Froth flotation

Froth Flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling, and waste-water treatment industries. Historically this was first used in the mining industry, where it was one of the great enabling technologies of the 20th century. It has been described as "the single most important operation used for the recovery and upgrading of sulfide ores".

History

The process was not froth flotation but used oil to agglomerate (make balls of) pulverized minerals, then separating them by water flotation, a method first developed by the brothers Bessel in the 1870s. The development of froth flotation has improved the recovery of valuable minerals, such as copper- and lead-bearing minerals. Along with mechanized mining, it has allowed the economic recovery of valuable metals from much lower grade ore than previously.

Process

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is achieved by first adding chemicals to the mixture to make the target particles hydrophobic. Air bubbles are then introduced into the mixture in a flotation tank. The hydrophobic particles attach to the air bubbles, which rise to the surface and form a froth layer that is then removed, while the hydrophilic particles remain in the liquid below.

Stages

1. Grinding: The ore is crushed and ground to a fine powder. 2. Conditioning: Reagents are added to the powdered ore to make the surface of the desired particles hydrophobic. 3. Froth Formation: Air is bubbled through the mixture, and the hydrophobic particles attach to the bubbles. 4. Collection: The bubbles and attached particles rise to the surface and form a froth that is skimmed off.

Chemicals Used

In froth flotation, various chemicals are used to aid the separation process. Collectors are used to increase the hydrophobicity of the particles. Frothers are added to stabilize the froth. Modifiers such as pH adjusters and depressants can also be used to enhance selectivity.

Applications

Froth flotation is widely used in the mineral processing industry to recover valuable minerals from ore. It is also used in the recycling industry to separate paper fibers from ink and other contaminants. In the environmental sector, it is employed in wastewater treatment to remove oils and other hydrophobic contaminants.

Advantages

The main advantage of froth flotation is its ability to selectively separate and recover valuable minerals from a mixture. It is a cost-effective and efficient method that can process large volumes of material.

Limitations

However, froth flotation also has its limitations, including the need for a specific chemical reagent for each type of mineral, potential environmental impacts from chemical use, and the requirement for skilled operators.

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  Flotation cell

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  Froth Flotation Plant at Argonne

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  Flotation at Falconbridge, Ontario

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  Flotation cell diagram

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  Jameson Cells at Mount Isa lead-zinc concentrator

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  Prominent Hill flotation

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  Potassium ethyl xanthate

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  Collectors used in flotation

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  Shifts in recovery curves