Electrochemical study and XPS analysis of chalcopyrite dissolution in sulfuric acid in the presence of ethylene glycol

The effect of ethylene glycol (EG) on chalcopyrite dissolution was studied in 1 M sulfuric acid at an open circuit potential and 25 °C. Electrochemical studies were performed having employed potentiodynamic and electrochemical impedance spectroscopy (EIS) techniques. Based on the results, the addition of 11% v/v of EG has decreased the current density from 10−4.7 to 10−5.1 A/cm2 and more addition of EG (22% v/v) has increased the current density. In the ferric-containing solution, while 5.5% v/v of EG was present, the addition of Fe3+ ions to the solution has decreased the polarization resistance value and resulted in a higher dissolution current. EIS results showed that increasing the EG concentration to 11% v/v caused an increase in both charge transfer and surface layer resistances. Besides, the composition of the inhibiting layer was studied having employed the XPS analysis. The result shows that the formation of the metal-deficient sulfide (Cu1-xFe1-yS2) is responsible for the inhibition of the chalcopyrite dissolution in 1 M sulfuric acid. However, the addition of EG to sulfuric acid media results in the appearance of the polysulfide (Cu1-x-zS2), elemental sulfur, and sulfate species on the chalcopyrite surface, which is dedicated to the facilitation of the mineral dissolution in the presence of ethylene glycol.