GB1092001A - New method of preparing manganese salts from pyrolusite ore - Google Patents

Abstract

Manganese values are obtained as soluble manganese salts from MnO2 ores containing much iron by treating the ore with an aqueous ferrous salt solution to reduce the manganese to manganous, e.g. by boiling for 4-6 hours under reflux, preferably on a sand bath or heating mantle, after which the solution is preferably allowed to settle and the clear liquor is decanted, siphoned or filtered off. Any unreacted ferrous iron is then oxidized to ferric by (a) bubbling air or oxygen through the hot solution, (b) adding a small amount of an oxidizing agent, e.g. H2O2, HNO3 or by (c) anodic oxidation, and precipitated as Fe(OH)3 or Fe2O3.nH2O by raising the pH to between 5 and 6.3, but preferably 5.3-5.5, with a base, e.g. NH3, KOH, NaOH or a NH3/NH4Cl mixture. A small amount of hydrazine hydrate may be added before the base, particularly if NH3 is used, to quicken the settling. Waste pickle liquor may be used as the ferrous solution, the free acid therein being preferably removed before use by iron metal e.g. scrap-iron, or by manganous oxide, e.g. as obtained by a reduction roast of MnO2. If desired, the remaining solution after precipitation may then be evaporated to obtain the manganese salt as a solid double salt with the salt of the base which was used for raising the pH of the solution.