Copper extraction

Extraction of copper

Copper extraction is done from the following ores

Pyrites (CuFeS2)

Cuprite (Cu2O2)

Chalcocite (Cu2S)

Malachite (CuCO3.Cu (OH) 2)

Extraction from copper pyrites

Concentration using froth floatation

The ore is ground into a fine powder, and then mixed with water and a suitable oil detergent. Air is then brown through the mixture.

A froth forms at the top of the mixture which contains the concentrated ore. While the impurities sink at the bottom.

The froth is skimmed and dried

The concentrated ore is then roasted in limited supply of air to obtain iron (II) oxide, copper (I) sulphide and sulphur (IV) oxide

 

CuFeS2 (s)  + O2 (g) → Cu2S (s) +   FeO(s) + SO2 (g)

 

Silica is then added and the mixture heated in absence of air

Silica (SiO2) reacts with iron (II) to form iron (II) silicate which separates out as slag

 

FeO (l) + SiO2 (l) → FeSiO3 (l) 

 

Copper (I) sulphide is then heated in a regulated amount of air where some of it is converted to copper (I) oxide

2Cu2S (l)  + 3O2 (g) → 2Cu2O (l) +   2SO2 (g)

Copper (I) oxide reacts with the remaining copper (I) sulphide forming copper

2Cu2S (l) + 2Cu2O (l)  → 6Cu (l) +   SO2 (g)

Sulphur (IV) oxide produced is either fed into sulphuric (VI) acid plant (contact process) or scrubbed using calcium hydroxide

2SO2 (g) + Ca(OH)2 (aq) → CaSO4 (s) + H2O (l)

Copper obtained is about 97.5% pure and called blister copper

More pure copper can be obtained by electrolysis

ELECTROLYSIS

Cathode is made of pure copper while anode is the impure copper

Electrolyte is copper (II) sulphate

Copper at anode dissolve

Cu(s)  → Cu2+ (aq)    +    2e

Pure copper is deposited at the cathode

Cu2+ (aq)+ 2e  → Cu(s)

 

Copper purification

Traces of Gold and silver are collected from the sludge

If copper carbonate is used it roasted to obtain Copper (II) oxide

CuCO3 (s) → CuO(s)   +      CO2 (g)

Copper (II) oxide is then reduced using coke and carbon (II) oxide as reducing agents

2CuO (s)  +   C (s) → 2Cu (s)    CO2 (g)

CuO (s) +   CO (g)  → Cu (s)    CO2 (g)




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