Aluminium: An Abundant Metallic Element

Aluminium (AL), also spelt or known Aluminium, is a chemical element and is a very lightweight white and silvery kind of metal of the boron group of the periodic table, which is one of the metallic elements that is found in abundance on Earth’s crust and is that nonferrous metal, used widely across the globe. Moreover, it never occurs in the metallic form due to its chemical activity but its compounds are available to some extent in vegetation, rocks, and animals. Besides, the term is derived from a Latin word called the alumen, which is mainly used to outline Aluminium potassium sulphate or potash alum. 

The element properties of Aluminium are as follows:

1. The atomic number of Aluminium is 13 whereas its weight is 26.98

2. The melting point of Aluminium is 660 degrees celsius while its boiling point reaches 2,467 degrees celsius.

3. Its valence is 3 and specific gravity is 2.70.

An Insight into the Topic: Aluminium Ore

We get minerals and ores in abundance in the earth’s crust. Some ores have proven themselves a great resource for mankind. Such as iron obtained from the ore of iron (Hematite) built the foundation of the industrial revolution. On the other hand, Aluminium was a crucial strategic resource for aviation during World War I and World War II. Still, Aluminium metal dominates in the various fields of the market due to its unique properties and easy and cost-effective extraction. Generally, Aluminium Ores are found in the form of their oxides. Bauxite is the most common Aluminium Ore and Hall – Heroult process is the major industrial process for the extraction of Aluminium from its oxide alumina. 

Nevertheless, Aluminium has a tendency to get along or combine with the elements that are common while its compounds are found in all common rocks and more like clay, slate, shale, schist, syenite, granite, and anorthosite. Moreover, in 1821, an iron-containing rock, which is considered the most important Aluminium Ore, consisting of around 52 per cent of Aluminium oxide was discovered by a person named Les Baux in the area of southern France and was popularly known as Bauxite. However, its impurities are titania, silica, and iron oxide.

What is Bauxite?

If we talk about Bauxite, it greatly differs in its physical appearance depending upon its impurities and composition. It varies in colour from grey to yellowish-white or from pink to brown or dark red if it has a great number of iron oxides. Moreover, except Antarctica, Bauxite is found in almost all the continents while its richest deposits lie in the subtropical and tropical climates, places having good amounts of rainfall with good drainage and warm temperatures.

Now in this article, we will discuss the occurrence and extraction of Aluminium in detail.

Occurrence of Aluminium 

As Aluminium is a highly electropositive element so it does not occur in the free state. It is one of the top five elements of the reactivity series. So, it is a highly reactive element or metal and generally reacts with atmospheric oxygen and is found in the form of its oxide. 

A mineral from which metal can be economically extracted in a maximum amount is called an ore. Most common Aluminium Ores are Bauxite, corundum, cryolite and alunite. In India, most of the Aluminium metal is extracted from its Bauxite ore. India has large deposits of Bauxite Aluminium Ore in Gujarat, Madhya Pradesh, Jharkhand, Uttar Pradesh, and Karnataka. Here we have given a list of common Aluminium Ores with their chemical formulae –

Ores 

• Bauxite 

• Corundum 

• Cryolite 

• Alunite 

Chemical Formula 

• Al₂O₃.2H₂O

• Al₂O₃

• Na₃AlF₃

• K.2SO₄.Al₂(SO₄)₃.4Al(OH)₃

Extraction of Aluminium from Bauxite 

The science of extracting pure metals by economically effective methods from their ores is called metallurgy. Metallurgy of Aluminium or the extraction process of Aluminium from its ore involves various methods. Mostly Aluminium is extracted from its ore called Bauxite. The extraction of Aluminium from its ore involves the following steps –

• Dressing or Concentration of the Bauxite ore by Hall’s method 

• Electrolysis by Hall – Heroult Method

Dressing or concentration of the Bauxite ore– Bauxite is generally found as an impure form of Aluminium oxide. The process which gives the ore such a physical form so that the gauge can be easily removed from it is called dressing of the ore. It is done by hand–picking, grinding, etc. 

