LAUSR

Abstract During the cyanidation of gold‑copper ores and concentrates, the chalcopyrite significantly increases cyanide consumption. The effects of PbO on the chalcopyrite dissolution mechanisms were studied by SEM and XPS analyses during cyanation. A small amount of PbO could promote the dissolution of chalcopyrite, while more PbO would inhibit dissolution. When 0.5 g/L PbO was added, the main lead compound on the surface of chalcopyrite was PbS, which could enhance the electron transfer between cyanide and chalcopyrite, thus facilitating the dissolution of chalcopyrite. The amount of PbS precipitates increased in the leaching system when the amount of PbO was more than 0.5 g/L. This reduced prominently the free sulfide ions concentration in the solution. PbS would be oxidized to form thiocyanate and lead (II) ions when the concentration of sulfur ions decreased continuously in the solution. These lead (II) ions would react with OH– to form Pb(OH)2 precipitates, which attach to the surfaces of chalcopyrite and inhibit its dissolution in cyanide solutions. The developed method can not only improve the leaching rate of gold but also reduce the consumption of reagents.