Question

An ore contains Pbs with impurity Zns. NaCN is added in the froth flotation process ZnS does not form the froth because​

Answer 1

$<bullet> For example, in order to separate two sulphide ores (ZnS and Pbs), NaCN is used as a depressant. It selectively allows PbS form froth, but prevents ZnS from coming to froth. This happens due to the fact that NaCN reacts with ZnS to form Na2[Zn(CN)4].$