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    A New Approach for Cu and Fe/FexB Production from Chalcopyrite by Molten Salt Electrolysis
    (Springer, 2020) Kartal, Levent; Daryal, Mehmet Barış; Timur, Servet
    In the present study, copper (Cu) and iron boride -( FexB) were produced for the first time through molten salt electrolysis using chalcopyrite -(CuFeS2) in an oxide- based borax electrolyte. Molten salt electrolysis was carried out at 1073 K and a current density of 600 mA/cm2 for 3600 s under galvanostatic conditions. Cu and Fe/FexB were deposited on the graphite crucible surface used as the cathode. The particles obtained as a result of electrolysis were examined by X-ray diffraction (XRD) and determined to contain Cu and Fe/FexB. The location and ratio of Cu and -FexB in the particles were investigated by using EDS mapping, energy-dispersive spectroscopy (EDS), and X-ray spectroscopy (XRD); Cu and Fe/FexB were found to be present throughout the particles at different ratios. Cu and Fe/FexB were successfully separated from each other by selective leaching of copper in a 1 M -NH3-H2O solution. The time-dependent dissolution behavior of Cu was investigated at pH 8, 298 K, 600 rpm stirring rate for 900-5400 s, and it was observed that the dissolution rate increased over time and all the copper had completely dissolved after 5400 s. After leaching particles were examined by XRD and SEM, it was revealed that Fe/FexB particles did not contain any Cu.
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    A New Approach for Cu and Fe/FexB Production from Chalcopyrite by Molten Salt Electrolysis
    (Springer Science and Business Media Deutschland GmbH, 2020) Kartal, Levent; Daryal, M.B.; Timur, S.
    Abstract: In the present study, copper (Cu) and iron boride (FexB) were produced for the first time through molten salt electrolysis using chalcopyrite (CuFeS2) in an oxide-based borax electrolyte. Molten salt electrolysis was carried out at 1073 K and a current density of 600 mA/cm2 for 3600 s under galvanostatic conditions. Cu and Fe/FexB were deposited on the graphite crucible surface used as the cathode. The particles obtained as a result of electrolysis were examined by X-ray diffraction (XRD) and determined to contain Cu and Fe/FexB. The location and ratio of Cu and FexB in the particles were investigated by using EDS mapping, energy-dispersive spectroscopy (EDS), and X-ray spectroscopy (XRD); Cu and Fe/FexB were found to be present throughout the particles at different ratios. Cu and Fe/FexB were successfully separated from each other by selective leaching of copper in a 1 M NH3–H2O solution. The time-dependent dissolution behavior of Cu was investigated at pH 8, 298 K, 600 rpm stirring rate for 900–5400 s, and it was observed that the dissolution rate increased over time and all the copper had completely dissolved after 5400 s. After leaching particles were examined by XRD and SEM, it was revealed that Fe/FexB particles did not contain any Cu. Graphical Abstract: [Figure not available: see fulltext.] © 2020, The Minerals, Metals & Materials Society.
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    Direct electrochemical reduction of copper sulfide in molten borax
    (Springer, 2019) Kartal, Levent; Timur, Servet
    In this study, for the first time, direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte. The effects of current density (100-800 mA/cm(2)) and electrolysis time (15-90 min) on both the cathodic current efficiency and copper yield were systematically investigated in consideration of possible electrochemical/chemical reactions at 1200 degrees C. The copper production yield reached 98.09% after 90 min of electrolysis at a current density of 600 mA/cm(2). Direct metal production was shown to be possible with 6 kWh/kg energy consumption at a 600 mA/cm(2) current density, at which the highest current efficiency (41%) was obtained. The suggested method can also be applied to metal/alloy production from single- and mixed-metal sulfides coming from primary production and precipitated sulfides, which are produced in the mining and metallurgical industries during treatment of process solutions or wastewaters.
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    Electrolytic production of Cu-Ni alloys in CaCl2-Cu2S-NiS molten salt
    (Elsevier Science Bv, 2018) Kartal, Levent; Timur, Servet
    An alternative metal/alloy production method, known as direct electrochemical reduction (DER), was introduced for the fabrication of CuNi alloys from mixed sulfides (Cu2S, NiS) under both galvanostatic and potentiostatic conditions. The influences of the process parameters (e. g., cell voltage and current) on the compositions of the reduced compounds were investigated to yield industrially desirable alloys, namely, CuNi10, CuNi20, and CuNi30. The electrochemical behaviors of Cu2S and NiS in CaCl2 melt were examined at a temperature of 1200 degrees C via cyclic voltammetry (CV). Based on the CV results, the cathodic reduction of Cu2S occurred in one step and cathodic reductions of NiS occurred in two steps, i. e., Cu2S double right arrow Cu for copper reduction and NiS. Ni3S2. Ni for nickel reduction. Galvanostatic studies revealed that it was possible to fabricate high-purity CuNi10 alloys containing a maximum sulfur content of 320x10(-6) via electrolysis at 10 A for 15 min. Scanning electron microscopy along with energy-dispersive X-ray spectrometry and optical emission spectroscopy (OES) examinations showed that it was possible to fabricate CuNi alloys of preferred compositions and with low levels of impurities, i. e., less than 60 x 10(-6) sulfur, via DER at 2.5 V for 15 min.
