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•Fe2O3 NPs were synthesized by chemical and green method.•Calcinated at 200 and 700 °C for maghemite and hematite phase, respectively.•Green Fe2O3 NPs showed higher photocatalytic ...performance for MO and MB dye.•Green Fe2O3 NPs showed higher % scavenging activity for DPPH assay.
In this study, iron oxide nanoparticles (Fe2O3-NPs) were synthesized by using chemical and green precipitation methods which were calcinated at 200 and 700 °C temperatures to acquire the maghemite and hematite phases, respectively. In these two different methods, the biomolecules like alkaloids, steroids, flavonoids, terpenoids, fatty acids and carbohydrates etc. present in Azadirachta Indica (A. indica) and polyvinylpyrrolidone (PVP), respectively, have been reported to act as encapsulating agents for Fe2O3 NPs. XRD, Raman, UV–visible, SEM-EDS, TEM and VSM spectroscopic techniques were used to analyze distinct physical and chemical properties. The synthesized Fe2O3 NPs exist as cubic and rhombohedral crystal lattices with spheroidal shapes having ferrimagnetic and antiferromagnetic properties for maghemite and hematite phases, respectively. The photocatalytic activity of synthesized Fe2O3 NPs was examined against anionic and cationic industrial dyes, methyl orange (MO) and methylene blue (MB) under the exposure of UV light. The degradation of MO and MB dyes were recorded up to 98 % and even 99 % in some cases. The antioxidant potential of Fe2O3 NPs has been evaluated up to 57 and 90 % from the chemical and green methods, respectively. Due to its chemical and biological stability, Fe2O3 is the most common photocatalyst used to remove organic pollutants from wastewater. The results of the current investigation showed that the photocatalytic and antioxidant activities of synthesized Fe2O3 NPs are significantly influenced by the encapsulation of NPs by PVP in chemical and A. indica in green precipitation methods.
Constraining the role of microbes in the structural iron (Fe) reduction of iron-bearing minerals improves our understanding of sediments and ice sheets as a source of dissolved Fe (dFe) to the ...oceans. However, bio-mediated structural Fe-reduction has yet to be studied in cryospheric environments. Here, we show that the Fe reducing psychrophile bacterium Shewanella vesiculosa, isolated from sea ice in Antarctica, reduced structural Fe in nontronite (NAu-2) and maghemite (γ-Fe2O3), common mineral phases in glacial ice, and marine sediments in Antarctica, during two freeze–thaw cycles (−10 °C to +15 °C), resulting in the release of dFe. The modification of turbostratically disordered nontronite (ferric iron dominant phase) to discrete ordered illite-like structure (ferrous iron dominant phase), and the aggregation of altered small maghemite particles with neoformation of vivianite (Fe3(PO4)2·nH2O) indicated the microbially induced reductive dissolution of nontronite and maghemite, respectively. The biotic Fe-reduction gradually decreased and ceased as the temperature approached freezing (−8 °C), however the rection reactivated in the thawing cycle (−7 to +15 °C). No discernable biotic Fe-reduction was measured for either mineral under freezing conditions, suggesting that temperature limits the activity of the microbes. Further, and regardless of temperatures during two freeze–thaw cycles, Fe-reduction was not observed in abiotic control. Overall, these results highlight the importance of microbially induced Fe reduction during seasonal freeze–thaw cycles of ice and sediments in continuous supplying bioavailable dFe to cryospheric environments and the often Fe-limited polar oceans.
In this study, superparamagnetic maghemite (γ-Fe2O3) nanosystems in the form of nanoparticles were fabricated through the co-precipitation method at different processing conditions. Additionally, ...novel γ-Fe2O3/ZnO heterostructures were fabricated using zinc acetate as the zinc source and polyvinyl pyrrolidone (PVP), and ethylenediaminetetraacetic acid (EDTA) as the capping agents. The results revealed that the size of the crystallites of the prepared maghemite nanopowders was between 6 nm and 7.8 nm depending on the synthesis temperature. The saturation magnetization value of maghemite nanopowders synthesized at 90 °C was measured to be 51.58 emu/g without hysteresis with negligible coercivity. FTIR analysis results proved the presence of ZnO in the maghemite core-based nanosystem. The formation of a ZnO coating using zinc acetate in the presence of PVP and EDTA as a capping agent caused a decrease in magnetization value to 12 emu/g. A ZnO coating provided better dispersion of maghemite nanoparticles and it also affected the drug (5-FU) delivery behavior. ZnO-coated nanoparticles showed prolonged and sustained drug release additionally, they continue to release the drug after 410 h. The 5-FU release kinetics of the prepared heterogeneous nanostructures fitted well with the Korsmeyer-Peppas model.
