Synthesis of birnessite-type sodium manganese oxide and the behavior under hydrothermal conditions

A birnessite-type sodium manganese oxide with a layered structure was synthesized by reacting Mn(NO3)(2) solution with a mixed solution of H2O2 and NaOH at room temperature. This sodium manganese oxide was hydrothermally treated in neutral, acidic, and alkaline solutions at 150 degrees C. The original samples which were synthesized at room temperature and hydrothermally treated samples were characterized by XRD and chemical analysis. The formation of the birnessite-type sodium manganese oxide is dependent on the mixed mole ratio of NaOH/Mn(NO3)(2). The fraction of the birnessite phase increased with increase in the mixed mole ratio of NaOH/Mn(NO3)(2) The birnessite-type manganese oxide has a basal spacing of 1.004 nm before air-drying, but it changes to 0.724 nm after the air-drying at room temperature. A good crystalline birnessite phase with a basal spacing of 0.724 nm was obtained by hydrothermally treating the birnessite-type sodium manganese oxide prepared at room temperature with a NaOH solution.