Comprehensive Reclamation of Valuable Metals from Au-Bearing Cyanide Residue by Chlorination Roasting-Carbothermic Reduction-Magnetic Separation: Recovery of Iron

Extraction of gold from the refractory gold ores is commonly practiced by cyanide leaching, which simultaneously generates a significant amount of hazardous cyanide tailings. The cyanide tailings, still bearing certain amounts of residual gold, subsequently go through chlorination roasting to further recover Au, Ag, and other nonferrous valuable metals, and consequently, rendering the tailings inert by forming a residue containing high concentrations of Fe. This study aims at recovering Fe from the pellet-form chlorination residue by carbothermic reduction, forming magnetic Fe3O4 or metallic Fe, followed by magnetic separation. The results show that by reduction roasting at 800 degrees C for 4 h, a maximum amount of Fe3O4 can be generated. However, the subsequent magnetic separation was poor due to the extremely fine particle sizes and complex mineralogical associations. Notably, carbothermic reduction at 1250 degrees C for 4 h resulted in the formation of a metallic Fe shell on the outer surface of each residue pellet. The magnetic separation resulted in the production of an Fe concentrate containing 82.17 wt% Fe with a total Fe recovery of 79.68 wt%.

Automated summary

Cyanide leaching is commonly used to extract gold from refractory gold ores, resulting in hazardous cyanide tailings which are further processed through chlorination roasting to recover valuable metals, forming high concentration Fe residues. Carbothermic reduction generates magnetic Fe3O4 or metallic Fe from chlorination residues, with subsequent magnetic separation producing high-quality Fe concentrate.