Making Aluminum

Aluminum is a relatively abundant element in the earth's crust. Minerals are a commercial source of aluminum is bauxite. Bauxite contains aluminum in the form of aluminum oxide (Al2O3). Processing of aluminum into pure aluminum can be done through two steps:
1. Bauxite refining stage in order to obtain pure aluminum oxide (alumina)
2. Phase smelting alumina
Bauxite refining stage is to eliminate the major impurities in bauxite. The main impurities of bauxite typically consist of SiO2, Fe2O3, and TiO2. The trick is to dissolve the bauxite in sodium hydroxide (NaOH),
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) ---> 2NaAl (OH) 4 (aq)
Aluminium oxide dissolves in NaOH while pengotornya insoluble. Impurity-impurity can be separated through filtering processes. Furthermore, aluminum was deposited from the filtrate by means of CO2 gas flow and dilution.
2NaAl (OH) 4 (aq) + CO2 (g) ---> 2Al (OH) 3 (s) + Na2CO3 (aq) + H2O (l)
Aluminum hydroxide precipitate is filtered, dried and then heated in order to obtain pure aluminum oxide (Al2O3)
2Al (OH) 3 (s) ---> Al2O3 (s) + 3H2O (g)
Next is the stage by way of reduction smelting alumina through electrolysis process according to Hall-Heroult process.
In the Hall-Heroult, aluminum oxide dissolved in molten kriolit (Na3AlF6) in graphite-coated steel vessel which also functions as a cathode. Further electrolysis carried out at temperature of 950 oC. Graphite rod used as anode.
Source: www.ibchem.com
In the process of electrolysis aluminum produced at the cathode and the anode form O2 and CO2 gas
Al2O3 (l) ---> 2Al3 + (l) + 3O2-(l)






Cathode: Al3 + (l) + 3e ---> Al (l)
Anode: 2O2-(l) ---> O2 (g) + 4 e
C (s) + 2O2-(l) ---> CO2 (g) + 4e

Posted in: Post-transition metals