Thermodynamic Features Research of Polymetallic Sulfide Raw Material Leaching

Abstract

Thermodynamic features studies of the polymetallic sulfide raw material nitric acid leaching were carried out. Elemental and phase composition of the raw material under investigation was studied with X-ray diffraction and electron microscopy methods. Calculations of the Gibbs energy change for the likely reactions of sulfide minerals with nitric acid were performed. The most favorable conditions for the leaching process were identified with a Pourbaix diagram. The results showed that for maximum transfer of the metal sulfides into sulfate form, the necessary initial oxidation potential is E >0.9 V wherein copper and zinc go into solution completely. The interaction of the metal sulfides with nitric acid leads to its degradation and the formation of nitrous gases. The resulting nitrogen oxides are oxidized to higher oxides in the absorption column to form a mixture of nitric and nitrous acids. The resulting mixture was used in the next leaching stages.