Preparation of electrolytic manganese dioxide (EMD) from low grade manganese ores/residues
Biswal, A., Nayak, B., Dash, B., Sanjay, K., Subbaiah, T. and Mishra, B.K. (2011) Preparation of electrolytic manganese dioxide (EMD) from low grade manganese ores/residues. In: European Metallurgical Conference, EMC 2011, 26 - 29 June, Dusseldorf; German pp. 1323-1334.
A process flow sheet for processing low-grade manganese ores / residues has been developed to produce electrolytic manganese dioxide (EMD) as an end product that is suitable for battery industry. Maganese nodules leach residue having ∼ 25 % manganese and ∼ 8 % iron with other minor impurities such as Cu, Ni, Co and Zn was leached in H2SO4 medium using activated charcoal as reductant followed by purification and electrowinning of EMD. The leaching process was optimized for different parameters viz. pulp density, acid concentration and amount of charcoal. The optimal parameters for leaching of 20 % pulp density are 0.055 g charcoal per gram of Mn material with 2 M sulfuric acid at room temperature for 4 h showing ∼ 90 % Mn extraction. The leach liquor was purified in two stages - first step by addition of KMnO4 to oxidize ferrous to ferric and precipitation of iron by rising pH to 4 with addition of Ca(OH)2 followed by second step of addition of sodium sulphide for removal of Cu, Ni, Co and Zn. The purified liquor obtained after bringing down impurity levels was used for the preparation of EMD. The conditions for preparation of EMD, ie. concentration of Mn and acidity, temperature, current density have been optimized. The optimal parameters for EMD preparation are [Mn]: 48 g/L; [H2SO4]: 25 g/L; 90 °C at a current density of 200 A/m2. The deposited EMD was characterized for particle size and morphology by XRD & SEM. The EMD was of γ-varity with irregular and agglomerated particles having discharge capacity of 290 mAh/g.
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