Froth flotation is used in the mineral processing industry to separate hydrophobic value minerals from hydrophilic gangue and is considered to be the most widely used method for ore beneficiation. It also is a highly versatile method for physically separating particles based on differences in the ability of air bubbles to selectively adhere to specific mineral surfaces in a mineral/water slurry.
The particles with attached air bubbles are then carried to the surface and removed, while the particles that remain completely wetted stay in the liquid phase. Froth flotation can be adapted to a broad range of mineral separations, as it is possible to use chemical treatments to selectively alter mineral surfaces so that they have the necessary properties for the separation.
In ore beneficiation, flotation is a process in which valuable minerals are separated from worthless material or other valuable minerals by inducing them to gather in and on the surface of a froth layer. Sulfide and non-sulfide minerals as well as native metals are recovered by froth flotation. This process is based on the ability of certain chemicals to modify the surface properties of the mineral(s). Other chemicals are used to generate the froth and still others are used to adjust the pH. Certain chemicals are even capable of depressing the flotation of minerals that are either to be recovered at a later time or are not to be recovered.
It is currently in use for many diverse applications, with a few examples being: separating sulfide minerals from silica gangue (and from other sulfide minerals); separating potassium chloride (sylvite) from sodium chloride (halite); separating coal from ash-forming minerals; removing silicate minerals from iron ores; separating phosphate minerals from silicates; and even non-mineral applications such as de-inking recycled newsprint. It is particularly useful for processing fine-grained ores that are not amenable to conventional gravity concentration. Sodium ethylxanthate(CH3CH2OCS2Na, the CAS NO. is 140-90-9) is predominantly used in the mining industry as a flotation agent.
There are many factors that determine the success of floating a hydrophobic particle within a flotation cell: bubble diameter, turbulence within the cell, velocity of rising air bubbles, contact angle, collision efficiency, attachment efficiency, and stability efficiency. Chemical modification of these properties enables the mineral particles to attach to an air bubble in the flotation cell. The air bubble and mineral particle rise through the pulp to the surface of the froth or foam that is present on the flotation cell. Even though the air bubbles often break at this point, the mineral remains on the surface of the froth. The mineral is physically separated from the remaining pulp material and is removed for further processing.
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