How do air bubbles collect copper minerals in a flotation cell?

In the flotation process, copper minerals are collected through the precise chemical modification of their surface properties.

To facilitate this, finely ground ore is mixed with water and specific chemical reagents to create a slurry. These reagents are essential because they bind to the surface of the copper minerals, rendering them hydrophobic—or water-repellent—while the unwanted waste material, known as gangue, remains wetted by the water.12

When the slurry is agitated by mechanical or pneumatic devices, air bubbles are introduced into the mixture. Because the copper minerals have been treated to be hydrophobic, they do not mix with the water and instead adhere to the surface of these rising air bubbles. As the bubbles ascend to the top of the flotation cell, they carry the copper particles with them, forming a mineral-rich froth on the surface. This froth is then skimmed off as a copper concentrate, while the hydrophilic gangue minerals remain in the cell to be discarded as tailings.12