Flotation

The anionic flotation method for collection of fatty acids was first used in Karlsbad (Germany) in 1934. It is based on the different ability of ores to hold at the interphase boundary in a liquid medium. It is possible to artificially alter the wettability of mineral surfaces by applying flotation reagents. Poorly-wetted (hydrophobic) particles stick to the air bubbles, float to the surface and form a mineralised foam whereas well-wetted (hydrophilic) particles do not stick to the bubbles.

Three types of flotation:
1. Film flotation. The crushed ore is poured from a low height to the water surface. Non-wettable particles remain on the surface and are distilled into the flotation product while wettable particles pass into the aqueous phase. This process is not widely used due to its low efficiency.

2. Oil flotation. Mineral particles are wetted with light oil dispersed in water forming aggregates of particles enclosed into oily membranes, which float to the surface.

3. Foam flotation. Floating (hydrophobic) particles are fixed to the air bubbles, which take them to the surface, forming a layer of mineralised foam. Hydrophilic particles remain inside. Foam flotation is widely used in the global potash industry.