- 3600 UV-Vis-NIR spectrophotometers.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Photocatalytic Activity Experiments\u003c/h2\u003e \u003cp\u003eThe photocatalytic activities of electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with porous against two pollutant dyes with different kind characteristics exhibiting anionic and cationic, respectively called methyl orange (MO), rhodamine B (RhB) dyes, were executed. The specific test solution used for photocatalytic performances of produced electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers has an identical concentration of 10 mg/L for both dye molecules. The solution was prepared by adding electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers photocatalysts (0.5 g/L) into dye solution (10 mg/L). Before solar irradiation, the solution was magnetically stirred in the dark for 60 minutes to provide an adsorption-desorption equilibrium on the surface of photocatalyst powders. Afterwards, the dispersion was put under an AM 1.5 solar simulator and irradiated by a 500 W xenon lamp under continuously magnetic stirring conditions. The samples were taken from the solution to identify the adsorption characteristic at indicated intervals. Before estimating absorption characteristics, all samples from the aqueous solution were centrifuged to separate the catalysts from the aqueous media. The UV/vis/NIR absorption spectra of samples from the aqueous solution were characterized to monitor photocatalytic performances of the produced electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers photocatalysts against dye molecules via a UV/vis spectrophotometer.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results And Discussion","content":"\u003cp\u003eWe wondered how precursor used as an iron source, depending on whether it includes hydrate, would affect fibres\u0026apos; morphologies. With this viewpoint, we fabricated electrospun nanofibres using iron chloride with hydrate and without hydrate. Besides, we wondered how their photocatalytic performances would change based on morphological differences. Microstructural features of as-synthesized PAN/Metal composite nanofibers are presented in figure 2. SEM micrographs show that PAN/Metal composite nanofibers collected on the aluminium foil were randomly distributed to form a web of fibres. PAN/Metal composite nanofibers produced by iron(III) chloride hexahydrate salt as an iron source are presented in figures 2a-b. The average diameters of PAN/Metal composite nanofibers produced using hydrated iron salt are 340 nm, as seen in figure 2a-b. The average diameters of PAN/Metal composite nanofibers formed by using anhydrated iron salt, which is wider than those produced by hydrated iron salt, are 532 nm, as seen in figure 2c-d.\u003c/p\u003e\n\u003cp\u003eThe PAN/Metal composite nanofibers fabricated by electrospinning are subsequently calcined to transform into metal oxide nanofibers and remove polymer components at 500 \u0026deg;C temperature for 2 hours. The micrographs belonging to transformed nanofibers after annealing are given in figure 3, and drastic changes in nanofibers are seen in the images. After the heat treatment, the diameter of the electrospun nanofibers inherently decreases due to the evaporation of the solvent and polymer. The average diameter of fabricated\u0026nbsp;\u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers is approximately 150 nm and 240 nm for Hyd-\u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003eand AnHyd-\u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, respectively. Both nanofibers also have a shrinkage ratio of %55 relative to their uncalcined forms. It should be noted that the shrinkage ratio of nanofibers due to the loss of the polymer after heat treatment is identical to each other, but their morphological feature is not. Their morphological differences are obviously seen when looking at STEM images of related nanofibers presented in figure 4. The named AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers consist of smaller grain, low porosity, and strictly form, whereas named Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers consist of bigger grain and higher porosity.