Reductive Leaching and Recovery of Nano-crystalline MnO from Low-Grade Pyrolusite Ore

In this study, tartaric acid was identified as an efficient reductant for the reductive leaching of manganese from low-grade pyrolusite ore in an HSO solution. The effect of HSO concentration, tartaric acid concentration, time, and temperature on the leaching efficiency of low-grade pyrolusite ore was investigated. Evidently, when taking into account the various parameter ranges, the greater portion of the increase in efficiency can be attributed to the concentration of tartaric acid and temperature. For instance, by increasing the concentration of tartaric acid within the range of 0 to 0.19 M, the efficiency of manganese has experienced a surge of roughly 62%. In addition, temperature has a favorable impact on the leaching efficiencies of both Mn and Fe; however, the effect is more pronounced for Mn. Specifically, when the temperature is raised from 25 to 85 °C, the leaching efficiency of Mn and Fe rises from 28.9 and 14.3% to 90 and 33.5%, respectively. At optimal leaching conditions (HSO concentration: 1.4 M, time: 150 min, temperature: 85 °C, and tartaric acid concentration: 0.16 M), 94% Mn and 41% Fe were leached. Fourier transform infrared spectroscopy (FTIR) confirmed the breakdown of the strong C=O stretching band for tartaric acid in the presence of HSO and the formation of new bonds at a lower wavelength. Based on the FTIR analysis conducted on the leaching solution, it was observed that the new bands remained consistent when soluble manganese was present. After the impurity removal from leachate, 96% of Mn was precipitated in the form of dioxide manganese by adding potassium permanganate as an oxidant. The results demonstrate that tartaric acid is a practical and efficient reductant for Mn recovery from low-grade pyrolusite ore. Graphical Abstract: [Figure not available: see fulltext.].