Study on Separation of Manganese from Iron in High-Iron Pyrolusite Ore by Leaching with Simulated Flue Gas

Abstract

Due to the depletion of high-grade manganese ore, much attention has turned to recover manganese from low-grade ores; however, these are usually associated with high-iron content. Moreover, the conventional process of extracting Mn from iron-rich low grade manganese oxide ore focused on recovery of Mn, while ignoring the leaching characteristics of Fe. Hence, simultaneous investigations on leaching behavior and separation efficiency of both manganese and iron were carried out for attaining high recovery of manganese with low iron content from the high-iron low-grade pyrolusite ore using simulated flue gas as the reductant. The effects of leaching parameters, flue gas components and initial particle size on the leaching efficiency of Mn and Fe were studied, and the results indicated that higher separation efficiency of Mn from iron was achieved at lower SO₂ concentration, O₂ concentration and suitable pulp density. The experimental validation revealed that 93.12% Mn and only 2.57% Fe were extracted under the optimal operating conditions: SO₂ percentage of 5%, O₂ percentage of 1%, reaction temperature of 35°C, solid-to-liquid ratio of 250 g/L, and more than 120 min. Kinetic modelling has indicated that the Mn leaching rate is controlled by the rate of diffusion of SO₂/O₂ from the gas phase to the liquid phase, and the rate of diffusion of product or reactants to the ore surface through an inert product layer is the rate-limiting step for Fe dissolution.