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIt is important to note that the size of the grains and porosity ratio in the iron oxide nanofibers changes by using metal salts as an iron source. As a result, it is observed that the used iron source to fabricate porous \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers, concerning whether metal salt contains hydrate or not, has an important influence on the final morphological characteristics of \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers. Araujo and co-researchers reported the avarage fibres\u0026rsquo; diameters of electrospun Fe2O3 was 360 nm and diameter distribution ranging from 200 to 900 nm calcinated at 800 \u0026deg;C by using Iron (III) nitrate nonahydrate and polyvinylpyrrolidone [\u003csup\u003e53\u003c/sup\u003e]. Another work executed by Petrovicov\u0026agrave; and coworkers reported that the diameters of hematite fibres calcined for 2 hours at 600 \u0026deg;C varied between 120 and 500 nm using iron (II) acetate and polyacrylonitrile (PAN) as precursors [\u003csup\u003e54\u003c/sup\u003e]. In that study, the smaller average diameter of hematite fibres could be fabricated after a lower calcination temperature.\u003c/p\u003e\n\u003cp\u003ePhase analysis of the produced electrospun\u0026nbsp;\u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003enanofibers crystals with highly and slightly porous was carried out using an X-ray diffractometer \u0026nbsp;(XRD) and obtained characteristic phase patterns of samples are shown in Fig 5. All of the observed diffraction peaks of produced porous nanofibres are well convenient with JCPDS file data \u0026nbsp;(JCPDS card no. 33\u0026ndash;0664), which is a trigonal hematite phase (\u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, space group: R-3c) with lattice parameters of a = b = 0.503 nm and c = 1.373 nm. It was observed that there are no peaks belonging to another phase. On the other hand, \u0026nbsp;It was observed that the (110) reflections created from electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers are more intense than those created from electrospun AnHyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers.\u003c/p\u003e\n\u003cp\u003eThe absorption/reflection characteristics and the calculated optical bandgap of produced electrospun \u0026alpha;-\u0026nbsp;Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers have been presented in figure 6a-d. The absorption spectrum curve of\u0026nbsp;electrospun \u0026alpha;-\u0026nbsp;Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers\u0026nbsp;as a function of wavelength are given in Figure 6b, derived from transforming the diffused reflectance of\u0026nbsp;nanofiber\u0026nbsp;powders\u0026nbsp;into the absorbance by utilizing the Kubelka-Munk (K-M) Reflectance Theory [\u003csup\u003e55\u003c/sup\u003e, \u003csup\u003e56\u003c/sup\u003e]. To determine the optical band gap values of\u0026nbsp;electrospun \u0026alpha;-\u0026nbsp;Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers, the Tauc relation below is used [\u003csup\u003e57\u003c/sup\u003e,\u003csup\u003e58\u003c/sup\u003e].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026alpha;h\u0026nu; = A(h\u0026nu;-E\u003csub\u003eg\u003c/sub\u003e)\u003csup\u003en\u003c/sup\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(1)\u003c/p\u003e\n\u003cp\u003eIn the equation given above, \u0026alpha; is the extinction coefficient and corresponds to F(R) in the Kubelka-Munk Reflectance Theory. The other variables of h, \u0026nu;, A, and E\u003csub\u003eg\u0026nbsp;\u003c/sub\u003ein the equation are Planck constant (J.s),\u0026nbsp;light frequency (s\u003csup\u003e-1\u003c/sup\u003e), proportionality constant, and optical bandgap of the material (eV), respectively. Some recent studies [\u003csup\u003e59\u003c/sup\u003e, \u003csup\u003e60\u003c/sup\u003e] report that the band type of the hematite has a direct allowed transition band. The bandgap values of\u0026nbsp;produced electrospun \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers were determined from the plot of (F(R)h\u0026nu;)\u003csup\u003e2\u003c/sup\u003e vs h\u0026nu; via extrapolating the straight portion to the energy axis at \u0026alpha;=0 for allowed direct transition as shown in figure 6c and 6d. The band gap value of AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers was calculated to be 1.90 eV. For Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers, that value was found to be 2.02 eV, which was slightly wider than that belonging to AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe valence and conduction band positions of the produced electrospun \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers can be calculated using the following empirical relation. [\u003csup\u003e61\u003c/sup\u003e]:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eE\u003csub\u003eCB\u0026nbsp;\u003c/sub\u003e = \u0026chi; \u0026ndash; E\u003csup\u003ee\u003c/sup\u003e \u0026ndash; \u0026frac12; E\u003csub\u003eg\u0026nbsp;\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; (2)\u003c/p\u003e\n\u003cp\u003eE\u003csub\u003eVB\u0026nbsp;\u003c/sub\u003e = E\u003csub\u003eCB\u003c/sub\u003e + E\u003csub\u003eg\u003c/sub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(3)\u003c/p\u003e\n\u003cp\u003ewhere \u0026chi; is the absolute electronegativity of the semiconductor, which is related to the first ionization energy and atomic electron affinity for constituent atoms of the semiconductor. The details of the empirical relation above could be found in the literature to determine absolute electronegativity [\u003csup\u003e62\u003c/sup\u003e, \u003csup\u003e63\u003c/sup\u003e]. The value of absolute electronegativity for hematite (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) is 5.88 eV [\u003csup\u003e64\u003c/sup\u003e]. \u0026nbsp;E\u003csup\u003ee\u003c/sup\u003e is the energy of free electrons on the hydrogen scale (4.5 eV). E\u003csub\u003eCB\u003c/sub\u003e, E\u003csub\u003eVB\u003c/sub\u003e, and E\u003csub\u003eg\u003c/sub\u003e conduction band potential, valence band potential, and semiconductor bandgap, respectively. Hence, E\u003csub\u003eCB\u0026nbsp;\u003c/sub\u003eand\u003csub\u003e\u0026nbsp;\u003c/sub\u003eE\u003csub\u003eVB\u0026nbsp;\u003c/sub\u003ewere calculated to be 0.37 eV and 2.39 eV, respectively, for electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers, whose optical bandgap value was found to be 2.02 eV via Tauc approximation, and the results are depicted in figure 6. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIt is well known that the degradation of chemical pollutants in aqueous solutions are emanated from highly reactive free radicals. The reactive oxygen species (ROS) [\u003csup\u003e65\u003c/sup\u003e], such as superoxide anion radical (\u003csup\u003e\u0026bull;\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e), singlet oxygen (\u003csup\u003e1\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) and hydroxyl radical (\u003csup\u003e\u0026bull;\u003c/sup\u003eOH), are produced in an aqueous media by induced reactions for decontamination of wastewater [\u003csup\u003e66\u003c/sup\u003e]. In the heterogeneous photocatalytic process, the reactive oxygen species are produced by photoinduced electrons (e\u003csup\u003e-\u003c/sup\u003e)-holes (h\u003csup\u003e+\u003c/sup\u003e) pairs in the presence of a photocatalyst. \u0026nbsp;[\u003csup\u003e67\u003c/sup\u003e, \u003csup\u003e68\u003c/sup\u003e]. In that work, photogenerated electron-hole pairs are generated by electrospun \u0026alpha;-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers utilising the visible region of the solar spectrum. The following factors specify the destiny of photogenerated electrons [\u003csup\u003e69\u003c/sup\u003e]: \u0026nbsp;\u003c/p\u003e\n\u003cp\u003ea) The photogenerated electrons are trapped to produce OH radicals by H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eadded because it acts as an electron acceptor:\u003c/p\u003e\n\u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003e\u0026rarr;\u003csub\u003e\u0026nbsp;\u0026nbsp;\u003c/sub\u003eFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003e(e\u003csub\u003ecb\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e, h\u003csub\u003evb\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e)\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;(4)\u003c/p\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026nbsp; \u0026nbsp;+ e\u003csub\u003ecb\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e\u003csub\u003e\u0026nbsp; \u0026nbsp;\u003c/sub\u003e\u0026rarr;\u003csub\u003e\u0026nbsp;\u0026nbsp;\u003c/sub\u003eOH\u003csup\u003e-\u0026nbsp;\u003c/sup\u003e+ OH\u003csup\u003e\u0026bull;\u003c/sup\u003e\u003csub\u003e\u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/sub\u003e(5)\u003c/p\u003e\n\u003cp\u003eb) The photogenerated electrons are trapped to create Fe\u003csup\u003e2+\u0026nbsp;\u003c/sup\u003eby the surface Fe\u003csup\u003e3+\u003c/sup\u003e in the following reactions:\u003c/p\u003e\n\u003cp\u003eFe\u003csup\u003e3+\u003c/sup\u003e\u0026nbsp; + e\u003csub\u003ecb\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e \u0026rarr; Fe\u003csup\u003e2+\u003c/sup\u003e \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; (6)\u003c/p\u003e\n\u003cp\u003eFe\u003csup\u003e2+\u003c/sup\u003e\u0026nbsp; + H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u0026nbsp; \u0026rarr; Fe\u003csup\u003e3+\u003c/sup\u003e + OH\u003csup\u003e-\u0026nbsp;\u003c/sup\u003e+ OH\u003csup\u003e\u0026bull;\u0026nbsp;\u003c/sup\u003e\u003csub\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/sub\u003e(7)\u003c/p\u003e\n\u003cp\u003eThe generated reactive oxygen species cause the degradation of organic dye molecules by transforming them into less harmful or harmless products via photocatalytic \u0026alpha;- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers in the presence of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, which takes place by the two factors above. Additionally, it is important to consider that the \u0026bull;OH radicals can be generated by the photolysis of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e under light irradiation. Fig. 7 shows a schematic illustration of the simplified free radical generation (\u0026bull;OH) mechanism and photocatalytic degradation of the MO and RhB dyes.