Electrochemical behavior of silver during cyanidation in the presence of sulfide minerals

The present work focuses mainly on the study of electrochemical phenomena induced by the presence of sulfide minerals during silver cyanidation. Firstly, an electrochemical study was carried out to characterize the electrochemical behavior of silver electrode in cyanide solution. The obtained results were useful to explain the mechanism of silver dissolution by cyanidation. Secondly, the effect of oxidants type and cyanide concentrations was carried out in order to identify optimal conditions for silver dissolution. Based on the obtained results, cyanidation tests were carried out in the absence and in the presence of sulfide minerals (chalcopyrite, sphalerite and galena). The results obtained by electrochemical methods (Open circuit potential, polarization curves, cyclic voltammetry, Tafel curves), complemented with scanning electron microscope (SEM) examination coupled with energy-dispersive X-ray spectroscopy (EDX), reveal that the limitation of silver cyanidation can be attributed to several factors. Passivation phenomenon occurs in the presence of galena, while galvanic interaction takes place in the presence of sphalerite. Chalcopyrite displays different impacts through liberated copper ions that overconsume available free cyanide. According to this study, impact of sulfide minerals on silver dissolution varies in the following order: chalcopyrite > galena > sphalerite.

Automated summary

The study focuses on electrochemical phenomena induced by sulfide minerals during silver cyanidation. The electrochemical behavior of silver electrode in cyanide solution was studied first to explain the mechanism of silver dissolution. The optimal conditions for silver dissolution were identified by investigating the effect of oxidants type and cyanide concentrations. Cyanidation tests were conducted in the presence and absence of sulfide minerals (chalcopyrite, sphalerite, and galena), and the results revealed that the limitation of silver cyanidation can be attributed to passivation phenomenon in galena, galvanic interaction in sphalerite, and overconsumption of available free cyanide due to liberated copper ions in chalcopyrite. The impact of sulfide minerals on silver dissolution varies in the order: chalcopyrite > galena > sphalerite.