Phase Transformation of Mackinawite by Using TG-DTA and In-situ XRD

Iron sulfide minerals are the common minerals on earth. As a precursor of iron sulfide minerals, the mackinawite (FeS) can be transformed into different type of iron sulfide minerals in the different environments. Mackinawite is usually generated in an anaerobic environment. Because of the layered structure, mackinawite can be used to adsorb heavy metals. Therefore, mackinawite is an important mineral to be deeply investigated.

In this study, we synthesized mackinawite in an anaerobic condition; it was fabricated by a hydrothermal method. After well preparation the mackinawite, the high temperature phase transition of mackinawite was studied via a thermogravimetry/differential thermal analysis (TG/DTA) and In-situ X-ray diffraction (XRD). Finally, the structure transformation (lattice image) of mackinawite was observed by using high resolution transmission electron microscopy (HRTEM).

The synthetic mackinawite exhibits disordered structure which is confirmed by XRD and HRTEM results. The TG-DTA result shows that there is a significant weight change from 170 to 250℃. It is also found that the mackinawite was gradually transformed into pyrrhotite at the beginning of 170℃ via in-situ XRD results. From the aforementioned results, it suggests that the mackinawite has a phase transition to pyrrhotite when the temperature is beyond 170℃ in an anaerobic environment.