Evaluate the Depression of High-Concentration Pyrite in Copper Flotation by High-Chromium Grinding Media

The copper (Cu) concentrators have to process high-pyrite-content ores due to rapid depletion of high-grade ores and a high demand for Cu by clean energy technologies. However, depressing high-concentration pyrite in copper flotation is challenging presently. For the first time, this study evaluated 30 wt% Cr steel, a type of high-chromium (HiCr) steel grinding media, which can effectively produce a high Cu concentrate grade in processing low-concentration pyrite ores, in treating 25% pyrite in a Cu feed at 1.7% Cu in comparison with treating 5% pyrite in a Cu feed at the same Cu grade. Flotation tests showed decreased Cu grade and Cu recovery as pyrite feed grade increased from 5% to 25%, which was attributed to the changed galvanic interaction between grinding media and sulfide minerals, supported by ethylene diamine-tetra acetic acid disodium extraction, pulp chemistry measurements, and electrochemical studies. As pyrite feed grade increased from 5% to 25%, the anodic role of 30 wt% Cr steel did not change, but the anodic role of chalcopyrite and the cathodic role of pyrite were enhanced, promoting chalcopyrite oxidation while retarding pyrite oxidation, both of which facilitated copper activation on pyrite and subsequent pyrite flotation. This study also compared 30 wt% Cr steel and traditional forged steel in depressing 25% pyrite in the feed, and forged steel poorly depressed pyrite due to a strong anodic role of forged steel and a strong cathodic role of pyrite during the galvanic interaction leading to strong copper activation on pyrite. This study points to a direction how to depress high-concentration pyrite in copper flotation.