Complete the following statement using every given options.
During the extraction of aluminium_____
Ingredients and gangue in bauxite

Options

A. Ingredients of gangue and bauxite.
B. Use of leaching during the concentration of ore.
C. Chemical reaction of transformation of bauxite into alumina by Hall's process.
D. Heating the aluminium ore with concentrated caustic soda.

Explanation

During the extraction of aluminium, the ingredients of gangue and bauxite . are separated by leaching. This is done by either Bayer's process or Hall's process. In Bayer's process, aluminium ore is heated with concentrated caustic soda while in Hall's process, it is heated with aqueous sodium carbonate to obtain water soluble sodium aluminate. In Hall's process, sodium aluminate is converted to aluminium hydroxide, which is obtained as precipitate of aluminium hydroxide is filtered , washed, dried and calcined to obtain pure alumina. Thus, the chemical reaction of transformation of bauxite into alumina by Hall's process involves leaching followed by calcination