Studies on the formation of manganese molybdate

Abstract

The reaction of MOO, with various osides of manganese (MnO, Mn2O3,Mn3O4 and MnO2) and with MnCO, has been studied in air and nitrogen atmospheres employing DTA, TG and X-ray diffraction methods, with a view to elucidating the conditions for the formation of MnMoO4. Thermal decomposition of MnCO3 has also been studied in air and nitrogen atmospheres to heIp understand the mechanism of the reaction between MnCO3 and MOO3. The studies reveal that, whereas MnO, Mn2O3 and MnO2 react smoothly with MOO3 to form MnMoO4. MnCO3 does not react with MOO3 in the temperature range investigated (480-600 C). An equimolar mixture of MnCO3 and MOO3 reacts in air to yield MnMoO4. while onIy a mixture of Mn3O4 and MOO3 remains as final product when the same reaction is carried out in nitrogen. Marker studies reveal that manganese ions are the main diffusing species in the reaction between MOO3 and manganese oxides that resuh in MnMoO4.