Occurrence and extraction of Copper

Copper occurs both in combined state and free state and also in many ores. The important ores of copper are copper pyrites (CuFeS2), cuprite and copper glance. The copper ores are mostly found in the north of India. The extraction of copper also involves many steps. The ore used for extraction is copper pyrites, which is crushed, concentrated and then heated in the presence of air. During heating the moisture gets expelled and the copper pyrites gets converted to ferrous sulfide and cuprous sulfide.

Blast furnace is used to heat the mixture of roasted ore, powdered coke and sand. In the blast furnace oxidation reactions takes place. Ferrous sulfide forms ferrous oxide which combines with silica and forms the slag (FeSiO2).

Cuprous sulfide forms cuprous oxide which is partially converted to cuprous sulfide.

This cuprous sulfide contains some amount of ferrous sulfide and this is called matte. Matte is removed from the base outlet of blast furnace. The removed matte is shifted into Bessemer converter which is lined inside with magnesium oxide. This converter has pipes through which hot air and SiO2 are sent in. In this converter Cu2S converts to Cu2O and FeS converts to FeO. The ferrous oxide forms slag with SiO2. The cuprous oxide formed reacts with Cu2S and forms copper.

The copper thus formed is to be purified by electrolysis.