How does flotation separate silver-bearing minerals from waste rock?

In silver processing, flotation is the primary method used to separate silver-bearing sulfide minerals from waste rock, known as gangue.12

The process works by exploiting the physicochemical surface properties of the minerals:3

• Preparation: The ore is crushed and finely ground to ensure the silver-bearing minerals are liberated from the waste rock.12
• Chemical Conditioning: The ground ore is mixed with water and specific chemical reagents. These reagents selectively coat the silver-bearing particles, making them hydrophobic (water-repelling).42
• Aeration: The mixture is agitated in a flotation cell, where air bubbles are introduced. Because the silver minerals are hydrophobic, they adhere to the rising air bubbles.243
• Separation: The bubbles carry the silver minerals to the surface, forming a mineral-rich froth that is skimmed off as a concentrate. The hydrophilic waste rock remains in the pulp and is discarded from the bottom of the cell as tailings.423

This method allows for a significant concentration of mineral values, often achieving a 30- to 40-fold increase in silver content.1