In froth flotation, depressants prevent non-target minerals from adsorbing collectors by forming hydrophilic films. Cyanide-based depressants are effective for pyrite, sphalerite, and chalcopyrite – in that order of depressant effectiveness.
Common cyanide depressants: sodium cyanide, potassium cyanide, yellow prussiate (ferrocyanide), and red prussiate (ferricyanide). Sodium cyanide is preferred for its lower cost.
Mechanism:
NaCN + H₂O → NaOH + HCN↑
HCN → H⁺ + CN⁻
Application guidelines:
- No inhibition: Pb, Tl, Bi, Sb, As, Sn, Rh minerals – cannot form stable cyano-complexes.
- Inhibition possible (higher dosage required): Pt, Hg, Ag, Cd, Cu minerals – form stable cyano-complexes.
- Strong inhibition (low dosage effective): Zn, Ni, Au, Fe minerals – form very stable cyano-complexes.
Due to cyanide’s ability to dissolve Au, Ag, Cu, Sb, and As minerals, non-cyanide depressants are strongly recommended for separation flotation involving these metals. Where cyanide use is unavoidable, minimize dosage and strictly enforce safety protocols.
Post time: Apr-13-2026
