Influence of grinding media and water quality on flotation performance of gold bearing pyrite

Flotation performance is strongly dependent on the surface properties of the constituent mineral particles, and may therefore serve as a diagnostic tool to evaluate grinding chemistry interactions. The surface properties can be altered by numerous factors such as the type of grinding media used in the preparation of the flotation feed, the presence of chemical species in the process water, and the characteristics of flotation reagents added. This paper investigates the influence of grinding media (forged steel, 18% chromium and ceramic) and water quality (tap water and synthetic process water) on floatability of gold bearing pyrite using XPS and EDTA extraction technique. The grinding of pyrite ore was performed in a Magotteaux Mill which allowed better simulation of plant chemical conditions by controlling pH and pulp potential during the grinding. Cupric ions were added as an activator prior to the grinding. This work demonstrated that there is no significant effect of water quality on flotation performance of pyrite. The results also showed that the pyrite recovery was slightly higher when the grinding was performed with the forged steel media rather than with the chromium media or the ceramic media. XPS and EDTA extraction technique demonstrated that the forged steel media produced more iron hydroxide species than the 18% chromium or the ceramic media, indicating the high corrosion rate of the forged media. XPS technique failed to explain the influence of different grinding media on the floatability of pyrite from its ore probably due to the insensitivity of XPS technique to detect the presence of a low amount of copper species on the surface of the particles collected by flotation. The results obtained from this study confirmed that the selection of grinding media may be important to maximize pyrite recovery by flotation. The conclusions should be limited to ores low (< 2%) in pyrite content, and where there are no reactive sulfides present other than pyrite. From an economic perspective, the marginal impacts on flotation should be balanced against grinding media wear.