Extraction Of Zinc

Zinc is one of the essential elements found abundantly on earth and in almost in many foods. This mineral is even found in the many cells of living organisms and assists the immune system to fight against germs and bacterias. It is located in the group 12 of the periodic table having an atomic number of 30 and its symbol being Zn.

Zinc appears in the form of lustrous and a bluish chemical metal. It is brittle at normal temperatures and is also malleable in nature.

How Zinc Is Obtained From Zinc Blende

Zinc is manufactured from zinc blende in various steps such as concentration, roasting, smelting and purification which are given below in detail.

  • Process Of Concentration:

Process of ConcentrationThe first process in the extraction of zinc is the concentration. As shown in the diagram below, this process involves the implementation of froth floatation method for the extraction of zinc ores from zinc blende. Zinc blende is mixed up in a large tank consisting of a mixture of pine oil and water. Later compressed air is passed through this combination. The froth containing the concentrated zinc sulphide ores settles on the surface leaving behind the impurities in water.

  • Process Of Roasting:

The next step is the process of roasting the ores of zinc. The concentrated ore is then treated at  9000 o c in the presence of excess air, on the base of a reverberatory furnace. This process of heating is called roasting. During this process, zinc oxide is obtained from the zinc sulphide ore. The equation for this process is as shown below

 

2ZnS + 3O2 —————-2ZnO + 2SO2

  • Process Of Smelting:

This process is called reduction. The mixture of zinc oxide and coke are heated in the presence of carbon to obtain zinc. The equation for this as shown below-

ZnO + C ————————-Zn + COProcess of SmeltingThe process is employed in a vertical container. In this whole process, the zinc oxide and coke are mixed in the ratio 2:1 and in the form of a compressed mixture. This mixture is introduced into the furnace and is heated inside at a temperature of about 1400 o c. Zinc is obtained in the form of vapors which later condenses in the condenser which gives out molten zinc or even called as spelter zinc.

  • Purification Process:

This is the last step of the entire process of zinc extraction. The molten zinc obtained from the previous process consists of some impurities in it. Hence the process of the removal of these impurities is called as Purification. This process can is done in two ways as given –

  1. Fractional distillation

In this process, the impurities such as Pb. Fe is in high concentration when compared to cd and Ar; hence it is heated at about 1000 o c which causes the distillation of Pb and Fe and then later again it is heated at about 800 o c thus distilling cd and as a result pure zinc is left behind.

  1. Electrolysis process

Electrolysis is one method of removing impurities from the zinc spelter. The method uses a zinc rod which acts as a cathode, while the impure zinc serves as an anode. ZnSO4 and dil H2SO4 are mixed up and used as an electrolyte. The current is passed through the electrolyte; zinc gets settled on the cathode leaving the impurities in the electrolyte solution.

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