Ion Flotation

the process of extracting ions from solutions by the flotation method, in which ionogenic surface-active materials are used as the collecting reagents.

Ionic flotation was proposed in the 1950’s by F. Seba (Republic of South Africa). Gas bubbles and the collector are introduced into the starting solution. The latter forms surface-active ions in the solution. The charge of these ions is opposite to the charge of the ions to be extracted. The compound formed by the surface-active ions and the ions to be extracted is concentrated at the surface of the gas bubbles and is carried by the bubbles into the foam. The foam is then separated from the solution and broken down. The extracted ion, which is concentrated in the foam product, is then isolated by various methods, depending on the concrete conditions (the nature of the ion and the collector, the purpose of the flotation, and other considerations).

Ion flotation is performed in flotation machines (pneumatic and other) designed in accordance with the particular nature of the process. Ion flotation is highly productive. It is most effective at low concentrations of the ions to be extracted (less than 10^-3-10^-2 g-ion/liter). Ion flotation can be used in hydrometallurgy, waste water purification, and analytical chemistry.

Ion flotation may be used for the extraction of any metals, most often among them molybdenum, tungsten, uranium, platinum, germanium, and rhenium. An industrial installation for the ion flotation of molybdenum with primary amines is under construction in the USSR. The foam product would be burned to obtain technical-grade molybdenum trioxide. Treatment with hot soda solutions is also possible. In this case, the molybdenum is transferred into an aqueous solution and may be precipitated as calcium molybdate, while the amine (as the free base) floats to the surface of the aqueous phase. Upon conversion to the hydrochloride it may be used for ion flotation again.