The leaching of manganese from pyrolusite ore by pyrite



A new method of leaching low-grade manganese ore (< 5% Mn) utilizing pyrite as a reagent was developed. By heating an aerated slurry of ore and pyrite and by recycling the leach liquor at controlled acidity to attack fresh ore, a manganous sulphate solution free of iron was obtained which when heated to about 175°C., yielded manganous sulphate monohydrate. During the leaching process, iron in the liquor was alternately oxidized by the pyrolusite and reduced by the pyrite. In an alternative leaching procedure, the heating of an aqueous slurry of pyrite in an autoclave first under oxygen pressure and then in the absence of oxygen produced an acidic ferrous sulphate solution suitable for the subsequent leaching of pyrolusite ore at ambient temperatures.