NOV 25, 2014

How to Extract Aluminium Oxide

Aluminium is the third most abundant element in the earth, behind oxygen and silicone. It forms approximately 8 % of the earth’s crust. The element is known to bond with other elements and for that reason, it’s hardly ever found in its original form.

The extraction of aluminium is typically achieved via a chemical process, followed by electrolysis. The first step is known as Bayer’s refining process.

Discovered by the Austrian chemist in 1888 bauxite is first crushed and grounded into powder form. Once this process has been completed, it is them mixed with a hot solution of caustic melts aluminium oxide to solution form, known as sodium aluminate.

Impurities like silicon oxides, lead and iron remain in solid form and are easily filtrated out. Once this process is completed liquid sodium aluminate is added, then by settling and vacuum filtering the solid is then washed, dried and heated at a high temperature to remove any liquor. The result is that we now have get white powdery aluminium oxide, also known as alumina.

The process of extracting aluminium oxide is known as Hall-Heroult smelting. The aluminium oxide is extracted using electrolysis. Two metal electrodes are submerged in liquid containing positive and negative irons, one electrode being positively charged and the other being negatively charged.

The anode (positive) and the negative (cathode) repel the opposite charge and attract any present iodes. In the smelting process the electrolyte is placed in an iron vat called a pot, which is then lined with graphite. This pot acts as a cathode.

Carbon is immersed in the electrolyte, which acts as an anode. Alumina is dissolved in synthetic cryolite at a very high temperature of 1000 degrees Celsius to form a molten solution. Despite the higher melting temperature of alumina the mixture allows for electrolysis to occur at lower temperatures.

Electricity is then passed through this molten material which causes the oxygen from the aluminium oxide to bond with the carbon of anode forming carbon dioxide gas. The aluminium attracts to the cathode and collects at the bottom of the pot and is then collected periodically from the bottom by a plug.

This is how to extract aluminium oxide. If you have any questions, please don’t hesitate to get in contact with us.

Created on 25th November 2014
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