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Öğe APPLICATION OF RESPONSE SURFACE METHOD TO COPPER CEMENTATION BY METALLIC ALUMINUM PARTICLES(Lviv Polytech Natl Univ, 2020) Demirkiran, Nizamettin; Ozdemir, G. Deniz Turhan; Dardagan, MerveIn the present study, the interactive effects of the process variables containing copper concentration, temperature, and time on the efficiency of copper cementation by metallic aluminum particles were examined by using response surface methodology (RSM). It was observed that the efficiency of cementation increased with an increase in the initial concentration of copper, temperature and time. The multiple regression analysis to the experimental data was applied to see the interactive effects of process variables. The second-order polynomial equation was obtained. The optimal values were found to be 0.075 mol/l, 303 K, and 90 min to maximize the amount of the deposited copper.Öğe Boric Acid Extraction from Calcined Colemanite with Ammonium Carbonate Solutions(Amer Chemical Soc, 2012) Kunkul, Asim; Aslan, Nezahat Ezgi; Ekmekyapar, Ahmet; Demirkiran, NizamettinColemanite, a calcium-borate hydrate, is found in significant amounts in Turkey. Colemanite is used as a raw material in the production of boric acid. In this study, the leaching kinetics of calcined colemanite in ammonium carbonate solutions was investigated in a batch reactor. The effects of calcination temperature, solution concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the dissolution rate were determined and evaluated. It was found that the dissolution rate of calcined samples was higher than that of the uncalcined sample. It was observed that the leaching rate of calcined colemanite enhanced with increasing calcination temperature up to 450 degrees C, and did not change above this temperature. Thus, it was found that the applied calcination temperature had a significant effect on the leaching of colemanite. It was determined that the leaching rate raised with an increasing ammonium carbonate concentration, increasing reaction temperature, and decreasing solid/liquid ratio. It was detected that calcium carbonate was not formed on the particle surface. The dissolution kinetics of calcined colemanite was examined using both heterogeneous and homogeneous reaction models, and it was determined that the reaction rate can be described by a first-order pseudohomogeneous reaction model. The activation energy for this process was calculated to be 59.03 kJ/mol.Öğe Copper adsorption by natural manganese dioxide(Elsevier Science Bv, 2015) Demirkiran, NizamettinThe adsorption of copper ions was investigated using pyrolusite ore as a low-cost alternative adsorbent source. Pyrolusite, which contains mainly MnO2, is a manganese ore. The effects of the initial concentration of copper(II) ions, initial pH of solution, adsorbent dosage and particle size on the adsorption process were examined. It was found that the percentage of the adsorbed copper increases with increasing the amount of adsorbent. It was observed that the maximum adsorption occurred at natural initial pH values for all copper concentrations. While the initial solution concentration, initial pH, contact time, stirring speed, particle size and adsorbent dosage were 2.5 mmol/L, natural, 180 min, 200 r/min, 120 mu m and 6 g/L, respectively, the efficiency of copper adsorption on pyrolusite ore was 96.5%. The isotherm and kinetic studies relating to this adsorption process were also made. It was determined that the equilibrium data followed the Langmuir isotherm model while the process kinetic could be described by the pseudo-second order kinetic model.Öğe Copper Cementation with Zinc Recovered from Spent Zinc-Carbon Batteries and Dissolution of Cement Copper in Hydrochloric Acid Solutions(Amer Chemical Soc, 2013) Demirkiran, NizamettinIn this study, the usability of waste zinc obtained from spent zinc carbon batteries for copper cementation was examined. The effects of the initial concentration of copper ions, rotation speed of the zinc plate, initial pH of solution, and reaction temperature on copper cementation were investigated. It was determined that the cementation rate increased with increasing concentration of copper ions, rotation speed, reaction temperature, and initial pH of solution. It was found that the cementation reaction followed first-order kinetics and was controlled by diffusion. Copper powder produced by cementation was characterized using X-ray diffraction and scanning electron microscopy techniques. The dissolution of cement copper in hydrochloric acid solution was determined for the purpose of the production of copper(II) oxychloride. The effects of acid concentration, temperature, and stirring speed on the dissolution of cement copper were investigated. It was observed that the dissolution of copper powder increased with an increase in acid concentration, stirring speed, and temperature.