An in situ characterization technique called electrochemical noise(ECN) was used to investigate the bioleaching of natural pyrite.ECN experiments were conducted in four active systems(sulfuric acid,ferric-ion,9k culture medium,and bioleaching solutions).The ECN data were analyzed in both the time and frequency domains.Spectral noise impedance spectra obtained from power spectral density(PSD)plots for different systems were compared.A reaction mechanism was also proposed on the basis of the experimental data analysis.The bioleaching system exhibits the lowest noise resistance of 0.101 MΩ The bioleaching of natural pyrite is considered to be a bio-battery reaction,which distinguishes it from chemical oxidation reactions in ferric-ion and culture-medium(9k) solutions.The corrosion of pyrite becomes more severe over time after the long-term testing of bioleaching. An in situ characterization technique called electrochemical noise (ECN) was used to investigate the bioleaching of natural pyrite. ECN experiments were conducted in four active systems (sulfuric acid, ferric-ion, 9k culture medium, and bioleaching solutions). ECN data were analyzed in both the time and frequency domains. Spectral impedance spectroscopy obtained from power spectral density (PSD) plots for different systems were compared. A reaction mechanism was also proposed on the basis of the experimental data analysis. bioleaching system exhibits the lowest noise resistance of 0.101 MΩ The bioleaching of natural pyrite is considered to be a bio-battery reaction, which distinguishes it from chemical oxidation reactions in ferric-ion and culture-medium (9k) solutions. The corrosion of pyrite becomes more severe over time after the long-term testing of bioleaching.