Sabri Çolak

Leaching kinetics of sphalerite with pyrite in chlorine saturated water

Abstract The leaching kinetics of sphalerite with pyrite, in water saturated in chlorine, has been investigated. The leaching rate of sphalerite and pyrite increased with decreasing particle size, and with increasing stirring rate and gas flow rate. Increase of reaction temperature caused the leaching rate of sphalerite to increase, and that of pyrite to increase in the temperature range of 12–20°C and to decrease in the temperature range of 30–70°C. The kinetics and mechanism of dissolution reaction for sphalerite and pyrite were found to be diffusion controlled through the product layer. The activation energy for sphalerite in the ore was calculated as 22.68 kj mol−1. The activation energies for pyrite were calculated as 43.28 kj mol−1 in the temperature range 12–20°C and 8.37 kj mol−1 in the temperature range 30–60°C.

Dissolution kinetics of chalcopyrite containing pyrite in water saturated with chlorine

Abstract In this work the dissolution kinetics of chalcopyrite in water saturated with chlorine have been investigated using particle size, reaction temperature and gas flow rate as parameters. It has been found that the dissolution rate decreased with an increase in particle size and reaction temperature, but increased with an increase in gas flow rate. The mechanism by which the dissolution proceeds has been deduced. It has been concluded that the dissolution is controlled by diffusion through the product layer. The activation energy was calculated as 9.06 kJ mol −1 .

Determination of the Optimum Conditions for Leaching of Malachite Ore in H2SO4 Solutions

The Taguchi method has been used to determine the optimum conditions for the dissolution of malachite ore in H2SO4 solutions. The chosen experimental parameters and their range were (i) reaction temperature: 15 to 45 °C, (ii) solid-to-liquid ratio: 1/10 to 1/3 g cm–3, (iii) acid concentration (in weight): 2 % to 10 %, (iv) particle size: –40 to –3.5 mesh, (v) stirring speed: 240 to 720 rpm, and (vi) reaction time: 5 to 45 minutes. The optimum conditions were found to be reaction temperature: 40 °C, solid-to-liquid ratio: 1/3 g cm–3, acid concentration (in weight): 10 %, particle size: –30 mesh, stirring speed: 480 rpm, and reaction time: 45 minutes. Under these optimum working conditions, the dissolution of copper and iron in malachite ore was 100 % and 58 %, respectively. Besides, alternative working conditions reducing the total cost and dissolution of iron were found.

Optimisation of the chlorination of gold in decopperized anode slime in aqueous medium

Abstract A study is conducted to determine optimum conditions for the chlorination of gold in decopperized anode slime with chlorine gas in aqueous medium by the Taguchi experimental design method. The effect of parameters such as reaction temperature, reaction period, stirring speed and solid–liquid ratio was sought. The optimum conditions were found to be reaction temperature 60°C, reaction period 4500 s, stirring speed 600 min−1 and solid–liquid ratio 0.1 g ml−1. The experimental results showed that, under optimal leaching conditions, the extraction of gold could be over 99%.

OPTIMIZATION OF LEACHING OF COPPER FROM OXIDIZED COPPER ORE IN NH3-(NH4)2SO4 MEDIUM

ABSTRACT Studies were carried out for selective leaching of Cu with simultaneous avoidance of iron dissolution during leaching of oxidized copper ore in an aqueous NH3-(NH4)2SO4 system. The effects of leaching parameters, such as ammonia concentration, ammonium sulphate concentration, leaching time, and solid-to-liquid ratio, were investigated on leaching of copper. A 2n factorial experimental design method in the dissolution experiments was used. In addition, the “Steepest Ascent” method was also applied to determine the optimum leaching conditions. It was observed that the most effective parameters on the leaching of copper were ammonia concentration and leaching time. Only 0.17% of iron in ore was dissolved in ammonia and ammonium sulphate medium. The optimum conditions established for maximum copper recovery were: ammonia concentration 2.824 mol L−1, ammonium sulphate concentration 0.236 mol L−1, solid-to-liquid ratio 0.167 g mL−1, leaching time 2 h. Fixed parameters chosen in the experiments were: room temperature, average particle size 2.8 mm, stirring speed 500 rpm. Under the optimum conditions established for maximum copper recovery, the percentage of leached copper was 98.87.

