With the recent increase in gold production, the manageable gold ore resources for cyanidation have been gradually depleted, and low-grade, fine-grained gold ores difficult to cyanide and refractory gold ores containing harmful impurities such as sulphur, arsenic and copper have become the main raw material for gold production. Generally, as the ultrafine gold particles are wrapped in pyrite and arsenopyrite in fine grained or disseminated form, gold particles are not exposed even if the ore is finely grinded, which results in low leaching rate for sulphur- and arsenic-rich refractory gold ores. Also, since arsenide reacts with cyanide during the leaching process and consumes the leaching agent and oxygen, it prevents gold leaching.
In order to extract gold from refractory gold ores effectively, oxidation pretreatment must be conducted prior to leaching to oxidize the sulfide-bearing gold particles and convert their physical and chemical properties.
Preoxidation of pyrite and arsenopyrite, especially to compare the oxidation mechanism and the oxidation-reduction potential of sulphur and arsenic and illustrate the effect of desulfidation and arsenic removal on the gold leaching ratio is significant for the pretreatment of the refractory gold ores containing pyrite and arsenopyrite in large quantities.
Kim Chang Sok, a researcher at the Science Engineering Institute, has investigated the thermodynamic features of preoxidation of pyrite and arsenopyrite, the main minerals of refractory gold ores, and the effect of pressure oxidation, one of the peroxidation methods, on chlorination leaching.
From the E-pH diagram of the pyriticarsenopyrite-H2O system, he has concluded that arsenopyrite under acidic conditions is more prone to wet oxidation than pyrite, and that the preoxidation process of pyrite-arsenopyrite-type gold ore can be considered with a focus on the pyrite.
For more information, please refer to his paper “Thermodynamic Behavior of Pyrite and Arsenopyrite in Preoxidation for Chlorination Leaching of Refractory Gold Concentrate” in “Journal of Chemistry” (SCI).
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