How to do the process of purification of iron
Answers
by the process called rusting
Extracting iron
The blast furnace
Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as haematite contain iron(III) oxide, Fe2O3. The oxygen must be removed from the iron(III) oxide in order to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions.
Blast furnace. Iron ore, carbon, limestone enter at top. Air enters at side near bottom. Three zones. Air into zone 1, waste gases out above zone 3. Slag out below zone 1, iron out at very bottom.
Carbon is more reactive than iron, so it can displace iron from iron(III) oxide. Here are the equations for the reaction:
Iron(III) oxide + carbon → iron + carbon dioxide
2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)
In this reaction, the iron(III) oxide is reduced to iron, and the carbon is oxidised to carbon dioxide.
In the blast furnace, it is so hot that carbon monoxide can be used, in place of carbon, to reduce the iron(III) oxide:
iron(III) oxide + carbon monoxide → iron + carbon dioxide
Fe2O3(s) + 3CO(s) → 2Fe(l) + 3CO2(g)
Raw materials for the reaction
Raw material Contains Function
Iron ore (haematite) Iron(III) oxide A compound that contains iron
Coke Carbon Burns in air to produce heat, and reacts to form carbon monoxide (needed to reduce the iron oxide)
Limestone Calcium carbonate Helps to remove acidic impurities from the iron by reacting with them to form molten slag
Air Oxygen Allows the coke to burn, and so produces heat
Removing impurities
The calcium carbonate in the limestone thermally decomposes to form calcium oxide.
calcium carbonate → calcium oxide + carbon dioxide
CaCO3(s) → CaO(s) + CO2(g)
The calcium oxide then reacts with silica (sand) impurities in the haematite, to produce slag - which is calcium silicate.
calcium oxide + silica → calcium silicate
CaO(s) + SiO2(s) → CaSiO3(l)
This reaction is a neutralisation reaction. Calcium oxide is basic (as it is a metal oxide) and silica is acidic (as it is a non-metal oxide).