with referencesto Aluminium answer thefollowing questions:
Any three of its feature.
Answers
Answer:
a) aluminum is obtained from bauxite
b) it is mineral formed due to the decomposition of rocks
c)The major impurities in Bauxite are iron oxides, silicon dioxide, the clay mineral kaolinite as well as small amounts of anatase.
d)
The extraction process converts the aluminium oxide in the ore to soluble sodium aluminate, 2NaAlO2, according to the chemical equation:
Al2O3 + 2 NaOH → 2 NaAlO2 + H2O
This treatment also dissolves silica, but the other components of bauxite do not dissolve. Sometimes lime is added at this stage to precipitate the silica as calcium silicate. The solution is clarified by filtering off the solid impurities, commonly with a rotary sand trap and with the aid of a flocculant such as starch, to remove the fine particles. The undissolved waste after the aluminium compounds are extracted, bauxite tailings, contains iron oxides, silica, calcia, titania and some unreacted alumina. The original process was that the alkaline solution was cooled and treated by bubbling carbon dioxide through it, a method by which aluminium hydroxide precipitates:
2 NaAlO2 + 3 H2O + CO2 → 2 Al(OH)3 + Na2CO3
But later, this gave way to seeding the supersaturated solution with high-purity aluminium hydroxide (Al(OH)3) crystal, which eliminated the need for cooling the liquid and was more economically feasible:
2 H2O + NaAlO2 → Al(OH)3 + NaOH
Some of the aluminium hydroxide produced is used in the manufacture of water treatment chemicals such as aluminium sulfate, PAC (Polyaluminium chloride) or sodium aluminate; a significant amount is also used as a filler in rubber and plastics as a fire retardant. Some 90% of the gibbsite produced is converted into aluminium oxide, Al2O3, by heating in rotary kilns or fluid flash calciners to a temperature in excess of 1000 °C.
2 Al(OH)3 → Al2O3 + 3 H2O
The left-over, 'spent' sodium aluminate solution is then recycled. Apart from improving the economy of the process, recycling accumulates gallium and vanadium impurities in the liquors, so that they can be extracted profitably.
e)Bayer process
Explanation:
Hope that it's helpful
Answer:
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