The extraction is done by electrolysis. The ions in the aluminium oxide must be free to move so that electricity can pass through it.
Aluminium oxide does not dissolve in water, but it does dissolve in molten cryolite. This is 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 cell. The negative electrodes cathodes and the positive electrodes anodes are made of graphite, a form of carbon. Home Chemistry Applied.
Questions and Answers. Referencing this Article. The Process. Yes No I need help. How is aluminum extracted using electrolysis.
I really need a lot of help Aluminum is extracted from aluminum oxide by a process called electrolysis. First of all, aluminum oxide needs to be in molten form to extract the aluminum ions. Aluminum oxide, however, has a high melting point. Therefore, aluminum oxide is dissolved in molten cryolite. Cryolite is a form of an aluminum compound that has a lower melting point that aluminum oxide. If you need to reference this article in your work, you can copy-paste the following depending on your required format: APA American Psychological Association Extraction of Aluminium by Electrolysis.
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Dressing or concentration of the bauxite ore— Bauxite is generally found as an impure form of aluminium oxide. The process which gives the ore such a physical form so that the gauge can be easily removed from it, is called dressing of the ore. It is done by hand — picking, grinding etc. Bauxite ore generally contains ferric oxide and silica as impurities. Dressing of bauxite ore is done by crushing and pulverizing. To remove ferric oxide impurities from the bauxite, magnetic separation method is used.
It takes place by following three steps —. Step 1. Conversion of impure bauxite into sodium aluminate — The ore is fused to red heat with sodium carbonate and formation of sodium aluminate takes place. Reaction involved is given below —. Step 2. Conversion of sodium aluminate into aluminium hydroxide —. Step 3. Conversion of aluminium hydroxide into pure alumina —. Its electrolysis is done with cryolite 3 parts by weight and fluorspar 1 part by weight. In this process for electrolysis an iron tank lined with heat resistant material and has a sloping floor, provided with an outlet for tapping molten aluminium metal is used.
Gas carbon or graphite are used as cathode and thick carbon rods are used as anode. Coke powder covering is used to prevent burning of carbon anodes and to prevent heat loss from molten electrolyte. In this process sodium, calcium and aluminium ions are formed which migrates towards the cathode.
However, only aluminium ions reach to the cathode due to their lower position in the electrochemical series.
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