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= Copper =
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Introduction
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Copper is a chemical element; it has symbol Cu (from Latin ) and
atomic number 29. It is a soft, malleable, and ductile metal with very
high thermal and electrical conductivity. A freshly exposed surface of
pure copper has a pinkish-orange color. Copper is used as a conductor
of heat and electricity, as a building material, and as a constituent
of various metal alloys, such as sterling silver used in jewelry,
cupronickel used to make marine hardware and coins, and constantan
used in strain gauges and thermocouples for temperature measurement.
Copper is one of the few metals that can occur in nature in a directly
usable, unalloyed metallic form. This means that copper is a native
metal. This led to very early human use in several regions, from .
Thousands of years later, it was the first metal to be smelted from
sulfide ores, ; the first metal to be cast into a shape in a mold, ;
and the first metal to be purposely alloyed with another metal, tin,
to create bronze, .
Commonly encountered compounds are copper(II) salts, which often
impart blue or green colors to such minerals as azurite, malachite,
and turquoise, and have been used widely and historically as pigments.
Copper used in buildings, usually for roofing, oxidizes to form a
green patina of compounds called verdigris. Copper is sometimes used
in decorative art, both in its elemental metal form and in compounds
as pigments. Copper compounds are used as bacteriostatic agents,
fungicides, and wood preservatives.
Copper is essential to all living organisms as a trace dietary mineral
because it is a key constituent of the respiratory enzyme complex
cytochrome c oxidase. In molluscs and crustaceans, copper is a
constituent of the blood pigment hemocyanin, replaced by the
iron-complexed hemoglobin in fish and other vertebrates. In humans,
copper is found mainly in the liver, muscle, and bone. The adult body
contains between 1.4 and 2.1 mg of copper per kilogram of body weight.
Etymology
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In the Roman era, copper was mined principally on Cyprus, the origin
of the name of the metal, from 'aes cyprium' (metal of Cyprus), later
corrupted to (Latin). ' (Old English) and 'copper' were derived from
this, the later spelling first used around 1530.
Physical
==========
Copper, silver, and gold are in group 11 of the periodic table; these
three metals have one s-orbital electron on top of a filled d-electron
shell and are characterized by high ductility, and electrical and
thermal conductivity. The filled d-shells in these elements contribute
little to interatomic interactions, which are dominated by the
s-electrons through metallic bonds. Unlike metals with incomplete
d-shells, metallic bonds in copper are lacking a covalent character
and are relatively weak. This observation explains the low hardness
and high ductility of single crystals of copper. At the macroscopic
scale, introduction of extended defects to the crystal lattice, such
as grain boundaries, hinders flow of the material under applied
stress, thereby increasing its hardness. For this reason, copper is
usually supplied in a fine-grained polycrystalline form, which has
greater strength than monocrystalline forms.
The softness of copper partly explains its high electrical
conductivity () and high thermal conductivity, second highest (second
only to silver) among pure metals at room temperature. This is because
the resistivity to electron transport in metals at room temperature
originates primarily from scattering of electrons on thermal
vibrations of the lattice, which are relatively weak in a soft metal.
The maximum possible current density of copper in open air is
approximately , above which it begins to heat excessively.
Copper is one of a few metallic elements with a natural color other
than gray or silver. Pure copper is orange-red and acquires a reddish
tarnish when exposed to air. This is due to the low plasma frequency
of the metal, which lies in the red part of the visible spectrum,
causing it to absorb the higher-frequency green and blue colors.
As with other metals, if copper is put in contact with another metal
in the presence of an electrolyte, galvanic corrosion will occur.
Chemical
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Copper does not react with water, but it does slowly react with
atmospheric oxygen to form a layer of brown-black copper oxide which,
unlike the rust that forms on iron in moist air, protects the
underlying metal from further corrosion (passivation). A green layer
of verdigris (copper carbonate) can often be seen on old copper
structures, such as the roofing of many older buildings and the Statue
of Liberty. Copper tarnishes when exposed to some sulfur compounds,
with which it reacts to form various copper sulfides.
Isotopes
==========
There are 29 isotopes of copper. and are stable, with comprising
approximately 69% of naturally occurring copper; both have a spin of .
The other isotopes are radioactive, with the most stable being with a
half-life of 61.83 hours. Seven metastable isomers have been
characterized; is the longest-lived with a half-life of 3.8 minutes.
Isotopes with a mass number above 64 decay by β−, whereas those with a
mass number below 64 decay by β+. Copper-64, which has a half-life of
12.7 hours, decays both ways.
and have significant applications. is used in Cu-PTSM as a
radioactive tracer for positron emission tomography.
Occurrence
============
Copper is produced in massive stars and is present in the Earth's
crust in a proportion of about 50 parts per million (ppm). In nature,
copper occurs in a variety of minerals, including native copper,
copper sulfides such as chalcopyrite, bornite, digenite, covellite,
and chalcocite, copper sulfosalts such as tetrahedite-tennantite, and
enargite, copper carbonates such as azurite and malachite, and as
copper(I) or copper(II) oxides such as cuprite and tenorite,
respectively. The largest mass of elemental copper yet discovered
weighed 420 tonnes and was found in 1857 on the Keweenaw Peninsula in
Michigan, US. Native copper is a polycrystal, with the largest single
crystal ever described measuring . Copper is the 26th most abundant
element in Earth's crust, representing 50 ppm compared with 75 ppm for
zinc, and 14 ppm for lead.