Öğe Determination of Optimum Process Conditions by Central Composite Design Method and Examination of Leaching Kinetics of Smithsonite Ore Using Nitric Acid Solution(Springer, 2021) Tanaydin, Mehmet Kayra; Tanaydin, Zumra Bakici; Demirkiran, NizamettinThe leaching behavior of Tunceli smithsonite ore in nitric acid was evaluated in two study steps including optimization of leaching process and kinetics modeling. The individual and synergistic effects of effective parameters such as nitric acid concentration, solid-to-liquid ratio, stirring speed, and temperature on the dissolution rate of zinc were investigated using central composite design. Four factors including temperature (30-50 degrees C), nitric acid concentration (0.2-0.5 mol/L), stirring speed (350-600 rpm), and solid-to-liquid ratio (0.004-0.01 g/L) were investigated. The dissolution percent of zinc (97%) was obtained in 120 min of leaching time: acid concentration 0.5 mol/L, temperature 50 degrees C, stirring speed 500 rpm, and solid-liquid ratio 2/500 g/mL at the optimum conditions obtained using the central composite design. The dissolution kinetics of smithsonite was examined according to heterogenous models and it was found that the dissolution rate was controlled by ash layer diffusion process. It was found that the leaching rate increased with increasing temperature, stirring speed, and acid concentration as well as decrescent particle size and solid/liquid ratio. The trial data were analyzed by statistical and graphical methods and the activation energy of this leaching process was determined to be 28.63 kJ.mol(-1). [GRAPHICS] .Öğe Dissolution kinetics of calcined ulexite in ammonium carbonate solutions(Korean Institute Chemical Engineers, 2007) Kunkul, Asim; Demirkiran, NizamettinThe leaching kinetics of calcined ulexite in ammonium carbonate was studied in this work. The effect of parameters of ammonium carbonate concentration, solid/liquid ratio, stirring speed, calcination temperature and reaction temperature was determined in the experiments. It was found that the conversion rate increased with increasing ammonium carbonate concentration, reaction temperature and decreasing solid/liquid ratio. However, the effect of stirring speed on the conversion rate was insignificant. The experimental data practised the heterogeneous and homogeneous models, and an acceptable model for the conversion rates of ulexite was determined to be a first-order pseudo-homogeneous reaction model. The activation energy of dissolution process was determined to be 35.3 kJ/mol.Öğe Dissolution kinetics of calcined ulexite in ammonium sulfate solutions(Cenim, 2018) Demirkiran, Nizamettin; Tanaydin, Mehmet Kayra; Ozdemir, G. Deniz TurhanUlexite is one of the boron minerals, which include a respectable amount of hydration water. It can be used as a raw material in the production of boron compounds. Some part of water in the composition of ulexite can be removed from the solid matrix applying dehydration treatment, and a porous structure can be obtained to increase the reaction rate. In the present study, the effect of dehydration temperature on dissolution kinetics of ulexite in ammonium sulfate solutions was researched in a batch reactor utilizing the parameters of solution concentration, solid-to-liquid ratio, stirring speed and reaction temperature. It was determined that the dissolution rate of calcined material increased with increasing solution concentration and reaction temperature and with decreasing solid-to-liquid ratio. The highest dissolution rate was attained with the sample calcined at 150 degrees C. It was found that the dissolution rate fit to the first order pseudo-homogeneous model. The activation energy of the dissolution process was estimated to be 42 kJ.mol(-1).