GB1070987A - Extraction of manganese from ores as manganous sulphate - Google Patents

Abstract

Materials containing carbonate and oxide manganese ores, dressing middle products and/or dressing barrens are wet-ground and the resulting slurry is reacted with oxygen containing waste gases or an air mixture both containing 0.2-5% by volume of sulphur dioxide in equipment ensuring contact over a large surface area, e.g. a flooding foam column, to produce manganous sulphate solutions. The manganese content of the manganous sulphate solutions may be recovered as manganic oxides by adding calcium carbonate (preferably ground limestone) to the solution, separating the precipitated iron and phosphorus content, adding calcium hydroxide solution and then separating calcium sulphate from the manganous hydroxide (if formed), e.g. by counter-current sedimentation, oxidizing the manganous hydroxide to manganic hydroxide, preferably by bubbling air through the solution, and then separating, drying and/or agglomerating the product obtained. Under certain conditions, e.g. manganous sulphate concentration not exceeding 5 g./l. and calcium hydroxide solution added until pH is 7 to 7.2, no precipitation of calcium sulphate occurs. Alternatively, impurities are removed and the resulting solution is electrolysed giving manganese metal. Further, the dissolved contaminants may be removed from the manganous sulphate solution with the aid of calcium carbonate, whereafter the manganese content is recovered either by crystallization as manganous sulphate, or, where a compound other than the sulphate is desired, by adding a solution of an inorganic salt (e.g. sodium bicarbonate) or an inorganic base (e.g. calcium hydroxide) and recovering the manganese in the form of a manganous salt other than the sulphate or manganous hydroxide respectively.