Typical background concentrations of copper do not exceed in the
atmosphere; in soil; in vegetation; 2 μg/L in freshwater and in
seawater.
Production
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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.
Sites include Chuquicamata, in Chile, Bingham Canyon Mine, in Utah,
United States, and El Chino Mine, in New Mexico, United States.
According to the British Geological Survey, in 2005, Chile was the top
producer of copper with at least one-third of the world share followed
by the United States, Indonesia and Peru. Chile, the world's largest
copper producer, supplies the US with 70% of refined copper and alloy
imports through 2024. Together with Canada (17%) and Peru (7%), they
account for 94% of U.S. copper imports. Copper can also be recovered
through the in-situ leach process. Several sites in the state of
Arizona are considered prime candidates for this method. The amount of
copper in use is increasing and the quantity available is barely
sufficient to allow all countries to reach developed world levels of
usage. An alternative source of copper for collection currently being
researched are polymetallic nodules, which are located at the depths
of the Pacific Ocean approximately 3000-6500 meters below sea level.
These nodules contain other valuable metals such as cobalt and nickel.
Reserves and prices
=====================
Copper has been in use for at least 10,000 years, but more than 95% of
all copper ever mined and smelted has been extracted since 1900. As
with many natural resources, the total amount of copper on Earth is
vast, with around 1014 tons in the top kilometer of Earth's crust,
which is about 5 million years' worth at the current rate of
extraction. However, only a tiny fraction of these reserves is
economically viable with present-day prices and technologies.
Estimates of copper reserves available for mining vary from 25 to 60
years, depending on core assumptions such as the growth rate.
Recycling is a major source of copper in the modern world.
The price of copper is volatile. After a peak in 2022 the price
unexpectedly fell. And by May 2024, the price on the London Metal
Exchange has reached an all-time high above $11,000 per ton.
The global market for copper is one of the most commodified and
financialized of the commodity markets, and has been so for decades.
Copper demand
===============
Total world production in 2023 is expected to be almost 23 million
metric tons. Copper demand is increasing due to the ongoing energy
transition to electricity. China accounts for over half the demand.
===Extraction===
The great majority of copper ores are sulfides. Common ores are the
sulfides chalcopyrite (CuFeS2), bornite (Cu5FeS4) and, to a lesser
extent, covellite (CuS) and chalcocite (Cu2S). These ores occur at
the level of <1% Cu. Concentration of the ore is required, which
begins with comminution followed by froth flotation. The remaining
concentrate is smelted, which can be described with two simplified
equations:
* Cuprous sulfide is oxidized to cuprous oxide:
:2 Cu2S + 3 O2 → 2 Cu2O + 2 SO2
* Cuprous oxide reacts with cuprous sulfide to convert to 'blister
copper' upon heating:
:2 Cu2O + Cu2S → 6 Cu + 2 SO2
This give crude copper, about 98% Cu by weight, which is purified by
electrolysis giving Cu at upto 99.99% purity. During the electrolysis
small amounts of silver and gold may be precipitated into a sludge
that can be reprocessed to recover the precious metals.
Aside from sulfides, another family of ores are oxides. Approximately
15% of the world's copper supply derives from these oxides. The
beneficiation process for oxides involves extraction with sulfuric
acid solutions followed by electrolysis. In parallel with the above
method for "concentrated" sulfide and oxide ores, copper is recovered
from mine tailings and heaps. A variety of methods are used including
leaching with sulfuric acid, ammonia, ferric chloride. Biological
methods are also used.
A potential source of copper is polymetallic nodules, which have an
estimated concentration 1.3%.
Recycling
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According to the International Resource Panel's Metal Stocks in
Society report, the global per capita stock of copper in use in
society is 35-55 kg. Much of this is in more-developed countries
(140-300 kg per capita) rather than less-developed countries (30-40 kg
per capita). In 2001, a typical automobile contained 20-30 kg of
copper. By 2014, the copper and copper alloy content of internal
combustion engine vehicles decreased to 16.8 kg, but increased again
to 24.5 kg by 2023. At the same time, a battery electric vehicle
already contains around 91 kg of copper and copper alloys.
Like aluminium, copper is recyclable without any loss of quality, both
from raw state and from manufactured products. An estimated 80% of all
copper ever mined is still in use today. In volume, copper is the
third most recycled metal after iron and aluminium. , recycled copper
supplies about one-third of global demand.
The process of recycling copper is roughly the same as is used to
extract copper but requires fewer steps. High-purity scrap copper is
melted in a furnace and then reduced and cast into billets and ingots.
Lower-purity scrap is melted to form 'black copper' (70-90% pure,
containing impurities such as iron, zinc, tin, and nickel), followed
by oxidation of impurities in a converter to form blister copper
(96-98% pure), which is then refined as before.
