Improvements in the production of manganese solutions and the electrowinning of metallic manganese therefrom

摘要

Manganese sulphate or chloride solutions free from iron and other heavy metal impurities are obtained by leaching a manganese-bearing furnace slag which contains bivalent manganese and metal sulphides capable of yielding sulphide iron under the reaction condition, with sulphuric or hydrochloric acid to form a slurry and thereafter adjusting the pH to between 4.0 and 7.5 by the addition of a base such as ammonia or lime in the presence of sufficient sulphide ions present in the slag or supplemented by additions such as hydrogen sulphide or ammonium sulphide to precipitate the heavy metals as sulphides, adding an oxidizing agent to precipitate residual iron and removing the precipitates from the thus purified solution. If less than 0.01 per cent heavy metal impurities are present the oxidizing agent is added to the treated leach liquor containing precipitated sulphides. A two stage precipitation is shown in Fig. 1, employing ammonia as base with the resultant production of a manganese and ammonium sulphate solution. Hydrogen peroxide is employed as oxidizing agent in the second precipitating stage. Of the chloride and sulphate solution production is associated with an electrolytic manganese production, the acid may be in part constituted by recycled anolyte, according to a typical example, a ferromanganese slag containing silica, magnesia, titania, alumina, sulphur, carbon, iron, copper, nickel and cobalt was leached with sulphuric acid and the pH of the resultant pulp was adjusted to 6.65 by ammonia gas. The sulphide precipitate was separated and the filtrate oxidized with hydrogen peroxide thereby precipitating residual iron to leave a high purity manganese and ammonium sulphate solution.