Aluminium

Principal ore : Bauxite, which is an impure form of aluminium oxide (Al₂O₃).

There is NO bauxite in the UK. Therefore, it must be imported from places (e.g. Jamaica) . This means that Aluminium smelters (factories that make Aluminium) tend to be on the coast to minimise transport costs, or in mountainous regions where there is available fast flowing water (Hydro-Electric Power). This presented difficulties in transporting raw materials and products.

Purified Bauxite is dissolved in molten Cryolite (an Aluminium containing mineral Na₃AlF₆). This is used because it has a lower melting point that Al₂O₃, so energy costs are lowered, but the electrolyte behaves as if it were Al₂O₃

N.B. Electrode reactions are endothermic.

At the Cathode (-)

Al²⁺_(l) + 3e^- à Al_(l)

Aluminium ions are attracted and discharged
These electrons come from the electric current
We see that Aluminium ions have been reduced - they have gained electrons

At the Anode (+)

Oxide ions are collected and discharged

2O^2- - 4e- à O₂

These electrons join the current in the external circuit
Due to the high temperatures of the cell, the Carbon anodes burn in the Oxygen produced at them.

C + O2 à CO2

This means that the anodes need to be regularly replaced.

Aluminium is the most abundant metal in the earth's crust, but it's uneconomical to extract it from most rocks and clays because :

Only the electrolyte is molten, the passage of electric current generates enough heat to keep it molten. This is the main reason for the process being continuous. The cell is constantly kept operational and regularly topped up with Aluminium Oxide and some Cryolite.

Very large currents are needed. For this reason, early aluminium smelters were often sited in mountainous regions, where there was access to relatively cheap hydroelectric power. This made transport of raw materials and products to their markets difficult

Recycling

The main reason for recycling is to conserve finite natural resources of bauxite and to preserve the landscape in the areas where bauxite is mined.
The overall process is slightly cheaper, but the saving in energy is nearly balanced by the collection of scrap Aluminium and its separation from other metals and coatings.

Properties of Aluminium

Aluminium has all the properties of a metal, with three extra properties making it particularly useful.

1. Low Density

2. Resistance to Corrosion - Aluminium is much more less reactive than its position in the reactivity series suggests. This is because it is covered with a thin, hard, invisible, uniform, unreactive protective layer of Aluminium Oxide. This layer may be thickened by a process known as Anodising.

3. Aluminium's Conduction of heat and electricity is higher than average.

Uses

1. Overhead Power Cables (Low Density and Conductivity)

2. Cooking Foil (Resistance to Corrosion).

3. Cooking pans (Low Density and Resistance to Corrosion).