Abstract
Cyanide tailings are the hazardous waste discharged after gold cyanidation leaching. The recovery of gold and iron from cyanide tailings was investigated with a combined direct reduction roasting and leaching process. The effects of reduction temperature, coal dosage and CaO dosage on gold enrichment into Au-Fe alloy (FexAu1−x) were studied in direct reduction roasting. Gold containing iron powders, i.e., Au-Fe alloy, had the gold grade of 8.23 g/t with a recovery of 97.46%. After separating gold and iron in iron powders with sulfuric acid leaching, ferrous sulfate in the leachate was crystallized to prepare FeSO4·7H2O with a yield of 222.42% to cyanide tailings. Gold enriched in acid-leaching residue with gold grade of 216.58 g/t was extracted into pregnant solution. The total gold recovery of the whole process reached as high as 94.23%. The tailings generated in the magnetic separation of roasted products, with a yield of 51.33% to cyanide tailings, had no toxic cyanide any more. The gold enrichment behaviors indicated that higher reduction temperature and larger dosage of coal and CaO could promote the allocation of more gold in iron phase rather than in slag phase. The mechanism for enriching gold from cyanide tailings into iron phase was proposed. This work provided a novel route to simultaneously recover gold and iron from cyanide tailings.
Highlights
Cyanidation leaching, which discharges a great amount of cyanide tailings, is the predominant process to produce gold around the world [1,2]
As toxic cyanides and heavy metals such as mercury and arsenic remain in cyanide tailings, they are extremely harmful to human beings and animals, and are classified as hazardous wastes in China [3,4,5,6,7]
Noble metals in cyanide tailings discharged after the roasting-cyanidation leaching are enclosed in iron oxide minerals
Summary
Cyanidation leaching, which discharges a great amount of cyanide tailings, is the predominant process to produce gold around the world [1,2]. The content of valuable metals such as gold and iron may be high in cyanide tailings. The gold grade and total iron (TFe) content of some tailings can reach 3-9 g/t and above 30%, respectively [8,9,10]. Attention should be paid to recovering valuable metals from cyanide tailings [11,12,13,14,15]. Noble metals in cyanide tailings discharged after the roasting-cyanidation leaching are enclosed in iron oxide minerals (e.g., hematite). To recover iron in the tailings, the magnetization roasting-magnetic separation is investigated to produce iron concentrates by reducing
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