Cuprous hydrometallurgy Party VI. Activation of chalcopyrite by reduction with copper and solutions of copper(I) salts

Chalcopyrite is reduced by solutions of copper(I) sulfate and copper(I) chloride to chalcocite (Cu₂S) and bornite (Cu₅FeS₄) whilst the iron reports to the solution. Factors which affect the rate and efficiency of reduction are examined. The reaction is rapid on fresh surfaces of chalcopyrite but slows markedly as a film of chalcocite or bornite forms. The reduction in the presence of copper metal goes to completion and gives a material which is more readily leached by oxidising agents than is chalcopyrite. Thus 99% of the copper in the reduced chalcopyrite is leached when copper(II) sulfate in aqueous acetonitrile is the oxidising agent, whereas only 30% of the copper is leached from pure chalcopyrite under similar conditions. Concentrated solutions of copper(I) salts are less effective in reducing CuFeS₂ in a heterogeneous solid-liquid reaction than is copper metal in a “galvanic” solid-solid reaction. Solutions of copper(II) sulfate plus concentrated copper(I) sulfate in dilute acetonitrile (4 M) containing copper sheets are an effective reductant for chalcopyrite.     

Recovery of copper from bornite and chalcopyrite by means of the pyridine and chloride ion donor systems

Recovery of copper from natural bornite and chalcopyrite by means of pyridine-hydrochloric acid mixtures and pyridine solutions of pyridine hydrochloride is described. The systems were found to be effective media for leaching of bornite and chalcopyrite. Total copper recovery from bornite is reached after 5 hours at 50°C. For dissolution of chalcopyrite an elevated temperature or prolonged time of leaching is necessary.     

Mechanism of Oxidation of Pyrite,Chalcopyrite and Bornite During Flash Smelting

Abstract

The oxidation processes of pyrite, chalcopyrite and bornite were studied under simulated flash smelting conditions. The influence of temperature, in the range from 733 to 1473 K and of oxygen partial pressure (3.5 and 21 kPa) on the degree of sulphide particle oxidation was determined. It was established that under the same conditions, the highest degree of oxidation was achieved for pyrite particles and the oxidation of bornite particles was the slowest process.

It was established with electron probe microanalysis (EPMA) that migration of iron ions towards the reaction surface took place during sulphide particle oxidation on flash smelting. This process considerably influenced the path of phase transformations in the oxidizable particles.

Based on the experimental results, a dependence has been found between the shape of reacted particle and the degree of particle phase transformation. Mechanisms have been proposed for pyrite, chalcopyrite and bornite oxidation in flash smelting, on the basis of results obtained.

The adequacy of mechanisms proposed was tested by investigating the shaft product taken from the flash smelting furnace (Pirdop, Bulgaria) obtained when sulphide copper blend was smelted to a matte containing 55% of Cu.

On a étudié les processus d’oxydation de la pyrite, de la chalcopyrite et de la bornite sous des conditions simulées de fusion flash. On a déterminé l’influence de la température, dans la gamme de 733 à 1473 K, et de la pression partielle de l’oxygène (3.5 et 21 kPa) sur le degré d’oxydation de particule de sulfure. On a établi que, sous les mêmes conditions, le plus haut degré d’oxydation est obtenu pour les particules de pyrite alors que l’oxydation des particules de bornite est le processus le plus lent.

On a établi au moyen d’analyse par microsonde électronique (EPMA) que la migration des ions de fer vers la surface de réaction a lieu pendant l’oxydation de la particule de sulfure au moment de la fusion flash. Ce processus influence considérablement la route des transformations de phase des particules oxydables.

Basé sur les résultats expérimentaux, on a trouvé une dépendance entre la forme d’une particule ayant réagi et le degré de transformation de phase de la particule. On propose des mécanismes d’oxydation de la pyrite, de la chalcopyrite et de la bornite dans la fusion flash, sur la base des résultats obtenus.

On a évalué l’adéquation des mécanismes proposés en étudiant le produit de la cuve pris du four de fusion flash (Pirdop, Bulgarie) obtenu lorsqu’un mélange de sulfure et de cuivre était fondu en une matte contenant 55% de Cu.     

