Asım Künkül

LEACHING KINETICS OF MALACHITE IN AMMONIA SOLUTIONS

Abstract In this study, the leaching kinetics of malachite in ammonia solutions was investigated in a magnetically stirred reactor, taking particle size, ammonia concentration, solid/liquid ratio and reaction temperature as parameters. It was observed that the leaching rate increases with increasing ammonia concentration, reaction temperature, decreasing solid/liquid ratio and particle size. The reaction order to the solid concentration is determined to be 1.0. It was also determined that the leaching process was controlled by the diffussion through the ash layer, which is the insoluble inert gangue material consisted of mainly SiO 2 , around the shrinking unreacted core. The activation energy for the leaching process was found to be 22.338 kJ mol −1 , and the Arrhenius constant was calculated to be 2.188 s −1 .

Dissolution kinetics of ulexite in ammonia solutions saturated with CO2

Abstract The dissolution kinetics of ulexite in ammonia solutions saturated with carbon dioxide were investigated. Experiments investigating the following parameters: concentration of ammonia; particle size; stirring speed; solid to liquid ratio; reaction temperature; and carbon dioxide flow rate; showed that ulexite can be dissolved completely in solutions of carbonic acid at atmospheric conditions. It was found that the dissolution rate increased with increasing ammonia concentration, reaction temperature and calcination temperature, and with decreasing particle size and solid to liquid ratio. It was observed that the flow rate of carbon dioxide and stirring speed have almost no effect on the dissolution rate. It was determined that the dissolution rate of ulexite can be described by a first-order pseudo-homogeneous reaction model and an empirical equation for the process was developed: −1 n (1−X)=1.0×10 5 (C A ) 0.22 (d) −0.92 ( S L ) −0.54 exp ( 6600 T −t) where CA is the ammonia concentration, d the initial particle size and ( S L ) the solid to liquid ratio. The activation energy for the process was found to be approximately 55 kJ mol−1.

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.

Modeling of drug release behavior of pH and temperature sensitive poly(NIPAAm-co-AAc) IPN hydrogels using response surface methodology and artificial neural networks

An interpenetrated polymer network (IPN) poly(NIPAAm-co-AAc) hydrogel was synthesized by two polymerization method: emulsion and solution polymerization. The pH- and temperature-sensitive hydrogel was loaded by swelling with riboflavin drug, a B2 vitamin. The release of riboflavin as a function of time has been achieved under different pH and temperature environments. The determination of experimental conditions and the analysis of drug delivery results were achieved using response surface methodology (RSM). In this work, artificial neural networks (ANNs) in MATLAB were also used to model the release data. The predictions from the ANN model, which associated input variables, produced results showing good agreement with experimental data compared to the RSM results.

Modeling of Swelling Behaviors of Acrylamide-Based Polymeric Hydrogels by Intelligent System

Hydrogels based on acrylamide (AAm) were synthesized by free radical polymerization in an aqueous solution using N,N’-methylenebisacrylamide (MBAAm) as crosslinker. To obtain anionic hydrogels, 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) and acrylic acid (AAc) were used as comonomers. The swelling behaviors of all hydrogel systems were modeled using an artificial neural network (ANN) and compared with a multivariable least squares regression (MLSR) model and phenomenal model. The predictions from the ANN model, which associated input parameters, including the amounts of crosslinker (MBA) and comonomer, and swelling values with time, produce results that show excellent correlation with experimental data. The parameters of swelling kinetics and water diffusion mechanisms of the hydrogels were calculated using the obtained experimental data. Model analysis indicated that the ANN models could accurately describe complex swelling behaviors of highly swellable hydrogels. GRAPHICAL ABSTRACT

Recovering of copper with metallic aluminum

Abstract The cementation of copper ions from aqueous copper sulfate solutions by using spherical aluminum metal particles was examined. The effects of the experimental parameters on copper cementation were investigated and evaluated. Reaction rate increases with increasing copper concentration, reaction temperature, stirring speed and decreasing pH. It was observed that the reaction follows the first-order kinetics, and progresses according to the diffusion controlling step.

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.

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.