Describe how copper is extracted from one of its ores

Extraction of copper from copper pyrites

1. Concentration of the ore by floatation method

The finely pulverized ore is mixed with water, containing ‘frothing’ agent (s).

Air is blown into the mixture, froth is produced and the earthly material is “wetted” and sinks.

The sulphide ore particles, rise to the surface in the froth and are skimmed off the surface.

Anti- frothing agent  is added to break up the froth, the concentrated ore is filtered and dried.

 

2. Roasting

The ore is then roasted in a limited supply of air to convert the iron into iron (II) oxide.

2CuFeS₂ (s) + 4O₂ (g)  → Cu₂S (s) + 3SO₂ (g) + 2FeO (s)

 

3. Addition of SiO₂ to remove impurities

Silica, SiO₂, is added to the mixture and heated in the absence of air to convert the iron (II) oxide into a slag of iron (II) silicate, FeSiO₃, which is poured away.

• FeO(s) + SiO₂ → FeSiO₃(s) (slag)

 

4. Conversion of copper sulphide to copper

The copper (I) sulphide is reduced to copper by heating in a controlled amount of air.

Cu₂S (s) + O₂ (g)  → 2Cu (s) + SO₂ (g)

 

5. Purification of copper by electrolysis

Anode: Impure copper: Cu(s) – 2e → Cu²⁺ (aq)

Cathode; pure copper strip: Cu²⁺(aq) + 2e → Cu(s)

Electrolyte: Copper sulphate

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