Galvanic interaction of grinding media with pyrite and its effect on floatation

A specialized grinding system linked to an electrochemical analysis set was used to quantify galvanic interactions between mild steel and pyrite. The individual polarization behaviour of mild steel and pyrite was measured in-situ of the mill. The extent of galvanic interactions between mild steel and pyrite was calculated from the electrochemical parameters. The galvanic current between mild steel and pyrite is dependent on the polarization behaviour, geometric relationship, and species in the grinding environment. The surface area ratio of mild steel to pyrite significantly affects the galvanic current density on mild steel, while its effect on pyrite is comparatively small. Dissolved oxygen played a pronounced role in determining galvanic current. Oxygen purging caused the highest galvanic current and the largest amount of EDTA extractable iron. Air purging produced intermediate values between oxygen and nitrogen purging. The amount of EDTA extractable iron derived from oxidation of grinding media during grinding is linear with the galvanic current density on mild steel. The floatability of pyrite is dependent on the galvanic current between mild steel and pyrite during grinding because the current is relative to the amount of iron oxidation species and the reduction rate on pyrite. (c) 2005 Elsevier Ltd. All rights reserved.