Transformations of Pyrite and Pyrrhotite in Supercritical Water

Abstract

The interaction of pyrite (FeS2) with water at the uniform heating (1.5 K/min) of the reaction mixture to 923 K and its subsequent cooling (about 3 K/min) to 423 K is studied. The reaction products are analyzed using the methods of mass-spectrometry, elemental and X-ray diffraction analyses, and scanning electron microscopy. It is established that H2S, SO2, and rhombic and hexagonal pyrrhotite (FeS) are formed while heating, and the subsequent cooling of the reaction system gives rise to the formation of H2S, H2, cubic pyrite, and monoclinic pyrrhotite exhibiting ferromagnetic properties. It is shown that the transformations FeS2 → FeS → FeS x (1 < x ≤ 2) are accompanied by changes in the morphology and size of particles.