Calcination and characterisation studies of a Brazilian manganese ore tailing

• Identified manganese minerals: spessartine, rhodonite, tephroite and rhodochrosite.
• Enrichment of manganese ore tailing by calcination (27.6% Mn to 32.1% Mn).
• Tailing Mn% raise is due the loss of CO2 and OH from carbonate and hydrated minerals.

This paper discusses the systematic analysis of the results of calcination as a function of size fraction performed on a sample of Brazilian silicate–carbonate manganese ore tailing at 800 °C. The raw materials and the corresponding calcination products were analysed using several analytical techniques, including determination of density, specific surface area and porosity, chemical analysis and X-ray diffraction. The morphology and chemical composition of the calcination products were analysed by using scanning electronic microscopy equipped with energy-dispersive X-ray spectrometer (SEM/EDS). Results indicate that the manganese ore tailing consists of silicates, namely, spessartine (Mn3Al2(SiO4)3), tephroite (Mn2(SiO4)) and rhodonite ((Mn,Fe,Mg,Ca)5(SiO3)5) and rhodochrosite (MnCO3). The loss of CO2 and OH during the thermal decomposition of the carbonate (rhodochrosite and dolomite) and hydrated minerals (kaolinite, muscovite and antigorite) in air atmosphere at 800 °C resulted in: (1) decrease of the specific surface area and porosity, (2) increase in the density and Mn grade from 27.6% to 32.2% and (3) increase in SiO2 grade from 26.7% to 30.1%. These results indicate that this material is within the chemical specifications of Fe–Si–Mn alloy.