State the role of silica in the metallurgy of copper.
During the roasting of pyrite ore, a mixture of FeO and Cu2O is obtained.
2 CuFeS2 + O2→ Cu2S + 2 FeS + SO2
2 Cu2S + 3 O2 → 2 Cu2O + 2 SO2
2 FeS + 3 O2 → 2 FeO + 2 SO2
The role of silica in the metallurgy of copper is to remove the iron oxide obtained during the process of roasting as ‘slag’. If the sulphide ore of copper iron, then silica (SiO2) is added as a flux before roasting. Then, FeO combines with silica to form silicate, FeSiO3 (slag).
FeO + SiO2→ FeSiO3 (slag)