Question

Write the principle behind the froth floatation process. What is the role of collectors in the process?

Answer 1

During froth floatation substances are basically separated on the basis of whether they are water repelling or have an affinity for water. Collectors and froth stabilizers are added to the suspension for proper froth floatation.

Complete step by step answer:
-First let us see what an ore is.
Any rock that contains one or more than one valuable minerals together, which can be extracted, refined and sold in the market at a profitable rate are known as ores. These ores are extracted from the minerals via mining and treated well enough (often via smelting) to extract the minerals from it and separate them from each other. One of these purification processes is froth floatation.
-We will now talk about what froth floatation is.
Froth floatation is basically the process of selective separation of hydrophobic substances from hydrophilic substances. In this beneficial materials are separated from the mixture by the creation of froth on which minerals separate out. Most commonly the ores of lead, copper and zinc are separated by this process.
-We will now talk about the basic principle of froth floatation.
This process starts with comminution where the surface area of the ore is increased. First the ores are crushed into very fine powder and mixed with water to form a mixture called slurry. To the slurry we add a surfactant chemical known as collector which enhances the hydrophobic nature of the mineral or increases the non-wettability of the metal part of the ore which allows the formation of froth. Froth stabilizers (like aniline and cresols) are also added to sustain the froth. All this converts the slurry into pulp which is then transferred to a container filled with water constantly stirred and paddled with air to create froth. Since the mineral is repelled by water it comes out in the form of froth which is separated and sent for further refining and extraction.
-As we discussed above the collectors are added to increase the hydrophobic nature of mineral or say the non-wettability of the mineral part of the ore and allows the formation of froth. A collector is an organic compound which attaches selectively to the mineral surface and adds water repelling nature to the particles which is extremely important for adhesion of mineral particles to air bubbles or froth. Some common collectors used are: pine oils, fatty acids, etc.

Note: A collector can be of 3 types: non-ionic, anionic or cationic.

1. Non-ionic collectors: They are simple hydrocarbon oils which increase the hydrophobic nature of minerals. For example: fuel oil, kerosene oil, etc.
2. Anionic collectors: They have a non-polar part and an ionic part of which the cationic part does not increase the hydrophobic nature of minerals. For example: soaps (carboxylates).
3. Cationic collectors: In these the cationic part increases the non-wettability of the metal part of the mixture.