The Roleof Gold-Complexing Ligands in the Electrochemical Leaching Process of Gold-Bearing Refractory Sulfide Minerals

The article examines how the oxidation state of gold-bearing flotation tailings—derived from the secondary dressing of sulfide ores and concentrates—depends on the presence of ligands with varying standard Red/Ox potentials in the leaching medium, specifically regarding gold compound systems in aqueous solutions. The effectiveness of processing such minerals depends primarily on the degree to which the mineral's mechanical sulfide structure is broken down and the disseminated gold is exposed for subsequent treatment. Therefore, it is crucial to select ligands for the leaching solution— characterized by specific standard redox potentials relevant to gold-compound systems in aqueous solutions—that facilitate the ready oxidation of sulfide sulfur and the disruption of the mineral's sulfide shell, thereby enabling the gold to pass into the leaching solution as stable complex compounds. It has been established that refractory sulfide minerals obtained from gold-bearing tailings from secondary enrichment of sulfide concentrates can be effectively processed electrochemically in an acidic electrolyte based on alkali metal chlorides in the presence of a thiourea ligand (with a low redox potential of -0.38 V) with high gold recovery (up to 87%).