Notes on the Occurrence and Principles of Extraction of Copper

Copper, with the symbol Cu and atomic number 29, is a chemical element. It is a ductile, soft, malleable metal with excellent thermal and electrical conductivity. A reddish-orange colour appears on a freshly exposed pure copper surface. The melting point of copper is 1083 °C (1981 °F), and the boiling point is 2567 °C (4653 °F). Copper belongs to the d-block elements known as the transition elements and is present in the 11th group of the modern periodic table.

Discovery of copper

Humans have used copper for almost 10000 years ago. Ancient copper jewellery and tools have been found in Mesopotamia (now Iraq, Iran and Syria) and Egypt. Copper was most likely discovered on the Indian subcontinent as well. There are records to suggest that Egyptians used copper chisels to carve the stone parts of their pyramids around 8000 BC.

The majority of the copper mined today comes from copper sulphide ores, which look like black rocks. Copper oxide ores are usually green or blue.

Native copper (an uncombined form of copper) is also found in considerably lesser levels and appears red or salmon-coloured.

Extraction of copper

Chalcopyrite (CuFeS2), commonly known as copper pyrite or copper iron sulphide, is the most common ore utilised in copper extraction.

Copper extraction from Copper Pyrites

The extraction of copper from copper pyrites is done using the following methods. 

1) Concentration of ore: In this process, the ore is crushed to a fine powder. Then, the mineral is separated from the other particles using the froth flotation method. This method separates hydrophobic from hydrophilic materials to extract the mineral ore by increasing its concentration.

2) Roasting: In a reverberatory furnace, concentrated ore and SiO2 are heated in excess of air. 

(Cu₂S + FeS + FeS₂)

2CuFeS₂ + O₂ → Cu₂S + 2FeS + SO₂1

2FeS + 30₂  → 2FeO +2SO₂↑ (Major oxidation)

2Cu₂S + 30₂ → 2Cu₂O +2SO₂↑ (Minor oxidation)

Cu₂O + FeS → Cu₂S + FeO

Reverberatory furnace:

S + O₂ → SO₂↑ ; 4As + SO₂ → 2As2O3↑ ; 4Sd + 3O₂ → 2Sb2O3↑    

Volatile impurities are removed in this step. The sulphide is heated in the presence of air in a free supply of air below m.p. Sulphur, phosphorus, arsenic and antimony impurities are transformed to their corresponding volatile oxides and subsequently eliminated.

(C) Slag formation: Ore that has been roasted is mixed with sand before being burned in a furnace.

FeO + SIO₂(flux) → FeSiO3(slag)

Slag available in the upper layer is removed. The underlying layer, which is mostly cuprous sulphide, Cu2S (98%), with a small quantity of iron sulphide, FeS (2%), is referred to as matte.

(D) Bessemerisation: This is the process of blowing air into a molten copper mat that has been placed in a Bessemer converter. The remaining products, including FeS, are oxidised and removed as slag in the last step of smelting (FeSiO3)

2FeS +30₂ → 2FeO +2SO₂

FeO + SiO₂ → fuse, FeSiO3(slag)

2Cu2S + 30₂  → 2Cu2O + 2SO2 (partial roasting)

Cu2S  + 2Cu2S  →  6Cu +SO2 (self reduction)

The Impure copper that has a blister-like appearance is referred to as blister copper.

(E) Poling: To convert any copper oxide contaminant into Cu, molten Cu is agitated with green wood poles.

Properties of copper

1. Patina. A green coating of copper sulphate forms on the metal’s surface as a result of corrosion; yet, this film is protective and prevents the metal from deteriorating further.
2. Corrosion resistance. After being buried for millennia, copper alloys have been unearthed in near-perfect form, demonstrating that this metal is very corrosion resistant.
3. Malleability and ductility. Copper is highly malleable (can be beaten into sheets) and ductile (can be drawn into thin wires). Overall, it is easy to handle for mechanical purposes.
4. Antibacterial. Antimicrobials, fungicides and wood preservatives are all made with copper compounds. This metal’s hygienic properties make it helpful in inhibiting bacterial growth.
5. Strength. Copper’s strength is one of its most valuable mechanical qualities. Copper, like its alloys, is a strong metal that does not fracture or become brittle when exposed to temperatures below 0 degree.
6. Non-magnetic. Because it is a non-ferrous metal, it can be used in military applications.
7. Easy to alloy. Copper’s capability to easily alloy with other metals such as zinc, tin, and nickel is another feature that makes it so valuable.
8. Conductivity. Due to its high electrical and thermal conductivity, copper is widely used in electrical appliances, electric wires and heat exchangers.

Uses of copper

Copper has numerous uses. Some of them are:

• It is utilised for home and commercial wiring and electrical power distribution.
• In electric motors and generators, it is used in windings.
• Automotive wire harnesses, starters and alternators all use copper.
• Because of its corrosion resistance, copper water pipes and tubes are used in plumbing.
• Copper is used in cooling tubes in radiators and heat exchangers because of its high thermal conductivity. It is also utilised as a roofing and other covering material due to its corrosion resistance and aesthetic appeal. 
• Copper sheets are used in sculptures (e.g., the Statue of Liberty in New York City).
• Copper is used to make hundreds of alloys with other metals to make brass and bronze for a variety of industrial and commercial applications that benefit from copper’s fundamental properties of electrical conductivity, thermal conductivity, and corrosion resistance. Alloys improve the hardness, strength, corrosion resistance, and softening resistance of copper.
• Copper alloy electrodes are used for welding, most notably spot welding in auto assembly, where steel is welded using electric current to quickly and effectively put the structure of the automobile together.

Conclusion

In this article we have discussed all things about copper starting from its discovery, properties, extraction process and its uses in our everyday life. We can conclude that copper is a very important element in our everyday life with a wide range of applications.