Reductive leaching of pyrolusite ore by using sawdust for production of manganese sulfate

Manganese compounds, such as manganese sulfate, can be obtained from pyrolusite, a manganese ore. Low-grade manganese ores is usually treated by hydrometallurgical methods. In this study, the leaching and recovery of manganese from pyrolusite ore in sulfuric acid solutions containing sawdust as reducing agent was investigated. The effects of experimental parameters, such as sulfuric acid concentration, sawdust amount, solid-to-liquid ratio, stirring speed, particle size, reaction temperature, and leaching time, on the manganese extraction from ore were examined. The results showed that the leaching rate of pyrolusite ore increased with an increasing sulfuric acid concentration, sawdust amount, stirring speed, reaction temperature and leaching time, and decreasing in solid to liquid ratio and particle size. The kinetic analysis of leaching process was carried out, and it was determined that the reaction rate was controlled by diffusion through the product layer under the experimental conditions in this work. The activation energy was found to be 22.35 kJ mol(-1). Manganese can be recovered as manganese sulfate by the evaporative crystallization of the purified leach liquor.