Fe(III)/Fe(II) reduction-oxidation mechanism and kinetics studies on pyrite surfaces

Abstract

In this paper, the electrochemical behavior of Fe(III) and Fe(II) couple on the pyrite surface was studied by application of the chronoamperometry technique in acidic solutions at room temperature and atmospheric pressure. The effect of the pyrite origin and the Fe(III) and Fe(II) ion concentration on the electron transfer kinetics of the Fe(III)/Fe(II) reaction was probed. Tafel behavior of the Fe(III)/Fe(II) couple redox reaction under the test conditions was developed. The Fe(III)/Fe(II) reaction on the pyrite electrodes with different origins demonstrated a common mechanism, despite different kinetics. The exchange current densities of the redox reaction had the same magnitude of 10−5Acm−2 for all samples. The value of cathodic transfer coefficients ranged between 0.4 and 0.5, while the lowest magnitude of anodic transfer coefficients was 0.23. It was shown that an increase of an order of magnitude of iron concentration did not have a significant effect on the Fe(III)/Fe(II) couple redox reaction exchange current density nor on the value of cathodic transfer coefficients of the reaction.