Influence of pre-aeration on cyanide leaching of a non-refractory sulphide gold and silver ore

The leaching behaviour of a sulphide gold-silver ore was investigated in terms of a relationship between gold and silver extractions and cyanide consumption. Ninity five Au % and 88.0% Ag extractions were obtained under the determined conditions of 24 h leaching duration, -74 μm particle size, 40% solids ratio, 4 g/dm³ NaCN concentration, and 450 rpm stirring speed with NaCN consumption of 3.35 g/dm³. Since the NaCN consumption was higher than in industrial applications, Pb(NO₃)₂ and H₂O₂ additions and aeration using an air pump were tested during leaching in order to decrease the consumption. While Pb(NO₃)₂ addition with aeration caused a decrease in the metal extractions, the individual or combined additions of H₂O₂ and aeration could not provide a reduction in the cyanide consumption. Therefore, the effect of the pre-aeration followed by cyanidation was tested. Eventually, applying 4 h of pre-aeration before a shorter leaching duration of 12 h provided 92.0% Au and 90.5% Ag extractions with a reduced NaCN consumption of 2.44 g/dm³.