The document summarizes the process of extracting aluminium from bauxite ore. Bauxite ore is dissolved in cryolite to lower its melting point before being electrolyzed in a molten electrolyte. During electrolysis, positively charged aluminium ions move to the negatively charged carbon cathode, gaining electrons and forming aluminium atoms. Negatively charged oxide ions move to the positively charged carbon anode, losing electrons and forming oxygen gas. Some oxygen reacts with the carbon anode to form carbon dioxide, requiring frequent anode replacement. The overall process uses electrolysis to extract aluminium from bauxite ore dissolved in cryolite.

1. Extraction of Aluminium
•To Know how aluminium is
extracted from the Bauxite
Ore.
•To know the process of
extraction.
Objective:

2. Aluminium: properties
• Aluminium is a reactive metal.
• We might expect it to corrode easily but a
strong coating of oxide on it’s surface prevents
this in most everyday situations.
• It has a low density which leads to its extensive
use in the aerospace industry.
Al Al Al AlAl Al
Al Al Al AlAl Al
O O O O O OO OO
Coating of
oxygen atoms
prevents further
attack

3. Raw Materials
• Ore bauxite aluminium oxide
• The ore is dissolved in cryolite to lower the
melting point.

4. Aluminium: ores
• It occurs as bauxite ore which is a form of
aluminium oxide.
• Because aluminium is so reactive carbon is
unable to pull away the oxygen from it.
• It is extracted by electrolysis of moltenmolten bauxite.
Early attempts at this failed because bauxite is
so hard to melt.
• If cryolite is added, the bauxite melts more
easily. This is an essential step in the extraction
process.

5. A bauxite / cryolite mixture is melted in a steel
container containing a carbon lining.
Graphite (carbon) anodes
Tank
lined
with
carbon
cathode
Molten electrolyte
bauxite + cryolite
Steel
case
Graphite anodes are inserted into the molten electrolyte
ready for electrolysis.
Electrolytic extraction

6. Aluminium formation
• Opposite charges
attract.
• And so positive
aluminium ions move
towards the negative
cathode.
• At the cathode these
ions gain electrons
and turn into
aluminium atoms.

7. Oxygen formation
• Negatively charged oxide
ions move to the anode.
• Here they lose 2 electrons
and so turn into neutral
oxygen atoms.
• These atoms rapidly join
into pairs to form normal
oxygen gas.

8. Carbon dioxide formation
• Remember the electrolysis is
carried out at high
temperature.
• Under these conditions quite
a lot of the oxygen reacts
with the carbon anode.
• Carbon dioxide is formed
and the anode is rapidly
eaten away and frequently
has to be replaced.

9. Extraction of aluminium: overall
siphon
Graphite / carbon anodes
Molten aluminium
Molten electrolyte
bauxite + cryolite
Tank
lined
with
carbon
cathode
Molten
aluminium
out
Steel
case
Vented cover

10. • Common aluminium ore
I axe tub
• Added to reduce melting point
City role
• The electrodes are made out of
Right ape
• Extracting aluminium is a
Cretin duo
bauxite
cryolite
graphite
reduction
Unscramble the words to end the sentences.

11. Aluminium – the overall process

12. 1. What do we call the substance added to
the aluminium ore prior to electrolysis?
Bauxite
Electrolyte
Cryolite

13. 2. What substance are the cathodes made
from?
Carbon
Iron
Aluminium

14. 3. What happens to the oxygen given off
during electrolysis?
It is given off as waste gases
It reacts with the carbon electrodes to form
carbon dioxide.
It is collected at the bottom of the chamber.