Copper
Copper is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish. It is used as a conductor of heat and electricity, a building material, and a constituent of various metal alloys.
Copper is one of the oldest metals ever used and has been one of the important materials in the development of civilization. Because of its properties, singularly or in combination, of high ductility, malleability, and thermal and electrical conductivity, and its resistance to corrosion, copper has become a major industrial metal, ranking third after iron and aluminum in terms of quantities consumed. Electrical uses of copper, including power transmission and generation, building wiring, telecommunication, and electrical and electronic products, account for about three quarters of total copper use. Building construction is the single largest market, followed by electronics and electronic products, transportation, industrial machinery, and consumer and general products. Copper byproducts from manufacturing and obsolete copper products are readily recycled and contribute significantly to copper supply.
In nutrition, Copper, along with iron, helps in the formation of red blood cells. It also helps in keeping the blood vessels, nerves, immune system, and bones healthy.
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[edit] Application
Most copper is used for electrical equipment (60%); construction, such as roofing and plumbing (20%); industrial machineri, such as heat exchangers (15%) and alloys (5%). The main long established copper alloys are bronze, brass (a copper-zinc alloy), copper-tin-zinc, which was strong enough to make guns and cannons, and was known as gun metal, copper and nichel, known as cupronickel, which was the preferred metal for low-denomination coins.
Copper is ideal for electrical wiring because it is easily worked, can be drawn into fine wire and has a high electrical conductivity.
[edit] Production
Most copper is mined or extracted as copper sulfides from large open pit mines in porphyry copper deposits that contain 0.4 to 1.0% copper. Copper is usually found in nature in association with sulfur. Pure copper metal is generally produced from a multistage process, beginning with the mining and concentrating of low-grade ores containing copper sulfide minerals, and followed by smelting and electrolytic refining to produce a pure copper cathode. An increasing share of copper is produced from acid leaching of oxidized ores.
[edit] Copper Mining
Metals are often found as compounds in ores. An ore is a rock or mineral that has enough metal in it to make it worth extracting. In the case of copper, it is worth extracting when there is about 2 kg of copper per 1000 kg of ore. The ores are extracted by either traditional mining (open pit or underground) or by leaching. The copper is then recovered using physical and chemical techniques.
Copper minerals and ore are found throughout the Earth's crust. They occur in both sedimentary and igneous rocks. The outer 10km of the crust contains 33g of copper for every tonne of rock. This is not enough to make it commercially viable to extract the rock. Copper mines are only set up where there is more than 5kg of copper per tonne of rock (0.5% by mass). Ideally, the figure should be closer to 2%.
[edit] Extracting Method
[edit] Traditional mining
- Underground - sinking a vertical shaft into the Earth to an appropriate depth and driving horizontal tunnels into the ore.
- Open pit - 90% of ore is mined by this method. Ores near the surface can be quarried after removal of the surface layers.
[edit] Leaching
The ore is treated with dilute sulphuric acid. This trickles slowly through the ore dissolving copper to form copper sulphate. The copper is recovered by electrolytic refining. Advantages of this process are:
- much less energy is use than in traditional mining
- no waste gases are given off
- it can be used on ores with as little as 0.1% copper - for this reason, leaching extraction is growing in importance.
[edit] Environmental Effects
As copper ends up in soil it strongly attaches to organic matter and minerals. As a result it does not travel very far after release and it hardly ever enters groundwater. In surface water copper can travel great distances, either suspended on sludge particles or as free ions.
Copper does not break down in the environment and because of that it can accumulate in plants and animals when it is found in soils. On copper-rich soils only a limited number of plants has a chance of survival. That is why there is not much plant diversity near copper-disposing factories. Due to the effects upon plants copper is a serious threat to the productions of farmlands. Copper can seriously influence the proceedings of certain farmlands, depending upon the acidity of the soil and the presence of organic matter. Despite of this, copper-containing manures are still applied.
Copper can interrupt the activity in soils, as it negatively influences the activity of microrganisms and earthworms. The decomposition of organic matter may seriously slow down because of this.
When the soils of farmland are polluted with copper, animals will absorb concentrations that are damaging to their health. Mainly sheep suffer a great deal from copper poisoning, because the effects of copper are manifesting at fairly low concentrations.
[edit] Health Effects
Long-term exposure to copper can cause irritation of the nose, mouth and eyes and it causes headaches, stomachaches, dizziness, vomiting and diarrhoea. Intentionally high uptakes of copper may cause liver and kidney damage and even death. Whether copper is carcinogenic has not been determined yet.
There are scientific articles that indicate a link between long-term exposure to high concentrations of copper and a decline in intelligence with young adolescents. Whether this should be of concern is a topic for further investigation.
Industrial exposure to copper fumes, dusts, or mists may result in metal fume fever with atrophic changes in nasal mucous membranes. Chronic copper poisoning results in Wilson’s Disease, characterized by a hepatic cirrhosis, brain damage, demyelination, renal disease, and copper deposition in the cornea.
