18/05/2025
COPPER (Cu)
Copper is one of the less reactive metals and belongs to a group of elements known as the noble metals which include silver and gold. It is very stable in air and can be found in the free metallic form in a few places. However, the principal source of the metal is copper pyrites, CuFeS2. Copper also also exists in the combined state as cuprite, Cu2O, malachite, CuCO3.Cu(OH)2, chalcocite, Cu2S, and bornite, Cu2S.Cu.FeS.
EXTRACTION
Copper is usually extracted from sulphide ores, such as copper pyrites, CuFeS2. The ore is concentrated by froth flotation. Then it is roasted in a limited supply of air to oxidize the iron and some of the sulphur in the ore to iron(II) oxide and sulphur IV oxide respectively.
2CuFeS2(s) + 4O2(g) ➡️ Cu2S(s) + 2FeO(s) + 3SO2(g)
Silicon IV oxide is added and the mixture is heated in the absence of air to convert the iron II oxide to iron II trioxosilicate (IV). The latter floats on copper (I) sulphide as slag and is removed.
FeO(s) + SiO2(s) ➡️ FeSiO3(s)
The copper I sulphide that remains is heated in a controlled amount of air to produce copper with a purity of about 97% - 99%.
Cu2S (s) + O2(g) ➡️ 2Cu(s) + SO2(g)
Where copper of high purity (99.95%) is required, the crude copper is made into anodes in an electrolytic cell containing pure copper cathodes and a copper II tetraoxosulphate VI solution and refined by electrolysis.
