this is a ppt about extraction of aluminium

1. Aluminium

2. Who discovered it Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a styptic. In 1761 Guyton de Morveau suggested calling the base alum alumine. In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first named alumium and later aluminium (see Spelling section, below). Friedrich Wöhler is generally credited with isolating aluminium (Latin alumen, alum) in 1827 by mixing anhydrous aluminium chloride with potassium. The metal, however, had indeed been produced for the first time two years earlier — but in an impure form — by the Danish physicist and chemist Hans Christian Ørsted. Humphry Davy Hans Christian Ørsted

3. The extraction of aluminium The extraction is done by electrolysis. Aluminium oxide has a very high melting point (over 2000°C) and it would be expensive to melt it. So instead it is dissolved in molten cryolite - an aluminium compound with a lower melting point than aluminium oxide. The use of cryolite reduces some of the energy costs involved in extracting aluminium. The diagram shows an aluminium oxide electrolysis tank. Both the cathode and the anode are made of graphite, a form of carbon. Aluminium forms at the negative electrode and sinks to the bottom of the tank, where it is tapped off. The equation for this reaction isAl3+ + 3e- Al Oxygen forms at the positive electrodes. The equation for this reaction is2O2- - 4e- O2 The oxygen reacts with the carbon of the positive electrodes, forming carbon dioxide, and they gradually burn away. Consequently the positive electrodes have to be replaced frequently, which adds to the cost of the process. Cryolite- (Na3AlF6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once large deposit at Ivittuut on the west coast of greenland, depleted by 1987.

4. Info About Aluminium Aluminium: Is strong, malleable and has a low density. Is resistant to corrosion. A good conductor of heat and electricity. Can be polished to give a highly reflective surface.

6. Importance of Recycling Due to the large energy use in the extraction process, it is vital that we recycle. Recycled aluminium only requires 5% of the energy needed to extract fresh aluminium. Remember to recycle, because energy can be better spent. A customised can

7. A Presentation by zohab