Galvanic interaction of grinding media with arsenopyrite and pyrite and its effect on gold cyanide leaching

This study investigates the galvanic interactions between different types of grinding media (forged steel, 30% chromium, and ceramic) with arsenopyrite and pyrite during the grinding process and their effects on gold cyanide leaching efficiency. Synthetic ores were prepared by mixing arsenopyrite or pyrite with clean gravity gold concentrate and quartz. The findings reveal that grinding with either 30% chromium or ceramic media resulted in more efficient gold leaching compared to forged steel media, largely due to the degree of iron hydroxide formation influenced by these interactions. Specifically, the greater formation of iron hydroxide when using forged steel resulted in the conversion of free cyanide to ferrocyanide, thereby reducing the cyanide availability for gold leaching. Additionally, the reduced dissolved oxygen content hampered the leaching process, especially during the initial stages. In contrast, lesser galvanic interaction in the presence of pyrite allowed for higher cyanide availability and ultimately improved gold extraction rates, with 70% gold extracted using 21% chromium media for pyrite, compared to 60% for arsenopyrite within 24 hours. Thus, the choice of grinding media significantly impacts cyanide consumption and gold recovery during the leaching process.