Copper hydrometallurgy——current status, preliminary economics, future direction and positioning versus smelting

The heap leaching of oxide copper ores with copper cathode recovery by solvent extraction and electro-winning is now well established as a low-cost method of copper recovery. This technology has recently been applied successfully to mixed oxide and chalcocite ores, notably in Chile at Cerro Colorado, Quebrada Blanca and Zaldivar.Currently, there are significant development efforts underway to try to extend heap leaching to chalcopyrite ores.The success of heap leaching/SX/EW has also led to a revival in the development of hydrometallurgical processes to recover copper from chalcopyrite and other copper concentrates. The current status of copper hydrometallurgy is re-viewed and the most commercially attractive potential applications are explored. The advantages and disadvantages of the hydrometallurgical treatment of chalcopyrite concentrates and its preliminary economics are compared with those for the current best practices in copper smelting and refining.     

The activox® process: Growing significance in the nickel industry

Metal-market analysts project a global nickel supply gap which will be filled by further high-pressure acid leach treatment of laterite ores and the commercialization of hydrometallurgical refineries to recover nickel from sulfide ores. The Activox® process is one such hydrometallurgical technology developed to recover a range of base and precious metals from sulfide ores and concentrates. The combination of ultrafine grinding and oxidative leaching extracted and enabled the recovery of 96.2% nickel, 88.3% cobalt, and 82.9% copper in the 310 kg/h Tati Hydrometallurgical Demonstration Plant.     

Copper leaching from chalcopyrite concentrates

Chalcopyrite (CuFeS₂) is one of the most abundant copper-bearing minerals, which accounts for approximately 70 percent of the world’s known copper reserves. For more than 30 years, a significant number of processes have been developed to leach copper from chalcopyrite concentrates. These processes recover copper via hydrometallurgical leaching of the copper component of chalcopyrite concentrates, followed by solvent extraction and electrowinning. A number of demonstration plant operations have been conducted, but as of this writing none of the processes have become completely commercially operational. Shije Wang is senior engineer at Kennecott Utah Copper Corporation.     

Dissolution kinetics of low grade complex copper ore in ammonia-ammonium chloride solution

The leaching kinetics of Tang-dan refractory low grade complex copper ore was investigated in ammonia-ammonium chloride solution. The concentration of ammonia and ammonium chloride, the ore particle size, the solid-to-liquid ratio and the temperature were chosen as parameters in the experiments. The results show that temperature, concentration of ammonia and ammonium chloride have favorable influence on the leaching rate of copper oxide ores. But, leaching rate decreases with increasing particle size and solid-to-liquid ratio. The leaching process is controlled by the diffusion of the lixiviant and the activation energy is determined to be 23.279 kJ/mol. An equation was also proposed to describe the leaching kinetics.     

堆浸法从含银氧化铁矿中提取银

云南个旧某矿氧化矿石中,除Sn以外还伴生有丰富的Ag。为了解决Ag的回收利用问题,作者等人对该矿石进行了柱浸、槽浸、堆浸和回收Ag的试验,取得较好的效果。用堆浸法进行较大规模的生产,Ag回收率为34．96％,达到综合回收利用资源的目的。     

Simulated small-scale pilot heap leaching of low-grade copper sulfide ore with selective extraction of copper

The bioleaching of low-grade copper sulfide ore and the selective extraction of copper were investigated. Lix984 dissolved in kerosene was used as extractant. The results show that it is possible to selectively leach copper from the ores by heap leaching. The copper concentration of leaching liquor after 250 d is 2.17 g/L, and the copper concentration is 0.27 g/L after solvent extraction. The leach liquor was subjected to solvent extraction, scrubbing and selective stripping for the enrichment of copper and the removal of impurities. The pregnant copper sulfate solution produced from the stripping cycle is suitable for copper electro-winning.     

Feasibility study on heap bioleaching of chalcopyrite

Bioleaching of chalcopyrite often encountered the formation of passivation layer, which inhibited the leaching process and resulted in a low leaching rate. This inhibitory effect can be eliminated by thermophilic biole- aching. The industrial test of BioCOP technology based on thermophiles was successfully completed, which confirmed the feasibility of chalcopyrite bioleaching. However, industrial leaching rate of chalcopyrite heap bioleaching is lower. This paper described the development status and industrial test of chalcopyrite heap bioleaching technology. The reasons for the lower efficiency of chalcopyrite heap bioleaching were analyzed. The strategies for successful chalcopyrite heap bioleaching were proposed.     