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    One-step electrochemical reduction of stibnite concentrate in molten borax
    (Springer, 2019) Kartal, Levent; Daryal, Mehmet Baris; Sireli, Gueldem Kartal; Timur, Servet
    In this study, antimony production from a stibnite concentrate (Sb2S3) was performed in one step using a molten salt electrolysis method and borax as an electrolyte. Electrochemical reduction of the stibnite concentrate was performed at 800 degrees C under galvanostatic conditions and explained in detail by the reactions and intermediate compounds formed in the borax. The effects of current density (100-800 mA center dot cm(-2)) and electrolysis time (10-40 min) on cathodic current efficiency and antimony yields were systematically investigated. During the highest current efficiency, which was obtained at 600 mA center dot cm(-2), direct metal production was possible with 62% cathodic current efficiency and approximately 6 kWh/kg energy consumption. At the end of the 40-min electrolysis duration at 600 mA center dot cm(-2) current density, antimony reduction reached 30.7 g and 99% of the antimony fed to the cell was obtained as metal.
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    Optimization of sulfuric acid leaching of roasted chalcopyrite concentrate with Box-Wilson experimental design
    (Springer International Publishing Ag, 2020) Sonmez, Ibrahim; Sahbudak, Kemal; Kartal, Levent; Alkan, Bulent
    Chalcopyrite (CuFeS2) is commonly used ore in production of copper, but leaching of this ore is very slow and inefficient due to passivation during leaching at atmospheric conditions. In this study, in order to overcome drawbacks of the passivation layers, the concentrate supplied from Eti Bakr A.S. Kure Plant in Turkey was roasted at 600 degrees C for 1 h and after leached. Box-Wilson procedure of statistical experimental design was utilized to identify the effects of significant leaching variables for instance leaching time (X-1; 10-120 min), solid/liquid ratio (X-2; 0.01-0.20), and H2SO4 concentration (X-3; 0.01-1.00 M) on Cu extraction (%) from roasted concentrate and was tried to be optimized. The coefficients of response functions have been calculated by regression analysis, and the estimates have been found to be well in line with the experimental outcomes. The optimal leaching parameters, time, solid/liquid rate and H2SO4 concentration were determined as 115 min, 0.116, and 0.71 M, respectively, and the highest Cu extraction (%) value was calculated as 92.45%.
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    Single step calciothermic synthesis of nickel boride particles in molten salt
    (Springer, 2023) Kartal, Levent
    Abstract In this study, production of nickel boride (NixB) via calciothermic reduction in molten salt has been studied. Firstly, the electrochemical behaviors of CaO and NiO in CaCl2 melt were examined by cyclic voltammetry (CV). Then, the influences of the process parameters (temperature (1173–1273 K) and time (15–60 min)) on the powders were investigated. Based on the CV results, it was understood that NiO reduction takes place in one step at -0.25 V. Temperature investigations revealed that Ni and Ni2B phases that were present at low temperatures disappeared as the temperature increased. The Ni3B and Ni2B ratios in the particles increased as the duration went on, and almost no Ni left in the particles after 60 min. The magnetic properties of the particles were investigated and, the saturation magnetization, coercive and remanent values were determined as 25.063 emu/g, 32.694 Oe, and 0.903 emu/g, respectively. © 2023, The Author(s) under exclusive licence to Australian Ceramic Society.
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    The removal of heavy metals from refinery effluents by sulfide precipitation
    (BERG FAC TECHNICAL UNIV KOSICE, 2023) Kartal, Levent; Şen, Aysel; Timur, Servet
    This study investigated the selective precipitation of copper (Cu2+), nickel (Ni2+) and zinc (Zn2+) ions from industrial wastewater by using sodium sulfide (Na2S). The effects of pH, time and free sulfide concentration on the selective precipitation were systematically investigated using synthetically prepared solutions and gold refinery wastewater. First, the optimum precipitation pH values of metals, the amount of Na2S and time were determined by using synthetic solutions containing Cu, Ni and Zn single metal ions. The highest precipitation efficiencies were obtained at a pH of 4, 5.3 and 5.3 for Cu, Ni and Zn, respectively. Based on these results, the effects of Na2S stoichiometry and time of precipitation were investigated with synthetically prepared solutions containing mixed metal ions (100?mg/L Cu2+, 90?mg/L Ni2+ and 100?mg/L Zn2+). Metal sulfide precipitation efficiencies increased with increasing amounts of Na2S and reached a maximum at a ratio of 1:1.75 (Metal ion: Na2S molar ratio). Lastly, the results obtained from the experiments performed with synthetic solutions were used for the metal sulfide precipitation from industrial wastewater. The precipitation from refining wastewater containing 10 g/L Cu2+, 0.3 g/L Ni2+ and 3 g/L Zn2+ ions was achieved at pH values from 2.3 to 5.3. At a pH of 2.3, Cu2+ precipitated as CuS (Cu2S) at 100% efficiency. While the Ni2+ concentration in the solution decreased by only 44% at a pH of 2.3, the Zn2+ concentration decreased by 52%. At a pH of 5.3, Cu2+ and Zn2+ precipitated together at 100%.