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Extraction of Metals

Electrolysis - General Description.

The elements in ionic compounds can be separated by electrolysis.

Metals above carbon in the reactivity series
(potassium, sodium, lithium, calcium, magnesium and aluminium)
are extracted by electrolysis.
Extraction from the metal ore involves reduction of the metal,
and electrons can reduce any metal ion.

metal ions  +  electrons       metal  atoms  (reduction).
non-metal ions  -  electrons        non-metal atoms (oxidation).

The electrodes are often made from graphite.
The liquid which conducts electricity is called the electrolyte.
The amount of electricity needed to produce a particular mass
of metal (or non-metal) can be calculated.

The negative electrode, called the cathode,
will attract positively charged metal ions.
The metal ions collect electrons from the cathode
and are discharged as metal atoms.

The positive electrode, called the anode,
will attract negatively charged non-metal ions.
The non-metal ions lose electrons to the anode
and are discharged as non-metal atoms.

For example, see lead bromide, magnesium chloride,
potassium chloride, sodium chloride and zinc chloride.
Electrolysis can also be used for metal plating.

Metals below carbon in the reactivity series are reduced
by heating with carbon because this is cheaper than electrolysis.

Metals above carbon in the reactivity series could be reduced
by reaction with a more reactive metal
but this is more expensive than electrolysis,
and is only used on a commercial scale for the extraction of titanium.

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Copyright © 2008 Dr. Colin France. All Rights Reserved.