Dissolution kinetics of magnesite mineral in water saturated by chlorine gas

Abstract In this study, the dissolution kinetics of magnesite mineral with Cl 2 gas in aqueous media were investigated. The effects of reaction temperature, particle size, solid-to-liquid ratio, gas flow rate and stirring speed on the dissolution process were determined. It was observed that the dissolution of the magnesite mineral increased with increasing reaction temperature, gas flow rate and stirring speed and with decreasing particle size and solid-to-liquid ratio. By analysis of the experimental data using heterogeneous kinetic models, it was determined that the dissolution process is controlled by resistance of the chemical surface reaction for range 12°–40°C and film diffusion for range 40°–70°C.

The optimisation of the dissolution of phosphate rock with Cl2SO2 gas mixtures in aqueous medium

Abstract In the present study, aimed at the production of phosphate compounds, the optimum process conditions were sought for the dissolution of phosphate rock from the Mardin-Mazidaǧi concentrate. The dissolution of this phosphate rock in aqueous solution saturated with a mixture of Cl2SO2 gases was optimized by passing Cl2 gas through the final solution. Reaction temperature, solid-liquid ratio, Cl2 gas flow rate, reaction period and stirring speed were employed as parameters. Using the Taguchi Fractional Design Method, it was found that the optimum process conditions, at which 93.35% P2O5 conversion was reached, were as follows: Reaction temperature: 20°C Solid-liquid ratio: 1 7 (w/v) Cl2 gas flow rate: 120 cm3 min−1 Reaction period:20 min Stirring speed: 600 min−1

Kinetics of the chlorination of pyrite in aqueous suspension

Abstract The kinetics of chlorination of pyrite in aqueous suspension have been investigated. The effects of pyrite particle size (106–125, 125–150, 150–180, 180–250, 250–425 μm), reaction time (0–14400 s), temperature (13–60°C), and speed of stirring (5–20 s −1 ) were studied. The experimental data were analyzed on the basis of the unreacted shrinking core model. The rate-controlling step was found to be the chemical reaction between chlorine and pyrite for the temperature range 13–35°C, but the diffusion of chlorine through the fluid film for the temperature range 40–60°C. The activation energies for the chemical- and diffusion-controlled cases were calculated as 36.7 and 3.7 kJ mol −1 respectively.

Dissolution kinetics of phosphate rock with Cl2 gas in water

Abstract In this study the dissolution kinetics of phosphate rock with C12 gas in aqueous media were investigated. The effect of particle size, solid-to-liquid ratio, gas flow rate, reaction temperature and stirring speed on the dissolution process were determined. It was observed that the dissolution of the phosphate rock increased with increasing gas flow rate and stirring speed and with decreasing particle size and solid-to-liquid ratio. Increasing reaction temperature increased the dissolution slightly between 12°C and 30°C and decreased it between 40°C and 80°C. By analysis of the experimental data using heterogeneous kinetic models it was determined that the dissolution process is controlled by diffusion through the fluid layer.

Leaching of FeS in aqueous chlorine solution

Abstract FeS leaching was carried out in aqueous chlorine solution at low temperatures (12–40°C) and ambient pressure ( ⋍610 mm Hg in Erzurum). The effects of particle size, reaction time, solid to liquid ratio, gas flow rate, temperature, and speed of stirring were investigated. The sulfide ion in the FeS was oxidized to sulfate and elemental sulfur during the leaching. Most of the oxidized sulfide ion was found in the solution as sulfate. All of the elemental sulfur was oxidized to sulfate as the reaction progressed to completion. The dissolution rate increased with increase in stirring speed and temperature, and with decrease in particle size, but it was not affected by the flow rate of Cl 2 and the solid to liquid ratio under the conditions covered in this study. The data were well correlated by the shrinking core-diffusion (through the fluid film) control model. The activation energy was calculated as 18.9 kJ mol −1 .