Process mineralogy of suspended particles from a simulated commercial flash smelter

Polished sections of pyrometallurgical intermediate products from a simulated commercial flash furnace were examined by reflected light microscopy, scanning electron microscopy-energy dispersive spectrometry and electron backscatter analysis, and microprobe analysis for phase and textural relationships. The smelter feed is a copper concentrate from a porphyry copper deposit. The concentrate consists primarily of chalcopyrite, bornite, and pyrite with smaller amounts of covellite, chalcocite, molybdenite, magnetite, galena, and sphalerite. The flash furnace reactions for pyrite and chalcopyrite can be observed by reflected light microscopy. Reacted angular particles of pyrite exhibit successive rims of fibrous pyrrhotite and hematite or magnetite. Reacted angular chalcopyrite particles show successive rims of bornite, digenite, and chalcocite. Spherical particles, formed by the complete melting of former pyrite and chalcopyrite particles, consist of variable amounts of granular pyrrhotite with magnetite rims and minor hematite. Spherical particles, formed by the complete melting of former chalcopyrite particles, exhibit exsolution intergrowths with varying proportions of intermediate solid solution, bornite, digenite, and chalcocite, and have rims of hematite, magnetite, and copper-iron spinel. Electron microprobe analyses show that the iron oxides contain significant copper and minor zinc in their structures. Sphalerite and molybdenite do not show evident mineralogical reactions.     

Mineralogical changes occurring during the ferric lon leaching of bornite

The reaction products formed during the leaching of bornite in either ferric chloride or ferric sulfate media depend on the leaching conditions as well as the particle size of the bornite. The extent of dissolution is always more vigorous in the ferric chloride system and increases with increasing temperature in either system. The reaction initially involves the rapid outward diffusion of copper to form slightly nonstoichiometric bornite (Cu_5-xFeS₄), chalcopyrite, and covellite. The non-stoichiometric bornite is progressively converted to a Cu₃FeS₄ phase, which varies considerably in its composition, and to covellite. Although the reaction at low temperature terminates at the Cu₃FeS₄ phase, leaching at higher temperatures results in further dissolution to elemental sulfur and soluble Cu²⁺ and Fe²⁺. The leaching ofmassive bornite illustrates the complexities of the leaching reaction more clearly than is observed for the finelypaniculate bornite. In leached massive bornite, a distinct covellite zone appears in the Cu₃FeS₄ phase; as well, chalcopyrite exsolution lamellae rimmed by a copper sulfide (possibly digenite) appear in the covellite zone, in the Cu₃FeS₄ phase, and in the nonstoichiometric bornite. The experimental leaching results, especially those involving massive bornite, are generally consistent with the mineralogical trends produced by supergene alteration of bornite ores, but a significant difference is that the Cu₃FeS₄ phase does not correspond closely to the mineral idaite.     

Process mineralogy of suspended particles from a simulated commercial flash smelter

Polished sections of pyrometallurgical intermediate products from a simulated commercial flash furnace were examined by reflected light microscopy, scanning electron microscopy-energy dispersive spectrometry and electron backscatter analysis, and microprobe analysis for phase and textural relationships. The smelter feed is a copper concentrate from a porphyry copper deposit. The concentrate consists primarily of chalcopyrite, bornite, and pyrite with smaller amounts of covellite, chalcocite, molybdenite, magnetite, galena, and sphalerite. The flash furnace reactions for pyrite and chalcopyrite can be observed by reflected light microscopy. Reacted angular particles of pyrite exhibit successive rims of fibrous pyrrhotite and hematite or magnetite. Reacted angular chalcopyrite particles show successive rims of bornite, digenite, and chalcocite. Spherical particles, formed by the complete melting of former pyrite and chalcopyrite particles, consist of variable amounts of granular pyrrhotite with magnetite rims and minor hematite. Spherical particles, formed by the complete melting of former chalcopyrite particles, exhibit exsolution intergrowths with varying proportions of intermediate solid solution, bornite, digenite, and chalcocite, and have rims of hematite, magnetite, and copper-iron spinel. Electron microprobe analyses show that the iron oxides contain significant copper and minor zinc in their structures. Sphalerite and molybdenite do not show evident mineralogical reactions.     

