The role of depressants in Froth Floatation method* is to

In froth floatation process, depressant prevents the formation of froth. It is used to separate two sulphide ores by preventing the formation of froth of one sulphide ore and allowing the other to form the froth e.g. NaCN, a depressant  selectively prevents Zns from coming in froth but allows PbS to come with the froth.