A Study of Pyrite/Solution Interface by Impedance Spectroscopy

Several equivalent circuit models are considered for analysis of the ac impedance spectrum of pyrite/solution interface. These models take into account the presence of coating layers and the contributions from surface roughness and diffusion. An optimization procedure is described to estimate the parameters of the equivalent circuit, namely, the value of various resistors, capacitors, etc. The procedure can also be used to identify the equivalent circuit which best describes the measured impedance spectrum. The impedance results of a pyrite electrode in sodium carbonate and borate solutions are analyzed in terms of the parameters of the equivalent circuit which best describe the spectra obtained under several conditions. Such an analysis was used to distinguish the type of electrode processes which control oxidation behavior of pyrite.