How will you prepare potassium permanganate from pyrolusite ore?

Explanation

Potassium permanganate is prepared from pyrolusite (MnO,) ore. The preparation involves the following steps.
(i) Conversion of `MnO_(2)` to potassium manganate:
Powdered ore is fused with KOH in the presence of air or oxidising agents like `KNO_(3)` . A green coloured potassium manganate is formed.
`2MnO_(2)+ 2KOH+ O_(2) to underset(underset("(Green)")("Potassium manganate"))(K_(2)MnO_(4))+ 2H_(2)O`
(ii) Oxidation of potassium manganate to potassium permanganate: Potassium manganate can be oxidised in two ways, either by chemical oxidation or electrolytic oxidation
(iii) Chemical oxidation: In this method potassium manganate is treated with ozone (`O_(3)`) or chlorine to get potassium permanganate,
`MnO_(4)^(2-)+ O_(3)+ H_(2)O to 2MnO_(4)^(-)+ 2OH^(-)+ O_(2)`
`2MnO_(4)^(2-)+ CI_(2) to 2MnO_(4)^(-) + 2CI^(-)`
(iv) Electrolytic oxidation: In this method aqueous solution of potassium manganate is electrolyzed in the presence of little alkali.
`K_(2)MnO_(4) hArr 2K^(+)+MnO_(4)^(2-)`
`H_(2)O hArr H^(+)+OH^(-)`
Manganate ions are converted into permanganate ions at anode.
`underset("(Green)")(MnO_(4)^(2-)) hArr underset("(purple)")(MnO_(4)^(-)) + e^(-)`
`H_(2)` is liberated at the cathode.
`2H^(+)+ 2e^(-) to H_(2)uarr`
The purple coloured solution is concentrated by evaporation and forms crystals of potassium permanganate on cooling.