Hydrothermal synthesis of Na-birnessite-type material using ores from Carajás (Amazon Region, Brazil) as Mn source

• The Na-birnessite synthesis from manganese ores is presented.
• Manganese ores were characterized and transformed into Mn3O4 under thermal treatment.
• The Mn3O4 phase was converted into Na-birnessite.
• The lamellar structure exhibits remarkable thermal stability and nanobelt morphology.

This work reports an alternative low-cost natural Mn source to obtain Na-birnessite-type material (Na-OL-1), based on the Mn-oxides ores from Azul mine (Carajás, Brazil). After thermal treatment, the Mn ores were converted to a single phase, which could be transformed into Na-OL-1 under hydrothermal treatment. The starting material and the synthesis processes were characterised by means of X-ray diffraction (XRD), Thermal analysis (TG–DTA), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and chemical analysis. The layered structure was synthesized hydrothermally at 170 °C for 5 days without impurities with thermal stability around 650 °C and platy crystals with hexagonal shape.

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