Effect of Mechanical Activation on Pressure Leaching of Küre Massive Rich Copper Ore

The effect of mechanical activation on metal dissolutions by pressure leaching of massive rich copper ore taken from Küre copper ore deposit (Turkey) was investigated. The dissolution efficiencies of sulfide minerals are significantly improved by ultrafine grinding, also known as mechanical activation. This grinding results in decrease of particle size and an increase in crystal distortion of sulfide minerals. Leaching efficiencies of copper, cobalt, and Zinc increased from 45.2%, 25.9%, and 87.7% to 98%, 85%, and 97%, respectively, after 3-h mechanical activation. At the end of the activation, leaching was carried out at a temperature of 110°C, 10-bar oxygen partial pressure, and 150-g/L solid concentration without addition of acid. This study has also indicated that mechanical activation involving fine milling as a pretreatment is not only effective on copper minerals dissolution but also on the dissolution of other associated minerals, such as cobalt and zinc sulfides.     

Factors affecting the leachability of Ni/Co/Cu slags at high temperature

An oxidative pressure acid leaching process was investigated for the extraction of Ni/Co/Cu/Zn metal values from base metal smelter slags. The process is applicable to smelting furnace dump slags, as well as to mid-stream converter slags. In addition to the economical advantages, extracting the base metal values from the dump slags produces an environmentally benign residue. To produce high level of extraction for the metal values, it is necessary to have the slag in crystalline structure. This, in turn, requires cooling the molten smelter slags sufficiently slowly during solidification. It was shown that if the same slags are quenched in water thereby producing an amorphous structure, the resulting metal extractions are substantially lower. The role of oxygen in the leaching reactions was also tested. The presence of oxygen is necessary for successful leaching of the metal values. After fine grinding, the slags were subjected to pressure acid leaching at 250 °C with an oxygen overpressure of 520 kPa. Sulfuric acid at a typical 0.3 acid to slag ratio was employed. Extractions higher than 90% of each of the nickel, cobalt, copper and zinc were achieved. Operating at 250 °C ensures that the concentration of Fe and Al impurity metals in leached solution remains very low. It was finally found that for high concentrations of divalent metals (Ni + Co + Cu + Mg) in the slag, a much higher quantity of sulfuric acid than the stoichiometric value is required. The latter is due to the drop of hydrogen ion concentration due to bisulphate formation.     

Recovery of germanium and other valuable metals from zinc plant residues

The main purpose of this study was to characterize and to extract germanium from the copper cake of Çinkur Zinc Plant. The physical, chemical and mineralogical characterization of the ground copper cake sample obtained from Çinkur showed that it was 84% below 147 μm containing 700 ppm germanium. The copper cake also contained 15.33% Cu, 15.63% Zn, 1.66% Cd, 1.33% Ni, 0.64% Co, 0.35% Fe, 2.62% Pb, 12.6% As, 0.18% Sb and 3.42% SiO₂. The mineralogical analysis indicated the complex nature of the copper cake which was mainly composed of metallic and oxidized phases containing copper, arsenic, zinc, cadmium, etc. The sulfuric acid leaching experiments were performed under the laboratory conditions. The optimum collective extraction of germanium and other valuable metals was obtained at a temperature range 60 to 85 °C for a leaching duration of 1 h with sulfuric acid concentration of 150 gpl and using a solid–liquid ratio 1/8 g/cc. Under these conditions, the recovery of germanium was 92.7% while the other metals were leached almost completely. The optimum selective leaching conditions of germanium was determined as half an hour leach duration, 1/8 g/cc solid–liquid ratio, 100 gpl sulfuric acid concentration and a temperature range 40 to 60 °C. Under these conditions the leach recovery of germanium was 78%. The dissolution's of other metals like cobalt, nickel, iron, copper, cadmium and arsenic were almost low. So, germanium would be separated more selectively at the following precipitation by tannin stage.     

Oxidative Leaching of Chalcopyrite by Cupric Ion in Chloride Media

In this study, chalcopyrite concentrate produced in Sarcheshmeh copper plant was subjected to oxidative leaching investigation by cupric ion to determine the effect of several parameters on the copper and iron dissolution, including temperature of leaching, time of holding and cupric concentration as oxidant agent in a range of 38–97 °C, 1.5–8.5 h and 0.2–0.8 M, respectively. The leaching media was chloride providing with 3 M HCl 37% and CuCl₂. The experiments were designed by central composite design method. The dissolution of copper and iron was examined. The maximum dissolution of copper 62.64%, was obtained at 85 °C, 7 h and oxidant concentration of 0.7 M. The kinetics model of chalcopyrite leaching and an optimized condition with maximum dissolution of copper and minimum dissolution of iron was obtained by Minitab^®18 software. Additionally, the thermodynamics of leaching was investigated by Pourbaix diagrams of copper and iron composition, using HSC Chemistry6 software. It was found that the oxidative leaching process is controlled by diffusion through passivation layer with an activation energy of 19.57 kJ/mol.