Environmental impacts
=======================
Copper mining creates direct environmental impacts from tailing,
overburden rocks, and abandoned mines. Tailing includes liquid waste
typically sulfide rich, generating acid mine drainage. The acid in
turn may leach heavy metals from surrounding soil. Overburden rocks
may also leach heavy metals in areas of high rainfall. These heavy
metals can accumulate in downstream farming areas and enter the food
chain. Some of these metals are known carcinogens.
Advocacy groups have reported that mining companies exploit local
populations by corrupting local officials in parts of the Philippines.
Indirect impacts include
greenhouse gas emissions primarily from electricity consumed by the
company, especially when sourced from fossil fuels, and from engines
required for copper extraction and refinement.
The environmental cost of copper mining was estimated at 3.7 kg -eq
per kg of copper in 2019. Codelco, a major producer in Chile, reported
that in 2020 the company emitted 2.8 t -eq per ton (2.8 kg -eq per kg)
of fine copper.
Alloys
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Numerous copper alloys have been formulated, many with important uses.
Brass is an alloy of copper and zinc. Bronze usually refers to
copper-tin alloys, but can refer to any alloy of copper such as
aluminium bronze. Copper-tin bronzes with various additional metals
have been use to create bells for centuries; the composition of the
alloy directly affects the tone and mechanical characteristics of the
instrument. Copper is one of the most important constituents of silver
and karat gold solders used in the jewelry industry, modifying the
color, hardness and melting point of the resulting alloys. Some
lead-free solders consist of tin alloyed with a small proportion of
copper and other metals.
The alloy of copper and nickel, called cupronickel, is used in
low-denomination coins, often for the outer cladding. The US five-cent
coin (currently called a 'nickel') consists of 75% copper and 25%
nickel in homogeneous composition. Prior to the introduction of
cupronickel, which was widely adopted by countries in the latter half
of the 20th century, alloys of copper and silver were also used, with
the United States using an alloy of 90% silver and 10% copper until
1965, when circulating silver was removed from all coins with the
exception of the half dollar--these were debased to an alloy of 40%
silver and 60% copper between 1965 and 1970. The alloy of 90% copper
and 10% nickel, remarkable for its resistance to corrosion, is used
for various objects exposed to seawater, though it is vulnerable to
the sulfides sometimes found in polluted harbors and estuaries. Alloys
of copper with aluminium (about 7%) have a golden color and are used
in decorations. 'Shakudō' is a Japanese decorative alloy of copper
containing a low percentage of gold, typically 4-10%, that can be
patinated to a dark blue or black color.
Compounds
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Copper forms a rich variety of compounds, usually with oxidation
states +1 and +2, which are often called 'cuprous' and 'cupric',
respectively. Copper compounds promote or catalyse numerous chemical
and biological processes.
Binary compounds
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As with other elements, the simplest compounds of copper are binary
compounds, i.e. those containing only two elements, the principal
examples being oxides, sulfides, and halides. Both cuprous and cupric
oxides are known. Among the numerous copper sulfides, important
examples include copper(I) sulfide () and copper monosulfide ().
Cuprous halides with fluorine, chlorine, bromine, and iodine are
known, as are cupric halides with fluorine, chlorine, and bromine.
Attempts to prepare copper(II) iodide yield only copper(I) iodide and
iodine.
:2 Cu2+ + 4 I− → 2 CuI + I2
Coordination chemistry
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Copper forms coordination complexes with ligands. In aqueous solution,
copper(II) exists as . This complex exhibits the fastest water
exchange rate (speed of water ligands attaching and detaching) for any
transition metal aquo complex. Adding aqueous sodium hydroxide causes
the precipitation of light blue solid copper(II) hydroxide. A
simplified equation is: Pourbaix diagram for copper in uncomplexed
media (anions other than OH- not considered). Ion concentration 0.001
m (mol/kg water). Temperature 25 °C.
:Cu2+ + 2 OH− → Cu(OH)2
Aqueous ammonia results in the same precipitate. Upon adding excess
ammonia, the precipitate dissolves, forming tetraamminecopper(II):
: + 4 NH3 → + 2 H2O + 2 OH−
Many other oxyanions form complexes; these include copper(II) acetate,
copper(II) nitrate, and copper(II) carbonate. Copper(II) sulfate forms
a blue crystalline pentahydrate, the most familiar copper compound in
the laboratory. It is used in a fungicide called the Bordeaux mixture.
Polyols, compounds containing more than one alcohol functional group,
generally interact with cupric salts. For example, copper salts are
used to test for reducing sugars. Specifically, using Benedict's
reagent and Fehling's solution the presence of the sugar is signaled
by a color change from blue Cu(II) to reddish copper(I) oxide.
Schweizer's reagent and related complexes with ethylenediamine and
other amines dissolve cellulose. Amino acids such as cystine form very
stable chelate complexes with copper(II) including in the form of
metal-organic biohybrids (MOBs). Many wet-chemical tests for copper
ions exist, one involving potassium ferricyanide, which gives a
red-brown precipitate with copper(II) salts.
