DIRECT ACID LEACHING OF PYROLUSITE ORE

摘要

The conventional thermal reduction leaching technology of pyrolusite ore for production of manganese sulfate solution is not economic due to high-energy consumption. This process is replaced by direct sulfuric acid leaching using hydrogen peroxide as a reducing agent. A pyrolusite ore from Sinai- Egypt with 37% MnO_2 and 51% Fe_2O_3 have been leached and the optimum conditions were determined, and found to be particle size 100% <100 mesh, H_2SO_4 concentration 15%, H_2SO_4:MnO_2 stoichiometric ratio 1.5, H_2O_2 concentration 30%, H_2O_2:MnO_2 stoichiometric ratio 1, temperature 40°C, time 10 min and liquid/solid ratio 4.57 g/g. Under these conditions 93.3% and 1.93% of manganese and iron were respectively leached out. Purification of solution has been achieved by addition of CaCO_3 to precipitate iron. The clear solution was concentrated by evaporation under reduced pressure at 8-10~3 Pa for 23 min to reach supersaturation. The produced manganese sulfate is monohydrate with 99.31% purity.