Copper hydrometallurgical process

In the most common hydrometallurgical process, the ore is leached with ammonia or sulfuric acid to extract the copper. These processes can operate at atmospheric pressure or as pressure leach circuits. Copper is recovered from solution by electrowinning, a process similar to electrolytic refining. The process is most commonly used for leaching low-grade deposits in situ or as heaps. 

The copper product is known as blister copper because of the appearance of air bubbles in the solidified metal. In the hydrometallurgical process, soluble Cu2+ ions are formed by the action of sulfuric acid on the ores. Then the metal is obtained by reducing these ions in aqueous solution either electrolytically or chemically, by using an inexpensive reducing agent that has a more negative standard potential than that of copper, such as hydrogen or iron (see Section 14.3) ... 

Anatread A hydrometallurgical process for extracting copper from a sulfide ore with ferric chloride solution. 

In the hydrometallurgical processes for extracting copper, soluble Cu2+ ions are formed by the action of sulfuric acid on the ores. Then the... 

Metals in Groups 11 and 12 are easily reduced from their compounds and have low reactivity as a result of poor shielding of the nuclear charge by the d-electrons. Copper is extracted from its ores either by pyrometallurgical or hydrometallurgical processes. 

The development of hydrometallurgical processes for the extraction of copper from ores and concentrates has been a widespread major research activity for the past 20 years. Coordination chemistry has been applied in many ingenious ways in attempts to devise novel and energy-efficient processes to replace the conventional smelting—electrorefining approach. Several of these processes... 

Cementation, the process by which a metal is reduced from solution by the dissolution of a less-noble metal, has been used for centuries as a means for extraction of metals from solution, and is probably the oldest of the hydrometallurgical processes. It is also known by other terms such as metal displacement or contract reduction, and is widely used in the recovery of metals such as silver, gold, selenium, cadmium, copper and thallium from solution and the purification of solutions such as those used in the electrowinning of zinc. The electrochemical basis for these reactions has been well established414 and, as in leaching reactions, comprises the anodic dissolution of the less-noble metal coupled to the cathodic reduction of the more-noble metal on the surface of the corroding metals. Therefore, in the well-known and commercially exploited44 cementation of copper from sulfate solution by metallic iron, the reactions are... 

Because of cost factors, solvent extraction applied to large scale hydrometallurgical processes, such as the recovery of copper from acidic ore leach solutions, is carried out with the most selective reagent for e.g., copper versus iron, which is not itself a liquid solvent, in a petroleum diluent that confers on the mixture the desired physical properties. For the particular case of copper recovery, commercial hydroxyoxime reagents have been used on a very large scale, but their discussion is outside the scope of this book. 

The Dowa Mining Company (K9) in Kosaka, Japan has developed a hydrometallurgical process shown in Fig. 15 to treat 2400 metric tons/ month of copper-zinc sulfide flotation concentrates. The microscopically fine mixture of copper and zinc sulfides was separated from lead sulfide and barite by flotation. The flotation concentrate analyzed 8.7% Cu,... 

Unfortunately, the copper product requires extensive refining before being marketable. Moreover, scrap iron cannot displace zinc, cadmium, or many other trace contaminants from solution. Zinc is more versatile than scrap iron, having a lower reduction potential. However, although zinc is used extensively in hydrometallurgical processes to cement copper, nickel, and cobalt from zinc leach solutions before electrolysis " and to recover gold and silver in the Merrill-Crowe process. the Zn + ions introduced into solution would be unacceptable for environmental applications, even if the process were economically attractive. 

T. N. Lung, The History of Copper Cementation on Iron—the World s First Hydrometallurgical Process from Medieval China, Hydrometallurgy, YI, 113-129 (1986). 

Many hydrometallurgical processes or process steps are used to upgrade concentrates, process recycled scrap metal, or purify aqueous process steams. Examples are (I) the leaching of molybdenite concentrate to remove Knpurities ,ft (2) leaching of tungsten carbide and molybdenum scrap-, (3) removal of copper impurities in nickel anolyte by cementation on metallic ruckel and (4) various methods for treating nuclear fuel elements. 

Among the various hydrometallurgical processes for copper recovery, those incorporating a controlled oxidation of the sulfide ore to elemental sulfur are of particular interest (9, 58). They avoid the production of possibly unneeded sulfuric acid or the costly collection and subsequent reduction of sulfur dioxide. 

Copper and zinc are the principal metals extracted by electrolysis in aqueous solution the total world production of both approaches 10 ton yr although the electrolytic route accounts for only 10% of the copper and 50% of the zinc produced. Moreover the large electrolytic plants are limited to sites in Africa, Australia and Canada where hydroelectric power is available close to the mines. Cobalt, nickel, chromium, manganese, cadmium, gallium, thallium, indium, silver and gold have also been reported to have been extracted by a hydrometallurgical process but, since these metals are only produced in a low tonnage, the electrolytic processes are on a small scale. 

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