Which copper ores are mined

Copper cathodes are hung between anodes. Can you recognise the shape of the suspension arms on the anodes from the picture of anode casting?

At the cathode the copper ions take back two electrons to return to being copper atoms. The purification happens because the other metals in the anode impurities will not dissolve in the electrolyte solution. They fall to the bottom of the tank. The cathodes are The blister copper anodes are immersed in an electrolyte containing copper sulfate and sulfuric acid. Pure copper cathodes are arranged between the blister copper anodes and a current of over A passes through the solution.

This is driven by a low voltage of about 1. What happens in electrolysis? Under these conditions, copper atoms dissolve from the impure anode to form copper ions. These migrate towards the cathodes where they are deposited back as pure copper atoms. They find themselves in an electric field between the electrodes.

Being positive, they move to the negative cathode where they pick up two electrons and go back to being metallic atoms with no charge. In an electric circuit, electron flow goes from negative to positive so the process transports electrons from the cathode to the anode. Gradually, the anode is eroded and the cathode grows. Insoluble impurities in the anode fall to the bottom as a sludge. What happens to the impurities? Gold, silver, platinum and tin are insoluble in this electrolyte and so do not deposit on the cathode.

Soluble impurities of iron and nickel dissolve in the electrolyte, which has to be continually purified to prevent excessive deposition onto the cathodes, which would reduce the purity of the copper. Recently, stainless steel cathodes have replaced copper cathodes.

Identical chemical reactions take place. Periodically, the cathodes are removed and pure copper is scraped off. This flow diagram summarises the sulfide ore processing stages. Find the two furnaces that send sulfur dioxide gas to the acid plant. Courtesy of Rio Tinto. Go to the download section to access zip files of all resources for each subject and age group for use offline. Copper is infinitely recyclable without losing any of its properties. This means it is not consumed and can be used and re-used over and over again.

Mining Metals Metals are often found as compounds in ores. Courtesy of Codelco. Web search hints: Porphyry copper — Nazca subduction — Global volcanism smithsonian Copper can be extracted from its ore by: Underground: sinking a vertical shaft into the Earth to an appropriate depth and driving horizontal tunnels into the ore. Courtesy of BHP Billiton. Copper ore is loaded into trucks. In some mines these trucks have no driver.

This truck carrying copper ore has no driver. It is guided by a GPS system. Can you see the GPS antenna? Ball mills crush the ore into a fine powder. This is a rare chance to see a mill and flotation building before the roof is built. Froth flotation tanks. The roasting process: changes some of the CuFeS 2 to copper oxide removes some of the sulfur as sulfur dioxide This is done by heating the concentrated ore from froth flotation.

Courtesy of Xstrata. SiO 2 slag This is very similar to the removal of impurities in the blast furnace. Blister copper from the smelter is poured into the anode casting moulds. The anodes are cast into slabs about 1 metre square with arms at the top corners for lifting. The anode casting turntable moves slowly round. The anodes can be lifted out at the far side. Questions and Activities Place these products in the extraction process in ascending order of copper content.

Use the flow chart as a guide: Matte Ore Cathode copper Blister Anode copper Copper concentrate Fire refined copper Use a periodic table to find the atomic masses of the elements in cuprite and chalcocite. Copper is found in the earth's crust and the oceans although the amount in the latter is thought to be negligible, amounting to no more than about eight months mine production at present-day rates.

The upper 10 kilometers of the crust is thought to contain an average of about 33 ppm of copper. For commercial exploitation, copper deposits generally need to be in excess of 0.

The known reserves of higher-grade ore in the world amount to nearly 1 billion tons of copper. At the present rate of mine production, which is about However, successful exploration for new mineral deposits, technological advances in mining and extractive metallurgy which enable the exploitation of leaner ores, thereby enlarging the pool of known reserves and copper uses which permit copper to be used more sparingly where larger quantities were used in the past and the continued recycling of scrap are likely to forestall indefinitely depletion of this valuable metal.

