SODIUM SULFIDE-ASSISTED GOLD RECOVERY FROM ARSENOPYRITE AND ROASTED ARSENOPYRITE

The addition of sodium sulphide was found to enhance the cyanidation o f gold from an arsenopyrite and a roasted arsenopyrite ore down to a s olution potential of approximately -350 mV (versus SCE). Lower potenti als reduced gold dissolution and were associated with the formation of a passivating gold-sulphide layer on gold. It is proposed that Na2S e nhances the dissolution of gold by inhibiting the formation of cyanide -consuming ferric oxides on the surface of the ore and converting exis ting oxides into sulphides. The concentration of cyanide had a marked effect on the dissolution of gold fi om the roasted arsenopyrite. A de crease in cyanide concentration at a fixed cyanide/ore ratio reduced t he adsorption of CN- on to the surface of the ore and effectively incr eased gold dissolution. This was explained by assuming that gold disso lution is limited by the diffusion of cyanide to Au-0 sites.