Question

describe the bayers process for concentration of bauxite

Answer 1

The Bayer process is the principal industrial means of refiningbauxite to produce alumina(aluminium oxide).Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al2O3), the rest being a mixture of silica, various iron oxides, and titanium dioxide.

Answer 2

Answer:

Bauxite ore $(Al_2O_3.2H_2O)$ is concentrated by Bayer's process with the help of caustic soda $( NaOH )$.

Explanation:

1. For concentration of bauxite ore, first it is taken in a ball mill.

2. There is is ground.

3. After grinding, it is leached by heating with concentrated caustic soda solution ( NaOH ) at 140 to 150 °C under high pressure for 2 to 8 hours in the digester.

4. As aluminium oxide is amphoteric in nature it reacts with base sodium hydroxide. This forms salt sodium aluninate and water.

5. But, ferric oxide is metallic oxide and basic in nature, it does not react with NaOH.

6. As a result of this, it can be filtered out easily.

7. After this, sodium aluninate is cooled upto 50°C. This forms precipitate aluminium hydroxide.

8. When aluminium hydroxide is formed, water is added to it. Then it is leached, filtered, washed, and dried.

9. And then aluminum hydroxide is heated at 1000 °C and finally alumina and water are obtained.

Chemical Reactions:

1. When sodium aluminte reacts with water, sodium hydroxide and aluminium hydroxide are formed.

$\boxed{NaAlO_{2}+2H_{2} O\longrightarrow\:NaOH+Al(OH) _{3}}$

2. When aluminium hydroxide formed in the first reaction is heated, alumina and water are formed.

$\boxed{2Al(OH)_{3} \overset{\Delta} {\longrightarrow} Al_{2}O_{3}+3H_{2}O}$

Additional Information:

1. Aluminium:

1. Aluminium is a moderately reactive element.

2. Symbol of aluminium is 'Al'.

3. Colour of aluminium is silver white.

4. Atomic number of aluminium is '13'.

5. Electronic configuration of aluminium is 2, 8, 3.

6. The valency of aluminium is 3.

2. Extraction of Aluminium:

Aluminium is extracted in two steps.

1. Concentration of Bauxite ore.

2. Electrolytic reduction of Alumina.