Question

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

Answer 1

As the name suggests depressants lead to depression in the froth formation and thus have found an important role in the froth floatation process.The froth floatation process is used in metallurgy to separate the ore and the impurities based on their differing solubilities in water.

Complete solution
We know that in the froth floatation process, we remove gangue from sulphide ores by making froth of particles of required minerals. We make use of collectors and froth stabilizers for doing that as collectors such as oils or fatty acids leads to an increased non-wettability for our mineral particles and on the other hand, froth stabilizers such as cresols and aniline help us in stabilizing the froth as it is a common knowledge that froth is lighter and thus we can skim it off, so we can easily remove the mineral particles in the similar manner.
Now let’s talk about depressants. Let’s assume that we have two different types of sulphide ores but we want only one of them in froth so that we can separate them. For this very purpose, we can use a depressant. Depressants prevent one of the sulphide ore to come into the froth but allow another sulphide ore to do so, selectively. For example, we can use sodium cyanide as a depressant in case of zinc sulphide and lead sulphide where it will allow lead sulphide to form the froth but will not allow zinc sulphide to come to the froth.
Hence, we can say that the role of depressants in the froth floatation process is to help us with selective froth formation of one sulphide ore and selective prevention for another.

Note:
We can also separate two sulphide ores by using water and oil in a suitable ratio adjusted accordingly. Pockets of air are passed to help the lighter material move upwards.