Experimental study on oxidation mechanism of pyrite under acidic conditions

Abstract

Abstract In this study, pyrite samples from the Yankan Coal Mine near the Shandi River in Yangquan City were studied in an oxidation dissolution experiment. Pyrite was studied at different solid-liquid ratios (1:100, 1:50, and 1:20), and the oxygen concentration used was equal to the value in the ambient environment, about 20.95% of the air volume. The pH, oxidation-reduction potential (Eh), and soluble salt concentration (EC), total iron concentration, and SO4 2− concentration in the solution at different reaction times were measured with respect to time. The oxidation reaction rate of pyrite was calculated using the SO4 2− concentration and the factors influencing the oxidation rate at different conditions were discussed. The experimental results showed that, after pyrite was oxidized and dissolved at solid-liquid ratios of 1:20, pyrite decrease from acid generation of the SO4 2−formation, then the pH of the solution increased, at solid-liquid ratios of 1:100, 1:50, and 1:20, the overall Eh and EC values decreased. No matter what solid-liquid ratio is adopted for the reaction, the Fe2+ concentration is higher than Fe3+ concentration, and the Fe2+ and total iron concentration all increase with the increase of solid-liquid ratio, while Fe3+ gradually increases, reaching a trend of relatively stable and slowly decreasing. The average apparent release rate of Fe was proportional to the different solid-liquid ratios. The oxidation reaction rate of pyrite under acidic conditions was directly related to the concentration of reactants, and a faster oxidation rate was observed at higher concentrations due to the larger reaction contact area.