Abstract:
The oxidizability of molybdenite was evaluated from the chemical potentials of the independent components, i.e., molybdenum and sulfur, at various stages of the oxidation process. The overall character of the dependence of the chemical potentials of sulfur and molybdenum on the concentration of nitric acid, and thus on the degree of decomposition of molybdenite, varies. During oxidation of molybdenite by nitric acid, the chemical potentials of molybdenum decrease and those of sulfur increase. This means that the process as a whole is limited by the oxidation of sulfur, which has a higher chemical potential than molybdenum and, moreover, one that is rising. An analysis of the changes in the chemical potentials of the components in this system enables us to identify the positive effect of calcium and of ferrous and ferric iron on the decomposition of molybdenite by nitric acid.