Deactivators

Froth flotation is a concentration process of separating materials based on their association with water and density. It is mostly used to separate the desired mineral component from a gangue. The physical-chemical properties of various materials are different. This is the principle for the separation of minerals using froth flotation. It has wide applications in the practical field. Some uses of froth floatation include separation minerals, separation of plastics, sewage water treatments and recycling of paper. The process requires several reagents to perform efficiently. Deactivators are one of the important reagents used in froth floatation.

Froth flotation

Froth flotation is a concentration process that selectively separates minerals based on their relation with water and their density. It is widely accepted over other separation methods like magnetic separation and gravity separation. The froth flotation method depends on the flotation reagents and not on the properties of minerals.

Froth flotation process

Ore is treated through processes like roughing, cleaning and scavenging to obtain the most concentrated form of our desired mineral without impurities.

• By a process called ‘liberation’, an ore is separated into various minerals.
• 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 the surface with air bubbles.
• Separation occurs when the froth is separated with a maximum concentration of the desired mineral.

List of chemicals used

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 use one pound of reagent for one ton of ore/minute normally.

• Collectors

We must 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 thiocarbanilide and fatty acid.

• Activators 

As the name suggests, activators encourage the binding between collector and desired mineral.

Examples: Copper sulphate

• Frothers

Frothers are foam creating reagents, which produce a small air bubble to which the desired mineral is attached. Frothers reduce the surface tension of water.

Examples: 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.

Examples: 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. Depressants act like an inhibitor.

Example: Dichromate, Sodium cyanide. 

Overview of deactivators

Deactivators are floatation reagents that usually work in association with activators. Activators like copper sulphate enhance the hydrophobic nature of desired minerals. Activators also help to levitate the desired mineral to air bubbles for binding. Deactivator does the opposite. It is used to retard the action of the activator. Copper flotation is deactivated when cyanide is added to the xanthate flotation of zinc sulphides. Depressants are also a kind of deactivator. The activator helps to levitate one mineral, whereas the deactivator retard the levitation of other minerals, which are not desired in our final concentrate.

In 1922, Sheridan and Griswold invented cyanide that can be used to depress iron sulphides. Similarly, agents like dextrin and starch can depress coal floatation. In 1930, Schafer found that dextrin and tannin can be used as a depressant in non-sulfide floatation. In 1949, it was found that Quebracho can be used as a depressant in cationic silica floatation. NaCN is used as a depressant to separate two sulphide ores. Zinc cyanide and synthetic functionalized polymers are some other examples of deactivators.

Conclusion

Froth flotation is a concentration process that selectively separates minerals based on their relation with water and their density. It is widely accepted over other separation methods like magnetic separation and gravity separation. Activator is kind of a catalyst promoting the binding between collector molecule and desired mineral. It helps to levitate one mineral in preference to another. Deactivators are floatation reagents that usually work in association with activators. It is used to retard the action of the activator. Copper flotation is deactivated when cyanide is added to the xanthate flotation of zinc sulphides. Depressants are also a kind of deactivator. The activator helps to levitate one mineral, while the deactivator retard the levitation of other mineral that is not desired in our final concentrate.