Question

Illustrate the role of depressant in froth floatation method

Answer 1

Answer: To selectively allow the formation of froth.

Explanation:

If we want to separate out two ores of sulfide  i.e. ZnS and PbS from the solution.On directly applying the froth floatation method we will obtain the froth in which both sulfide ores will be present , which will be of no use.

So in order to prevent this froth containing both sulfides ,we add NaCN to the solution. NaCN will selectively form a complex with zinc sulfide and will prevent its froth formation. Thus NaCN acts as a depressant.

[tex] 4NaCN+ZnS\rightarrow Na_2[Zn(CN)_4]+Na_2S[/tex]