Öğe Dissolution kinetics of colemanite in HCl solutions by measuring particle size distributions(Taylor & Francis Inc, 2018) Sis, Hikmet; Bentli, Ismail; Demirkiran, Nizamettin; Ekmekyapar, AhmetDissolution kinetics of colemanite in hydrochloric acid solutions was investigated in this study. Particle size distribution data was, for the first time in the literature, utilized to investigate dissolution kinetics of colemanite. The size distribution of colemanite particles was measured in the reaction vessel during reaction, and the kinetic models were applied to particle size data. For comparison, the kinetic models were also fitted to the fractional conversion data, calculated from Ca concentration of the medium. Additionally, electrical conductivity and pH of the reaction medium were also recorded while measuring particle size distribution. Among the heterogeneous and pseudo-homogeneous models, Avrami model was found to be the best model to fit the particle size and fractional conversion data.Öğe Dissolution kinetics of metallic zinc obtained from spent zinc-carbon batteries in nitric acid solutions(Wiley, 2021) Demirkiran, Nizamettin; Senel, MerveIn this study, the dissolution kinetics of metallic zinc pieces obtained from waste zinc-carbon batteries was investigated using nitric acid solutions. The effects of the concentration of nitric acid, amount of metallic zinc, reaction temperature and stirring speed on the dissolution process were determined, and a mathematical model to represent the dissolution kinetics was presented. It was observed that the dissolution rate increased with increasing nitric acid concentration, stirring speed and reaction temperature and with decreasing amount of metallic zinc. While the concentration of nitric acid, reaction temperature, stirring speed, amount of zinc, and reaction time were 0.15 M, 30 degrees C, 400 rpm, 0.1 g, and 20 min, respectively, the amount of dissolved zinc was found to be 98.3%. The result of the kinetic analysis showed that the dissolution rate fit to the pseudo-first order kinetic. The activation energy for the dissolution process was calculated to be 12.89 kJ/mol. It was determined that the dissolution process was controlled by diffusion. Zinc ions in the resulting solution after the dissolution treatment was recovered by precipitation method using sodium bicarbonate solution. It was determined that zinc ions were precipitated as zinc hydroxy-carbonate compound. Zinc compound obtained was subjected to the calcination treatment, and zinc oxide was produced.Öğe Dissolution kinetics of ulexite in acetic acid solutions(Elsevier, 2008) Ekmekyapar, Ahmet; Demirkiran, Nizamettin; Kuenkuel, AsimUlexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kj/mol. (c) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe Dissolution kinetics of ulexite in ammonium nitrate solutions(Elsevier Science Bv, 2009) Demirkiran, NizamettinIn this study the dissolution kinetics of the boron mineral ulexite, a sodium-calcium-borate hydrate (Na(2)O center dot 2CaO center dot 5B(2)O(3)center dot 16H(2)O), in ammonium nitrate solutions was investigated in a batch reactor. The effects of solution concentration, particle size, solid/liquid ratio. and reaction temperature on the dissolution rate were determined. It was found that the dissolution rate increased with increase in ammonium nitrate concentration and reaction temperature, and with decrease in particle size and solid/liquid ratio. No effect of stirring speed was observed on the conversion. It was determined that the dissolution rate fit to the chemical reaction control model. The activation energy of this dissolution process was found to be 58.2 kJ/mol. (C) 2008 Elsevier B.V. All rights reserved.Öğe Dissolution of thermally dehydrated ulexite in ammonium acetate solutions(Elsevier, 2013) Demirkiran, Nizamettin; Bayrakci, Nazli; Asin, CelalUlexite, a boron mineral, contains a substantial amount of hydration water. Using calcination method, some part of water in the composition of solid can be removed from the solid matrix, and a porous structure can be obtained to increase the reaction rate. The dissolution of the calcined ulexite samples at various temperatures was investigated. Ammonium acetate was used as a leach reagent. The effects of some reaction parameters on the dissolution of the calcined ulexite were examined. It is found that the dissolution rate of calcined samples is higher than that of the uncalcined sample. The dissolution rate of the calcined ulexite is enhanced with increasing calcination temperature up to 150 degrees C. It is determined that the reaction rate conforms to the chemical reaction model. The activation energy of the dissolution process was calculated to be 41.5 kJ/mol.