Wrought iron is the purest form of iron. Write a reaction used for the preparation of wrought iron from cast iron. How can the impurities of sulphur, silicon and phosphorus be removed from cast iron ?

Explanation

Wrought iron contains lesser proportion of carbon contents `(0.2` to `0.5%)` as compared to cast iron `(2.5` to `4.5%)`. In order to reduce the percentage of carbon, cast iron is heated with haematite `(Fe_(2)O_(3))` at a temperature above `1073` K in a reverberatory furnace.
`Fe_(2)O_(3)(s)+3C(s) overset("heat") to underset(("Cast iron")) (2 Fe(s)) + 2 CO(g)`
Lime stone `(CaCO_(3))` is added as flux in the extraction of cast iron from haematite ore. Upon decomposition, it provides `CaO`. In the Blast furnace, the impurities of silicon, sulphur and phosphorus are converted into their respective oxides. These combine with `CaO` to form corresponding salts which pass into the slag.
`{:(SiO_(2)+CaO to CaSiO_(3) ("Slag")),(SO_(3)+CaO to CaSO_(4)("Slag")),(P_(4)O_(10)+6CaO to 2Ca_(3) (PO_(4))_(2)("Slag")):}`