An investigation into the flotation behaviour of pyrrhotite

It is well-known that pyrrhotite is a slow floating mineral and there are many studies investigating its behaviour in the presence of pentlandite with which it most frequently occurs. In the treatment of massive sulphides the process often aims to depress the pyrrhotite whereas in other applications such as the treatment of platinum group elements (PGE) losses of the mineral may result in losses of PGEs as well as a reduced availability of sulphides required for smelter operation. The causes of pyrrhotite's poor floatability and reagent usage and the conditions encountered at the pHs typical of circuits treating pyrrhotite bearing ores are still a subject of considerable research. The present study was undertaken to measure the extent and rate of reaction of a relatively pure pyrrhotite sample using a standard xanthate collector at different pHs and conditioning times. The role of copper sulphate as an activator and guar as a depressant were also investigated. The effect of these treatments on the hydrophobicity of the pyrrhotite was determined by microflotation tests. This study has shown that under most conditions surface coverage of SIBX-originated species on the pyrrhotite equates to multi-layer coverage and that this is promoted by the pre-treatment with copper sulphate. Longer conditioning times increase surface coverage and recovery. Guar when added before copper sulphate using different addition regimes will depress the pyrrhotite. The findings and their significance for pyrrhotite flotation on flotation plants are discussed.

Research Highlights
► Pyrrhotite adsorbs multi-layer coverage by xanthate from pH 5–10.
► Adsorption of xanthate is slow but increases with longer conditioning times.
► Flotation rates are slow at higher pHs.
► Iron hydroxide species and guar depress pyrrhotite.
► Copper sulphate acts as activator for the flotation of pyrrhotite.