Extraction of Zinc

Zinc is greyish in its appearance and a brittle metal at normal room temperature. Being the 24th most abundant substance in the earth’s crust. It does not originate in its original form as it is a highly reactive metal. But it is combined with others and is distributed widely. The largest ores that can be worked upon are Asia, Australia, and America. Its main ore is sphalerite, also called zinc sulphide mineral. In India, Zawar in Rajasthan produces the purest form of zinc. 

Properties of Zinc

Zinc has certain properties or characteristics that make it unique in its sense. These properties are:

• It is a bluish-white metal

• It is glossy and diamagnetic in texture

• It has a crystal structure in a hexagonal shape

• It is less dense than iron

• It is flexible at a temperature between 100 to 150 degrees Celsius

• It is a good conductor of electricity

• It has a melting point of just 419 degrees Celsius and a boiling point of 907 degrees Celsius

• It is hard and brittle at many temperatures

• It burns to produce Zinc Oxide, which is popularly called philosophers wool

Utilities of Zinc

Like any other metal, it has several utilities that help produce various things. Some of these utilities are as follows:

• Zinc is utilised for galvanising sheets of iron

• Zinc is applied for the extraction of gold and silver through the process called cyanide process

• Zinc is used to make plates and rods, further utilised in batteries and dry cells

• When crushed, Zinc becomes zinc dust, which is then used as a reducing agent in the laboratory

• Zinc oxides are utilised as a white pigment in paints and as a catalyst in rubber production

Ores of Zinc

Main ores from where one can get Zinc are Zinc blende, Calamine, and Zincite. The main ore from where the extraction of Zinc takes place mostly is Zinc blende(ZnS). Most of the Zinc blende is found in Zawar mines around Udaipur in Rajasthan in India. Zinc ores have a 40% presence in North America and Australia. Zinc sulphide is also known as sphalerite, a ferrous state of zinc blend called marmatite, and zinc carbonate is called calamine or smithsonite. 

Extraction of Zinc

The extraction process of Zinc from its ore is called the zinc extraction process. The extraction of Zinc contains physical and electrochemical procedures. Depending on the nature of the ore, its source, and the rules of a particular country, the zinc extraction process differs accordingly.

Process of Extraction of Zinc

There are many steps followed in the extraction of Zinc from its ores. These are:

1. Concentrating

2. Roasting

3. Reducing

4. Purifying

Concentrating 

The ores must first be concentrated through the froth-floatation process; only then could the zinc extraction process begin. The floth floatation process is usually utilised for sulphide ores.

Roasting

When the concentrating process is done successfully, the extraction of Zinc is taken to the next step by roasting. In roasting, a sulphide ore (zinc ore) is roasted at a high temperature in the air. This procedure is usually used with sulphide minerals. The zinc ore is transformed into oxide during heating, and sulphur dioxide results from the release of sulphur.

Reducing

With moderate activity and place in the centre of reactivity, zinc is reduced by carbon. Zinc oxide is crushed into thin pieces and combined with coke. This combination is heated in clay containers at a temperature of 1673k. The carbon from the coke is the reducing agent, and it degrades the zinc oxide to zinc. 

However, the zinc earned from this heating process turned to vapours at that moment because the boiling point of zinc is far lower than the temperature at which zinc is reduced. However, the vapours of zinc leave contaminate on the floor of the container. The vapours of zinc are chilled into a solid form of zinc. This zinc is nevertheless still filled with impurities and is further refined with electrolysis to move to the next step in the extraction of zinc. This process is also called the Belgian Process.

Purifying

The last step in extracting zinc is the refinement of the obtained zinc (a crude form of zinc). This refinement is done through the process called electrolytic refining. In this process, the electrolytic cell consists of contaminated zinc as an anode and a pure fine sheet of zinc as a cathode. Zinc Sulphate is applied as an electrolyte with a minimum quantity of sulphuric acid. When an electric current is passed, the pure form of zinc is deposited on the cathode. The dirt deposits around the anode in the state of sludge. 

Conclusion

The process used for the extraction of zinc from zinc oxide relies on the state of the ore. There is a requirement for the concentration of zinc ores before they can be refined for the final extraction of zinc. Extraction of zinc from its ore is generally through the self-reduction method. Economic leaching is allowed through new and modern methods of extraction of zinc. 

New techniques are coming into existence to make the zinc extraction process easier and more efficient from various ores of zinc, especially zinc extraction from zinc oxide. Here we got a fair understanding of various processes required in extracting zinc from zinc oxide and that refinement is the most important step in the extraction of zinc.