Patent ID: 8911611

Claim:
A method of obtaining electrolytic manganese from treated sludge of exhaust gases from silico- and ferroalloy production furnaces, comprising: a sulfation step wherein the sludge is treated with sulfuric acid within a furnace and heated until dry, in which near-stoichiometric consumption of the acid is used; a lixiviation step following the sulfation step, comprising mixing the product of the sulfation step with sulfuric acid to produce a leach solution; a primary purification step following the lixiviation step, comprising the removal of impurities, comprising primarily aluminum and iron, by the adjustment of the pH of the leach solution through the addition of lime so as to cause the precipitation of the impurities as hydroxides wherein the precipitates are removed from the leach solution by filtration to form a primary solution; an organic removal step, comprising passing the primary solution obtained from the primary purification step through an active carbon filter; a secondary purification step, following the organic removal step, comprising a step of removing additional impurities, comprising primarily zinc, by the addition of a sulfur containing compound under slightly acidic conditions causing the additional impurities to precipitate out as sulfides so as to form a secondary solution; a conditioning step, comprising steps of: (a) increasing the pH of the secondary solution; followed by (b) a crystallization step wherein the secondary solution having the increased pH is treated in a crystallizer under conditions to favor the precipitation of calcium and magnesium as ammonium salts; and concluding with an electrolysis step, wherein the electrolysis step results in a manganese purity of 99.9%.