Development of an Analytical Technique to Determine the Fractions of Vanadium Cations with Different Valences in Slag
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ome iron ores, e.g., the ores in Sweden and in some parts of China, contain considerably high concentration of vanadium oxide. Vanadium oxide is reduced to metallic vanadium and dissolved in hot metal in blast furnace. The dissolved vanadium is oxidized in the converter when decarburization takes place. A large amount of vanadium oxides ends up in the converter slag. The disposed converter slag cannot be reused because of its high content of vanadium (up to 3 mass pct V), whereas the high value of vanadium in the slag is a waste of a natural resource. To develop a technique to recover vanadium from the slag, the thermodynamic data are essential.[1] Vanadium exists as different cations in slag. The dependence of the fractions of these cations on both oxygen potential and slag composition could be one of the main reasons for the scarcity of the thermodynamic data. The difficulties in determining the fractions of V2+, V3+, V4+, and V5+ in the slag have complicated the situation. To the knowledge of the current authors, there is no systematic method to analyze the concentrations of the different vanadium cations in the slag, although efforts have been made to quantify the trace amount of total vanadium in the samples.[2–6] Mass spectroscopy can measure the concentrations of V2+, V3+, V4+, and V5+ cations,[3,4] but only in the region a few micron meters near the surface of the sample. It is difficult to apply this technique to a slag analysis. X-ray absorption spectroscopy (XAS) has been
HUI WANG, Senior Engineer, is with the Department of Processing Mineralogy, Beijing General Research Institute of Mining and Metallurgy, Beijing 100044, P.R. China. FAN LI, Associate Professor, is with the Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, P.R. China. DU SICHEN, Professor, is with the Department of Material Science and Engineering, Royal Institute of Technology, 100 44 Stockholm, Sweden. Contact e-mail: [email protected] Manuscript submitted July 13, 2010. Article published online November 4, 2010. METALLURGICAL AND MATERIALS TRANSACTIONS B
employed to analyze the valence state of vanadium in Li2O-VOx-P2O5 electronic ionic conducting glasses.[6] However, the result of XAS may lead to different interpretations by different fitting models. Because the slag system is complicated, the determination of thermodynamic data based on only this technique would be difficult. X-ray photoelectron spectroscopy combined with X-ray diffraction (XRD), thermal analysis, and infrared spectroscopy has been applied in investigating the oxidation state of vanadium in stoichiometric or nonstoichiometric nanosized vanadium-iron spinels.[5] Although the analyzed results on the surface of sample are accurate, the easy contamination of the surface of the slag sample would make the application of this technique somewhat difficult. Moreover, standard samples of different valences of vanadium are always needed in this technique. It is almost impossible to find the standard
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