The effect of sulfide minerals on the leaching of gold in aerated cyanide solutions

The effect of galvanic interactions and sulfide mineral dissolution on the gold leaching kinetics in aerated cyanide solutions is investigated. Gold leaching kinetics were measured using a rotating electrochemical quartz crystal microbalance (REQCM), which measures the leaching rates in-situ. When the mineral is electrically in contact with gold, the gold dissolution rate increases as a result of the extra surface area available for oxygen reduction. However the leaching behavior of gold in the presence of soluble sulfide minerals is complicated. It is shown that the formation of sulfide ions in solution results in the passivation of the dissolution of gold. The addition of lead was found to be an effective means of alleviating this problem, as lead promotes the removal of sulfide by precipitation as PbS.