Developments in Selective Flotation of Complex Copper-Lead-Zinc

Sulphur dioxide has been successfully used as a depressant for galena and sphalerite in selective copper flotation of complex fine-grained sulphide ores. Dosage of the gas demands care and that is why it is not used as often as it could be. The sulphur dioxide gas has been replaced by a solution of sulphur dioxide forming salt with improved selectivity. Easy dosage of the reagent and use of selective copper mineral collectors has demonstrated better process control with upgraded products. On an Australian Cu-Pb-Zn ore the key to improved process was the finding that gangue minerals of the ore have buffer capacity to allow the stagewise addition of acidic reagent solution and still maintain the narrow pH range of selective separation of chalcopyrite and galena even with simple manual process control.

On a Russian Cu-Pb-Zn ore good selectivity against galena and sphalerite was obtained in the flotation of bornite and chalcopyrite as a high grade copper concentrate. Stagewise grinding-flotation with three grinding steps were used to obtain reasonable liberation of copper minerals and to maintain the optimum selectivity.     

The leaching of copper from sulphur activated chalcopyrite with cupric sulphate in nitrile-water mixtures

If chalcopyrite is roasted with sulphur at 400–450°C pyrite and idaite or bornite are produced. Bornite plus pyrite are also prepared by roasting a 1:1 mixture of chalcopyrite and covellite. These copper-iron sulphides were leached with acidified aqueous cupric sulphate solutions containing acetonitrile or hydracrylonitrile and the results are compared with leaching with acidified cupric chloride in brine. The nitrile route has the advantage of a less corrosive sulphate medium for subsequent copper recovery processes.Bornite appears to be the most attractive product from the roasting of sulphur and chalcopyrite because much of its copper can be readily leached. Iron reports to the solution only in the latter stages of extraction. Up to 80% of the copper in this bornite is leached with CuSO₄/RCN/H₂O at 60°C. Copper is recovered from the resulting cuprous sulphate solution by electrowinning with inert anode. The products are copper cathodes and cupric sulphate, which is recycled. The leach residue may be used to reactivate further chalcopyrite or is leached of its copper by established routes.     

The kinetics of dissolution of bornite in acidified ferric sulfate solutions

Sintered disks of synthetic bornite were dissolved in acidified ferric sulfate solutions at temperatures ranging from 5δ to 94δC. The dissolution occurs in two stages; in the first a nonstoichiometric bornite with up to 25 pct deficiency of copper is formed. In the second, the nonstoichiometric bornite is converted to chalcopyrite and elemental sulfur, which accumulates on the disk surface. At temperatures below 35°C, the reaction follows parabolic kinetics and stops at the nonstoichiometric bornite stage. At higher temperatures it continues through to chalcopyrite and follows linear kinetics. Both the parabolic and linear processes have activation energies of 5 to 6 kcal per mole. At higher temperatures the sensitivity of the reaction rate to changes in stirring velocity indicates control by diffusion through the liquid boundary layer. Natural and synthetic bornite dissolve by the same process and at essentially the same rate.     