Mechanism of silver-influenced bacterial leaching of chalcopyrite, pyrite and a copper ore

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Study on bioleaching of primary chalcopyrite ore with thermoacidophilic archae

A high temperature-tolerating thermoacidophilic archae （TA） was isolated from water samples collected from a hot sulfur-containing spring in the Yunnan Province, China, and was used in bioleaching experiments of a low-grade chalcopyrite ore. The TA grow at temperatures ranging from 40 to 80℃, with 65℃ being the optimum temperature, and at pH values of l.5 to 4.0, with an optimum pH value of 2.0. The bioleaching experiments of the chalcvpyrite ore were conducted in both laboratory batch bioreactors and leaching columns. The results obtained from the bioreactor experiments showed that the TA bioleaching rate of copper reached 97% for a 12-day leaching period, while the bioleaching rate was 32.43% for thiobacillus ferrooxidans （Tf） leaching for the same leaching time. In the case of column leaching, tests of a two-phase leaching （196 days）, that is, a two-month （56 days） Tf leaching in the first phase, followed by a 140-day TA leaching in the second phase were performed. The average leaching rate of copper achieved for the 140-day TA leaching was 195mg/（L.d）, while for the control experiments, it was as low as 78mg/（L .d） for the Tf leaching, indicating that the TA possesses a more powerful oxidizing ability to the chalcopyrite than Tf Therefore, it is suggested that the two-phase leaching process be applied to .for the heap leaching operations, whereas, the TA can be used in the second phase when the temperature inside the heap has increased, and the primary copper sulfide minerals have already been partially oxidized with Tf beforehand in the first phase.     

STUDY ON BIOLEACHING OF PRIMARY CHALCOPYRITE ORE WITH THERMOACIDOPHLIC ARCHAE

A high temperature-tolerating thermoacidophilic archae (TA) was isolated from water samples collected from a hot sulfur-containing spring in the Yunnan Province, China, and was used in bioleaching experiments of a low-grade chalcopyrite ore. The TA grow at temperatures ranging from 40 to 80℃, with 65℃ being the optimum temperature, and at pH values of 1.5 to 4.0, with an optimum pH value of 2.0. The bioleaching experiments of the chalcopyrite ore were conducted in both laboratory batch bioreactors and leaching columns. The results obtained from the bioreactor experiments showed that the TA bioleaching rate of copper reached 97% for a 12-day leaching period, while the bioleaching rate was 32.43% for thiobacillus ferrooxidans (Tf) leaching for the same leaching time. In the case of column leaching, tests of a two-phase leaching (196 days), that is,a two-month (56 days) Tf leaching in the first phase, followed by a 140-day TA leaching in the second phase were performed. The average leaching rate of copper achieved for the 140-day TA leaching was 195mg/(L· d), while for the control experiments, it was as low as 78mg/(L· d) for the Tf leaching, indicating that the TA possesses a more powerful oxidizing ability to the chalcopyrite than Tf. Therefore, it is suggested that the two-phase leaching process be applied to for the heap leaching operations, whereas, the TA can be used in the second phase when the temperature inside the heap has increased, and the primary copper sulfide minerals have already been partially oxidized with Tf beforehand in the first phase.     

Sustainable copper extraction from mixed chalcopyrite–chalcocite using biomass

This paper elaborated on the sustainability of the copper extraction process. In fact, an alternative copper extraction route from mixed sulphide ores, chalcopyrite and chalcocite using mesophilic biomass consortium at 33.3 °C and ferric leaching process were attempted. Bioleaching experiments were settled with a fraction size of −75+53 µm. Bacteria were used as the catalyst. A copper yield of 65.50% was obtained. On the other hand, in ferric leaching process, with a fraction size of −53+38 µm, when the temperature was increased to 70 °C, the copper leaching rate increased to 78.52%. Thus, comparatively, the mesophilic bioleaching process showed a more obvious advantage in copper extraction than leaching process with a high temperature. However, it has been resolved from the characterization performed using SEM−EDS, FTIR and XRD observations coupled with different thermodynamic approaches that, the indirect mechanism is the main leaching mechanism, with three transitory mechanisms (polysulphide, thiosulphate and elemental sulphur mechanisms) for the mixed chalcopyrite−chalcocite ore. Meanwhile, the speciation turns into Cu₂S−CuS−Cu₅FeS₄−Cu₂S before turning into CuSO₄. While ferrous oxidation and the formation of ferric sulphate occur, and there is a formation of strong acid as bacteria digest sulphide minerals into copper sulphate at low temperature, which is why this copper production scenario requires a redox potential more than 550 mV at room temperature for high copper leaching rate.     

