Wednesday, August 26, 2020

Reduction Of Metal Oxides

          Extraction of metals from their respective ores. In this method we can get metal oxides again we adding some reducing agent and heated up. It will give pure metals.


     Smelting is a process of reduction of metal oxide to metal by carbon, carbon monoxide, or aluminum. In this metal oxide is heated above the melting point of the metal.


Oxide of ion can be reduced by carbon monoxide.

Fe2O3  +  3CO  ———>  2Fe   +   3CO2            

         Limestone ( CaO ) is a basic flux. Silica gangue present in the ore in its acidic nature. The limestone combines with silica gangue to form calcium silicate( slag ). 

  CaO    +      SiO2      ———>    CaSiO3

(Flux)       ( Gangue)                      (Slag)

             The concentrated ore ( copper pyrite ) heated in a reverberatory furnace. It will form metal sulphides FeS and Cu2S. Both are soluble and form a copper matte.

2CuFeS2  +  O2  ———>  2FeS  +  2Cu2S  +  2SO2

FeS oxidized to FeO.

FeS  +  O  ———>   FeO   +   SO2

Now the ferrous oxide ( flux ) reacted with the silica ( gangue ) to form ferrous silicate  ( slag ).

    FeO     +       SiO2       ———>      FeSiO3

  (Flux)        (  Gangue)                      (Slag)

The remaining copper sulphide is further oxidised to its oxide to form the metallic copper.

Cu2S  +  3O2  ———>  2Cu2S  +  2SO2

2Cu2O  +  Cu2S  ———>  6Cu  +  SO2

This metallic copper  has blistered appearance due to the evolution of   SO2  gas. This copper is called Blistered copper.

Reduction By Carbon:

        In this method oxide ( ZnO ) ore is mixed with coal ( Coke ) and heated strongly in a furnace. This process only applied to the metal which do not form carbides with carbon. 

Examples :

ZnO  +  C  ———>  Zn  +  CO

Mn3O4  +  4C  ———>  3Mn  +  4CO

Cr2O3  +  3C  ———>  2Cr  +  3CO

Reduction Of hydrogen;

              This process only applied to the metal which have less electro -positive character than hydrogen.

Ag2O  +  H2  ———>  2Ag  +  H2O

Fe2O4  +  4H2  ———>  3Fe  +  4H2O

Reduction By Metal:

B2O3  +  6Na  ———>  2B  +  3Na2O

Rb2O3  +  3Mg  ———>  2Rb  +  3MgO

TiO2  +  2Mg  ———>  Ti  +  2MgO

In this process metal oxides reduced by metal.

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