Mineralogical Characterization and Leaching Kinetic Investigation of Nigerian Bismutite-Rich Zinnwaldite Ore by Methanesulfonic Acid

Abstract

The global demand for bismuth has increased significantly, a trend heightened by stricter environmental regulations. As a critical metal, bismuth is essential for advancements in the pharmaceutical industry. This study investigates the leaching kinetics of bismuth from bismutite-rich zinnwaldite ore using methanesulfonic acid (MSA, CH3SO3H) as a biodegradable leaching agent. Experiments were designed to assess the effect of MSA concentration, iron powder concentration, reaction temperature, and particle size on leaching efficiency. The optimal leaching conditions were determined to be a MSA concentration of 3.0 mol/L, iron powder at 0.5 mol/L, leaching time of 120 min, temperature of 80 degrees C, and particle size of 45 & micro;m. Under these conditions, the bismuth leaching efficiency reached 92.30%. Kinetic modelling demonstrated that the leaching process is governed by diffusion through a product layer, with a reaction order of 0.908 and an apparent activation energy of 17.35 kJ/mol. X-ray diffraction analysis of the leach residue identified quartz (Si6.00O6.00: 91-900-5019), and minor residual polylithionite K(Al0.90Li0.90Fe0.80Mn0.20 (Si3.10Al0.90)(OH0.40)F1.60: 00-042-1399) as the main undissolved phases.