Extraction of Metals - Result Question 42
####42. Extraction of copper from copper pyrite $\left(CuFeS _2\right)$ involves
(2016 Adv.)
(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 $SO _2$
(d) refining of ‘blister copper’ by carbon reduction
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Solution:
- $CuFeS _2$ (copper pyrite) is converted into copper into following steps:
Step I Crushing (grinding ) followed by concentration by froth-floatation process.
Step II Roasting of ore in the presence of $SiO _2$ which removes iron as slag $\left(FeSiO _3\right)$.
$$ \begin{aligned} 2 CuFeS _2+O _2 & \longrightarrow Cu _2 S+2 FeS+SO _2 \ 2 FeS+3 O _2 & \longrightarrow 2 SO _2+2 FeO \ FeO+SiO _2 & \longrightarrow FeSiO _3 \text { (Slag) } \end{aligned} $$
Step III Self-reduction in Bessemer converter
$$ 2 Cu _2 S+3 O _2 \longrightarrow 2 Cu _2 O+2 SO _2 $$
$$ 2 Cu _2 O+Cu _2 S \longrightarrow 6 Cu+SO _2 $$
Copper obtained is blister copper ( $98 %$ pure).
Step IV Refining of blister copper is done by electrolysis Impure copper-Anode Pure copper- Cathode
At anode $: Cu \longrightarrow Cu^{2+}+2 e^{-}$
At cathode : $Cu^{2+}+2 e^{-} \longrightarrow Cu$
Carbon-reduction method is not used. Thus, (d) is incorrect.
