Yazar "Ekmekyapar, Ahmet" seçeneğine göre listele
Listeleniyor 1 - 10 / 10
Sayfa Başına Sonuç
Sıralama seçenekleri
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 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 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 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 Kinetic Investigation of Reaction Between Mineral Ulexite and Citric Acid(Taylor & Francis Inc, 2010) Ekmekyapar, Ahmet; Kunkul, Asim; Demirkiran, NizamettinIn this study, the dissolution kinetics of ulexite, a sodium-calcium-borate hydrate (Na2O center dot 2CaO center dot 5B2O3 center dot 16H2O) in citric acid solutions was investigated in a batch reactor. The rate of dissolution can be expressed according to surface chemical reaction controlling with changing fluid reactant concentration. The activation energy of the process was found to be 39.4kJ/mol.Öğe Modeling of the Size Distribution Resulting from Dissolution of Spherical Solid Particles in Turbulent Flow(Taylor & Francis Inc, 2012) Ekmekyapar, Ahmet; Kunkul, Asim; Yuceer, Mehmet; Kelbaliyev, GudretThe process of dissolution of solid particles in turbulent flow regime is of importance in many industrial applications. A new size distribution takes place due to dissolving during the motion of a solid-liquid suspended system in a stirred vessel. An analytical relationship was derived to represent the concentration profile in diffusion boundary layer between solid and liquid. An expression was obtained between mass transfer flow from spherical particle area and particle size changing with time during dissolution of solids. A mathematical model was developed for calculating particle size distribution varying with time during dissolution of spherical solid particles. The Focker-Planck equation was used to construct the distribution function varying with particle size. Model parameters were estimated by the Genetic Algorithm, the validity of the model was confirmed with experimental data.Öğe Nonisothermal Dehydration Kinetics of Tincalconite by Thermal Analysis Data(Soc Chemical Eng Japan, 2009) Ekmekyapar, Ahmet; Basar, Canan Akmil; Yuceer, MehmetIn the present study, the thermal decomposition kinetics of tincalconite was investigated by using thermo gravimetric (TG) and differential thermal analysis (DTA) data. The modified form of asymptotic expansion of the temperature integral integral(infinity)(x)(e(-x)/x(2))dx, which is employed in a wide range of x = E/RT ratios, was used to perform the kinetic analysis. An empirical model was suggested for calculation of activation energy for non-isothermal decomposition kinetics of solids. The calculation of activation energy of tincalconite was carried out by means of different methods. It was determined that the process takes place in two steps and fits a first order reaction kinetic model. The results obtained from five methods were generally in good agreement.Öğe Reductive leaching of pyrolusite ore by using sawdust for production of manganese sulfate(Pleiades Publishing Inc, 2012) Ekmekyapar, Ahmet; Asin, Celal; Demirkiran, Nizamettin; Kunkul, Asim; Baysar, Ahmet; Ceylan, KadimManganese compounds, such as manganese sulfate, can be obtained from pyrolusite, a manganese ore. Low-grade manganese ores is usually treated by hydrometallurgical methods. In this study, the leaching and recovery of manganese from pyrolusite ore in sulfuric acid solutions containing sawdust as reducing agent was investigated. The effects of experimental parameters, such as sulfuric acid concentration, sawdust amount, solid-to-liquid ratio, stirring speed, particle size, reaction temperature, and leaching time, on the manganese extraction from ore were examined. The results showed that the leaching rate of pyrolusite ore increased with an increasing sulfuric acid concentration, sawdust amount, stirring speed, reaction temperature and leaching time, and decreasing in solid to liquid ratio and particle size. The kinetic analysis of leaching process was carried out, and it was determined that the reaction rate was controlled by diffusion through the product layer under the experimental conditions in this work. The activation energy was found to be 22.35 kJ mol(-1). Manganese can be recovered as manganese sulfate by the evaporative crystallization of the purified leach liquor.
