Preparation of trimanganese tetroxide by air oxidizing free divalent manganese ions

A new method for the preparation of trimanganese tetroxide(Mn3O4)by air direct oxidizing free divalent manganese was made at a certain temperature and pH value varying correspondingly according to the change of manganese ion concentration.The results show that the rate of oxidization of manganese hydroxysulfate is slower than that of manganese hydroxide,and the package of manganese hydroxysulfate is a basic reason for high sulfate content in Mn3O4.In comparison with the method in which Mn3O4 is prepared by air direct oxidizing the hydrolyzates of manganese,the proposed method can efficiently reduce impurity contents of Ca2+,Mg2+ and SO2-4 in Mn3O4.