Person: AKTAŞ, SERDAR
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AKTAŞ
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SERDAR
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Publication Metadata only Investigation of Alkaline Leaching Parameters on Stibnite Concentrate(SPRINGER HEIDELBERG, 2020) ÇETİNER, BURCU NİLGÜN; Aktas, Serdar; Cetiner, Burcu NilgunAccording to critical statistical studies, antimony is one of the rarest elements in the world, and global resources could be exhausted by 2050. In light of these observations, its extraction will be costly due to poor-quality ore, deep mining, remote locations, and high energy consumption. In the present study, an alkaline leaching process was carried out on stibnite concentrate to evaluate the effect of reaction parameters on the percentage of antimony extraction. The leaching efficiencies of different sulfur and hydroxide sources were studied and compared to one another to create a better understanding of the reaction process. Kinetic models were investigated to identify the reaction pathway and calculate the activation energy. The activation energy of the stibnite dissolution was assessed as 19.13 kJ/mol using a two-dimensional diffusion-reaction model. The value of activation energy indicates the quantity of energy necessary for a reaction to proceed. As expected, potassium hydroxide leaching was significantly more successful than was sodium hydroxide; however, in terms of economics, the use of sodium hydroxide was found to be more cost-efficient. Interestingly, this finding indicated that caustic leaching is still the most effective method for stibnite extraction.Publication Metadata only Recycling of precious materials by modified electrospun membranes(DESALINATION PUBL, 2021) AKTAŞ, SERDAR; Zeytuncu-Gokoglu, Bihter; Tasdemir, Reyhan Sengur; Tanc, Beril; Aktas, Serdar; Koyuncu, IsmailIn this study, adsorption of gold (Au) and platinum (Pt) ions by electrospun polyacrylonitrile (PAN) natural keratin- modified membranes with high sulfur content and affinity toward precious metals were investigated. Different adsorption parameters, sorbent amount, contact time, temperature and pH of solution on adsorption (%) were studied in detail in batch sorption. First, a PAN nanofiber membrane was fabricated by an electrospinning technique as a low-cost method for producing nanofiber membranes and was then modified with the natural keratin (human hair) by hydrolysis in a basic solution. A PAN-keratin nanofiber membrane was characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy (FTIR and SEM, respectively). FTIR verified the modification of PAN with keratin in which the spectrum of the resulting membrane showed significant changes, by using this modified nanofiber membrane, Au adsorption of 99% was achieved while the Pt adsorption showed a maximum of 37%. The reason for this finding may be because the electronegativity of Au is higher than Pt. When the adsorption isotherms were investigated, it was noted that the Langmuir isotherm fit better than the Freundlich isotherm. 1.0 M thiourea solution was used as a desorption reagent for both Au and Pt ions. Reusability studies showed that the adsorption capacity can remain up to 90 % after four times of usage. This finding indicates that the adsorption process of precious ions onto the electrospun membrane is a monolayer adsorption process.Publication Metadata only Recovery of Ruthenium Via Zinc in the Presence of Accelerator(SPRINGER INDIA, 2018) AKTAŞ, SERDAR; Aktas, Serdar; Morcali, Mehmet Hakan; Aksu, Kemal; Aksoy, BurakIn this study, the recovery of ruthenium from spent bath solutions via cementation reaction with zinc powder was investigated. Studied parameters included the quantity of zinc, reaction temperature, reaction time and sodium chloride additions to understand their effects on the reaction. Tests were performed in a temperature controlled water-bath with temperatures between 20 and 70 A degrees C at atmospheric pressure. Furthermore, in order to determine activation energy of cementation reaction, several mathematical kinetic models were used and the activation energy, which was calculated from best fit, was found to be 12.48 kJ/mol. Addition of sodium chloride to the solution greatly accelerated the cementation reaction, in that, more the addition of sodium chloride, the better was the precipitation efficiency. In the absence of sodium chloride at 25 A degrees C a percentage of ruthenium recovery was below 75% whereas 1000 mg sodium chloride addition at 65 A degrees C ensured a percentage of ruthenium recovery more than 95%. This corresponded to more than about 28% increase.Publication Metadata only Synthesis of nanosized Cr2O3 from turkish chromite concentrates with sodium borohydride (NaHB4) as reducing agent(ELSEVIER SCIENCE BV, 2016) AKTAŞ, SERDAR; Morcali, Mehmet Hakan; Eyuboglu, Cagri; Aktas, SerdarIn this work, we investigated chromium extraction using a pyrometallurgical process and the subsequent production of nano-sized chromium oxide from Turkish chromite concentrate by assessing the effects of the base amount, fusion temperature, and fusion time on the chromium