Thermal stability of rubidium birnessite-type material synthesized from Mn residues from Amazon Region

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Abstract
13-011 Thayná Ferreira Azevedo do Mar, I.c.(Universidade Federal do Oeste do Pará); Azevedo, T.F.(Universidade Federal do Oeste do Pará); FIGUEIRA, B.A.(Universidade Federal do Oeste do Pará); Rivas Mercury, J.M.(Instituto Federal do Maranhão); da Costa, M.L.(Federal University of Pará); Poellmann, H.(Martin Luther Universität); We report the synthesis of octahedral layered birnessite-type phase with Rb+ as interlayer cation (Rb-OL-1) from manganese residues at mining site from Carajás Mineral Province (Pará State, northern Brazil). Firstly, the synthetic route employed dissolution of Mn residues followed by re-precipitation of the birnessite-type phase with Na+ interlayer, which was ion exchanged with an aqueous solution of Rb+ at room temperature while stirring overnight. The X-ray diffraction patterns clearly showed the conversion of Mn residues into manganese oxide octahedral layer with basal spacing around 7.22 Å and (C2/m) monoclinic structure. The unit cell parameters were calculated as: a = 3.566(8) Å, b = 3.522 (7) Å and c = 7.333 (1) Å, as well as average crystallite size (58 nm) by Scherrer Equation. FTIR spectra of the product revealed diagnostic bands around 833, 751, 614, 500 and 445 cm-1 and could be assigned to the layered framework structure. After thermal treatment up 700 ºC, the X-ray diffraction analysis showed the transformation to RbMn8O16 having (I4/m) tetragonal structure (a = 9.811 Å and c = 2.881 Å).
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