EIS studies of chalcopyrite involving iron(II) ions
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In this work, we present an Electrochemical Impedance Spectroscopy (EIS) study using a carbon paste electrode modified with chalcopyrite (CuFeS2) containing 50 wt% of the mineral (particle size < 38 μm) and graphite (particle size < 20 μm) in naturally aerated salt acid solutions (pH 1.8) without and with the addition of 0.100 mol L-1 of ferrous ions. The aim was to evaluate the influence of the solution potential on the behavior of chalcopyrite electrode in the presence and absence of iron(II) ions. Additionally, we evaluated the influence of the bacteria Acidithiobacillus ferrooxidans in the system containing iron(II) ions without applying potential. Therefore, EIS was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The results showed that the combination of iron(II) ions with the imposition of low potential values (0.100 Fe2+ ions with +0.300 V/Ag|AgCl|KCl3mol/L) activates the chalcopyrite surface and enhances the copper recovery.