# 6.2 What is the role of depressant in froth floatation process?

Role of depressant in froth flotation method is to separate two sulphid ores by adjusting one ore to form froth. For example- $NaCN$ is used as a depressant it selectively prevents $ZnS$ to coming to the froth but allows PbS with the froth. NaCN react with $ZnS$ to form $Na_{2}[Zn(CN)_{4}]$
$4NaCN+ ZnS\rightarrow Na_{2}[Zn(CN)_{4}]+ Na_{2}S$