Question

The bauxite ore of aluminium is concentrated by froth flotation

• A. True
• B. False

Answer 1

The correct option is B

False

Froth floatation is mainly used for sulphide ores. It takes advantage of the difference in the wetting properties of the ore and the gangue particles.

1. Sulphide ore particles are wetted by oil.
2. Gangue particles are wetted by water.
3. Thus froth carries the ore particles to surface and is easily separated from gangue

Bauxite being an oxide ore froth flotation cannot be used. Thus we make use of leaching to concentrate the bauxite ore.

Leaching is a chemical separation which involves treatment of ore with a suitable reagent (NaOH) to make the metal soluble and impurities being unaffected. This leached metal can easily be separated.

$A{l}_2{O}_3.2H_{2}O\left(s\right)$ $+2NaOH\left(aq\right)$ $+H_{2}O\left(l\right)$ $\to$ $2Na\left[Al\right(OH{)}_4\left]\right(aq)$

$2Na\left[Al\right(OH{)}_4]$ $+2C{O}_2$ $\to$ $A{l}_2{O}_3$ . $x{H}_{2}O$ $+2NaHC{O}_3$

$A{l}_2{O}_3$ . $x{H}_{2}O$ $\to$ $A{l}_2{O}_3$ $+x{H}_{2}O$