Aluminium extraction

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Slide 1:

Aluminium It is a metal with a low density which means it is lightweight for its size. Aluminium is used for aircraft, trains, overhead power cables, saucepans and cooking foil.

General:

General Aluminium has a low density which means it is lightweight for it size. Is strong, malleable Good conductor of heat and electricity. It resist corrosion. It cannot be extracted by reduction . Extraction is expensive because there are several stages involved and the processes require a lot of energy .

Slide 3:

Aluminium resists corrosion as it has a very thin layer of its oxides on the surface, which stops air and water getting to the metal.

Extraction of metals:

Extraction of metals Only some unreactive metals such as silver, gold and platinum can occur freely in nature. Most metals react with other elements to form ores.

Major steps in extraction of metal:

Major steps in extraction of metal Ore concentration Ore is purified and concentrated, unwanted rocks removed Reduction to crude metal Metal oxides to be reduced to metals, resulting in a mixture of metals collected Refining to obtain pure metal To obtain a specific metal, purify and remove unwanted metal impurities

Ways of Extraction:

Ways of Extraction Potassium K Sodium Na Calcium Ca Magnesium Mg Aluminium Al Zinc Zn Iron Fe Tin Sn Lead Pb Copper Cu Mercury Hg Silver Ag Gold Au Platinum Pt Extracted by electrolysis of molten chlorides Extraction by reduction of oxides using carbon Extraction by electrolysis of molten Al 2 O 3 dissolved in cryolite Roasting ore by heating alone

Slide 7:

Extraction Unlike iron, aluminium cannot be extracted from their oxides by reduction with carbon because: It is more reactive than carbon, so the reaction does not work.

Ores:

Ores A rock is a mixture of minerals. A mineral is any solid compound or ore found naturally in the earth’s crust. Examples: haematite (iron), malachite (copper), bauxite (aluminium)

What is Aluminium Ore called? :

What is Aluminium Ore called? Aluminium ore is called bauxite. What is the Chemical Formula for Aluminium Oxide? Al 2 O 3 .

The extraction of aluminium:

The extraction of aluminium Cryolite is added to lower the melting point & to dissolve the ore & bauxite ore of aluminium oxide is continuously added When p.d is applied, Al 3+ is attracted to the negative cathode O 2- is attracted to the positive anode At the cathode, Al 3+ gains 3 electrons from the cathode to form molten aluminium , which is tapped off Al 3+ (l) + 3e -  Al (l) At the anode, O 2- loses 2 electrons to the anode to form oxygen 2O 2- (l)  O 2 (g) + 4 e - Oxygen released attacks carbon anode, to form Carbon monoxide/dioxide. Carbon anode dissolved. Needs to be replaced regularly

Slide 12:

In order to isolate pure aluminium, impurities must be removed from the bauxite. This is done by the Bayer process , which involves treatment with sodium hydroxide solution , followed by purification using electrolysis . { ref:wikipedia } Aluminium is mined in huge scales as bauxite.

Uses of Aluminium:

Uses of Aluminium Uses Properties Overhead electric cables Low density, light Resistant to corrosion (protected by aluminium oxide) Good electrical conductivity Food containers Non-toxic Resistant to corrosion Good conductor of heat Aircraft body Low density, light High tensile strength Resistant to corrosion