conversion. Nano-sized chromium oxide (Cr2O3) can be employed in many applications, such as catalysis, wear resistant materials, and advanced colorants, etc. To convert Cr(III) to Cr(VI) in the form of potassium chromate, potassium hydroxide (KOH) was employed under air flowing at a rate of 20.0 L/min. The kinetics of conversion from Cr(III) to Cr(VI) were also explored. Dissolution of the resulting potassium chromate in distilled water and pH neutralization afforded precipitation of aluminum hydroxide, which could be removed by filtration. The Cr(VI) in solution was subsequently converted to Cr(III) using sodium borohydride. The resulting chromium hydroxide was converted to nano sized chromium oxide by heating at ambient pressure and temperatures between 1073 K and 1473 K. Heating to lower temperatures was found to be associated with a smaller particle size. (C) 2016 Elsevier B.V. All rights reserved.Publication Metadata only Cementation of rhodium from waste chloride solutions using copper powder(ELSEVIER SCIENCE BV, 2012) AKTAŞ, SERDAR; Aktas, SerdarThis work investigated the cementation of rhodium from waste chloride solutions using metallic copper powder. The effects on the rhodium precipitation (%) caused by the quantity of copper, reaction temperature and reaction time were explored in detail. In addition, the cementation kinetics of rhodium were studied, and the activation energy was determined to be 64.48 kJ/mol, which indicates that the reaction is chemically controlled. It was demonstrated that less than 40% of the rhodium could be precipitated using excessive quantities of copper powder (e.g., stoichiometric ratio of Cu/Rh = 40.3) at room temperature for 1 h, which resulted in a cementation reaction that was too slow. Increasing the reaction temperature to 55 degrees C resulted in almost 99% cementation after 1 h, even using stoichiometric ratio of Cu/Rh = 16.1. After a detailed observation of the dissolution behavior of the copper powder during the cementation process, it was demonstrated that most of the copper is preferentially consumed by free acid, a finding corroborated by pH measurements. (C) 2012 Elsevier B.V. All rights reserved.Publication Metadata only Production of Chromium Oxide from Turkish Chromite Concentrate Using Ethanol(WALTER DE GRUYTER GMBH, 2015) ÖZBEY, SEMİH; Aktas, S.; Eyuboglu, C.; Morcali, M. H.; Ozbey, S.; Sucuoglu, Y.In this study, the possibility of chromium extraction from Turkish chromite concentrate and the production of chromium oxide were investigated. For the -conversion of chromium(III) into chromium(VI), NaOH was employed, as well as air with a rate of 20 L/min. The effects of the base amount, fusing temperature, and fusing time on the chromium conversion percentage were investigated in detail. The conversion kinetics of chromium(III) to chromium(VI) was also undertaken. Following the steps of dissolving the sodium chromate in water and filtering, aluminum hydroxide was precipitated by adjusting the pH level of the solution. The chromium(VI) solution was subsequently converted to Cr(III) by the combination of sulfuric acid and ethanol. Interestingly, it was observed that ethanol precipitated chromium as chromium(VI) at mildly acidic pH levels, although this effect is more pronounced for K2Cr2O7 than Na2Cr2O7. On the other hand, in the strongly acidic regime, ethanol acted as a reducing agent role in that chromium(VI) was converted into Cr(III) whereas ethanol itself was oxidized to carbon dioxide and water. Subsequently, chromium hydroxide was obtained by the help of sodium hydroxide and converted to chromium oxide by heating at 800 degrees C, as indicated in thermo gravimetric analysis (TGA).Publication Metadata only Oxidative dissolution of nickel matte in dilute sulfuric acid solutions(ELSEVIER, 2019) AKTAŞ, SERDAR; Morcali, Mehmet Hakan; Khajavia, Leili Tafaghodi; Aktas, Serdar; Dreisinger, David BruceNickel matte (Ni3S2) is the most common feedstock for producing nickel oxide and nickel metal in associated refineries. Nickel matte is produced from sulfide or laterite ores, and contains around 73 wt% nickel. This study investigated the dissolution parameters of nickel matte in dilute sulfuric acid media in the presence of air as oxidant with the goal of presenting a cost-effective process for leaching nickel matte. The dissolution experiments were carried out to examine the following effects: air flow rate, stirring speed, S/L ratio, acid concentration, reaction temperature, reaction time and the amount of ferrous sulfate added. Nickel extraction of 90% and cobalt extraction of 80% were achieved using dilute H2SO4 and sparging of air as a source of oxygen. To increase the dissolution percentage of the matte, ferrous sulfate addition was studied and the oxidation and reduction potential (ORP) was measured to investigate the effect of ferrous ions on nickel and cobalt recovery. The highest nickel dissolution percentage (95%) was observed with the initial addition of 1200 mg/L Fe (II). Characterization of samples has been carried out with quantitative X-ray diffraction (XRD) and scanning electron microscopy, along with an energy dispersive system (SEM-EDS).