It is very important to selectively reduce manganese oxide over iron oxide
for extraction of Mn from iron-rich manganese ore. In this study, reductive
roasting of an iron-rich manganese oxide ore with elemental sulfur as
reductant was investigated. The experimental results demonstrated that
manganese dioxide can be selectively reduced with elemental sulfur and
extracted via acid leaching, which was largely depended on the sulfur
addition. Lower sulfur addition (S/Mn molar ratio<1.0) results in higher
selectivity, which is independent of roasting temperature. More than 95%
manganese and less than 10% iron were extracted through acid leaching under
the roasting conditions of 400-600?C with S/Mn molar ratio of 0.6. The
contents of manganese sulfide and sulfate in the roasted product increased
with increasing sulfur addition, while they decreased distinctly at
temperatures above 550?C. The thermodynamic analysis also proved that
manganese dioxide is more easily reduced than iron oxide by sulfur at 300-900
K. The phase transformations during reductive roasting revealed that sulfides
(MnS and FeS2) were favored at temperatures lower than 550?C whereas the
oxides (MnFe2O4 and Fe3O4) were predominant at higher temperatures. The
reduction of iron oxide mainly occurred at large sulfur additions (S/Mn>2.0)
and the roasting temperature exerted a significant impact on the phase
composition of roasted product.
Reductive roasting of iron-rich manganese oxide ore with elemental sulfur for selective manganese extraction
