The influence of cyanide salts and ferrous sulphate on pyrite flotation

The effect of cyanide salts as depressants, i.e. sodium cyanide (NaCN) and complex cyanide salts such as potassium ferricyanide (K3Fe(CN)6) and potassium ferrocyanide (K4Fe(CN)6), as well as combination of sodium cyanide with ferrous sulphate (FeSO4/NaCN) on pyrite flotation was investigated. Tests covered the frothless flotation of pyrite under different concentrations of depressants at various solution pH’s with potassium butyl xanthate (KBX) as collector. Flotation test results have shown that NaCN, and even more the combination of reagents FeSO4/NaCN are more successful in pyrite depression than complex cyanide salts, such as K3Fe(CN)6 and K4Fe(CN)6. Surface characteristics of pyrite were studied using rest potential (Eh) measurements and infrared attenuated total reflection spectroscopy (ATR-IR). In the presence of tested reagents in the flotation system, iron cyanide compounds and hydrated iron oxides were formed on pyrite surface. The composition of formed compounds depends not only on cyanide ions in the solution, but also on the pH of the system and solution species. These compounds, depending on the reagents used, are responsible for the resulting efficiency of the pyrite depression.