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Superparamagnetic nanoparticles containing chelating ligands have gained significant attention in biomedical engineering because of their potential to realize targeted drug delivery, diagnostic ...imaging, and hyperthermia therapy. In this study, we develop the development of chelate ligand-attached superparamagnetic nanoparticles using nitrilotriacetic acid (NTA) and maghemite (γ-Fe2O3) as key components. To smoothly attach NTA to the surface of γ-Fe2O3 nanoparticles, amino functionalization was performed using polyethyleneimine (PEI) and (3-Aminopropyl) triethoxysilane (APTES), which form easily to silane and polymer structures at the oxide surface and have amine groups at the end, as the polymeric and inorganic precursors, respectively. The surface characteristics of nanoparticles were analyzed in terms of surface charge, while focusing on the effects of amino functionalization and NTA attachment, and the behavior of NTA conjunction through peptide bonds. This study provides an examination of the physicochemical property changes, such as magnetism, surface charge, and morphological changes, that colloidal particles undergo due to property changes caused by the attachment of chelating ligands.
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•γ-Fe2O3-NTA nanoparticles were fabricated through amino functionalization.•(3-Aminopropyl) triethoxysilane (APTES) and polyethyleneimine (PEI) were used as precursors for γ-Fe2O3 surface modification.•NTA was successfully conjugated to γ-Fe2O3 nanoparticles via cross-linking.•The morphology of NTA attachment was depended on the type of amine precursors.
Acid dyes found in textile industrial effluents are hazardous aromatic pollutants which ionize in aqueous environments. Owing to their non-biodegradability, conventional wastewater treatment ...processes are not able to remove them and sorptive treatment systems can alternatively be employed. In this study, a nano γ-Fe
O
based magnetic cationic hydrogel, synthesized through a facile method, was applied for the removal of two acid dyes (Acid Red 27 and Acid Orange 52). The sorption performance (e.g., capacity and kinetics) and solution matrix effects (e.g., pH and competing anions) were investigated. Furthermore, different regeneration conditions (e.g., composition, strength and amount) were tested to develop a suitable regeneration strategy, based on which, reusability of the material was investigated for 30 consecutive sorption-desorption cycles. The material exhibited a rapid sorption rate (99% dye removal within 5min) and sorption isotherm data agreed well with the Langmuir model with an estimated maximum capacity of 833mg/g and 1430mg/g for Acid Red 27 and Acid Orange 52, respectively. The high sorptive performance persisted not only over a wide pH range but also over 30 consecutive rounds of sorption-desorption. Moreover, the impregnated γ-Fe
O
nanoparticles rendered the hydrogel superparamagnetic allowing its convenient magnetic separation.
In this work, complete elimination of Escherichia coli and Salmonella typhimurium was achieved in 120 min using a heterogeneous photo-Fenton process under sunlight at pH 6.5 in distilled water. A ...face-centered composite central design 22 with one categoric factor and three replicates at the central point was used to evaluate the effect of iron (III) oxide concentration (0.8–3.4 mg L−1), H2O2 (2–10 mg L−1), and the type of iron oxide phase (maghemite and hematite) on the inactivation of both bacteria. The results showed that the amount of catalyst, H2O2 concentration and their interaction were significant factors (p < 0.05) in the elimination of the microorganisms. Thus, under the best conditions (3.4 mg L−1 of iron (III) oxide and 10 mg L−1 of H2O2) in the experimental ranges, complete inactivation of E. coli and S. typhimurium was achieved (6-log reduction) in 120 min using the photo-Fenton treatment with both iron-oxide phases. Furthermore, the photocatalytic elimination of both bacteria by the photo-Fenton process using hematite and maghemite in secondary-treated wastewater effluent was performed obtaining slower inactivation rates (1.2–5.9 times) than in distilled water due to the matrix effect of the effluent from a wastewater treatment plant. Nevertheless, the process continued to be effective in the effluent, achieving complete bacterial elimination in 150 min using the hematite phase. Additionally, the SEM images of the bacterial cells showed that the heterogeneous photo-Fenton treatment generated permanent and irreversible cell damage, resulting in complete cell death.
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•E. coli and S. typhimurium were eliminated in 120 min by a photo-Fenton process at near-neutral pH.•The amount of Fe3+ and H2O2 were significant variables in bacterial elimination.•The hematite phase was effective in the disinfection of water from WWTP effluent.•SEM images revealed extensive cell damage caused by the photo-Fenton process.•Photo-Fenton treatment prevented bacterial regrowth.