Organocopper chemistry
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Compounds that contain a carbon-copper bond are known as organocopper
compounds. They are very reactive towards oxygen to form copper(I)
oxide and have many uses in chemistry. They are synthesized by
treating copper(I) compounds with Grignard reagents, terminal alkynes
or organolithium reagents; in particular, the last reaction described
produces a Gilman reagent. These can undergo substitution with alkyl
halides to form coupling products; as such, they are important in the
field of organic synthesis. Copper(I) acetylide is highly
shock-sensitive but is an intermediate in reactions such as the
Cadiot-Chodkiewicz coupling and the Sonogashira coupling. Conjugate
addition to enones and carbocupration of alkynes can also be achieved
with organocopper compounds. Copper(I) forms a variety of weak
complexes with alkenes and carbon monoxide, especially in the presence
of amine ligands.
Copper(III) and copper(IV)
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Copper(III) is most often found in oxides. A simple example is
potassium cuprate, KCuO2, a blue-black solid. The most extensively
studied copper(III) compounds are the cuprate superconductors. Yttrium
barium copper oxide (YBa2Cu3O7) consists of both Cu(II) and Cu(III)
centres. Like oxide, fluoride is a highly basic anion and is known to
stabilize metal ions in high oxidation states. Both copper(III) and
even copper(IV) fluorides are known, K3CuF6 and Cs2CuF6, respectively.
Some copper proteins form oxo complexes, which, in extensively studied
synthetic analog systems, feature copper(III). With tetrapeptides,
purple-colored copper(III) complexes are stabilized by the
deprotonated amide ligands.
Complexes of copper(III) are also found as intermediates in reactions
of organocopper compounds, for example in the Kharasch-Sosnovsky
reaction.
Biochemistry
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The biological role for copper commenced with the appearance of oxygen
in Earth's atmosphere.
Copper proteins have diverse roles in biological electron transport
and oxygen transportation, processes that exploit the easy
interconversion of Cu(I) and Cu(II). electronic-book electronic-
Copper is essential in the aerobic respiration of all eukaryotes. In
mitochondria, it is found in cytochrome c oxidase, which is the last
protein in oxidative phosphorylation which stores energy in ATP. The
copper atoms are alternatively reduced and oxidized during the
electron transfer to oxygen. Copper is also found in many superoxide
dismutases, proteins that catalyze the decomposition of superoxides by
converting it (by disproportionation) to oxygen and hydrogen peroxide:
* Cu2+-SOD + O2− → Cu+-SOD + O2 (reduction of copper; oxidation of
superoxide)
* Cu+-SOD + O2− + 2H+ → Cu2+-SOD + H2O2 (oxidation of copper;
reduction of superoxide)
The protein hemocyanin is the oxygen carrier in most mollusks and some
arthropods such as the horseshoe crab ('Limulus polyphemus'). Because
hemocyanin is blue, these organisms have blue blood rather than the
red blood of iron-based hemoglobin. Structurally related to hemocyanin
are the laccases and tyrosinases. Instead of reversibly binding
oxygen, these proteins hydroxylate substrates, illustrated by their
role in the formation of lacquers.
Several copper proteins, such as the "blue copper proteins", do not
interact directly with substrates; hence they are not enzymes. These
proteins relay electrons by the process called electron transfer.
A unique tetranuclear copper center has been found in nitrous-oxide
reductase.
Copper levels are closely regulated in both prokaryotic and eukaryotic
cells to balance critical physiological need but avoid toxicity.
Scientific study of the processes that control copper levels have led
to the discovery of numerous compounds with medical application. For
example, compounds which were developed for treatment of Wilson's
disease have been investigated for use in cancer therapy.
Bioremediation
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'Chromobacterium violaceum' and 'Pseudomonas fluorescens' can both
mobilize solid copper as a cyanide compound. The ericoid mycorrhizal
fungi associated with 'Calluna', 'Erica' and 'Vaccinium' can grow in
metalliferous soils containing copper. The ectomycorrhizal fungus
'Suillus luteus' protects young pine trees from copper toxicity. A
sample of the fungus 'Aspergillus niger' was found growing from gold
mining solution and was found to contain cyano complexes of such
metals as gold, silver, copper, iron, and zinc. The fungus also plays
a role in the solubilization of heavy metal sulfides.
Nutrition
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Copper is an essential trace element in plants and animals, but not
all microorganisms. The human body contains copper at a level of about
1.4 to 2.1 mg per kg of body mass.
Absorption
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Copper is absorbed in the gut, then transported to the liver bound to
albumin. After processing in the liver, copper is distributed to other
tissues in a second phase, which involves the protein ceruloplasmin,
carrying the majority of copper in blood. Ceruloplasmin also carries
the copper that is excreted in milk, and is particularly well-absorbed
as a copper source. Copper in the body normally undergoes
enterohepatic circulation (about 5 mg a day, vs. about 1 mg per day
absorbed in the diet and excreted from the body), and the body is able
to excrete some excess copper, if needed, via bile, which carries some
copper out of the liver that is not then reabsorbed by the intestine.
