Metal flotation

Flotation is the process of separation of crushed solids (metal ores) based on the difference in wettability of components.

As a result of flotation processes, the particles of useful components are separated from the gangue. Before separation, however, the raw materials must be properly crushed (into fine and light powders) so that after they are adsorbed on the surface of air bubbles they can float to the surface.

Flotation is carried out in an aqueous medium, in a suspension of solid particles. It consists of selective attachment of air bubbles, dispersed in the suspension, to particles having hydrophobic surface. Only metal particles have the ability to adsorb on the surface of bubbles. The resulting formation (air bubble/particle) is lighter than water and flows on its surface in the form of foam. Then the foam enriched with metal is collected and the residue is returned to the process. Gangue particles do not bind with air bubbles. These operations must be repeated a few times to make sure that metal is recovered to an appropriate degree.

Additives ensure that the process is carried out efficiently and effectively. These are foam-forming substances which cause the formation of denser and more stable foam during the process; surface wettability modifiers which increase the flotation efficiency; and so-called collectors which selectively adsorb on the surface of particles.

Flotation processes are also used in the paper industry to recycle waste paper and in waste water treatment plants.