The interaction between grinding media and collector in pyrite flotation at neutral and slightly acidic pH

Abstract

Gold often coexists with pyrite as micron and submicron-inclusions and pyrite is therefore floated to maximize gold recovery in gold processing plants. In practice, different types of grinding media and a great range of pH and collector concentrations are used for pyrite flotation without scientific guidance. In this study, the effect of three different types of grinding media including forged steel, 15% chromium steel and 30% chromium steel on pyrite flotation at a range of collector (potassium amyl xanthate) concentration was investigated at pH 5.0 and 7.0, and the underpinning mechanism was determined through pulp chemistry measurement, X-Ray Photoelectron Spectroscopy (XPS) surface analysis and electrochemical measurement. It was found that grinding media had a different effect on pyrite flotation at pH 5.0 and 7.0. At pH 5.0, both iron contamination originating from grinding media and xanthate oxidation played an important role in pyrite flotation. While iron contamination on the pyrite surface depressed pyrite flotation, it might be reduced by xanthate oxidation. This explains higher pyrite flotation after grinding with chromium steel than forged steel and at a higher collector concentration. At pH 7.0, pyrite flotation was mainly controlled by xanthate concentration. At a low xanthate concentration, pyrite oxidation was the predominant anodic reaction and pyrite flotation was poor due to the inability to form dixanthogen. At a high xanthate concentration, the formation of dixanthogen became predominant, which facilitated pyrite flotation.