Pressure leaching of copper minerals in perchloric acid solutions

The leaching of covellite (CuS), chalcocite (Cu₂S), bornite (Cu₅FeS₄), and chalcopyrite (CuFeS₂) was carried out in a small, shaking autoclave in perchloric acid solutions using moderate pressures of oxygen. The temperature range of investigation was 105° to 140°C. It was found that covellite, chalcocite, and bornite leach at approximately similar rates, with chalcopyrite being an order of magnitude slower. It was found that chalcocite leaching can be divided into two stages; first, the rapid transformation to covellite with an activation energy of 1.8 kcal/mole, followed by a slower oxidation stage identified as covelite dissolution with an activation energy of 11.4 kcal/mole. These two stages of leaching were also observed in bornite with chalcocite (or digenite) and covellite appearing as an intermediate step. No such transformations were observed in covellite or chalcopyrite. Two separate reactions were recognized as occurring simultaneously for all four minerals during the oxidation process; an electrochemical reaction yielding elemental sulfur and probably accounting for pits produced on the mineral surface, and a chemical reaction producing sulfate. The first reaction dominates in strongly acidic conditions, being responsible for about 85 pct of the sulfur released from the mineral, but the ratio of sulfate to elemental sulfur formed increases with decreasing acidity. Above 120°C the general oxidation process appears to be inhibited by molten sulfur coating the mineral particles; the sulfate producing reaction, however, is not noticeably affected above this temperature. For chalcopyrite, activation energies were determined separately for the oxygen consumption reaction and for the production of sulfate, with values of 11.3 and 16.0 kcal/mole respectively. This paper is based upon a thesis submitted by F. LOEWEN in partial fulfillment of the requirements of the degree of M.A. Sc. in Metallurgical Engineering at The University of British Columbia.     

Selective dissolution of uranium from a copper flotation concentrate

The copper flotation concentrate produced from the Olympic Dam copper— uranium gold deposit in South Australia contains uranium associated with the copper sulphide and gangue minerals. Work with a copper concentrate in which the copper mineralization was of the chalcocite-bornite type has shown that 94–97% uranium can be dissolved with sulphuric acid (> 40 g/L) at 30–60°C in 24 h. The addition of an oxidant was not necessary. Copper was leached from the concentrate along with the uranium. In the first 15 min, 5–7% copper dissolved but thereafter virtually no further copper dissolved when the reaction was carried out under nitrogen or argon (i.e., in the absence of oxygen). In air and oxygen, copper dissolution continued over the 24 h of the reaction. The initial rapid dissolution of copper was associated with oxidation of djurleite to roxbyite and dissolution of surface oxidation products. In air and oxygen, oxidation of roxbyite and bornite to blaubleibender covellite was associated with further dissolution of copper. The redox potential of the suspensions was controlled by reactions of the copper sulphide minerals. For reactions under nitrogen the redox potential of the system was 225–250 mV vs. saturated calomel electrode (SCE), while in air or oxygen the potential gradually rose (to 350 mV vs. SCE) as successive copper sulphides were oxidized. These results, and work at the Olympic Dam metallurgical pilot plant, have shown that uranium can be removed selectively from copper flotation concentrates produced from the Olympic Dam deposit.     

The effect of contact of copper sulphide grains on the initial rate of leaching in oxygenated sulphuric acid solution

The initial stage of leaching of chalcocite, bornite, and chalcopyrite as well as chalcocite-chalcopyrite and bornite-chalcopyrite mixtures in oxygenated aqueous sulphuric acid was investigated at 368 K. It was determined that chalcopyrite accelerates the rate of copper leaching from chalcocite due to grain contact between chalcocite and chalcopyrite. In contrast, chalcopyrite decreases the rate of dissolution of bornite.     

Effect of the composition of some sulphide minerals on cyanidation and use of lead nitrate and oxygen to alleviate their impact

An investigation was carried out on synthetic ores containing high purity pyrite, pyrrhotite and chalcopyrite and on two gold ores currently processed to evaluate the impact of cyanicides on cyanidation and to improve the leaching performance by using a pre-leaching, injecting oxygen and adding lead nitrate. With regard to the synthetic ores, it was found that pyrrhotite did not generate a high cyanide consumption while pyrite and chalcopyrite were detrimental. Pre-leaching was deleterious for the ore containing chalcopyrite while pre-leaching with lead nitrate was very efficient to decrease the reactivity of the ore containing pyrite. The two gold ores studied had very different compositions. The low sulphide ore had a low sulphide content (1.36% S), present as pyrrhotite while the second had a very high sulphide content (20.2% S), in the form of pyrite, pyrrhotite and chalcopyrite. The efficiency of the process conditions was peculiar to the ores. The high sulphide ore required a stronger, longer pre-leaching period (12 h) with greater amounts of lime (7.0 kg/t) and lead nitrate (600 g/t) than the low-sulphide ore. The ore with a low sulphide content required a pre-leaching of only 1 h with a small quantity of Pb(NO₃)₂ (50 g/t) and leaching can be performed at 360 ppm NaCN to allow a recovery of 96.4% Au and a low cyanide consumption at 0.18 kg/t. As for the high sulphide ore, cyanidation had to be conducted at 560 ppm NaCN to recover 88.4% Au with a cyanide consumption of 0.80 kg/t. An increase in the amount of lime enhanced oxidation of soluble sulphides. Lead nitrate stabilized copper and iron dissolution by forming a passivation layer at the surface of sulphide minerals. Lead nitrate also prevented the formation of a passive layer at the surface of gold.     

