Spectra Fitting of Impedance By Differential Evolution Algorithm for Galena Anodic Oxiation in Presence of Xanthate

Abstract

In this work, we present results for the study of the oxidation and adsorption mechanism for galena in presence of xanthate. This study was performed with impedance measurements and its spectral fitting from a mechanistic approach obtaining the transfer functions for total impedance from a reaction mechanism proposed. At our best knowledge, there are no similar studies for this system from the mechanistic point of view, although they do exist from the equivalent circuits approach. The spectra were fitted using a differential evolution algorithm (DE), which include 19 optimization parameters. All the parameters obtained from the fitting were satisfactory, since all of them have physical meaning, showing trends according to the expected; so that the fundamental kinetic information obtained for the interfacial processes for galena/xanthate system are valid. The proposed reaction mechanism includes the presence of two intermediates-adsorbed X2ads and Pb(X) 2ads, (adsorbed dixantogen and adsorbed lead xanthate, respectively) which inhibit the oxidation process of the galena surface. On the other hand, the inductive loops observed at positive polarization potentials could be associated with a process of surface relaxation due to the adsorption-desorption of the intermediates-adsorbed species.