A specific depressant, , is added to a flotation tank containing a mixture of Galena () and Sphaleri — Metallurgy and Isolation of Elements Chemistry Question
Question
A specific depressant, $NaCN$, is added to a flotation tank containing a mixture of Galena ($PbS$) and Sphalerite ($ZnS$). What is the exact chemical mechanism by which this depressant facilitates separation?
Answer: B
💡 Solution & Explanation
$NaCN$ acts as a depressant for $ZnS$. It selectively reacts with $ZnS$ to form the highly stable and water-soluble complex sodium tetracyanozincate(II), $Na_2[Zn(CN)_4]$, preventing it from forming a froth, while $PbS$ floats.
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