The bauxite ore of aluminium is concentrated by froth flotation
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.
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.
Al2O3.2H2O(s) +2NaOH(aq) +H2O(l) → 2Na[Al(OH)4](aq)
2Na[Al(OH)4] +2CO2 → Al2O3 . xH2O +2NaHCO3
Al2O3 . xH2O → Al2O3 +xH2O