The ore mined from the earth contains some unwanted substances called gangue. Enrichment of ore is done by various methods depending upon the nature of the impurities. Hydraulic washing is the process based on the difference in densities of ore and gangue particles. Froth floatation method is used for ores with different wetting properties of ore and gangue particles. On adding sulphide ore in a mixture of oil and water, the sulphide particles are wetted by oil and gangue particles are wetted by water. On passing air in this mixture, sulphide ore particles form light oily froth and reach the surface whereas gangue particles settle down at the bottom. Few ores are enriched by chemical processes.
WHich method is used for the purification of bauxite ore ?

Options

A. Levigation
B. leaching
C. Electrolysis
D. Magnetic separation

Answer

B

Explanation

Bauxite `Al_(2)O_(3)` is concentrated by leaching `Al_(2).2H_(2)O + 2NaOH to 2NaAlO_(2) + 3H_(2)O`
`NaAlO_(2) + 2H_(2)O to Al(OH)_(3) + NaOH`
`2Al(OH)_(3) overset(Delta)to Al_(2)O_(3) + 3H_(2)O`