Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395

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  • Article
    Citation - WoS: 10
    Citation - Scopus: 11
    Production of Mn3O4 Nanoparticles From a Manganiferous Iron Ore via Reductive Leaching, Precipitation, and Calcination
    (Elsevier, 2022-02) Altiner, Mahmut; Top, Soner; Bouchekrit, Chafia; Kursunoglu, Sait
    The synthesis of Mn3O4 nanoparticles from a manganiferous iron ore through reductive leaching, precipitation, and calcination was investigated. The reductive leaching results showed that Mn (99.9%) was almost completely extracted into the leaching solution along with a substantial amount of Mg (99.9%), Al (99.5%), Ca (80%), and Fe (22.9%) under the following conditions: 30 g/L tartaric acid as a reducing agent, 1 M HCl solution, leaching temperature of 90 ?, and leaching duration of 3 h. In the first precipitation step, Fe and Al were expelled from the pregnant leach solution by the addition of NaOH prior to conducting the precipitation experiments for the production of manganese carbonate (MnCO3) particles from the purified solution. In the second precipitation step, MnCO3 particles were produced using sodium carbonate (Na2CO3) as the precipitating agent. The effects of parameters such as reaction temperature, Na2CO3 concentration, and experimental duration were investigated using the Taguchi approach. Manganse(II) was precipitated in the form of MnCO3 particles (97.4%) under the following conditions: a temperature of 30 ?C, Na2CO3 concentration of 0.014 mol/L, and duration of 30 min. The precipitate was observed to have a structure similar to that of rhodochrosite (MnCO3). Thermogravimetric/ differential thermal analyses were subsequently performed in three different atmospheres (air, oxygen, and nitrogen) to select a suitable atmosphere for calcination. The experimental results indicated the formation of hausmannite (Mn3O4) with a purity of 97.5% Mn3O4, 0.42% MgO, 1.66% CaO, and 0.34% FeO. The specific surface area, particle size, Curie temperature, magnetisation, coercivity, and remanence ratio of the final product obtained via 3 h of calcination at 350 C were estimated to be 133.3 m(2)/g, < 142.2 nm, 56 K, 10.10 Am-2/kg, 0.35 T, and 0.19, respectively. The characterisation results revealed the excellent low-temperature ferromagnetic properties of the produced Mn3O4 nanoparticles.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 6
    Modification of Surface Charge Characteristics for Unsupported Nanostructured Titania-Zirconia UF/NF Membrane Top Layers With Calcination Temperature
    (Springer, 2019-04-18) Erdem, Ilker; Ciftcioglu, Muhsin
    Ceramic membranes are more advantageous alternatives especially for harsh working conditions when compared with the polymeric membranes. The porous multilayer structure of the ceramic membranes (composed of support, intermediate, and top layers) can be prepared via different oxides. Titania and zirconia, having superior properties, are mainly preferred for the top layer formation. The separation properties of the membrane are both dependent on pore morphology and surface charge of the oxide(s) forming the top layer. The effect of surface charge in separation may be very significant in case of filtration of charged species with relatively lower mass as in the ultrafiltration (UF) and nanofiltration (NF). In this study, unsupported membrane top layers were prepared with varying titania/zirconia ratios by sol-gel technique. Their surface charges at different pH conditions after calcination at varying temperatures (400 degrees, 500 degrees, and 600 degrees C) were determined. The surface charge of the pure titania (full Ti) top layer was decreasing with the increasing calcination temperature. The highest magnitudes of zeta potential for both acidic and basic conditions were measured via Zr rich top layer (TiZr2575) at calcination temperatures >= 500 degrees C, which was composed of anatase, rutile (titania), and tetragonal (zirconia) phases after calcination. The tailor-made top layer can be prepared with modifications during membrane preparation.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 8
    Influence of Calcination Temperature on Microstructure and Surface Charge of Membrane Top Layers Composed of Zirconia Nanoparticles
    (Australian Ceramic Society, 2015) Erdem, I.; Ciftcioglu, M.; Ciftҫioğlu, M.
    The purpose of the research is to investigate the changes in microstructure and physicochemical characteristics, mainly surface charge (i.e. zeta potential) of zirconia membrane top layer during calcination. Zirconia is one of the most commonly preferred materials for ceramic membrane top layers due to its superior durability. The physicochemical properties of the top layer composed of submicron / nano particles is necessary not only for Donnan exclusion but also for dynamics of membrane fouling. In the present research the possibility of preparation of zirconia top layers with varying surface charge with changing calcination temperature was shown and a correlation between phase transformation and surface charge was determined.