Dietary recommendations
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The U.S. Institute of Medicine updated the estimated average
requirements (EARs) and recommended dietary allowances (RDAs) for
copper in 2001. If there is not sufficient information to establish
EARs and RDAs, an estimate designated Adequate Intake (AI) is used
instead. The AIs for copper are: 200 μg of copper for 0-6-month-old
males and females, and 220 μg of copper for 7-12-month-old males and
females. For both sexes, the RDAs for copper are: 340 μg of copper for
1-3 years old, 440 μg of copper for 4-8 years old, 700 μg of copper
for 9-13 years old, 890 μg of copper for 14-18 years old and 900 μg of
copper for ages 19 years and older. For pregnancy, 1,000 μg. For
lactation, 1,300 μg. As for safety, the Institute of Medicine also
sets tolerable upper intake levels (ULs) for vitamins and minerals
when evidence is sufficient. In the case of copper, the UL is set at
10 mg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as
Dietary Reference Intakes.
The European Food Safety Authority (EFSA) refers to the collective set
of information as Dietary Reference Values, with Population Reference
Intake (PRI) instead of RDA, and Average Requirement instead of EAR.
AI and UL are defined the same as in the United States. For women and
men ages 18 and older, the AIs are set at 1.3 and 1.6 mg/day,
respectively. AIs for pregnancy and lactation is 1.5 mg/day. For
children ages 1-17 years, the AIs increase with age from 0.7 to 1.3
mg/day. These AIs are higher than the U.S. RDAs. The European Food
Safety Authority reviewed the same safety question and set its UL at 5
mg/day, which is half the U.S. value.
For U.S. food and dietary supplement labeling purposes, the amount in
a serving is expressed as a percent of Daily Value (%DV). In 2019,
100% of the Daily Value was revised to 0.9 mg to bring it into
agreement with the RDA.
Deficiency
============
Because of its role in facilitating iron uptake, copper deficiency can
produce anemia-like symptoms, neutropenia, bone abnormalities,
hypopigmentation, impaired growth, increased incidence of infections,
osteoporosis, hyperthyroidism, and abnormalities in glucose and
cholesterol metabolism. Conversely, Wilson's disease is genetic
disease that causes an accumulation of copper in body tissues.
A minimum dietary value for healthy growth in European rabbits has
been reported to be at least 3 ppm in the diet. However, higher
concentrations of copper (100 ppm, 200 ppm, or 500 ppm) in the diet of
rabbits may favorably influence feed conversion efficiency, growth
rates, and carcass dressing percentages.
Severe deficiency can be found by testing for low plasma or serum
copper levels, low ceruloplasmin, and low red blood cell superoxide
dismutase levels; these are not sensitive to marginal copper status.
The "cytochrome c oxidase activity of leucocytes and platelets" has
been stated as another factor in deficiency, but the results have not
been confirmed by replication.
Toxicity
==========
Chronic copper toxicity does not normally occur in humans because of
transport systems that regulate absorption and excretion. No retention
of copper is expected to occur at the 5mg/day level.
Research has shown a link between copper level regulation in the body
and several neurological diseases especially Alzheimer's disease. The
studies suggest the issue is an age-related breakdown of internal
regulation mechanism rather than an exposure toxicity.
Gram quantities of various copper salts have been taken in suicide
attempts and produced acute copper toxicity in humans resulting in
irreversible liver failure.
Autosomal recessive mutations in copper transport proteins also cause
regulation failure, leading to Wilson's disease with copper
accumulation, cirrhosis of the liver, and psychiatric symptoms.
Human exposure
================
In the US, the Occupational Safety and Health Administration (OSHA)
has designated a permissible exposure limit (PEL) for copper dust and
fumes in the workplace as a time-weighted average (TWA) of 1 mg/m3.
The National Institute for Occupational Safety and Health (NIOSH) has
set a recommended exposure limit (REL) of 1 mg/m3, time-weighted
average. The IDLH (immediately dangerous to life and health) value is
100 mg/m3.
Copper is a constituent of tobacco smoke. The tobacco plant readily
absorbs and accumulates heavy metals, such as copper from the
surrounding soil into its leaves. These are readily absorbed into the
user's body following smoke inhalation. The health implications are
not clear.
Copper Age
============
Copper occurs naturally as native metallic copper and was known to
some of the oldest civilizations on record. The history of copper use
dates to 9000 BC in the Middle East; a copper pendant was found in
northern Iraq that dates to 8700 BC. Evidence suggests that gold and
meteoric iron (but not smelted iron) were the only metals used by
humans before copper. The history of copper metallurgy is thought to
follow this sequence: first, cold working of native copper, then
annealing, smelting, and, finally, lost-wax casting. In southeastern
Anatolia, all four of these techniques appear more or less
simultaneously at the beginning of the Neolithic .
Copper smelting was independently invented in different places. The
earliest evidence of lost-wax casting copper comes from an amulet
found in Mehrgarh, Pakistan, and is dated to 4000 BC. Investment
casting was invented in 4500-4000 BC in Southeast Asia Smelting was
probably discovered in China before 2800 BC, in Central America around
600 AD, and in West Africa about the 9th or 10th century AD. Carbon
dating has established mining at Alderley Edge in Cheshire, UK, at
2280 to 1890 BC.
Ötzi the Iceman, a male dated from 3300 to 3200 BC, was found with an
axe with a copper head 99.7% pure; high levels of arsenic in his hair
suggest an involvement in copper smelting. Experience with copper has
assisted the development of other metals; in particular, copper
smelting likely led to the discovery of iron smelting.
