Leveraging strategies to increase gold cyanidation in the presence of sulfide minerals — Packed-bed electrochemical reactor approach

Several leveraging strategies were explored to improve gold leaching during cyanidation in the presence of pyrite, chalcopyrite, sphalerite and chalcocite. Galena, used a source of lead, was found to largely neutralize the negative effect of sulfide minerals dissolution on gold leaching, especially in the cases of pyrite, chalcopyrite and sphalerite. Pyrite–galena galvanic interactions improved gold leaching while for chalcopyrite, sphalerite and chalcocite active galvanic interactions with galena were found to be detrimental to gold leaching. Pre-oxidation of metal sulfides prior to cyanidation significantly increased gold leaching rate when gold–pyrite galvanic interactions were disabled, while their enablement identified pyrite pre-oxidation as counter-productive. Pre-oxidation of mixed mineral systems of pyrite–chalcopyrite and pyrite–sphalerite showed that enabling galvanic interactions between the associated minerals during pre-oxidation controlled gold leaching in the subsequent cyanidation process. For pyrite, lead nitrate addition during pre-oxidation resulted in a significant increase of gold leaching, whereas its addition to subsequent cyanidation canceled the positive effects of pre-oxidation on gold dissolution.