Mechanochemical reduction of natural pyrite by aluminum and magnesium

• MSR of pyrite with Mg cannot proceed to completion after 280 min intensive milling.
• MSR of pyrite with Al is proceed to completion under nonstoichiometric condition.
• ZVI and Al2S3 compound was prepared by pyrite mechanochemical reduction by Al.

Mechanochemical reaction of pyrite with aluminum and magnesium were carried out for pyrite reduction using a planetary ball mill in an inert atmosphere. Thermodynamic studies indicated that the mechanochemical reactions are mechanically-induced self-propagating reaction (MSR). The XRD patterns of pyrite and magnesium mechanochemical reaction proved the reaction could not be complete after 280 min milling under the test conditions. On the other hand, the mechanochemical reaction between aluminum and pyrite completed after 120 min under similar milling conditions. The results confirm that in the primary MSR reactions troilite (FeS) phase was formed as an evidence for non-stoichiometric mechanochemical reaction. Thus, the mechanochemical reaction primary test of pyrite and aluminum was corrected with addition of more aluminum. The XRD results verified the troilite could be completely eliminated from the final product and the iron and aluminum phases contained main constituents of the obtained powder. The FE-SEM images indicated that the particles are about 100 nm to less than 1 μm in size. Finally, from SEM/EDS and XRF results, the zero-valent iron (ZVI) particles were surrounded by aluminum sulfide phase comparing.