Browsing by Subject "Magnetite"

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  • Song, Jianzhi; Srivastava, Varsha; Kohout, Tomas; Sillanpää, Mika; Sainio, Tuomo (2021)
    The treatment of stormwater to remove and recover nutrients has received increasing interest. The objective of this study was to develop a novel adsorbent that is easy to handle, has good adsorption capacity, and is economical to use. A novel nanocomposite of montmorillonite (MT)-anchored magnetite (Fe3O4) was synthesised by co-precipitation as an adsorbent for ammonium. The MT/Fe3O4 nanocomposite had pore sizes (3–13 nm) in the range of narrow mesopores. The dispersion of the anchored Fe3O4 was confirmed by transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The nanocomposite exhibited higher affinity towards ammonium than the original MT. The Langmuir isotherm model was found to be the most suitable model to explain the ammonium adsorption behaviour of the nanocomposite. The maximum adsorption capacity for ammonium was 10.48 mg/g. The adsorption mechanism was a combination of ion exchange and electrostatic interaction. In an authentic stormwater sample, the synthesised adsorbent removed 64.2% of ammonium and reduced the amount of heavy metal contaminants including Mn, Ni, Cu and Zn. Furthermore, the ammonium loading on MT/Fe3O4 during adsorption functionalised the adsorbent surface. Additionally, the spent nanocomposite showed potential for rare earth elements (REEs) adsorption as a secondary application, especially for the selective adsorption of Sc3+. The versatile application of montmorillonite-anchored magnetite nanocomposite makes it a promising adsorbent for water treatment. Graphic abstract: [Figure not available: see fulltext.].
  • Hameed, Aneela; Mushtaq, Hafiza Mehvish; Akhtar, Saeed; Ismail, Tariq; Hussain, Majid; Sheikh, Ahsan Sattar; Merani, Zulfiqar Ali; Ghafar, Abdul (2019)
    Magnetite (Fe3O4) is getting popular due to its super-paramagnetic properties, high biocompatibility and lack of toxicity to humans. Magnetite (Fe3O4) nanoparticles have high surface energy thus these nanoparticles aggregate quickly. This aggregation strongly affects the efficiency of these nanoparticles. So these magnetite nanoparticles are coated with organic or inorganic substance to prevent aggregation. These coatings not only stabilize magnetic nanoparticles but can also be used for further functionalization. The aim of this study was to evaluate the efficiency of functionalized magnetite to remove pathogenic bacteria (E.coli and B.cereus) from milk considering binding capability of magnetite with bacterial cell wall. Magnetite (Fe3O4) was prepared by co-precipitation method and subsequently functionalized with oleic acid (OA) and ethylene diamine (EDA). In present study role of magnetite (Fe3O4) and functionalized magnetite (EDA-Fe3O4, OA-Fe3O4) in removal of pathogenic bacteria (E.coli and B.cereus) from milk was investigated. The morphology of functionalized magnetite was determined by Scanning Electron microscopy (SEM). Their removal efficiency was studied based on time (10, 20 and 30 minutes). Concentration of uncoated magnetite (Fe3O4) and coated magnetite (EDA-Fe3O4, OA-Fe3O4) was fixed at 4mg/50mL. Magnetite was successfully synthesized in range of +/- 3nm. Highest capturing efficiency (74.45%) of oleic acid magnetite (OA-Fe3O4) was observed for Bacillus cereus at 30 minutes. However for Escherichia coli, both ethylene-diamine magnetite (EDA-Fe3O4) and oleic acid magnetite (OA-Fe3O4) showed maximum capturing efficiency (61.65% and 63.91% respectively). It was concluded from the study that magnetite coated with oleic acid and ethylenediamine removed pathogenic bacteria from milk efficiently. However, more research is required to study the effect of these magnetic nanoparticles on nutritional composition of milk.
  • Kivelä, Feliks (Helsingin yliopisto, 2022)
    The crystal structure of magnetite (Fe3O4) involves Fe2+ ions in sites with octahedral (Oh) symmetry and Fe2+ and Fe3+ ions in sites with tetrahedral (Td) symmetry. Magnetite exhibits several interesting physical phenomena, such as the Verwey transition, in which the roles of the different Fe sites are an active subject of research. In the X-ray standing wave (XSW) technique, incoming and diffracted X-ray beams interfere inside a crystal, creating a standing wave with the periodicity of the diffracting atomic lattice. The phase of the wave, i.e. whether the nodes are located on the lattice planes or between them, can be adjusted by finely tuning the diffraction angle. Changing the phase in this way makes it possible to selectively vary the contributions of different atoms and absorption types (dipole versus quadrupole) to the measured total absorption spectrum. Iron K-edge absorption spectra in magnetite were studied in the presence of an XSW in an experiment conducted at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. This thesis presents an analysis of the data gathered during the experiment, with the goal of decomposing the experimentally measured pre-edge peak into its constituent components. The methods used in the analysis include principal component analysis and fitting predicted absorption peaks calculated with the Quanty software to the experimental data. The results show the dipole and quadrupole contributions of the tetrahedral sites responding to changes in the phase of the XSW in opposite ways in a manner consistent with theoretical predictions.
  • Lempinen, Janne; Muuri, Eveliina; Lusa, Merja; Lehto, Jukka (2018)
    The sorption of inorganic radiocarbon on goethite, hematite and magnetite was studied as a function of carbon concentration, pH and ionic strength. It was discovered that the sorption of radiocarbon on magnetite was negligible in all studied conditions. The distribution coefficients of radiocarbon on hematite and goethite decreased with increasing pH whereas the ionic strength had only a slight decreasing effect on radiocarbon sorption. The sorption on goethite and hematite was modelled with PhreeqC using a generalized double-layer surface complexation model.