Dissolving Aluminium Oxide in Cryolite

During the process of extracting aluminium from bauxite, it is required that the alumina is dissolved in Cryolite. The dissolution of the alumina in Cryolite is done using a transparent quartz crucible.

The procedure for dissolving the alumina in Cryolite involves three stages. The first stage is the formation of the electrolyte. The second stage is the cathodic reaction, and the third stage is the dissolution.

In the first stage, sodium aluminate is diluted with water to form the sodium hydroxide solution. The solution is then heated until the water is evaporated. Then, it is filtered to remove the water. In the second phase, the solution is cooled to about 50 degC. This is followed by the secondary cathodic reaction of deposition of sodium. The sodium ion is carried by 95% of the current. The dissolution velocity of the alumina depends on its type. Its speed increases with the temperature of the alumina.

The metal ions have a high melting point. They are usually conductors of electricity. Copper, lead, and iron can be extracted from oxides with the help of reducing agents. However, the process involves air pollution. The carbon monoxide produced during the process can cause atmospheric pollution.

When the aluminum ions are reacted with the negative cathode, they lose their electrons. This is why it is important that the alumina ions are free to move in the liquid. It is also important that the anode is replaced periodically.

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