How does flotation concentrate ores containing platinum-group metals?

Platinum-group metals are typically recovered from copper or nickel sulfide minerals, which are concentrated using flotation separation.3

The flotation process works by exploiting the physicochemical surface properties of minerals, specifically their wettability. Because platinum-group metals are often associated with sulfide minerals, the process involves the following steps:1

• Surface Modification: Chemical reagents are added to a pulp of ground ore and water to alter the surface of the target mineral particles, making them hydrophobic (water-repelling).12
• Bubble Attachment: When air is passed through the flotation cell, these hydrophobic particles adhere to the rising air bubbles.12
• Froth Removal: The bubbles carry the mineral-rich particles to the surface, forming a froth that is skimmed off as a concentrate.12
• Separation: Unwanted minerals, which are hydrophilic (water-attracting), remain in the pulp and are removed as tailings from the bottom of the cell.1

In some cases, gravity separation is performed before flotation to further increase the concentration of the metals.3