Recovery prediction of copper oxide ore column leaching by hybrid neural genetic algorithm

The artificial neural network (ANN) and hybrid of artificial neural network and genetic algorithm (GANN) were applied to predict the optimized conditions of column leaching of copper oxide ore with relations of input and output data. The leaching experiments were performed in three columns with the heights of 2, 4 and 6 m and in particle size of <25.4 and <50.8 mm. The effects of different operating parameters such as column height, particle size, acid flow rate and leaching time were studied to optimize the conditions to achieve the maximum recovery of copper using column leaching in pilot scale. It was found that the recovery increased with increasing the acid flow rate and leaching time and decreasing particle size and column height. The efficiency of GANN and ANN algorithms was compared with each other. The results showed that GANN is more efficient than ANN in predicting copper recovery. The proposed model can be used to predict the Cu recovery with a reasonable error.     

纳米比亚某含银硫化铜矿选矿试验研究

纳米比亚Karas矿区罗雷铜矿区的原生矿铜主要以黄铜矿、斑铜矿等硫化铜矿物形式存在,银分别以银黝铜矿为主的独立银矿物和以黄铜矿为载体的载体银矿物形式存在,铜、银品位分别为0.60%和3.03 g/t。浮选试验结果表明,矿样适当细磨至-0.074 mm占80%,以石灰做调整剂,Z200做捕收剂,在矿浆pH值为8的条件下,可获得铜品位22.3%,银品位61.8 g/t的含银铜精矿,铜、银回收率分别为90.6%和51.8%。     

Catalytic effect of activated carbon on bioleaching of low-grade primary copper sulfide ores

The catalytic effect of activated carbon on the bioleaching of low-grade primary copper sulfide ores using mixture of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans was investigated. The results show that the addition of activated carbon can greatly accelerate the rate and efficiency of copper dissolution from low-grade primary copper sulfide ores. The solution with the concentration of 3.0 g/L activated carbon is most beneficial to the dissolution of copper. The resting time of the mixture of activated carbon and ores has an impact on the bioleaching of low-grade primary copper sulfide ores. The 2 d resting time is most favorable to the dissolution of copper. The enhanced dissolution rate and efficiency of copper can be attributed to the galvanic interaction between activated carbon and chalcopyrite. The addition of activated carbon obviously depresses the dissolution of iron and the bacterial oxidation of ferrous ions in solution. The lower redox potentials are more favorable to the copper dissolution than the higher potentials for low-grade primary copper sulfide ores in the presence of activated carbon.     

四川丹巴铜炉房金矿床矿石选冶方法研究

通过多次对金矿石的选冶试验研究工作,使金精矿经沸腾焙烧预处理后Au、Ag、Cu、S的浸出回收率均得到显著提高,其中硫脲法Au、Ag、Cu的浸出率分别为99.4%、95.8%、98.0%;氰化法 Au、Ag、Cu的浸出率分别为:99.4%、89.4%、93.3%.最终确定矿石的最佳选冶方案为:原矿破碎→球磨→浮选富集→金、银、铜精矿→沸腾焙烧→烟气制硫酸,焙砂经硫酸浸出萃取电解回收铜后,再经硫脲法回收金银.     

Combining sulfate electrowinning with chloride leaching

Although the chloride leaching of copper sulfide concentrates has proved highly efficient, electrowinning from chloride solutions presents many difficulties, notably in cell design and the handling of the powder product. Sulfate electrowinning,on the other hand, continues to improve and has played a significant part in the widespread adoption of the solvent extraction-electrowinning process for copper recovery from low-grade ores. It has been found that the two steps can be combined by introducing a novel solvent extraction process after chloride leaching. This article presents the results of laboratory tests to prove the feasibility of this approach and discusses how it can be integrated into a commercially viable flow sheet.     