For example, in the first mile depth of the crust of the continents, it is estimated that there is 3x 10 18 metric tons of copper diffusely distributed. The relatively concentrated portion of this copper is only a small fraction of the whole, constituting an estimated 10 10 metric tons in deposits with a grade of 0. At current world mine production, this represents a million years' supply of copper theoretically available in the mineable portion of the earth's crust.

Table 4 shows some of the most common copper minerals. Some of these have long had a value in their own right, such as malachite, prized for its unusual and pleasing appearance and used for millennia in jewelry and ornaments. The barren rock, or gangue has to be separated from the sulfide minerals in order to smelt the metallic copper from the ore.

By far the greatest proportion of copper is extracted from the sulfides of copper, iron and sometimes other metals. Such ores originate from sulfur-bearing volcanic magmas, which have separated into metal sulfides and siliceous melts. The copper has concentrated almost entirely into the sulfide fraction, and if this becomes separated from the siliceous melt it can become deposited in veins or in fissures in the host rock by hydrothermal or other geological activity.

In many ores and most of those found in the Western USA the copper minerals occur as a dispersion of fine particles. Such ores are called porphyries. Where mineralized rocks become outcropped or shattered, the sulfide minerals undergo chemical changes due to air, groundwater and heat, giving rise to the other main variety of copper minerals - the oxidized ores.

There is no shortage of copper resources. In fact, copper is one of the most abundant of the metallic elements in the earth's crust.

Commercially exploited deposits of copper ores are found in many parts of the world, frequently associated with mountain-building processes. Deposits occur at many locations in the western cordillera of the Americas, mainly in the United States and Chile, and in areas of the North American plains like Michigan, Ontario, Quebec and Manitoba, at sites associated with the Pre-Cambrian shield.

Copper is also found in many other countries throughout the world. In addition, huge quantities of copper are known to exist as "deep-sea nodules" scattered on the ocean floor, although high recovery costs has thus far prevented their commercial exploitation. Chile and the USA are, respectively, the world's two leading copper-producing nations, Chile having overtaken the USA in the early s. Extraction Ores are first mechanically crushed and ground so that nearly all copper mineral particles are freed from the gangue.

Flotation by the injection of air and violent agitation is carried out with the pulverized ore held in suspension in water, to which surface-active agents have been added. Since each mine site is unique in its mineral composition, concentration, and quantities, the most economical and profitable processing of ore must be determined by the mine planners.

When it is economically feasible, a mine may extract both types of copper minerals; when it is not possible, mines will only process either the copper oxides or the copper sulfides. The first steps of copper processing are the same for both ores: mining and transporting. Copper mining is usually performed using open-pit mining , in which a series of stepped benches are dug deeper and deeper into the earth over time.

To remove the ore, boring machinery is used to drill holes into the hard rock, and explosives are inserted into the drill holes to blast and break the rock.

The resulting boulders are then ready for hauling; specialized haul trucks, conveyors, trains, and shuttle cars can all be used to haul the ore from the blasting site to the processing site. The size of the equipment needed to haul the tons and tons of ore is gigantic.

Most ores are then sent through a primary crusher, which is typically located very close to or sometimes in the pit. This primary crusher reduces the size of the ore from boulder to golf ball-sized rocks.

Oxide ores are generally processed using hydrometallurgy. This process uses aqueous water-based solutions to extract and purify copper from copper oxide ores at ordinary temperatures, usually in three steps: heap leaching, solvent extraction, and electrowinning. Heap Leaching is the process of using percolating chemical solutions to leach out metals.

Heap leaching is very commonly used for low-grade ore, which would otherwise not be economical to send through a milling process. Following mining, transporting, and crushing to a consistent gravel or golf ball-size, the crushed ore is piled into a heap on top of an impenetrable layer, on a slight slope. The leaching reagent dilute sulfuric acid is sprayed through sprinklers on top of the heap pile and allowed to trickle down through the heap, where it dissolves the copper from the ore.

The second step is solvent extraction , in which two immiscible un-mixing liquids are stirred and allowed to separate, causing the cooper to move from one liquid to the other. The pregnant leach solution is mixed vigorously with a solvent. The copper migrates from the leach solution into the solvent. The two liquids are then allowed to separate based on solubility, with copper remaining in solution in the solvent, and impurities remaining in the leach solution.