In-situ study of the decomposition of pyrite in an oxygen atmosphere

Abstract

In-situ 57Fe Mössbauer spectroscopy has been used to study the decomposition of mineral pyrite of various sizes and pyrite in coal in an oxygen atmosphere at different temperatures between 25 and 400 °C. The study has shown that the oxidation of pyrite in Illinois No. 6 (IL6) coal occurs in three steps: 1. (1) to iron sulphates between 25 and 310 °C; 2. (2) to γ—Fe 2O 3 between 310 and 325 °C; and 3. (3) to α—Fe 2O 3 between 325 and 400 °C. For mineral pyrite, the oxidation has been found to be dependent on the particle size and results in the formation of iron sulphates and α—Fe 2O 3. From the amount of conversion of pyrite in the IL6 coal (almost 100%) and the mineral pyrite (maximum of 7 ± 2%) it has been concluded that the oxidation of the two types of pyrite is entirely different and the oxidation of pyrite in coal is highly influenced by the coal constituents.