Considering the recent focus of the Nigeria Government to grow and develop the nation’s economy through the solid minerals sector reform, this study has been devoted to the kinetics of a Nigerian goethite ore by hydrochloric acid leaching for improved iron and steel industries applications. This study was performed in three different phases. In the first phase, acidic leaching of iron from a goethite ore was examined and the influence of the operating variables including: HCl concentration, leaching temperature, stirring speed and particle sizes was examined experimentally. The optimum condition was found to be HCl concentration of 1.81M, temperature of 80°C, 200 rpm stirring speed and particle size 0.09 μm for iron in the range of investigated parameters. Under those conditions, the highest iron recovery was obtained to be 95.67 %. In the second phase, the dissolution kinetics of iron was evaluated by the shrinking core models. The finding reveals that diffusion through the fluid was the leaching kinetics rate controlling step of the iron. The activation energy (Ea) was found to be 14.54 kJmol-1 for iron. Equation representing the leaching kinetic of iron was achieved to be 1−2/3α - (1 − x)2/3 = 0.7272 × e−38.29/8.314×T × t. The final stage of the experiment was carried out by characterizing the leached residues by X-ray diffractometer (XRD) and scanning electron microscopy (SEM), the result showed majorly the presence of rutile (TiO2), anglesite (PbSO4), and traces of iron-silicate face like pyrite (FeS), quartz (SiO2).
Keywords: kinetics modelling, leaching, low-grade, recovery, shrinking core
Dissolution and characterization studies on the purification of muscovite ore in hydrochloric acid for use in paint production was investigated. Specific dissolution parameters including the effects of acid concentration as well as temperature on the dissolution of muscovite ore were studied. Important instrumentation techniques such as X-ray Fluorescence (XRF), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were employed for the better explanation of the dissolution process so as to fathom the availability of elements and compounds within the ore. The results revealed that the dissolution rates were considerably influenced as the acid concentration and temperature increased, while at optimal leaching conditions, about 85 % of the ore was found to have been reacted by 2.5 mol/L at 75oC temperature and at 120 minutes of leaching time. The reaction order for the dissolution can be deduced to be half order reaction as the value obtained was in the bracket of 0.50. The reaction kinetic data revealed the dissolution mechanism to involve diffusion and surface chemical mechanisms as the rate-controlling mechanisms while the different instrumentation techniques corroborated the dissolution as well as purification of the muscovite ore as an ingredient for possible use in paint production.
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