Flottation

Flottation, often written flotation in American English, is a separation process used to separate and concentrate minerals or other particulates on the basis of differences in surface properties. In a flotation cell, a slurry is aerated so that hydrophobic particles attach to ascending air bubbles. The bubbles rise to the surface, forming a froth that can be skimmed off as a concentrate, while hydrophilic particles remain in the liquid as tailings. The method is a cornerstone of mineral processing and is also used in some wastewater treatment and recycling operations.

The effectiveness of flottation depends on surface chemistry and particle size. Collectors are reagents that render target minerals hydrophobic, enhancing bubble attachment. Frothers help create a stable froth network. Modifiers and depressants adjust the pulp chemistry to suppress unwanted minerals and control pH. The process is most efficient for fine to moderately fine particles and often requires stagewise conditioning and cleaning to improve grade and recovery. In practice, various cell designs and configurations are used to optimize bubble generation, residence time, and froth stability.

Equipment and operation vary but typically include flotation cells such as mechanical or pneumatic machines, and, in some installations, flotation columns or Jameson cells. The slurry is conditioned with reagents, air is introduced to form bubbles, and a froth layer is collected as concentrate while the remaining slurry becomes tailings. Flottation is widely applied to recover copper, zinc, lead, nickel, gold, and other metals from ores, as well as to coal, industrial minerals, and de-inking or wastewater treatment applications.

See also mineral processing, froth flotation cell, flotation reagents.