Production in the Old Copper Complex in Michigan and Wisconsin is
dated between 6500 and 3000 BC. A copper spearpoint found in Wisconsin
has been dated to 6500 BC. Copper usage by the indigenous peoples of
the Old Copper Complex from the Great Lakes region of North America
has been radiometrically dated to as far back as 7500 BC. Indigenous
peoples of North America around the Great Lakes may have also been
mining copper during this time, making it one of the oldest known
examples of copper extraction in the world. There is evidence from
prehistoric lead pollution from lakes in Michigan that people in the
region began mining copper . Evidence suggests that utilitarian copper
objects fell increasingly out of use in the Old Copper Complex of
North America during the Bronze Age and a shift towards an increased
production of ornamental copper objects occurred.
Bronze Age
============
Natural bronze, a type of copper made from ores rich in silicon,
arsenic, and (rarely) tin, came into general use in the Balkans around
5500 BC. Alloying copper with tin to make bronze was first practiced
about 4000 years after the discovery of copper smelting, and about
2000 years after "natural bronze" had come into general use. Bronze
artifacts from the Vinča culture date to 4500 BC. Sumerian and
Egyptian artifacts of copper and bronze alloys date to 3000 BC.
Egyptian Blue, or cuprorivaite (calcium copper silicate) is a
synthetic pigment that contains copper and started being used in
ancient Egypt around 3250 BC. The manufacturing process of Egyptian
blue was known to the Romans, but by the fourth century AD the pigment
fell out of use and the secret to its manufacturing process became
lost. The Roman Vitruvius said in the first century BC that the blue
pigment was made from copper minerals or bronze, lime, and a flux like
natron and this basic recipe has been confirmed in modern times.
The Bronze Age began in Southeastern Europe around 3700-3300 BC, in
Northwestern Europe about 2500 BC. It ended with the beginning of the
Iron Age, 2000-1000 BC in the Near East, and 600 BC in Northern
Europe. The transition between the Neolithic period and the Bronze Age
was formerly termed the Chalcolithic period (copper-stone), when
copper tools were used with stone tools. The term has gradually fallen
out of favor because in some parts of the world, the Chalcolithic and
Neolithic are coterminous at both ends. Brass, an alloy of copper and
zinc, is of much more recent origin. It was known to the Greeks, but
became a significant supplement to bronze during the Roman Empire.
Ancient and post-classical
============================
In Greece, copper was known by the name (χαλκός). It was an important
resource for the Romans, Greeks and other ancient peoples. In Roman
times, it was known as 'aes Cyprium', being the generic Latin term
for copper alloys and 'Cyprium' from Cyprus, where much copper was
mined. The phrase was simplified to 'cuprum', hence the English
'copper'. Aphrodite (Venus in Rome) represented copper in mythology
and alchemy because of its lustrous beauty and its ancient use in
producing mirrors; Cyprus, the source of copper, was sacred to the
goddess. The seven heavenly bodies known to the ancients were
associated with the seven metals known in antiquity, and Venus was
assigned to copper, both because of the connection to the goddess and
because Venus was the brightest heavenly body after the Sun and Moon
and so corresponded to the most lustrous and desirable metal after
gold and silver.
Copper was first mined in ancient Britain as early as 2100 BC. Mining
at the largest of these mines, the Great Orme, continued into the late
Bronze Age. Mining seems to have been largely restricted to supergene
ores, which were easier to smelt. The rich copper deposits of Cornwall
seem to have been largely untouched, in spite of extensive tin mining
in the region, for reasons likely social and political rather than
technological.
Copper was the most extensively used metal among natives of North
America, with evidence for use going back 7000 years.
Native copper is known to have been extracted from sites on Isle
Royale with primitive stone tools between 800 and 1600 AD. Copper,
probably from pure nuggets found in the Great Lakes area, was worked
by repeated hammering and annealing in the North American city of
Cahokia (near modern day Missouri) around 1000-1300 AD. There are
several exquisite copper plates, known as the Mississippian copper
plates that have been found in North America in the area around
Cahokia dating from this time period (1000-1300 AD).
In South America a copper mask dated to 1000 BC found in the
Argentinian Andes is the oldest known copper artifact discovered in
the Andes. Peru has been considered the origin for early copper
metallurgy in pre-Columbian America, but the copper mask from
Argentina suggests that the Cajón del Maipo of the southern Andes was
another important center for early copper workings in South America.
Copper metallurgy in Peru dates to around 500 BC with larger scale
production beginning around 900 AD as part of the rise of the Sican
culture in northern Peru. The production continued through a series of
conquests by the Chimor and Inca cultures, ending with the Spanish
conquest in 1532.
The cultural role of copper has been important, particularly in
currency. Romans in the 6th through 3rd centuries BC used copper lumps
as money. At first, the copper itself was valued, but gradually the
shape and look of the copper became more important. Julius Caesar had
his own coins made from brass, while Octavianus Augustus Caesar's
coins were made from Cu-Pb-Sn alloys. With an estimated annual output
of around 15,000 t, Roman copper mining and smelting activities
reached a scale unsurpassed until the time of the Industrial
Revolution; the provinces most intensely mined were those of Hispania,
Cyprus and in Central Europe.
