Abstract
Chalcopyrite (CuFeS₂) is the most abundant copper-bearing mineral, yet its oxidative dissolution kinetics are strongly influenced by solution chemistry, particularly the nature of dissolved anions. In this study, we systematically investigate the effect of various inorganic anions on the oxidative dissolution behavior of chalcopyrite under controlled electrochemical conditions. Using a combination of potentiostatic polarization, electrochemical impedance spectroscopy (EIS), and solution analysis, the dissolution kinetics of chalcopyrite were examined in electrolytes containing chloride, sulfate, nitrate and nitrite at comparable ionic strengths.
The results demonstrate that anion identity plays a critical role in modulating both the surface reaction pathway and the overall dissolution rate. Activation energy analysis derived from temperature-controlled electrochemical impendance spectroscopy (EIS) and linear polarization resistance (LPR) measurements reveals the influence of anions on the apparent activation barrier for anodic dissolution.
In addition, it was also found that none of the analyzed anions prevent the effect of passivation in acidic media as the surface product generated during the oxidation process show higher open circuit potential (OCP), higher charge transfer resistance (RCT) and lower system capacitance than the freshly polished mineral sample. The passivation kinetics was studied through the potentiostatic/galvanostatic polarization analysis. Through Avrami-type analysis at the normalized active fraction, n ≈ 1 were found for all anion system which means the passivation layer grows in “site-by-site deactivation / 1D growth” from rather than 2D/3D growth with continuous nucleation at different rate (k).