What is Aluminium?
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:
The atomic number of Aluminium is 13 whereas its weight is 26.98
The melting point of Aluminium is 660 degrees celsius while its boiling point reaches 2,467 degrees celsius.
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.
FAQs on Aluminium: An Abundant Metallic Element
1. What are the fundamental properties of Aluminium as a chemical element?
Aluminium is a chemical element with the symbol Al and atomic number 13. It is a lightweight, silvery-white, and non-magnetic metal. A key characteristic is its low density and its ability to resist corrosion through the formation of a passive oxide layer. It belongs to the boron group (Group 13) in the periodic table and is a good conductor of heat and electricity.
2. Why is Aluminium known as the most abundant metallic element?
Aluminium is called the most abundant metallic element because it makes up about 8% of the Earth's crust by mass. It is the third most abundant of all elements in the crust, after oxygen and silicon. However, it is never found in its free, metallic form in nature due to its high reactivity. Instead, it exists in compounds, most commonly in minerals like Bauxite.
3. What is Bauxite, and why is it the primary ore of Aluminium?
Bauxite is a sedimentary rock that is the world's main source of Aluminium. It is not a specific mineral but a mixture of hydrated aluminium oxides, primarily containing gibbsite (Al(OH)₃), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH)). It is considered the primary ore because it contains a high concentration of aluminium compounds from which the metal can be extracted economically.
4. How is pure Aluminium extracted from Bauxite ore?
The extraction of pure Aluminium from Bauxite is a two-step process:
- Bayer's Process: The Bauxite ore is first purified to produce alumina (aluminium oxide, Al₂O₃). In this chemical process, Bauxite is crushed, digested in a hot solution of sodium hydroxide, which dissolves the aluminium compounds, leaving behind impurities like iron oxides as a solid residue.
- Hall-Héroult Process: The purified alumina is then dissolved in molten cryolite (Na₃AlF₆) and electrolysed to produce pure Aluminium. This electrolytic reduction is highly energy-intensive, requiring massive amounts of electricity.
5. Why does Aluminium resist corrosion even though it is a highly reactive metal?
Although Aluminium is chemically reactive, it is highly resistant to corrosion due to a phenomenon called passivation. When fresh Aluminium is exposed to air or moisture, it instantly forms a very thin, tough, and transparent layer of aluminium oxide (Al₂O₃) on its surface. This oxide layer is non-reactive and strongly bonded to the metal, acting as a protective barrier that prevents the underlying Aluminium from coming into contact with air and water, thus stopping further oxidation.
6. What are the most common uses of Aluminium based on its properties?
Aluminium's unique properties make it suitable for a wide range of applications:
- Aerospace & Transportation: Its low density and high strength-to-weight ratio make it ideal for manufacturing aircraft, cars, and trains.
- Packaging: Its malleability, ductility, and barrier properties are used to make beverage cans and food foils.
- Construction: It is used in window frames, doors, and roofing due to its corrosion resistance and light weight.
- Electrical Transmission: Its high electrical conductivity and low density make it a preferred material for overhead power lines.
7. What are Aluminium alloys, and why are they important?
Aluminium alloys are mixtures created by combining pure Aluminium with other elements like copper, magnesium, silicon, manganese, and zinc. Pure Aluminium is soft and not very strong. Alloying is done to significantly enhance its properties, such as increasing its strength, hardness, and workability, while retaining its light weight and corrosion resistance. These enhanced properties make Aluminium alloys essential for high-performance applications in industries like aerospace and automotive.
8. Why are the largest producers of Bauxite not always the largest producers of Aluminium metal?
The production of Aluminium metal from Bauxite is not solely dependent on the availability of the ore. The critical factor is the enormous amount of electrical energy required for the Hall-Héroult electrolysis process. Consequently, countries with access to cheap and abundant electricity (often from hydroelectric power) are major Aluminium producers, even if they have to import Bauxite. This is why nations like Canada and Norway are major Aluminium producers, while Bauxite-rich countries like Guinea or Jamaica may not have the energy infrastructure to be top producers of the final metal.
