Extraction of Aluminium, Aluminium Ore, Concentration of Ore (For CBSE, ICSE, IAS, NET, NRA 2022)

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Extraction of Aluminium

  • A soft, silvery-white, corrosion-resistant metal. It is the most abundant metal in the earth՚s crust as it makes up of the crust and it is the third most abundant element after oxygen and silicon. Bauxite ore is the major source of aluminium till date which is a mixture of hydrated aluminium oxide.
  • Aluminium can also be recovered from cryolite and alunite. It is also found in gemstones such as garnet, topaz and chrysoberyl. The chemical symbol of this metal is Al. In the boron group with symbol Al, aluminium is a chemical element and is the most commonly used non-ferrous metal.
  • Aluminium ore is called bauxite. The bauxite is purified to produce aluminium oxide, a white powder from which aluminium can be extracted. The extraction is done by electrolysis. The ions in the aluminium oxide must be free to move so that electricity can pass through it.

Aluminium Ore

Ores of Aluminium

  • Aluminium is a highly reactive metal, belonging to the IIIA group of the periodic table. In nature, aluminium is found in the form of its oxide in its ores. The important ores of aluminium are
    • Bauxite –
    • Corundum –
    • Cryolite –

Metallurgy of Aluminium

Aluminium is mostly extracted from its bauxite ore. Dressing of ore: The ore is crushed and pulverized.

Concentration of Ore

  • Bauxite is the name given to aluminium ore. To generate aluminium oxide, bauxite is purified, a white powder form which aluminium can be extracted.
  • Aluminium oxide has a very high melting point of more than so melting it would be costly. Aluminium oxide in water does not dissolve, but in molten cryolite, it dissolves.
Aluminium Alloy

Aluminium Alloy

Pure aluminium is a silver-white metal with many desirable features. It՚s light, non-toxic, non-magnetic, and non-sparking. It՚s a bit ornamental. It՚s created, machined, and cast readily. Pure aluminium is soft and lacks strength, but it has very helpful characteristics for alloys with tiny quantities of copper, magnesium, silicon, manganese and other components.

Bayer՚s Process

In this process, aluminium ore is treated with concentrated sodium hydroxide. Soluble sodium aluminate is formed which is filtered off. The filtrate on heating with water gives aluminium hydroxide which gives alumina on strong heating.

Hall-Heroult Process

  • The Hall-Heroult process is widely used in the extraction of aluminium. In Hall-Heroults process, pure is mixed with or . This results in lowering of the melting point of the mixture and increases its ability to conduct electricity. A steel vessel with the lining of carbon and graphite rods is used.
  • The carbon lining acts as cathode and graphite act as an anode. When electricity is passed through the electrolytic cell which consists of carbon electrodes oxygen is formed at the anode. This oxygen formed reacts with the carbon of the anode to form carbon monoxide and carbon dioxide. In this method of production of aluminium for every 1 kg of Al produced, approximately 0.5 Kg of carbon anode is burnt.
Extraction of Aluminium

Extraction of Aluminium

Aluminium ions are created at the adverse cathode from the aluminium oxide and then sink down because they are heavier than the cryolite solution. Then, the liquid shape of the aluminium that has sunk to the bottom. On the other side, at the positive anode, the oxygen from the aluminium oxide forms and responds to carbon dioxide with the graphite carbon.

The overall reaction is:

The electrolytic reactions are:

At the Cathode

At the Anode

During the process of electrolysis,

  • Aluminium ions that are positively loaded gain electrons from the cathode and form molten aluminium.
  • Oxide ions lose anode electrons and form molecules of oxygen

In the electrochemical sequence means reactivity series, aluminium is too big to be removed from its ore by carbon reduction. The required temperatures are too high to be economical.

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