Question

How can copper be extracted from their ore?

Answer 1

Extraction of copper from copper pyrites involves the following steps:

1. Crushing and concentration: The ore is crushed and then concentrated by the froth-flotation process.

2. Roasting: The concentrated ore is roasted in excess of air. During the process of roasting,

i) moisture and volatile impurities are removed.

ii) sulphur, phosphorus, arsenic and antimony are removed as oxides. Copper pyrite is partly converted into sulphides of copper and iron.

$2CuF3S_2+O_2\to C{u}_{2}S+2FeS+S{O}_2$

3. Smelting: The roasted ore is mixed with powdered coke and sand and is heated in a blast furnace to obtain matte and slag. The slag is removed as waste. (Matte = Cu2S + FeS)

4. Bessemerisation: The molten matte is transferred to Bessemer converter in order to obtain blister copper. Ferrous sulphide from matte is oxidised to ferrous oxide, which is removed as slag using silica.

$2FeS+3O_2\to 2FeO+2S{O}_2$

$FeO+Si{O}_2\to \underset{Ironsilicate}{FeSi{O}_3}\left(slag\right)$

$2C{u}_{2}S+3O_2\to 2C{u}_{2}O+2S{O}_2$

$2C{u}_{2}O+C{u}_{2}S\to \underset{Blistercopper}{6Cu}+S{O}_2$

5. Refining: Blister copper contains 98% of pure copper and 2% of impurities and is purified by electrolytic refining.