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Froth flotation separates materials based on their association with water. Association with water means that they are either hydrophilic (water-loving) or hydrophobic (water-repelling). Other than the water association, froth flotation also depends on factors like the density of materials, as it is a concentration process. A typical froth flotation includes 5 steps- Liberation, Conditioning, Flotation, frothing and separation. They use many chemicals, normally known as flotation reagents as collectors, activators, frothers, depressants and modifiers.
Froth flotation
Froth flotation is a concentration process of separating materials based on their association with water and density. It is most commonly used to separate the desired mineral component from a gangue. Physic- chemical properties of various chemicals are different. This is the principle for the separation of minerals using froth flotation.
Froth flotation process
Ore is treated through roughing, cleaning and scavenging to obtain the most concentrated form of our desired mineral without impurities.
- An ore is separated into various minerals by a process called ‘liberation’.
- Provide a hydrophobic environment for desired minerals using chemicals or surfactants by ‘conditioning’.
- A sludge form of minerals with water and frother is added to the flotation column by ‘flotation’.
- Frothing takes place with the incorporation of air and only desired minerals or metal levitate to surface with air bubbles- ‘Frothing’.
- Separate the froth with a maximum concentration of the desired mineral- ‘separation’.
List of chemicals used- meaning
For the process of froth flotation, we use various reagents. Most of them are in liquid form. If that is in dry form, it must feed dry. We normally use one pound of reagent for one ton of ore/minute.
- Collectors
We shall make our desired mineral hydrophobic to get it bound to air bubbles. Collectors act as a base for making minerals hydrophobic. It increases their floating capacity making them easy to separate.
Examples: Xanthates, thiourea thiocarbamide and fatty acid.
- Activators
As the name suggests, activators encourage the binding between collector and desired mineral.
Example: Copper sulphate
- Frothers
Frothers are foam creating reagents, which produce small air bubbles to which desired mineral is attached. Frothers reduce the surface tension of water.
Example: pine oil, cresylic acid and poly glycol.
- Modifiers
Interaction between mineral and collector should take place to run the froth flotation. Modifiers change the characteristics of a mineral and insist it attaches with the collector.
Example: lime and soda ash (pH modifier), phosphates and silicates (anionic modifier), Starch and dextrin (cationic modifier).
- Depressants:
These are the reagents used to depress the flotation of certain minerals other than the desired one. This one is acting like an inhibitor.
Example: Dichromate, Sodium cyanide.
List of chemicals-Questions
- Explain activators
As the name suggests, activators encourage the binding between collector and desired mineral.
Example: Copper sulphate.
- Explain depressants
These are the reagents used to depress the flotation of certain minerals other than the desired one. This one is acting like an inhibitor.
Example: Dichromate, Sodium cyanide.
- Explain collectors
We shall make our desired mineral hydrophobic to get it bound to air bubbles. Collectors act as a base for making minerals hydrophobic. It increases their floating capacity making them Easy to separate.
Examples: Xanthates, thiourea thiocarbamide and fatty acid.
- Explain modifiers
Interaction between mineral and collector should take place to run the froth flotation. Modifiers change the characteristics of a mineral and insist it attaches with the collector.
Example: lime and soda ash (pH modifier), phosphates and silicates (anionic modifier), Starch and dextrin (cationic modifier).
- What are frothers? Mention examples.
Frothers are foam creating reagents, which produce small air bubbles to which desired mineral is attached. Frothers reduce the surface tension of water.
Example: pine oil, cresylic acid and poly glycol.
Conclusion
Froth flotation separates materials based on their association with water. Association with water means whether they are hydrophilic (water-loving) or hydrophobic (water-repelling). Other than the water association, froth flotation also depends on the density of materials. It is a concentration process. A typical froth flotation includes 5 steps- Liberation, Conditioning, Flotation, frothing and separation. Froth flotation has wide recognition in practical life. Some of the uses of froth floatation include separation minerals, separation of plastics, sewage water treatments and recycling of paper. The froth flotation requires flotation reagents to work properly.
Froth flotation chemicals or reagents are mostly found in liquid form. In the case of dry reagents, they should be fed dry. Collectors, activators, frothers, modifiers and depressants are the reagents used in froth flotation. A large amount of reagents is used in the process. All these chemicals washing down to the environment causes serious pollution.
