KINETICS OF ACID LEACHING REFINING OF AN INDUSTRIAL FE-SI ALLOY

The effects of the three leaching parameters (concentration of HCl and FeCl3 and stirring) on the purification of an industrial Fe-Si alloy, containing phases such as Fe-Al-Si-Ca (caalsifer) and FeSi2, with a high Ca/Al ratio, were studied. The leaching residues, after analysis for particle size distribution, were characterized chemically, morphologically by scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and structurally by X-ray diffraction. The experimental results conform with the cracking shrinking model, according to which a mechanism is proposed for the dissolution of the main impurities (Ca, Al and Fe). The leaching of these impurities was found to depend on the composition of the phases and nature of their distribution. For the proposed model, the leaching of the impurities are under chemical reaction control, which is in agreement with the microstructure observed by SEM/EDS.