Preparation of High Purity Manganese Sulfate from the Reduction of Pyrolusite Using Scrap Iron as the Reductant

In this paper,the leaching of manganese sulfate from pyrolusite with scrap iron as a reductant in dilute sulfuric acid solution was studied.Optimal parameters that affect the leaching efficiency of manganese sulfate were determined by the single factor method.The results shows that the leaching rate of manganese can reach more than 95%under the condition of Fe to MnO2 molar ratio of 0.78,H2SO4 to MnO2 molar ratio of 2.1,reaction temperature 50℃,reaction time 80min.Calcium carbonate was added to the leaching solution to adjust pH 5~6 so that iron、aluminum and other impurities were removed by becoming iron hydroxide、aluminum hydroxide and other precipitations.Heavy metal ions were removed by adding barium sulfide to the leaching solution to form sulfide precipitations.After being filtrated,manganese difluoride was added to the filtrate to precipitate Ca2+、Mg2+ and other impurities.After standing,the solution was then filtrated and high purity manganese sulfate solution was obtained.Crystallized manganese sulfate was obtained after being concentrated.Manganese sulfate purity can reach more than 99%and impurity contents were lower than those what the national standard claims.