What is hydrometallurgy process ?

Explanation

It is the process of extraction of metal from its ore by dissolving the ore in a suitable solvent, filtering the solution and then precipitating the metal by adding suitable substance. Less reactive metals like Cu, Ag, Au are extracted from their respective ores by this method.
For example, in the extraction of gold (Au) the ore is made to react with KCN (aq) in the presence of air `(O_(2))` when gold dissolves leaving behind the earthy impurities.
`8Au+8KCN+2H_(2)+O_(2) to 4K[Au(CN)_(2)]+4KOH`
From this soluble complex, gold can be recovered by adding zinc.
`2K[Au(CN)_(2)]+Zn to K_(2)[Zn(CN)_(4)]+2Au`.