Behavior and mechanism of extracting manganese from braunite by pyrolysis reduction-acid leaching of sawdust

Abstract

In this study, a novel method for extracting manganese from braunite through sawdust pyrolysis reduction roasting followed by acid leaching was investigated. The thermodynamic properties, mass loss and the composition of the released gases were analyzed using thermodynamic simulation software and thermogravimetric mass spectrometry (TG-MS). The reaction mechanism and kinetic equation for braunite reduction via sawdust pyrolysis were determined using the Kissinger method and Coats-Redfern model. Optimal process parameters were identified through parametric experiments and phase analysis. Results showed that reducing gases (CH_4, CO, C₂H₄, H₂) released during sawdust pyrolysis reacted with braunite, with the highest reaction rate at approximately 320°C. The kinetic equation is expressed as $\frac{d\alpha }{\mathrm{dT}}=\frac{3.09\times {10}^{14}}{\beta }exp\left(-\frac{179.24}{\mathrm{RT}}\right)\times \left(\frac{3}{2}\right)\times {(1-\alpha )}^{\frac{4}{3}}\times {\left({\left(1-\alpha \right)}^{\frac{-1}{3}}-1\right)}^{-1}$, where the activation energy is 179.24 kJ/mol. Optimal conditions included a roasting temperature of 550 °C, sawdust dosage at 75 % of braunite mass, and a roasting time of 30 min, yielding a manganese extraction rate exceeding 92 %. These findings confirm the method’s feasibility and offer new insights into braunite processing.