Chromium(VI) removal by maghemite nanoparticles Jiang, Wenjun; Pelaez, Miguel; Dionysiou, Dionysios D. ...
Chemical engineering journal (Lausanne, Switzerland : 1996),
04/2013, Letnik:
222
Journal Article
Recenzirano
► Co-precipitation synthesis of maghemite nanoparticles. ► The adsorption of Cr(VI) follows a pseudo-second-order kinetic model. ► The adsorption of Cr(VI) occurs in two phases. ► Accurate modeling ...using Langmuir and Langmuir–Freundlich isotherms. ► Solution pH and presence of humic acid influence adsorption.
Maghemite nanoparticles were prepared by a co-precipitation method and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and desorption isotherms. The Brunauer–Emmett–Teller surface area, average particle size, pore volume and porosity of maghemite were 73.8m2g−1, 17.2±4.4nm, 0.246cm3g−1, and 56.3%, respectively. Removal of Cr(VI) by the maghemite nanoparticles follows a pseudo-second-order kinetic process. Intraparticle diffusion kinetics implies the adsorption of Cr(VI) onto the maghemite occurs via two distinct phases: the diffusion controlled by external surface followed by an intra-particle diffusion. The equilibrium data was nicely fit to the Langmuir and Langmuir–Freundlich (L–F) models and indicates the adsorption of Cr(VI) is spontaneous and highly favorable. The heterogeneity index, 0.55, implies heterogeneous monolayer adsorption. The adsorption Cr(VI) is favorable under acidic and neutral conditions with maximum removal observed at pH 4. The adsorption of Cr(VI) is modestly inhibited by the presence of ⩾5ppm humic acid. In summary, the adsorption of Cr(VI) by maghemite nanoparticles is rapid, can be accurately modeled, and is effective under a variety of conditions. Our results indicate these magnetic materials have promising potential to cleanup Cr(VI) contaminated waters to acceptable drinking water standards.
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•Transformation of scrap iron from blacksmith’s backyard to magnetic iron oxide nanoparticles.•Utilization of waste iron by scalable synthesis.•Use of urea as scaffold for shape ...-directed synthesis of magnetic nanoparticles.•Shape and size affect the magnetic behavior of the nanoparticles.
One of the biggest challenges of present-day scientific research is the disposal and/or recycling of environmental waste. In this work, scrap iron obtained from a blacksmith’s backyard was used as precursor for the synthesis of magnetic nanomaterials. Highly magnetic iron based nanomaterials were synthesized in presence of urea and alkali by carefully tuning the precursor concentration and temperature. Characterization of the synthesized nanomaterials was done by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FTIR) and Mössbauer spectroscopy. The magnetic behavior of the synthesized iron-oxide nanoparticles was studied using a squid magnetometer. The net impact of the work reported herein is based on the principle of “Wealth-from-Waste”. Waste scrap iron was converted by a scalable synthetic strategy to useful nanomaterials with potential magnetic applications.
Maghemite (γ-Fe2O3) nanoparticles have been synthesized using a wet chemical route, optimizing the reaction time, PH value and size of the crystallite during synthesis. The Powder X-ray diffraction ...(XRD) measurements confirmed the presence of an impurity free maghemite phase in our sample with an average crystallite size of 16 nm as calculated from the Debye–Scherrer equation. In physical characterization, the room temperature hysteresis (M−H loop) and blocking temperature (as observed from the M-T plot) revealed that the particles are in the superparamagnetic phase at room temperature. Dielectric behaviour of γ-Fe2O3 with respect to the variation of frequency and temperature was also performed. At room temperatures, we observe a decaying behaviour of both dielectric constant (έ) and tangent looses (tanδ) at smaller frequencies while at higher frequencies both saturate to smaller constant values. In temperature dependent dielectric properties we notice that the dielectric constant (both real and imaginary parts) show an increasing trend with increasing temperatures but an overall slower enhancement at elevated frequencies. The former effect can be attributed to the possible delocalization of impurities at higher temperatures while the latter effect can be explained as an inability of the electric dipole moments to respond at higher frequencies.
•Maghemite (γ-Fe2O3) nanoparticles were synthesized by wet chemical route.•Structure was confirmed through X-ray Diffraction (XRD) analysis.•The magnetic characterization was performed.•Dielectric behaviour of γ-Fe2O3 with respect to the variation of frequency and temperature was performed.
