Preparation of the high pure manganese oxide by pyrolysis of the solution extrated from ferromanganese dust in AOD process

초록

The high pure manganese oxides were made from the dust, generated in AOD process that produces a medium-low carbon ferromanganese and collected in the bag filter. Manganese oxide content in the dust was about 90%, and its phase was confirmed as Mn3O4. In the extraction of manganese, because of remaining amorphous MnO2, the dust was reduced to MnO by roasting with charcoal. The pulp density of the reduced dust can control pH of the solution more than 4 and then Fe ion is precipitated to a ferric hydroxide. Because a ferric hydroxide co precipitates with Si ion etc, Fe, Si ion was removed from the solution. Heating made water to be volatized and nitrates was left in reactor. Then nitrates were a liquid state and stirring was possible. Among the nitrates in reactor, only the manganese nitrate which have the lowest pyrolysis temperature pyrolyzed into β-MnO2 powder and NO2(g) at the temperature less than 200°C. When the pyrolysis of manganese nitrate has been completed about 90%, injection of water stopped the pyrolysis. Nitrates of impurity dissolved and the spherical high purity β-MnO2 powders were obtained by filtering and washing. Mn2O3 or Mn3O4 powder could be manufactured from β-MnO2 powder by controlling the heating temperature. Lastly, a manufactured manganese oxide particle has 99.97% purity.