Öğe EXAMINATION OF THE USE OF AMMONIUM ACETATE AS LIXIVIANT IN RECOVERY OF ZINC FROM WASTE BATTERIES AND KINETIC ANALYSIS(Gh Asachi Technical Univ Iasi, 2015) Demirkiran, NizamettinThis study is focused on the dissolution kinetics of zinc oxide in ammonium acetate solutions to recover the zinc from alkaline and zinc-carbon spent battery powders. This study represents a first step for further studies in which actual waste powder is to be used. Therefore, the experiments were performed by using pure zinc oxide powder to evaluate the dissolution behavior of zinc. The effects of ammonium acetate concentration, reaction temperature, stirring speed and solid to liquid ratio on the dissolution of zinc oxide were examined, and a kinetic analysis was performed by using the heterogeneous and homogeneous reaction models. It was determined that the dissolution rate increased with increasing ammonium acetate concentration and reaction temperature, and with decreasing solid to liquid ratio. It was found that zinc oxide was dissolved approximately 99.5 % under the experimental conditions at 1 M, 40 degrees C, 400 rpm, 1/250 g/mL, and 15 min. The kinetic analysis results showed that the dissolution rate fit to the first-order pseudo-homogeneous reaction model. The activation energy of the dissolution process was calculated to be 43.83 kJ/mol. According to the results of this study, ammonium acetate can be used as an effective leach reagent to extract the zinc from spent battery powder.Öğe Immobilization of Glucose Oxidase in GLYMO/MTEOS Sol-Gel Film for Glucose Biosensor Application(Slovensko Kemijsko Drustvo, 2012) Demirkiran, Nizamettin; Ekinci, ErgunAn electrochemical biosensor was developed by using the sol-gel coating solution. The modified platinum electrode used in the study was constructed by immobilization of glucose oxidase under a layer of sol-gel film. The coating solution was prepared by using GLYMO, and MTEOS. Electrochemical measurements were carried out amperometrically by determining hydrogen peroxide produced by the enzymatic reaction between glucose and glucose oxidase. It was ob served that the amperometric response of the enzyme electrode was linear for gluco se concentrations in the range from 2 to 10 m M. The response time of the biosensor to reach a steady-state cur rent value was approximately 80 s. The glucose selectivity of the biosensor was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, oxalic acid, and ascorbic acid. It was ob served that the interfering molecules did not cause any observable signal. The stability of the sensor was investigated, and it was found hat the initial sensor response decreased approximately 44% over a period of 30 days of storage in dry state at 4 degrees C.Öğe IMMOBILIZATION OF GLUCOSE OXIDASE IN SILICA SOL-GEL FILM FOR APPLICATION TO BIOSENSOR AND AMPEROMETRIC DETERMINATION OF GLUCOSE(Soc Chilena Quimica, 2012) Demirkiran, Nizamettin; Ekinci, Ergun; Asilturk, MeltemIn this study, an electrochemical biosensor was developed by using a sol-gel coating solution. The modified platinum electrode used in the study was constructed by immobilization of glucose oxidase under a layer of sol-gel film. The sol-gel coating solution was prepared by using GLYMO, TEOS, and MTEOS. Electrochemical measurements were carried out amperometrically by determining hydrogen peroxide produced by the enzymatic reaction between glucose and glucose oxidase. The amperometric responses of the resulting enzymatic electrode to glucose were rapid. It was observed that the amperometric response of the enzymatic electrode was linear for glucose concentrations in the range from 2 to 18 mM with 50 s response time. LOD and LOQ for the enzymatic electrode were calculated to be 0.055 mM and 0.184 mM, respectively. It was determined that the developed biosensor had an acceptable reproducibility. The selectivity of the biosensor was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, oxalic acid, and ascorbic acid. The stability of the biosensor was investigated, and it was found that the sensor response decreased by 59% of its initial response over a period of 30 days of storage in dry conditions at 4 degrees C.