A ferrous chloride-oxygen leach process for nickel-copper sulphide concentrations

This paper describes a ferrous chloride-oxygen leach process for recovery of nickel and copper values from sulphide concentrates available in India. The sulphide concentrates aareleached with a stirred solution of ferrous chloride in a glass-lined reactor operated at various temperatures and oxygen pressures. In this single step process, copper and nickel are converted into their water soluble chloride forms, whereas iron is rejected as hydrated iron oxide with simultaneous generation of sulphur in the non-polluting elemental form. The influence of various parameters such as (i) amount of ferrous chloride (60–100% stoichiometric), (ii) oxygen pressure (0.308–0.515 MPa), (iii) leaching temperature (90–120°C) and (iv) duration of leaching (2–10 h) on the leaching process has been examined. It has been possible to recover 94–99% nickel and 98% copper with low iron contamination by using optinum conditions, such as a stoichiometric amount of ferrous chloride, a temperature of 110°C, an oxygen pressure of 0.377 MPa and a duration of 8 h.     

Leaching of chalcopyrite with ferric ion. Part I: General aspects

This paper presents a review of the literature on chalcopyrite leaching with ferric sulphate in acid medium. The effects of several parameters (ferric salt anion, oxidant concentration, pH and temperature) are examined and possible explanations are offered for the passivation of this sulphide during dissolution. The main theories related with chalcopyrite passivation point to the formation of a diffusion layer surrounding the chalcopyrite during dissolution, consisting of: bimetallic sulphide, copper polysulphide with a deficit of iron with respect to chalcopyrite, and elemental sulphur. Recent studies suggest that ferric ion plays two important and opposite roles in this process: as a mineral oxidizing agent and as the agent responsible for chalcopyrite passivation.     

Rational Processing of Refractory Copper-Bearing Ores

The results of material composition studies of four samples of refractory copper-bearing ores of the Uzelga deposit are presented along with the results of studies of technological solutions to increase their processing parameters. The refractoriness of ores is associated with a thin dissemination up to micron size and close interbreedings of ore and rock minerals. Iron sulfides are presented by a wide range of minerals: pyrite and marcasite, melnikovite, arsenic pyrite, and arsenopyrite; sooty melnikovite has an increased flotation activity. The grinding of iron sulfides from 89 to 29% is followed by a proportional increase in easily floatable rock minerals to 45% and clay to 9%. These properties make these sulfides difficult to process and retain ore refractoriness to the flotation concentration. The content of copper sulfides in ore samples varies from 3.32 to 7.29%; the relative portion of copper sulfide in a form of tennantite in different samples of deposit varies from 29 to 93%. Copper is also present in a form of chalcopyrite and bornite. The best flotation activity of tennantite can be seen in a neutral and slightly acidic medium, in contrast with the standard flotation regime for chalcopyrite and bornite with butyl xanthate in a high-alkaline calcareous medium. Free grains of copper minerals can be selectively extracted into intercycled concentrates during grinding of no more than 60% of the class–71 μm. The technology of flotation in a low-alkaline medium with M-TF selective sulfhydril collector in the intercycle copper flotation and refinement cycle of the copper concentrate is developed for refractory copper-bearing ores with a variable tennantite content. Aeration is applied to suppress the flotation activity of melnikovite, which makes it possible to attain 80% copper recovery into a conditional copper concentrate. The fine inclusions of bornite, tennantite, chalcopyrite, and sphalerite into pyrite makes it rational to obtain copper–pyrite and copper–zinc–pyrite products with a yield up to 12% for pyro- and hydrometallurgical processing, along with the isolation of enriched copper concentrates.     

