This paper presents voltammetric and electrochemical impedance studies of the anodic oxidation of chalcopyrite in the presence of highly concentrated sodium isopropyl xanthate solutions. The voltammetric response of the system displays a passivating effect on the chalcopyrite surface with the addition of xanthate due to its adsorption, which also impedes the transportation of oxidized species, i.e., Fe 2+ and Cu 2+ from the mineral matrix outwards the interface. The impedance spectra obtained near the polarization potential, at which the passivating effect is observed in the voltammograms shows a pseudocapacitive effect in the system, which is associated to the adsorption of xanthate and blocking the interface. The impedance spectra obtained show three time constants associated with the oxidation reactions of chalcopyrite and xanthate and the formation of covellite and cuprous xanthate on the mineral surface, the EIS results are according to the voltammetric response obtained for the system.
This work is aimed to simulate experimental impedance spectra for the anodic oxidation of galena-xanthate system at high collector concentrations. The simulations are based on a proposed kinetic model, which includes three reversible reactions at three different polarization potentials -0.3 V, 0.1 V and 0.2 V. The first part of the mechanism involves the oxidation and adsorption of xanthate, X -, at a potential of -0.3 V. The second one considers the reaction of the xanthate adsorbed on the galena surface towards the formation of dixanthogen, (X) 2 , and lead xanthate PbX 2 . Finally, the third mechanism step takes into account the evolution of PbX 2 towards the formation of lead hydroxide Pb(OH) 2 . According to the experimental and simulated impedance spectra obtained at potentials 0.1 V and 0.2 V, the system displays an inductive loop attributed to a relaxation of the interface due to adsorptiondesorption of adsorbed intermediates X ads , PbX 2ads and Pb(OH) 2 . These results provide new findings that contribute to a better understanding of the surface modification processes taking place at the interface galena-xanthate in flotation systems.
This paper deals with a study of the oxidation processes of the PbS-sodium isopropyl xanthate system in alkaline conditions (pH 8, similar to flotation circuits Pb-Cu) by using cyclic voltammetry and Electrochemical Impedance Spectroscopy (EIS). Three oxidation peaks are identified in the voltammograms that correspond to reactions previously reported in the literature. A plot of the differential capacitance of the double layer vs. potential gives a potential of zero charge (PZC) of -0.31 V vs. SCE for the system, that coincides with an oxidation peak attributed to the adsorption of xanthate. EIS at PZC for different xanthate concentrations evidence an adsorption processes via a charge transfer mechanism under diffusional control. EIS data at potentials more positive than PZC display an inductive loop that is related to a charge transfer processes involving the reaction of the adsorbed intermediates with the consequent modification of the PbS-sodium isopropyl xanthate interface.
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