     

A kinetic study on the pressure leaching of sphalerite

The dissolution of sphalerite (ZnS) in sulfuric acid solution under oxygen pressure was investigated. Effects of temperature, percent solids, agitation, sample size, oxygen partial pressure and foreign ions were evaluated. The effect of hydrogen pretreatment on sphalerite leaching rate was also examined. Leaching of sphalerite at 90°C and 150 psi oxygen pressure was found to occur at a constant rate. This rate was determined from the experimental data observed under the different leaching conditions mentioned above. The constant leaching rate was attributed to the chemical reaction occurring on the surface of the flat-plate type sphalerite sample. The rate-controlling step of the reaction was determined to be the oxidation of hydrogen sulfide to elemental sulfur. Oxidation of hydrogen sulfide was studied through the addition of iron and through the observation of the change in iron concentration during leaching. The oxidation was concluded to be by reaction with ferric ion rather than by direct oxygen oxidation. Leaching tests run with samples pretreated with hydrogen do not show any increase in the rate of zinc extraction. M. T. HEPWORTH, formerly with University of Denver.     

Kinetics of copper dissolution during pressure oxidative leaching of lead-containing copper matte

The kinetics of pressure oxidative leaching of lead-containing copper matte with sulfuric acid was investigated. The effects of particle size, leaching temperature, oxygen partial pressure and sulfuric acid concentration on the kinetics and mechanism of copper extraction were studied. It was found that the reaction kinetic model follows the shrinking core model of chemical reaction control and the apparent activation energy was determined as 39.1 kJ/mol. The order of the reaction with respect to total pressure was found to be 0.64. The kinetic equations for the effect of particle size, leaching temperature, total pressure and sulfuric acid concentration were obtained and a mathematical model of copper extraction from lead-containing copper matte was developed as:

This equation estimates the extraction of copper with very good agreement (r = 0.99) between the experimental and calculated values.     

Contribution à l'étude de la lixiviation de la chalcopyrite

A study of the kinetics of chalcopyrite dissolution in sulfuric acid medium under oxygen pressure of 70 psia (0.48 MPa) was made on a chalcopyrite concentrate as function of acid concentration, temperature, and grain size. An evaluation of the real surface, an examination of the surface of the grains by scanning electronic microscope, and an analysis of the residue by energy dispersion of X-rays were carried out for different leaching periods. The dissolution kinetics vary sensibly with grain size, leaching temperature and normality of the original solution. 80% of copper can be leached out of the concentrate after 10 hours of dissolution at 90'C with a solution of 1.8 N sulfuric acid and for a grain dimension of 5 pm. An exponential function is found suitable to explain the kinetics of leaching till the slowing of the copper dissolution is achieved. The nature of the attack is electrochemical with different forms. Crevice corrosion under deposits is an important contributing factor in dissolution and in slowing of the dissolution at the end of the process.     

Pressure oxidation kinetics of orpiment (As2S3) in sulfuric acid

Pressure oxidation kinetics of a massive orpiment (As₂S₃) sample in sulfuric acid solution were systematically investigated. The effects of temperature (170 to 230 °C), mean particle size (48 to 125 μm diameter) and oxygen partial pressure (345 to 1035 kPa) were evaluated. Oxidation rates were found to be affected significantly by changes in temperature and particle size, but were relatively insensitive to changes in oxygen partial pressure. Kinetics appear to be controlled by product layer diffusion over the temperature range of 170 to 210 °C, due to the formation of elemental sulfur on particle surfaces. However, Arrhenius activation energies over this range are large (> 40 kJ/mol) and increase with decreasing temperature, perhaps reflecting the kinetics of sulfur oxidation rather than diffusion. Above 210 °C the rate-controlling step is a surface reaction with an activation energy of approximately 33.8 kJ/mol. The reaction order at 210 °C is approximately 0.2 with respect to oxygen partial pressure.     

Leaching of Chalcopyrite Concentrate with Hydrogen Peroxide and Sulfuric Acid in an Autoclave System

In this study, leaching of chalcopyrite concentrate was investigated in an autoclave system using hydrogen peroxide and sulfuric acid. By decomposition of hydrogen peroxide, the active oxygen formed can provide both high oxidation potential and high pressure in a closed vessel for leaching. Preliminary studies showed that hydrogen peroxide can be used as an oxidant instead of oxygen gas in the autoclave. Central composite design (CCD) was used to examine the effects of the experimental parameters on the copper and iron extraction as a response. The proposed model equation using CCD showed good agreement with experimental data, the correlation coefficients R ² for copper and iron being 0.84 and 0.86, respectively. The optimum conditions to obtain the main goal of maximum copper and minimum iron extraction from chalcopyrite were determined as to be sulfuric acid concentration of 2.5 M, hydrogen peroxide concentration of 2.3 M, leaching time of 24 minutes, chalcopyrite amount of 3.17 g (in 50-mL solution), stirring speed of 630 rpm, and leaching temperature of 351 K (78 °C). Under the optimum condition, 76 pct of copper and 9 pct of iron were extracted from chalcopyrite concentrate. Extraction yield results of metals indicate that selective leaching of chalcopyrite can be achieved using hydrogen peroxide and sulfuric acid in an autoclave system.     