Bauxite ore generally contains ferric oxide and silica as impurities. Dressing of Bauxite ore is done by crushing and pulverising. To remove ferric oxide impurities from the Bauxite, a magnetic separation method is used. The ore obtained is concentrated by Hall’s method. 

The concentration of Bauxite by Hall’s method – The hall method of concentration of Bauxite was invented in 1886 by the American chemist Charles Martin Hall. This is the reason the method is named Hall’s method. It takes place by following three steps –

Step 1. Conversion of impure Bauxite into sodium aluminate – The ore is fused to red heat with sodium carbonate and the formation of sodium aluminate takes place. The reaction involved is given below –

Al₂O₃.2H₂O + Na₂CO₃ + heat 🡪 2NaAlO₂ +2H₂O +CO₂

Step 2. Conversion of sodium aluminate into Aluminium hydroxide – 

2NaAlO₂ +3H₂O +CO₂ 🡪 Na₂CO₃ + 2Al(OH)₃

Step 3. Conversion of Aluminium hydroxide into pure alumina – 

2Al(OH)₃ 1100℃→ Al₂O₃ + 3H₂O

Electrolysis by Hall – Heroult Method – Alumina is highly stable oxide and melts at 2050℃ that’s why alumina cannot be directly electrolyzed. Its electrolysis is done with cryolite (3 parts by weight) and fluorspar (1 part by weight). In this process for electrolysis, an iron tank lined with heat resistant material and has a sloping floor, provided with an outlet for tapping molten Aluminium metal is used. Gas carbon or graphite are used as cathode and thick carbon rods are used as the anode. Coke powder covering is used to prevent the burning of carbon anodes and to prevent heat loss from the molten electrolyte. A direct current of 100 A is passed through the electrolyte and the temperature is maintained at 950℃. In this process sodium, calcium, and Aluminium ions are formed which migrates towards the cathode. However, only Aluminium ions reach the cathode due to their lower position in the electrochemical series. Thus, pure Aluminium gets deposited at the cathode and melts due to the 950℃ temperature of the electrolyte, as it is heavier than electrolyte, so it gets deposited at the base of the electrolytic tank. While at anode nascent oxygen is formed which reacts with carbon of coke and forms carbon mono oxide which reacts with atmospheric oxygen and forms carbon dioxide. Although nascent oxygen formed at anode reacts with carbon of carbon-anode as well. That’s why carbon – anodes are consumed gradually and need to be replaced from time to time. 

Reactions involved in the electrolysis are given below –

Al₂O₃ ↔ 2Al₊₃ + 3O_-2

Na₃AlF₃ ↔ 3Na+ + Al₊₃ + 6F-

CaF₂ ↔ Ca₊₂ + 2F-

At Cathode –

2Al₊₃ + 3e− → Al

At Anode –

O_-2 - 2e− 🡪 OO

2OO 🡪 O2

C(coke) + OO 🡪 CO

2CO + (air)O₂ 🡪 2CO₂

Thus, pure Aluminium metal is obtained from the chief ore of Aluminium which is Bauxite. 

Uses of Aluminium 

Due to its properties, Aluminium is used in a number of fields. The main uses of Aluminium are as follows –

• It is widely used in aviation. 

• We have been using Aluminium vessels for ages. Many types of utensils of Aluminium are available. As it is a good conductor of heat.

• It is used in many alloys.

• It is used in electric wires. As it is a very good conductor of electricity. 

• It is used as Aluminium foil to keep things warm. 

• It is used in the packaging industry.

• Paints are prepared by mixing Aluminium powder in linseed oil.

• It is used in explosives.

• It is used in the extraction of gold and silver.

• It works as a reducing agent for many organic reactions. 

• It is used in thermite welding. 

This ends our coverage on the topic “Aluminium Ore: Extraction of Aluminium”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions to NCERT Textbook problems based on this topic, then log on to the Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests, and much more.