A novel process for silver recovery from a refractory Au–Ag ore in cyanidation by pretreatment with sulfating leaching using pyrite as reductant

• Hosting in the crystal lattices of manganese has caused silver refractoriness.
• Destroying the lattice structures of manganese is essential to liberate silver minerals.
• MnO2 could be reduced to Mn2 + by pyrite and dissolved completely in acidic solution through the pretreatment process.
• A pretreatment-cyanidation process was developed to increase silver cyanidation performance.

A novel process was developed to markedly increase silver cyanidation performance from a refractory gold–silver ore in Beiya, Yunnan province, China. Before cyanidation, the process employs a pretreatment step that aims at liberating the silver grains by destroying the crystal lattices of manganese minerals. The pretreatment step could be described as a reductive sulfating leaching technology to preferentially dissolve the manganese minerals, with silver remaining in the leaching residue for subsequent cyanidation, and the most important finding of the study is that pyrite could be used as a reductant through the process. The result indicates that the recovery of silver has a remarkable 43.92% increase compared to a direct cyanidation process without pretreatment step.