Enhanced leaching of manganese from low-grade pyrolusite using ball milling and electric field.

ABSTRACT

In this study, electric field and ball milling were used to leach Mn2+ from low-grade pyrolusite (LGP). The effects of current density, reaction time, reaction temperature, ball-to-powder weight ratio, and ball milling time on the leaching efficiency of Mn2+ from LGP as well as the leaching mechanism were systematically studied. The results showed that the combined use of electric field and ball milling enhanced the leaching of Mn2+ from LGP. The leaching efficiency of Mn2+ reached 97.79% under the optimum conditions of LGP-to-pyrite mass ratio of 10.18, current density of 30 mA/cm2, LGP-to-H2SO4 mass ratio of 10.4, liquid-to-solid ratio of 51, ball-to-powder weight ratio of 11, ball milling time of 2 h, temperature of 80 °C, and leaching duration of 120 min. This value was 25.95% higher than that attained without ball milling and 41.45% higher than that attained when neither ball milling nor electric field was employed. Pyrite was fully oxidized to generate additional SO42- and Fe3+, and was further hydrolyzed to form jarosite (KFe3(SO4)2(OH)6) and hydronium jarosite (Fe3(SO4)2(OH)5·2H2O) via ball milling and electric field application. Moreover, the electric field changed the surface charge distribution of the mineral particles and promoted collisions between them as well as the collapse of the crystal lattice, further improving the leaching efficiency of Mn2+ from LGP. This study provided a new method for leaching Mn from LGP.