\u003c/p\u003e\n\u003cp\u003eThe degradation rate of pollutants in aquatic media is assigned through monitoring changes in their absorption characteristics as a function of time. Briefly, \u0026nbsp;the light absorption changes by a species in solution are dependent on its absorptivity and concentration according to the Beer-Lambert Law. It is said that the absorbance\u0026apos;s maximum values should gradually decrease depending on the undegraded dye concentration remaining in the solution because of the degradation of organic molecules during photocatalytic reactions. With this perspective, the degradation rate of dye as a function of time in any photocatalytic process can easily be calculated by Beer-Lambert Law, given by the following equation [\u003csup\u003e70\u003c/sup\u003e] :\u003c/p\u003e\n\u003cp\u003eA= \u0026epsilon; l c\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;(8)\u003c/p\u003e\n\u003cp\u003ewhere A is absorbance, \u0026epsilon; is molar absorption coefficient (M \u003csup\u003e-1\u003c/sup\u003ecm\u003csup\u003e-1\u003c/sup\u003e), l is the optical path length (cm) of light in the medium, and c is the molar concentration of the absorbing species in the medium.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe examined photocatalysis of electrospun nanofibers fabricated by two different iron salts of precursors against rhodamine B (RhB) and methyl orange (MO), respectively, exhibiting different ionic characteristics. The absorption spectrum changes (in a and b) obtained from heterogeneous photocatalysis and their related transformed concentration vs time graphics (c) are represented in figures 8 and 9. When looking at the absorptivity of electrospun nanofibers after stirring for 1 hour in the dark, electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers showed higher adsorption towards different characteristics of dyes relative to the AnHyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers. In the case of the photocatalysis of RhB, AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers degraded %56 of the dye in 2 hours while Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers degraded all of the dye molecules in the aquatic media. In the photocatalytic degradation experiment of methyl orange (MO), electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers with highly porous destroyed all MO dye molecules in 90 minutes, whereas Hyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers could degrade as low as %13 of dye in 120 minutes. The electrospun Hyd- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers, which were smaller in diameter and highly porous, exhibited higher photocatalytic performances against both dyes according to electrospun AnHyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers. Also, the electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003enanofibers were better for degrading MO than for degrading RhB.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe efficient removal of model dyes (RhB and MO) through heterogeneous photocatalytic processes in this work could have resulted from several incorporated sophisticated effects. First, the morphology of the fibres owns orientated nanograins with a few ten nanometers in size and is highly porous, which could enhance the charge transfer mechanism and facilitate electron-hole pair separation. The shorter charge transfer pathway causes faster e\u003csup\u003e\u0026minus;\u003c/sup\u003e-h\u003csup\u003e+\u0026nbsp;\u003c/sup\u003echarge transfer towards the surface before their recombination happens, leading to an enhanced photodegradation rate [\u003csup\u003e71\u003c/sup\u003e]. The observed enhancement in the photocatalytic activity of the electrospun Hyd-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers might be due to its multiple light scattering processes leading to reduced e\u003csup\u003e\u0026minus;\u003c/sup\u003e-h\u003csup\u003e+\u003c/sup\u003e recombination rate in the porous architecture. The highly porous architecture can increase light-harvesting efficiency by scattering enhancement and trapping [\u003csup\u003e72\u003c/sup\u003e]. \u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe visible-driven α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with highly porous