The gates of the Temple of Jerusalem used Corinthian bronze, a copper,
silver, and gold alloy treated with depletion gilding which
successively removes oxidized copper to create a gold surface coat.
The process was most prevalent in Alexandria, where alchemy, inspired
by the chemical treatment resulting in gold appearance, is thought to
have begun.
Modern
========
The Great Copper Mountain was a mine in Falun, Sweden, that operated
from the 10th century to 1992. It satisfied two-thirds of Europe's
copper consumption in the 17th century and helped fund many of
Sweden's wars during that time. It was referred to as the nation's
treasury; Sweden had a copper backed currency.
Copper is used in roofing, currency, and for photographic technology
known as the daguerreotype. Copper was used in Renaissance sculpture,
and was used to construct the Statue of Liberty; copper continues to
be used in construction of various types. Copper plating and copper
sheathing were widely used to protect the under-water hulls of ships,
a technique pioneered by the British Admiralty in the 18th century.
The Norddeutsche Affinerie in Hamburg was the first modern
electroplating plant, starting its production in 1876.
During the rise in demand for copper for the Age of Electricity, from
the 1880s until the Great Depression of the 1930s, the United States
produced one third to half the world's newly mined copper. Major
districts included the Keweenaw district of northern Michigan,
primarily native copper deposits, which was eclipsed by the vast
sulphide deposits of Butte, Montana, in the late 1880s, which itself
was eclipsed by porphyry deposits of the Southwest United States,
especially at Bingham Canyon, Utah, and Morenci, Arizona. Introduction
of open pit steam shovel mining and innovations in smelting, refining,
flotation concentration and other processing steps led to mass
production. Early in the twentieth century, Arizona ranked first,
followed by Montana, then Utah and Michigan.
Flash smelting was developed by Outokumpu in Finland and first applied
at Harjavalta in 1949; the energy-efficient process accounts for 50%
of the world's primary copper production.
The Intergovernmental Council of Copper Exporting Countries, formed in
1967 by Chile, Peru, Zaire and Zambia, operated in the copper market
as OPEC does in oil, though it never achieved the same influence,
particularly because the second-largest producer, the United States,
was never a member; it was dissolved in 1988.
In 2008, China became the world's largest importer of copper and has
continued to be as of at least 2023.
Applications
======================================================================
The major applications of copper are electrical wire (60%), roofing
and plumbing (20%), and industrial machinery (15%). Copper is used
mostly as a pure metal, but when greater hardness is required, it is
put into such alloys as brass and bronze (5% of total use). For more
than two centuries, copper paint has been used on boat hulls to
control the growth of plants and shellfish. A small part of the copper
supply is used for nutritional supplements and fungicides in
agriculture. Pure copper's ductility, weakness and high friction
between copper chips and cutting tools makes machining of copper
difficult; alloys are preferred for good machinability.
Wire and cable
================
Despite competition from other materials, copper remains the preferred
electrical conductor in nearly all categories of electrical wiring
except overhead electric power transmission where aluminium is often
preferred. Copper wire is used in power generation, power
transmission, power distribution, telecommunications, electronics
circuitry, and countless types of electrical equipment. Electrical
wiring is the most important market for the copper industry. This
includes structural power wiring, power distribution cable, appliance
wire, communications cable, automotive wire and cable, and magnet
wire. Roughly half of all copper mined is used for electrical wire and
cable conductors. Many electrical devices rely on copper wiring
because of its multitude of beneficial properties, such as its high
electrical conductivity, tensile strength, ductility, creep
(deformation) resistance, corrosion resistance, low thermal expansion,
high thermal conductivity, ease of soldering, and ease of
installation.
For a short period from the late 1960s to the late 1970s, copper
wiring was replaced by aluminium wiring in many housing construction
projects in America but improper design resulted in fire hazards. The
safety issues have since been solved by use of larger sizes of
aluminium wire (#8AWG and up), and properly designed aluminium wiring
is still being installed in place of copper. For example, the Airbus
A380 uses aluminum wire in place of copper wire for electrical power
transmission.
Electronics and related devices
=================================
Integrated circuits and printed circuit boards increasingly feature
copper in place of aluminium because of its superior electrical
conductivity; heat sinks and heat exchangers use copper because of its
superior heat dissipation properties. Electromagnets, vacuum tubes,
cathode-ray tubes, and magnetrons in microwave ovens use copper, as do
waveguides for microwave radiation.
Electric motors
=================
Copper's superior conductivity enhances the efficiency of electrical
motors. This is important because motors and motor-driven systems
account for 43-46% of all global electricity consumption and 69% of
all electricity used by industry. Increasing the mass and cross
section of copper in a coil increases the efficiency of the motor.
Copper motor rotors, a new technology designed for motor applications
where energy savings are prime design objectives, are enabling
general-purpose induction motors to meet and exceed National
Electrical Manufacturers Association (NEMA) premium efficiency
standards.
Architecture
==============
Copper has been used since ancient times as a durable, corrosion
resistant, and weatherproof architectural material. Roofs, flashings,
rain gutters, downspouts, domes, spires, vaults, and doors have been
made from copper for hundreds or thousands of years. Copper's
architectural use has been expanded in modern times to include
interior and exterior wall cladding, building expansion joints, radio
frequency shielding, and antimicrobial and decorative indoor products
such as attractive handrails, bathroom fixtures, and counter tops.
