Ahmet Ekmekyapar

Reductive leaching of pyrolusite ore by using sawdust for production of manganese sulfate

Manganese 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.

Kinetic Investigation of Reaction Between Mineral Ulexite and Citric Acid

In this study, the dissolution kinetics of ulexite, a sodium-calcium-borate hydrate (Na2O·2CaO·5B2O3·16H2O) 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 39.4 kJ/mol.

Dissolution kinetics of colemanite in HCl solutions by measuring particle size distributions

ABSTRACT Dissolution 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.

Modeling of the Size Distribution Resulting from Dissolution of Spherical Solid Particles in Turbulent Flow

The 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.

Investigating dissolution of colemanite in sulfuric acid solutions by particle size measurements

ABSTRACT Dissolution 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.