Leaching Kinetics of Pyrolusite by Macromolecular Melanoidins of Molasses Alcohol Wastewater in H2SO4

The kinetics of reductive leaching of manganese from low grade pyrolusite using melanoidins of molasses alcohol wastewater as reducing agent in dilute sulfuric acid was investigated. The shrinking core model was applied to quantify the effects of reaction parameters on leaching rate of manganese. The leaching rate increases with the increase of the leaching temperature, sulfuric acid concentration and melanoidins concentration and the decreases of the particle size of pyrolusite. The leaching process follows the kinetics of a shrinking core model and the apparent activation energy is 56.2 kJ·mol-1. The experimental results indicate a reaction order of 0.54 for sulfuric acid concentration and 0.93 for melanoidins concentration. It is concluded that the reductive leaching of pyrolusite with macromolecular melanoidins of molasses alcohol wastewater is controlled by the diffusion through the ash/inert layer composed of the associated minerals.