Pressure oxidation leaching of chalcopyrite: Part II: Comparison of medium temperature kinetics and products and effect of chloride ion

Pressure oxidation reaction kinetics and products are compared for the recovery of copper from a chalcopyrite concentrate under medium temperature conditions at 125–150 °C, as patented and promoted by various commercial operations, normally referred to as the Anglo/UBC, CESL and NSC (nitrogen species catalysed) processes. The main aim was to compare the effect of additives on the dispersion of molten sulfur and recovery of copper, and develop a better understanding of the role of chloride ion.Greater than 94% copper was extracted from the concentrate under all process conditions (except NSC) within 30 min. The extraction of the remaining copper in some instances took substantially longer due to poor dispersion of sulfur and agglomeration of the sulfide minerals. The partial oxidation of sulfide to elemental sulfur was about 70–80% at 150 °C and was greater in the presence of chloride ion and at higher initial acidity. Iron was leached and re-precipitated forming a number of different phases depending upon the acidity and salinity. These phases including hematite, jarosite and goethite were characterised using Quantitative X-ray Diffraction (QXRD) analysis. Hematite formation was favoured at higher temperatures (≥ 150 °C), low acidity and low to moderate salinity. Goethite formation was favoured at lower temperatures (< 150 °C) and by low acidity and low salinity. Jarosite was formed under conditions of moderate to high acidity and its formation was enhanced/stabilised in the presence of sodium ions. It was demonstrated that the basic copper salt, antlerite, could be produced under conditions of low acidity.Chloride ion addition and high acid concentrations enhanced copper extraction kinetics and recovery, and inhibited the oxidation of sulfur to sulfate. This suggests that chloride ion is adsorbed on the sulfur surface to restrict direct oxygen reaction. Chloride ion also enhances the anodic oxidation of mineral sulfides and the dispersion of molten sulfur.     

锡烟尘氧压浸出综合回收铟锡锌试验研究

以硫酸为浸出剂,采用氧压浸出的方法进行了含铟锡烟尘提铟试验研究。考察了氧分压、硫酸初始浓度、液固比、浸出温度、浸出时间等因素对铟浸出率的影响,确定了氧压浸出的最佳条件。试验结果表明,含铟物料在液固比4：1,硫酸寝浓度150g/L,温度150℃,压力0．7MPa,时间2．5h的条件下氧压浸出,可获得In93．66％的浸出率。     

Kinetics of vanadium dissolution from black shale in pressure acid leaching

The leaching kinetics of vanadium from black shale in the sulphuric acid-oxygen system is presented. The effects of agitation speed, leaching temperature in the range of 110-150 °C, sulphuric acid concentration, oxygen partial pressure and particle size on the rate of vanadium leaching were determined. The results indicate that the rate is nearly independent of agitation above 200 rpm and increases with increasing temperature, sulphuric acid concentration and oxygen partial pressure. As leaching occurs, there is a progressive dissolution of a vanadium-bearing alumino-silicate phase, while the inert quartz phase assembles onto the mineral surface and remains as an “ash” layer. The leaching kinetics was analyzed by using a new variant of the shrinking core model (SCM) in which both the interfacial transfer and diffusion across the product layer affect the leaching rate. The determined activation energy was found to be 40.14 kJ/mol and the reaction orders with respect to sulphuric acid concentration and oxygen partial pressure were 0.61 and 1.67, respectively. A semi-empirical rate equation was derived to describe the process.     

Recovery of cobalt,nickel and copper from converter slag through roasting with ammonium sulphate and sulphuric acid

Roasting of copper converter slag containing 4.03% copper, 1.98% nickel and 0.48% cobalt with ammonium sulphate open to atmosphere has been carried out in order to achieve sulphation of copper, nickel and cobalt followed by leaching of the metal values as soluble sulphates with water. The effect of parameters such as temperature (200–600°C), time (15–120 min), and amount of ammonium sulphate (0.5–2.5 times stoichiometric) has been studied. Under atmospheric conditions, using 2.5 times the stoichiometric requirement of ammonium sulphate, the recovery of copper, nickel and cobalt was found to be 85%, 81% and 85%, respectively. Similar studies were carried out with sulphuric acid. The influence of experimental variables such as the amount of sulphuric acid (0.25–2 times stoichiometric), roasting temperature (100–300°C) and time (15–120 min) has been studied. Under optimum conditions, i.e., at 150°C and a roasting time of 60 min with the stoichiometric amount of sulphuric acid, recoveries of copper, nickel and cobalt were 95, 90 and 99%, respectively, along with a contamination of 60–80% iron. Removal of most of the iron from the leach liquors has been effected with ammonia liquor and lime as precipitants. A two-stage roasting operation using sulphuric acid, first at 150°C and then at 650°C, has resulted in bringing the iron content down to about 3% in the sulphation product without much affecting the recovery of other metal values.     