Öğe Investigating dissolution of colemanite in sulfuric acid solutions by particle size measurements(Taylor & Francis Inc, 2019) Sis, Hikmet; Bentli, Ismail; Demirkiran, Nizamettin; Ekmekyapar, AhmetDissolution properties of colemanite and gypsum formation in sulfuric acid were investigated by measuring size distribution of particles in the reaction cell with time. After termination of the reaction, the remained material in the cell was analyzed to find out unreacted and reacted fractions. The results showed that the reaction of colemanite particles with sulfuric acid led to reduction in particle sizes and the degree of reduction depended on acids concentration and reaction time. The dissolution period and point of gypsum formation were clearly distinguished and marked on particle size plots.Öğe INVESTIGATION OF COPPER CEMENTATION KINETICS BY ROTATING ALUMINUM DISC FROM THE LEACH SOLUTIONS CONTAINING COPPER IONS(Oficyna Wydawnicza Politechniki Wroclawskiej, 2012) Ekmekyapar, Ahmet; Tanaydin, Mehmet; Demirkiran, NizamettinRecovery of metallic copper from the leach solution containing copper (II) ions by cementation process using aluminum disc has been examined. Solutions obtained from the leaching of malachite in aqueous acetic acid solutions were used in the study. It was determined that the cementation rate increased with increasing solution concentration, temperature and rotating speed, and decreasing solution pH. The reaction rate fits to the first order pseudo homogeneous reaction model and is controlled by diffusion. The activation energy of this process was calculated to be 32.6 kJ/mol.Öğe Investigation of Leaching Kinetics of Copper from Malachite Ore in Ammonium Nitrate Solutions(Springer, 2012) Ekmekyapar, Ahmet; Aktas, Evrim; Kunkul, Asim; Demirkiran, NizamettinThe production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303 K to 323 K [30 A degrees C to 50 A degrees C]) and diffusion through a porous product layer (323 K to 343 K [50 A degrees C to 70 A degrees C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50 kJ/mol, respectively.Öğe Investigation of selective leaching and kinetics of copper from malachite ore in aqueous perchloric acid solutions(Taylor & Francis Inc, 2019) Tanaydin, Mehmet Kayra; Demirkiran, NizamettinIn this study, the leaching kinetics of malachite in perchloric acid solutions was investigated. The dissolution behaviors of copper, zinc, and iron in the ore matrix were determined at different acid concentrations and reaction temperatures. It was observed that the concentration of perchloric acid had a major effect on the dissolution of copper, zinc, and iron. It was determined that the effect of temperature on the dissolution of these species was not as significant as concentration impact. The results obtained shown that copper in the ore matrix was completely leached while zinc and iron were partially dissolved in perchloric acid solutions. In addition, the effects of the acid concentration, reaction temperature, stirring speed, particle size, and solid-to-liquid ratio on the leaching of malachite were researched. In these experiments, it was observed that the leaching rate of copper increased with increasing solution concentration, stirring speed, and reaction temperature, and with decreasing solid-to-liquid ratio and particle size. A kinetic analysis was performed, and it was found that the rate of leaching reaction obeyed the mixed kinetic control model in the unsteady state. The activation energy of the leaching process was calculated to be 34.69 kJ/mol.Öğe INVESTIGATION OF THE USE OF AMMONIUM ACETATE AS AN ALTERNATIVE LIXIVIANT IN THE LEACHING OF MALACHITE ORE(Assoc Chemical Eng, 2013) Kunkul, Asim; Gulezgin, Abdulvahap; Demirkiran, NizamettinSolutions containing ammonia allow for selective leaching of copper from a copper ore. In this study, the leaching and kinetics of malachite ore were examined using ammonium acetate solutions as an alternative lixiviant The effects of some experimental parameters on the leaching of malachite ore were investigated. A kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature and stirring speed, and decreasing particle size and solid-to-liquid ratio. It was found that the leaching reaction followed the mixed kinetic control model. The activation energy of this leaching process was determined to be 59.6 kJ moll. Consequently, it was determined that ammonium acetate solutions could be used as an effective leaching agent for copper extraction from malachite ore.
