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Extraction of alluminum - Coggle Diagram
Extraction of alluminum
ORES OF ALUMINIUM :
Bauxite
Cryolite
Corundum
Bauxite is reacted with - conc. soln. of NaOH under pressure for 2 hrs as a first step in obtaining
Hence impurities-are separated out Therefore caustic alkali-is added to bauxite ore during purification of bauxite
The impurities present in bauxite - mainly Fe-O and SiO2 & remain unaffected with conc. NaOH-since impurities are not amphoteric .Bauxite being amphoteric-reacts with the base forming - salt and water.
SODIUM ALUMINATE - ALLUMINIUM HYDROXIDE
NaAlO₂+ 2H₂O = NaOH + Al(OH)3
50-60 C
sodium aluminate NaAlO₂ is diluted with H₂O & crystals of Al(OH)3, are added to it
CONVERSION OF Al(OH),- TO PURE ALUMINA
2Al(OH)3 = (1100 C) + 3H2O
Conversion of CONCENTRATED ORE TO ITS OXIDE
Step not necessary in metallurgy of aluminium, since ore is already an oxide
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