Beneficiation of Two Different Low-Grade Nigerian Manganese Ore Deposits to Improve its Quantitative Composition

Abstract

The beneficiation potential of two low-grade manganese ores from the Mopa-Muro (Kogi State) and Oban Massif (Cross River State) deposits, Nigeria, was investigated using liberation study, gravity separation, and froth flotation techniques combined with thermal treatment at 950 and 1050°C. Prior to beneficiation, the ores were crushed, milled, and classified into particle sizes of 75, 105, 300, and 425 μm. Mineralogical and structural characterization of the beneficiated ores was carried out using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. XRD analysis identified pyrolusite (MnO₂), manganosite (MnO), spessartine [Mn₃Al₂(SiO₄)₃], and quartz (SiO₂) as the major mineral phases in both deposits, while goethite [FeO(OH)] was detected only in the Oban Massif ore. Quartz was confirmed as the principal gangue mineral, indicating strong interlocking between manganese-bearing minerals and silicate impurities. The liberation study produced the highest beneficiation efficiency, increasing the pyrolusite content in the Mopa-Muro ore from 10.7% to 75.0%, corresponding to an improvement of 64.3 percentage points, while the Oban Massif ore exhibited a smaller increase from 10.5% to 14.7% (4.2 percentage points). Froth flotation resulted in pyrolusite enrichment from 31.0% to 64.0% (33.0 percentage points) for the Mopa-Muro ore, whereas manganosite increased from 41.0% to 57.0% (16.0 percentage points) in the Oban Massif concentrate. Gravity separation produced moderate upgrading, with manganosite increasing from 15.0% to 40.0% (25.0 percentage points) in the Mopa-Muro ore and spessartine increasing from 23.0% to 49.0% (26.0 percentage points) in the Oban Massif ore. FTIR spectra revealed characteristic Mn–O stretching vibrations within the 775–1029 cm⁻¹ region, confirming the presence of pyrolusite, manganosite, and spessartine, while the absence of sharp absorption bands between 3670 and 3550 cm⁻¹ indicated effective dehydration and the absence of free hydroxyl functional groups following calcination. The results further demonstrated that increasing calcination temperature from 950 to 1050°C and reducing particle size significantly enhanced mineral liberation and beneficiation efficiency. Although the beneficiated concentrates did not attain the chemical specifications required for metallurgical-grade manganese ores, they exhibited substantial improvement in manganese mineral concentration and are suitable for the production of spiegeleisen (low-grade ferromanganese) and other medium-grade manganese applications.

Also available @ http://doi.org/10.5281/zenodo.21313433