Extraction of Copper from Copper Pyrite

Copper occurs both in native state as well as in combined state. The chief ore of copper are:

  • Copper Pyrite (CuFeS2)
  • Cuprite (Cu2O)
  •  Cupper Glance (Cu2S)
  • Malachite [CuCO3.Cu(OH) 2]

 

Extraction of copper:

Copper is extracted from is chief ore, copper pyrite. The various steps involved in the extractions are:

a. Crushing and concentration:

The ore is crushed in jaw crusher and powdered in ball mills. It is concentrated by froth floatation process. In this method, powdered ore is mixed with water and pine oil in a tank. The mixture is agitated with compressed air. The ore particles are preferentially wetted by oil and thus rise to the surface in the form of froth from where it is skimmed off. The earthy and siliceous impurities are preferentially wetted by water and sink at the buttom of the tank.

Froth flotation process

b. Roasting:

The concentrated ore is heated strongly in presence of excess of air in a reverberatory furnace. As a result, the impurities of sulphur, phosphorous, antimony are removed in the form of volatile oxide.
$$\ce{S + O2->SO2 ^ }$$
$$\ce{P4 + 5O2->2P2O5 ^ }$$
$$\ce{4As + 3O2->2As2O3 ^ }$$
$$\ce{2Sb + 3O2->2Sb2O3 ^ }$$
During roasting process, copper pyrite is converted into the mixture of ferrous sulphide and copper sulphide which are partially oxidized.
$$\ce{2CuFeS2 + O2->[\Delta]Cu2S + 2FeS + O2}$$
$$\ce{2Cu2S + 3O2->[\Delta]2Cu2O + 2SO2}$$
$$\ce{2FeS + 3O2->[\Delta]2FeO + 2SO2}$$

c. Smelting:

Smelting of copper in Blast furnace

The roasted ore is mixed with sand, flux and coke and then heated strongly in blast furnace. The blast furnace is lined inside with fire bricks. A blast of hot air is introduced from the lower part of the furnace. As a result of smelting, following reaction occurs.

$$\ce{FeS + O2->[\Delta]FeO + SO2}$$
$$\ce{FeO + SiO2->[\Delta]\underset{Slag}{FeSiO3}}$$A part of cuprous sulphide is also oxidized into cupric oxide.
$$\ce{Cu2S + O2->[\Delta]Cu2O + SO2}$$
Any cuprous oxide formed above combines with ferrous sulphide to give black colored cuprous oxide and ferrous oxide.
$$\ce{Cu2O + FeS->Cu2S + FeO}$$
The ferric oxide thus formed combines with silicon dioxide to give slag.
$$\ce{FeO + SiO2->$\underset{\text{Slag}}{\ce{FeSiO3}}$}$$

The molten mette is collected for the futher purification. The poured 50% molten matte is called copper mate.

d. Bessimerization:

Bessemer’s convertor

The molten matte is mixed with little silica and converted into a Bessemer converter. The blast of hot air is blown through the side of converter.
$$\ce{2FeS + 3O2->[\Delta]2FeO + 2SO2}$$
$$\ce{FeO + SiO2->[\Delta]\underset{Slag}{FeSiO3}}$$

The slag is removed and air blast is blown continously. Cu2S is then oxidized to Cu2 O and gradually gives copper.
$$\ce{2Cu2S + 3O2->2Cu2O + SO2 ^ }$$
$$\ce{2Cu2O + Cu2S->6Cu + SO2 ^ }$$

Remember: Copper loses SO2 gas in the form of bubbles on cooling. Hence, there appears some blisters on the surface of the copper. This copper is known as blister copper. This copper is 98% pure.

Purification:

Purification of copper can be done by electrolytic refining and polling or fire refining. In polling, impure silver is stirred with poles of green wood. Hydrocarbons present in the silver reduces the oxide impurities as thereby acting as a reducing agent. This copper is called tough cake copper, which is 99% pure. The following reaction occurs in polling.
$$\ce{3Cu2O + CH4->[\Delta]6Cu + 2H2O + CO}$$

Remember: Here methane in the reactant side is obtained from the green wood.

e. Electro refining: In this process, impure copper is made anode and the sheet of pure copper is made cathode. In this process copper metal is deposited on the cathode side and the impurities are collected below the anode called as anode mud. The copper thus obtained is 99.99% pure.
The following reaction takes place:
$$\ce{ CuSO4Cu^++ + SO4^–}$$
At anode: $\ce{Cu – 2e^- ->Cu^++}$ (Oxidation)
At cathode: $\ce{Cu^++ -2e^- ->Cu}$ (Reduction)

Electro refining

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5 Responses to “Extraction of Copper from Copper Pyrite”

  1. Bhagwati Shrestha

    Pretty Good!!!

  2. Devanand Chaudhary

    so helpful!
    thanks.

  3. Deepesh

    Very good

  4. Mayank

    GOOD!!!!!!!

  5. Sachin

    Thanks…!!!!!