Question

What is the role of depressant in froth floatation process?

Answer 1

Depressants prevent certain types of particles from forming froth with bubbles. Due to this, we can separate two sulphide ores.

For example, sodium cyanide is a depressant used for an ore containing $ZnS$ and $PbS$. $NaCN$ forms a layer of the complex $N{a}_2\left[Zn\right(CN{)}_4]$ on the surface of $ZnS$ and prevents it from forming a froth. Thus, it acts as a depressant. However, $NaCN$ does not prevent $PbS$ from forming froth and allows it to come with froth.