Hydrothermal purification and enrichment of Chilean copper concentrates: Part 1: The behavior of bornite,covellite and pyrite

The nature and basic kinetics of the hydrothermal reactions of bornite, covellite and pyrite with copper sulfate solutions were investigated, as a previous study on the behavior of the bulk Chilean copper concentrates. The reaction of bornite produced digenite at < 160 °C and djurleite above this temperature. The reaction products formed a continuous, non porous layer. The rates were of zero order with respect [Cu²⁺]_(aq), and the activation energy was ～ 100 kJ/mol. Covellite was transformed to digenite at < 200 °C and to chalcocite (Q and M) at > 200 °C. The reaction was characterized for an irregular nucleation and growth of the products, which were non-protective. The order with respect the [Cu²⁺]_(aq) was 0.6 and the activation energy ～ 110 kJ/mol. The pyrite reaction was significant at > 200 °C and extensive at 240 °C. It produced a mixture of digenite/chalcocite-Q, with small amounts of djurleite. The transformation has a high Philling–Betworth ratio (～ 1.6), causing the break of the product layers. The reaction order and the activation energy were also 0.6 and ～ 110 kJ/mol, respectively. The rate of the bornite reaction should be controlled by solid-state ionic diffusion, whereas for covellite and pyrite the rates should be limited by electrochemical processes. Towards the hydrothermal transformation, the reactivity of the main phases present in Chuquicamata-type concentrates was: bornite > chalcopyrite > covellite > sphalerite > pyrite.     

黄铜矿的湿法冶金工艺研究进展

介绍了黄铜矿湿法冶金的最新进展及工艺特性，探讨了黄铜矿湿法冶金的发展前景。Dynatec加煤粉流程和CESL二段浸出流程很好地解决了中温压力氧化酸浸过程中单质硫的影响，对材质的耐腐蚀性要求低，在低能耗下获得了高的浸出效果，对于主要分布于黄铜矿中的含金铜精矿，可获得很高的金回收率。Intec和Hydro Copper工艺在常压低温氯化介质中很好地浸出黄铜矿精矿，并能同时回收伴生的贵金属．生产的中间产品铜粉可直接加工高附加值产品，能耗低，回收率高，是复杂铜精矿湿法冶金的途径．Geocoat工艺的诞生使得高品位黄铜矿精矿大规模高温细菌氧化浸出成为现实，它克服了细菌浸出对设备要求高的缺点，利用堆浸的优势，以低的运行成本获取高的黄铜矿浸出率。     

Microbiological leaching of a chalcopyrite concentrate by Thiobacillus ferrooxidans

The microbiological leaching of a chalcopyrite concentrate has been investigated using a pure strain of Thiobacillus ferrooxidans. The optimum leaching conditions regarding pH, temperature, and pulp density were found to be 2.3, 35 degrees C, and 22% respectively. The energy of activation was calculated to be 16.7 kcal/mol. During these experiments the maximum rate of copper dissolution was about 215 mg/liters/hr and the final copper concentration was as high as 55 g/liter. This latter value is in the range of copper concentrations which may be used for direct electrorecovery of copper. Jarosite formation was observed during the leaching of the chalcopyrite concentrate. When the leach residue was reground to expose new substrate surface, subsequent leaching resulted in copper extractions up to about 80%. On the basis of this experimental work, a flow sheet has been proposed for commercial scale biohydrometallurgical treatment of high-grade chalcopyrite materials.     

Galvanic conversion of chalcopyrite

Galvanic interaction between particulate chalcopyrite (CuFeS₂) and copper results in the rapid conversion of chalcopyrite to chalcocite. The effects of temperature, surface area, concentration of sulfuric acid and agitation were systematically evaluated. The kinetics were found to be controlled by a steady-state current flow controlled by the effective anodic and cathodic surface areas involved in the galvanic couple. The experimental activation energy was 11.5 and stoichiometric data and reaction products have been characterized. The overall kinetic system has been evaluated based upon an electrochemical model.