Lead extraction

LEAD EXTRACTION

Lead extraction may be done from the following ores.

Galena – lead (II) sulphide

Cerussile lead (II) carbonate

Anlesite lead (II) sulphate

First the ore is ground into fine powder and then concentrated by froth floatation

2PbS(s)  + 3O2 (g)  → 2PbO (s) +   2SO2 (g)

Reduction

Lead extraction is done by reduction and then purification may be done by electrolysis.

The lead (II) oxide from the roaster is mixed with coke and limestone and heated in a blast furnace where it is reduced

PbO (s) + C(s)  → Pb (s)   + CO (g)

Iron is added to reduce any remaining lead (II) sulphide

2PbS(s) + Fe (s) → FeS (s) +   Pb (s)

Limestone decomposes to calcium oxide and carbon (IV) oxide

CaCO3 (s)  → CaO (s)     + CO2 (g)  

Calcium oxide combines with silica to form slag

CaO(s)  +   SiO2 (s)  → CaSiO3(l)

The iron (II) sulphide and calcium silicate form slag which is tapped off separately from the lead

The lead obtained is not pure

More pure lead can be obtained by blowing a blast of hot air through the molten impure lead

Oxygen in the air oxidises the impurities into compounds which are less dense than lead hence float on lead and are skimmed off.

More pure lead can be obtained by electrolysis

Electrolysis

Electrolyte is a soluble salt of lead

Cathode is made of pure lead while anode is the impure lead

Lead at anode dissolve

Pb(s)  → Pb2+ (aq)+    2e

Pure lead is deposited at the cathode

Lead purification

Lead purification

 



METALS WORD FILE