Electric field enhancement in leaching of manganese from low-grade manganese dioxide ore: Kinetics and mechanism study

Abstract

In this work, hydrometallurgical leaching process intensified by electric field for leaching manganese from low-grade manganese dioxide ore was developed to increase the leaching efficiency of manganese. The leaching kinetics and mechanism were studied. The leaching parameters on manganese extraction, such as concentration of FeSO4, concentration of H2SO4, liquid to solid ratio, leaching temperature, current density, were studied. The results showed that the leaching efficiency of Mn could reach up to 98.2% under the optimum conditions of 0.65M FeSO4, liquid–solid ratio of 5.5mL/g, 1.6M H2SO4, current density of 900A/m2, temperature of 353K. The leaching process followed the shrinking core model, the reaction rate was controlled by diffusion through a product layer. The macroscopic kinetic equation of the leaching process was1−23X−1−X23=5.67×10−3FeSO41.419H2SO41.686ls1.239j0.777exp−19.68RTtand the Ea (apparent activation energy) was 19.68kJ/mol. During the leaching process, the newly formed Fe3+ that generated from the oxidation of ferrous on manganese dioxide surface was reduced to Fe2+ by electric field to ensure the Fe2+ in the solution keeps at a high level. The cycling of Fe3+ and Fe2+ ensured the high leaching efficiency of manganese during the process and reduced the dosage of the reducing agent.