Some of copper's other important benefits as an architectural material
include low thermal movement, light weight, lightning protection, and
recyclability.
The metal's distinctive natural green patina has long been coveted by
architects and designers. The final patina is a particularly durable
layer that is highly resistant to atmospheric corrosion, thereby
protecting the underlying metal against further weathering. It can be
a mixture of carbonate and sulfate compounds in various amounts,
depending upon environmental conditions such as sulfur-containing acid
rain. Architectural copper and its alloys can also be 'finished' to
take on a particular look, feel, or color. Finishes include mechanical
surface treatments, chemical coloring, and coatings.
Copper has excellent brazing and soldering properties and can be
welded; the best results are obtained with gas metal arc welding.
Antibiofouling
================
Copper is biostatic, meaning bacteria and many other forms of life
will not grow on it. For this reason it has long been used to line
parts of ships to protect against barnacles and mussels. It was
originally used pure, but has since been superseded by Muntz metal and
copper-based paint. Similarly, as discussed in copper alloys in
aquaculture, copper alloys have become important netting materials in
the aquaculture industry because they are antimicrobial and prevent
biofouling, even in extreme conditions and have strong structural and
corrosion-resistant properties in marine environments.
Antimicrobial
===============
Copper-alloy touch surfaces have natural properties that destroy a
wide range of microorganisms (e.g., 'E. coli' O157:H7,
methicillin-resistant 'Staphylococcus aureus' (MRSA),
'Staphylococcus', 'Clostridium difficile', influenza A virus,
adenovirus, SARS-CoV-2, and fungi). Indians have been using copper
vessels since ancient times for storing water, even before modern
science realized its antimicrobial properties. Some copper alloys were
proven to kill more than 99.9% of disease-causing bacteria within just
two hours when cleaned regularly. The United States Environmental
Protection Agency (EPA) has approved the registrations of these copper
alloys as "antimicrobial materials with public health benefits"; that
approval allows manufacturers to make legal claims to the public
health benefits of products made of registered alloys. In addition,
the EPA has approved a long list of antimicrobial copper products made
from these alloys, such as bedrails, handrails, over-bed tables,
sinks, faucets, door knobs, toilet hardware, computer keyboards,
health club equipment, and shopping cart handles. Copper doorknobs are
used by hospitals to reduce the transfer of disease, and Legionnaires'
disease is suppressed by copper tubing in plumbing systems.
Antimicrobial copper alloy products are now being installed in
healthcare facilities in the U.K., Ireland, Japan, Korea, France,
Denmark, and Brazil, as well as being called for in the US, and in the
subway transit system in Santiago, Chile, where copper-zinc alloy
handrails were installed in some 30 stations between 2011 and 2014.
Textile fibers can be blended with copper to create antimicrobial
protective fabrics.
Folk medicine
===============
Copper is commonly used in jewelry, and according to some folklore,
copper bracelets relieve arthritis symptoms. In one trial for
osteoarthritis and one trial for rheumatoid arthritis, no differences
were found between copper bracelet and control (non-copper) bracelet.
No evidence shows that copper can be absorbed through the skin.
See also
======================================================================
* Copper in renewable energy
* Copper nanoparticle
* Erosion corrosion of copper water tubes
** Cold water pitting of copper tube
* List of countries by copper production
* Metal theft
** Operation Tremor
* Anaconda Copper
* Antofagasta PLC
* Codelco
* El Boleo mine
* Grasberg mine
* Copper foil
Notes
======================================================================
Pourbaix diagrams for copper |200px |200px |200px |200px
|in pure water, or acidic or alkali conditions. Copper in neutral
water is more noble than hydrogen. |in water containing sulfide |in 10
M ammonia solution |in a chloride solution
Further reading
======================================================================
*
*
* Current Medicinal Chemistry, Volume 12, Number 10, May 2005, pp.
1161-1208(48) Metals, Toxicity and Oxidative Stress
*
* [
http://www.memsnet.org/material/coppercubulk/ Material: Copper
(Cu), bulk], MEMS and Nanotechnology Clearinghouse.
*
External links
======================================================================
* [
https://www.copper.org/education/history/timeline/ Copper
Timeline], an interactive history.
* [
http://www.periodicvideos.com/videos/029.htm Copper] at 'The
Periodic Table of Videos' (University of Nottingham)
*
[
https://www.dcceew.gov.au/environment/protection/npi/substances/fact-sheets/copper-and-compounds
Copper and compounds fact sheet] from the National Pollutant Inventory
of Australia
* [
https://copperalliance.org/ International Copper Association and
the Copper Alliance], a business interest group
* [
https://www.copper.org/ Copper.org] - official website of the
Copper Development Association, a North American industry association
with an extensive site of properties and uses of copper
*
[
https://www.indexmundi.com/commodities/?commodity=copper&months=300
Price history] of LME Copper, according to the IMF
License
=========
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License URL:
http://creativecommons.org/licenses/by-sa/3.0/
Original Article:
http://en.wikipedia.org/wiki/Copper
