The synthesis of cryptomelane with raw product manganese sulfate from manganese mines

Raw product MnSO4·H2O from manganese mines of Guangxi was utilized to synthesize cryptomelane by an inexpensive and practical method.K-brinesstie was prepared by oxidation of the mixture of MnSO4 and KOH solutions with soluble oxygen and excessive OH-,and then transformed to cryptomelane during the heating process.According to the experimental results,the optimal operational parameters were confirmed:0.2 M MnSO4·H2O and 1 M KOH in 500 mL system at room temperature reacted for 3 hours with 30 L/min air flow rate and 100 r/min stirring rate;the precipitate was washed again and again till pH=12,and dried and ignited at 600℃ for 1 hour.The results obtained provide fundamental data for further processing of manganese product on a large scale.