Experimental Study of Ferrous Calcium Silicate Slags: Phase Equilibria at {\text{P}}_{{{\text{O}}_{2} }} Between 10–8?atm and 10–9?atm

The phase equilibria of ferrous calcium silicate slags (“FeO _x ”-CaO-SiO₂) have been investigated at an oxygen partial pressure of 10^–8 atm at temperatures between 1423 K and 1623 K (1150 °C and 1350 °C), and at an oxygen partial pressure of 10^–9 atm at temperatures of 1473 K and 1573 K (1200 °C and 1300 °C). High-temperature equilibration/quenching/electron probe X-ray microanalysis (EPMA) techniques were applied to acquire accurate information on the phase equilibria of the system. Phase diagrams showing the liquidus isotherms of the systems at the selected oxygen partial pressures are provided. The solubilities of components in the solids of primary phases are presented. The system and conditions selected are relevant to industrial copper smelting.     

Leaching behavior of ilmenite with sulfuric acid

A study of the rate of dissolution of ilmenite in sulfuric acid solutions has been carried out. The effects of temperature, particle size, stirring speed, and concentration of sulfuric acid on the rate of dissolution of ilmenite has been investigated. Temperature range studied in this investigation was 88° to 115°C, and the Arrhenius activation energy was found to be 64.4 kJ (15.4 kcal) per mole. The rate of dissolution increased with concentration of sulfuric acid up to about 14 M sulfuric acid and decreased beyond this concentration. The maximum recovery at 14 M H₂SO₄ can be explained partially by the fact that H⁺ ion concentration peaks at about this concentration. Furthermore, reaction products, TiOSO₄ and FeSO₄, cover the surface of ilmenite when high concentrations of sulfuric acid are used, while these products are dissolved in water and removed from the surface when diluted sulfuric acid is involved. Based on the results obtained in this study, it can be concluded that the overall leaching of ilmenite with sulfuric acid at 88° to 115°C is described best by surface chemical reaction limiting with an order of 0.55 with respect to sulfuric acid concentration.     

富钴结壳湿法冶金工艺中硫化渣的加压浸出

富钴结壳活化硫酸浸出液经过中和除铁、硫化沉淀后得到的渣采用加压浸出工艺处理,考察了温度、压力、酸度、液固比等因素对加压浸出过程的影响,确定了加压浸出条件,此时镍、钴的浸出率大于99.8%,铜的浸出率大于98%,加压浸出得到的镍、钴、铜混合溶液可进一步萃取分离得到纯净的金属溶液。     

某浮选铜精矿中铜、金浸出试验研究

在氯盐酸性体系中,对某浮选铜精矿进行了加压氧化浸铜的试验研究,探讨了温度、氧气分压、硫酸用量、氯化钠用量等对铜精矿中铜、铁浸出的影响。试验结果表明：在氧化温度110℃、氧分压0．45MPa、矿样粒度-0．043mm占85％、硫酸用量90g／L、氯化钠用量30g／L、液固比5／1、浸出时间2、5h、搅拌速度750r／min初始条件下,获得铜浸出率为92．18％。铜浸出渣经摇床重选脱硫,脱硫渣氰化浸金。当浮选精矿铜浸出率达到90％上时,对应渣中金的氰化浸出率都在96％以上。     

Mixed-control kinetics of oxygen leaching of chalcopyrite and pyrite from porous primary ore fragments

The leaching of individual copper ore fragments was investigated under oxygen pressure of 690 to 3100 kPa. After 500 hours of leaching at 90°C under 3100 kPa oxygen pressure, 50 pct of copper was extracted from an ore particle of 0.57 cm size, while 1300 hours were needed to extract 90 pct of copper under the same experimental conditions. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains and the pore diffusion of dissolved oxygen within the ore fragment was formulated to interpret the experimental results. Both chemical reaction and diffusion were found to be important to the overall leaching rate in the particle size range tested. The model can also be used to predict the leaching behavior of particles of different sizes at different temperatures and oxygen partial pressures. H. K. LIN, formerly Graduate Student in the Department of Metallurgy and Metallurgical Engineering, University of Utah