Question

What is the role of depressant in the froth floatation process?

Answer 1

Depressants are also known as deactivators which deactivates the minerals surface by resisting it towards the action of collectors. The depressant increases the selectivity of the floatation.

Complete step by step answer:
-The froth floatation process is a method employed to separate the minerals from the impurities by forming froth in which the minerals separates out.
-In the froth floatation method, first the surface area of the ore is increased. Firstly the ore is crushed fine powdered size particles and mixed with the water. The mixture is called a slurry. A collector is then added to the slurry which acts as a surfactant chemical. This increases the hydrophobic nature of the mineral.
-The slurry is then changed to pulp which is added with water in the container and air is passed through the container to form bubbles. The mineral being hydrophobic gets repelled by the water and gets attached to the bubbles. With the rise of air bubbles with the sticky minerals is called froth which is then separated by the process of refining and extraction.
-In froth floatation method, the depressant is used to separate two sulphide ores by preventing the formation of froth by one ore and allow the other ore to be attached with the froth.
-Example: For separating two ores ZnS and PbS, NaCN is used as a depressant. It allows PbS to form froth and prevents ZnS to come in contact with the froth.

Note:
The depressant is a selective depressant. The depressants are the enemies of collectors used in the process. The depressant can be inorganic and organic depending on the ore.