Impedance study during anodic oxidation of native galena in a highly concetrated xanthate solution

Abstract

A double-layer capacitance and EIS studies on galena in absence and presence of sodium isopropyl xanthate at high concentrated solution in a wide range of polarization potentials is presented. A cyclic voltammetry study complements the EIS and double-layer capacitance data. The shape of the capacitance-potential curve as a function of the xanthate concentration evidences a large surface modification of the galena interface at high thiocollector concentrations. Potential Zero Charge (PZC) for the system at -0.31 V vs. SCE coincides with the oxidation and adsorption of xanthate (X -) on the galena surface, determined from the capacitance-potential curves. The impedance spectrum for the system obtained in the presence of X - (0.1 M) at the PZC show two time-constants associated to the oxidation and adsorption of X - and the subsequent formation of dixanthogen (X) 2 according to experimental results obtained and previous data published in the literature. EIS data at more positive potentials than PZC (+0.1 V, 0.2 V) show an inductive loop which is associated to a charge transfer processes which involves the reaction of the adsorbed intermediates Pb(X) 2 and Pb(OH) 2 with the consequent modification of the PbS-sodium isopropyl xanthate interface. These results provide new findings that contribute to a better understanding of the galena-xanthate interface at high xanthate concentrations. © 2011 by ESG.