Extraction of Zinc from Zinc Oxide Chemistry Notes
Extraction of Zinc from Zinc Oxide :
→ The atomic number of zinc is 30. It belongs to d-block of periodic table. It does not occur in native state. It usually found in combined state. The principle ores of zinc are as follow:
- Zinc blende – Zns
- Zincite – Zno
- Calamine – ZnCO3
- Willemite – Zn2SiO4
- Franklinite – ZnO. Fe2O3
Zinc is extracted mainly by zinc blende. The main steps involved in the extraction of zinc are as follow:
→ Concentration : Pulverised ore is concentrated by froth floatation process.
→ Roasting: The concentrated ore is heated in excess supply of air at about 1200 K temperature. Then zinc sulphide is oxidised into zinc oxide. If small amount of ZnSO4 is present then it is also oxidised into Zno. The related reactions are as follow:
If the calamine ore is used then the reaction will be as follows:
→ Reduction by Coke (Carbon) : Roasted ore is heated with coke at 1673 K temperature in fire clay retort. Where ZnO is reduced into Zn.
→ The zinc obtained from the above process has impurities of lead, arsenic etc. It has about 97.8% zinc. This impure zinc is known as ‘zinc spalter’, which is further purified by fractional distillation.