Effect of temperature on leaching behavior of copper minerals with different occurrence states in complex copper oxide ores

The effect of temperature on leaching behavior of copper minerals with different occurrence states in complex copper oxide ores was carried out by phase analysis means of XRD, optical microscopy and SEM−EDS. The results indicated that at ambient temperature, the easily leached copper oxide minerals were completely dissolved, while the bonded copper minerals were insoluble. At lukewarm temperature of 40 °C, it was mainly the dissolution of copper in isomorphism state. With increasing temperature to 60 °C, the copper leaching rate in the adsorbed state was significantly accelerated. In addition, when the temperature increased to 80 °C, the isomorphic copper was completely leached, leaving 11.2% adsorbed copper un-leached. However, the copper in feldspar−quartz−copper−iron colloid state was not dissolved throughout the leaching process. Overall, the leaching rates of copper in different copper minerals decreased in the order: malachite, pseudo-malachite > chrysocolla > copper-bearing chlorite > copper-bearing muscovite > copper-bearing biotite > copper-bearing limonite > feldspar−quartz−copper−iron colloid.     

Treatment of copper ores and concentrates with industrial nitrogen species catalyzed pressure leaching and non-cyanide precious metals recovery

Today, with a stringent economic and environmental climate prevailing in the copper business, there is increased interest in evaluating new processing alternatives for production. Hydrometallurgical pressure oxidation of copper concentrates is one of the more viable approaches, and several technological candidates have emerged. Of these, an overlooked but, ironically, the first industrially proven methodology utilized nitrogen species catalyzation in the oxidizing pressure-leach system to produce copper via solvent extraction/electrowinning. Given its advantages, this may prove to be a feasible process alternative for the future. In this article, the history of the system and its application to copper concentrates and ores will be outlined. In particular, a non-cyanide methodology for effective recovery of precious metals from chalcopyrite concentrates will be discussed. For more information, contact C.G. Anderson, Montana Tech, the Center for Advanced Mineral and Metallurgical Processing, Room 221 ELC Building, Butte, Montana, 59701; (406) 496-4794; fax (406) 496-4512; e-mail CAnderson@mtech.edu; www.mtech.edu/camp.     

The cuprex metal extraction process: Recovering copper from sulfide ores

The Cuprex? metal extraction process produces cathode-grade copper using a hydrometallurgical process based on chloride leaching of sulfide ore concentrates. The process incorporates several novel steps to overcome the major problems associated with earlier chloride-based processes, including mild leaching conditions using ferric chloride as leachant and solvent extraction of copper usinga novel reagent. This produces a highly concentrated cupric chloride electrolyte from which cathode-grade copper is electrowon in the Metclor cell. The technical viability and robustness of the core technology have been proven in a series of large-scale pilot trials. More recent work has concentrated on supplementary processes to convert the copper powder product to an article of commerce and to recover valuable by-products. A fully integrated scheme is now being developed with updated cost estimates.     

Copper and elemental sulphur from chalcopyrite by pressure leaching

Processes employing direct oxidation under an over-pressure of air or oxygen in an aqueous sulphuric acid medium have been developed in the Sherritt Gordon Laboratories for iron, nickel, cobalt, zinc and lead sulphide concentrates. This study has recently also been extended to chalcocite, Cu₂S, concentrates. The rising interest in processes employing direct aqueous oxidation is stimulated by the fact that elemental sulphur can be produced as a by-product rather than sulphur dioxide or sulphuric acid.The present paper outlines a process which features the direct pressure oxidation of the most abundant copper sulphide mineral, chalcopyrite, CuFeS₂. The optimum conditions for a practical pressure leaching step have now been developed in the laboratory which results in the production of copper sulphate solution suitable for copper winninq by electrolysis, hydrogen reduction, solvent extraction combined with electrolysis, or other means. The leach residue yields pure elemental sulphur by-product. Copper and elemental sulphur recoveries of 98 and 85% respectively have been recorded. The fastest oxidation rate, corresponding to a leach retention time of 2.5 hr, was obtained when the copper concentrate was ground to 99.5% — 325 mesh, when a 50% stoichiometric excess of concentrate over the amount of available sulphuric acid for copper was used and when the oxygen partial pressure and temperature were maintained at 500 psi and 240°F, respectively. In an idealized form, the pressure leaching reaction can be expressed as follows:—CuFeS₂ + H₂SO₄ + 1 1/40₂ + 1/2H₂O → CuSO₄ + Fe(OH)₃ + 2S°After separation of the copper sulphate solution by filtration, elemental sulphur and excess concentrate ore recovered from the iron oxide tailing by flotation. The tailing, containing iron oxide and insolubles, is rejected. The elemental sulphur is separated from the concentrate by hot filtration, solvent extraction, distillation, or other means, and the unleached chalcopyrite is recycled to the leaching step.