Question

which of the following acts as depressant in froth floatation process of galena which contains ZnS?
​(a) sodium ethyl xanthate
(b) pine oil
(c) copper sulpahte solution
(d)NaCNot KCN

Answer 1

which of the following acts as depressant in froth floatation process of galena which contains ZnS?
​(a) sodium ethyl xanthate
(b) pine oil
(c) copper sulpahte solution ✔✔
(d)NaCNot KCN

Answer 2

Answer:

The depressant which is used in the froth floatation process of galena contains $ZnS$ is $NaCN$ or $KCN$.

Therefore, option d) $NaCN$ or $KCN$ is correct.

Explanation:

Depressants:

• Depressants are deactivators that prevent the formation of froth in the froth floatation process.
• It helps to separate the two sulphide ores by preventing the froth formation of one ore and allowing the other to form froth.

So, in the given case of froth floatation process of galena which contains $ZnS$, the depressant used is $NaCN$.

• Sodium cyanide, $NaCN$, is used as a depressant an ore containing $ZnS$ and $PbS$ ( galena ).

This happens because $NaCN$ reacts with $ZnS$ to form $Na_{2}[Zn(CN)_{4}]$.

• $4NaCN + ZnS \rightarrow Na_{2}[Zn(CN)_{4}] + Na_{2}S$

• $NaCN$ forms a layer of the complex $Na_{2}[Zn(CN)_{4}]$ on the surface of $ZnS$ and thus prevents it from forming the froth.
• Just like $NaCN$, $KCN$ also used as a depressant in the froth floatation process of $ZnS$ and $PbS$.

Therefore, $NaCN$ or $KCN$ acts as a depressant.

Also, $NaCN$ or $KCN$ does not prevent $PbS$ from forming the froth and allowing it to come with froth.