were fabricated by electrospinning the PAN/Metal composite nanofibers, followed by calcination at 500\u0026deg;C temperature for 2 hours. We observed that a precursor used as an iron source, depending on whether it includes hydrate, played an important role in fibres' final morphologies and size in diameter. The electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofiber synthesized from an iron source with a hydrated were smaller in fibre diameter and showed higher porous morphology than those synthesized under similar conditions. In the heterogeneous photocatalysis of the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers against two model dyes representing anionic (MO) and cationic (RhB) characteristics, both electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers showed good photocatalytic activity against used model pollutants. The α- α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers produced using iron(III) chloride hexahydrate exhibited a higher photocatalytic degradation rate against both dye pollutants relative to the α- α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers produced using iron(III) chloride. Furthermore, the highest degradation rate was observed against anionic dye (MO) by the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with highly porous. Depending on the used iron sources and associatively their final morphological characteristics, it was observed that their photocatalytic degradation performances were seriously affected. It is suggested that electrospun α- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers, especially those with highly porous and smaller diameters, are suitable candidates as a visible-light-driven semiconductor material to use in advanced oxidation processes for removing pollutants from wastewater.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eWe would like to gratefully acknowledge Inovenso Co. Ltd. for the electrospinning device as a courtesy and Aksa Co. Ltd. for polymer supply.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e[ ] https://sdgs.un.org/goals\u003c/li\u003e\n \u003cli\u003e[ ] Qu, X., Brame, J., Li, Q. and Alvarez, P.J., 2013. Nanotechnology for a safe and sustainable water supply: enabling integrated water treatment and reuse. 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Nano letters, 11(2), pp.666-671.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Bartin University","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hematite, Porous Nanofibers, Electrospinning, Heterogeneous Photocatalysis, Water Remediation","lastPublishedDoi":"10.21203/rs.3.rs-2202218/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2202218/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with mesoporous were fabricated by annealing electrospun Poly(acrylonitrile-co-vinyl acetate) (PAN)/Iron(III)chloride and Poly(acrylonitrile-co-vinyl acetate) (PAN)/Iron(III)chloride hexahydrate composite nanofibers. The used precursor for the iron source drastically affected the final morphologies of the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers depending on whether it was hydrated. As a result of that, the photocatalytic performances of electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers exhibited significant differences from each other. It was observed that the electrospun α-Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with highly porous, derived from a hydrated iron salt source, exhibited excellent photocatalytic activity against synthetic dye with anionic and cationic. The results here suggest that the electrospun α- Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e nanofibers with highly porous were fabricated in the study, which exhibited excellent photocatalytic activity, can provide promising activities to remove organic contaminants from wastewater. Likewise, these nanofibers with highly porous can show high performances in solar-related applications such as water splitting and photovoltaics.\u003c/p\u003e","manuscriptTitle":"Production of Highly Porous Electrospun α-Fe2O3 Nanofibers For Environmental Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-10-26 17:04:19","doi":"10.21203/rs.3.rs-2202218/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"acbeb256-ffaf-4948-b5b0-ee880e28f19c","owner":[],"postedDate":"October 26th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":16518832,"name":"Materials Engineering"}],"tags":[],"updatedAt":"2022-10-26T17:04:19+00:00","versionOfRecord":[],"versionCreatedAt":"2022-10-26 17:04:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-2202218","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2202218","identity":"rs-2202218","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}