Electrochemical insights into the direct dissolution of impure sphalerites and their partial oxidation in an acidic environment.

This study examined the electrodissolution mechanism of five impure sphalerite samples, which differ significantly in purity levels, along with their partially oxidized counterparts in a 0.5 M HSO. Partially oxidized samples were prepared through an incomplete leaching of sphalerite using HSO with Fe(SO).HO as an oxidizing agent. The original sphalerite samples and the partially oxidized samples were referred to as SP and POS samples, respectively. Analyses using XRD, SEM, Raman spectroscopy, and electrochemical techniques suggested presence of elemental sulfur and a metal-deficient layer on the surface of the POS samples. Cyclic voltammetry revealed that the sample with the highest iron content exhibited the highest electrochemical response, while the sphalerite with the highest lead concentration had the lowest activity. Electrochemical impedance spectroscopy (EIS) studies showed that impedance values were higher in the POS samples compared to the PS samples, indicating a correlation within the passivation phenomenon. In conclusion, these findings suggested that the sphalerite dissolution process is primarily controlled by charge transfer and kinetic polarization. This understanding can lead to the development of more selective and sustainable extraction methods and improving the overall economic viability of zinc hydrometallurgical operations.