The effect of cathodic surface areas on galvanic interactions between grinding media, chalcocite and pyrite and subsequent mineral flotation

Sulphide mineral processing often involves grinding media and a number of types of sulphide minerals at various ratios of feed grades, but conventional studies on galvanic interactions for sulphide mineral processing often looked into dual-phase galvanic contacts with an equal surface area of anode and cathode. For the first time, this study investigated the galvanic interaction of a tri-phase galvanic system (GM-Cc-Py) consisting of grinding media, chalcocite and pyrite with different surface area ratios of pyrite to chalcocite (Py/Cc) to reflect the practical nature. The electrochemical studies found that chalcocite acted as a cathode in the galvanic system in the absence of pyrite, but it was switched to an anode after the addition of pyrite at Py/Cc = 1. An increase in pyrite surface area not only further anodised grinding media and chalcocite, but also increased the galvanic interaction and the oxidation of anodic materials. This nature of galvanic interactions was found to impact the pulp chemistry after grinding and also the mineral flotation behaviour. A greater pyrite surface area caused a more reducing pulp condition and higher chalcocite oxidation, both promoting copper activation on pyrite and then pyrite flotation. This study identified a high amount of pyrite recovered in copper mineral flotation at a high pyrite feed grade and suggested solving this problem by altering the cathodic role of pyrite.