The process of selective leaching of vanadium by oxalic acid direct leaching was studied, compared with sulfuric acid direct leaching, by using a mica-type vanadium bearing stone coal from Hubei province. The effects of dosage of H+, leaching time, leaching temperature and water-mineral ratio on V2O5and Fe2O3leaching rate were investigated under the condition of CaF2dosage of 5% (mass fraction). Results indicated that when the dosage of H+was 12 mol·kg-1, leaching time was 6 h, leaching temperature was 95℃and water-mineral ratio was 1.5∶1.0 (L·kg-1), the leaching rate of V2O5was 71.5% by oxalic acid direct leaching and 74.1% by sulfuric acid direct leaching. The leaching rates of Fe2O3were 3.4% and 13.0% corresponding to oxalic acid direct leaching and sulfuric acid direct leaching, which meant the amount of iron leached by oxalic acid direct leaching accounted for 26.2% by sulfuric acid direct leaching. From X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses, it could be concluded that the diffraction peak and the characteristic IR adsorption peak of mica were changed in both two leaching systems, which indicated the crystal structure of mica was destroyed as the vanadium was leached. Compared with the diffraction peak of pyrite in raw ore, the diffraction peak of pyrite in oxalic acid leaching residue almost had no change but the diffraction peak intensity of pyrite in sulfuric acid leaching residue became weak, which indicated the amount of iron leached by sulfuric acid leaching was more than that of oxalic acid leaching, and the analyses were consistent with the experiment results.
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