Question

Extraction of copper from copper pyrite $\left(CuFe{S}_2\right)$ involves:

• A. Crushing followed by concentration of the ore by froth-floatation
• B. Removal of iron as slag
• C. Self reduction step to produce 'blister copper' following evolution of $S{O}_2$
• D. Refining of 'blister copper' by carbon reduction

Answer 1

Answer: (A), (B), (C)

Self reduction step to produce 'blister copper' following evolution of $S{O}_2$

$CuFe{S}_2$ (copper pyrite) is converted into copper into following steps:

Step I: Crushing (grinding) following by concentration by froth-floatation process.

Step II: Roasting of ore in the presence of $Si{O}_2$ which removes iron as slag $\left(FeSi{O}_3\right).$
$2CuFe{S}_2+O_2\to C{u}_{2}S+2FeS+S{O}_2$
$2FeS+3O_2\to 2S{O}_2+2FeO$
$FeO+Si{O}_2\to \underset{\left(slag\right)}{FeSi{O}_3}$

Step III: Self-reduction in Bessemer converter.
$2C{u}_{2}S+3O_2\to 2C{u}_{2}O+2S{O}_2$
$2C{u}_{2}O+C{u}_{2}S\to 6Cu+S{O}_2$
Copper obtained is blister copper (98% pure).

Step IV: Refining of blister copper by electrolysis.
Impure copper - Anode
Pure copper - Cathode
At anode: $Cu\to C{u}^{2+}+2e^{-}$
At cathode: $C{u}^{2+}+2e^{-}\to Cu$

Carbon reduction method is not used. Thus, (d) is incorrect.