Effects of arsenopyrite oxidation on gold dissolution in a copper(II)–ethylenediamine–thiosulfate solution

Thiosulfate (S2O32−)-based gold extraction—an environment-friendly alternative to cyanide-based gold extraction—has notable potential for application in industries. However, resolving the detrimental impacts of arsenopyrite on gold ore leaching remains a challenge for various leaching methods. This study investigated the effects of arsenopyrite oxidation on gold dissolution in a copper(II) (Cu2+)–ethylenediamine (en)–S2O32− gold-leaching system. During gold leaching, arsenopyrite oxidation considerably influences the properties of the leaching system, thereby increasing the rate of gold dissolution. Moreover, the effects of solution pH, system composition, and dissolved oxygen on gold dissolution were evaluated during the surface oxidation of arsenopyrite. Further, 48 h after arsenopyrite addition, FeOOH and NaAsO3 were added to the gold foil surface in the leaching system to investigate the effects of excessive arsenopyrite oxidation on gold leaching. Electrochemical tests demonstrate that the surface oxidation of arsenopyrite increases the potential of gold in the leaching system. In addition, X-ray photoelectron spectroscopy results show that the chemical states of arsenopyrite surface elements primarily change from As(I)–S to As(V)–O, Fe(II)–AsS to Fe(III)–AsS, and S22− to S2−. These results are important for the green hydrometallurgy of refractory gold ores.