F. Rahman, M. Skyllas-Kazacos
Apr 21, 1998
Citations
1
Influential Citations
144
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Quality indicators
Journal
Journal of Power Sources
Abstract
Abstract The specific energy of the vanadium redox battery is determined by the solubility of the four vanadium oxidation states in sulfuric acid. While recent studies have shown that a higher vanadium concentration than that initially proposed might be feasible, further reliable solubility data for the various vanadium ions is required if the electrolyte composition is to be properly optimized. This study describes the results of a solubility study of vanadyl sulfate in sulfuric acid. VOSO 4 is the species which exists in the discharged positive half-cell of the vanadium redox cell. The solubility data have been generated in sulfuric acid concentrations that range from 0 to 9 mol/l and at temperatures between 10 and 50°C. The solubility of VOSO 4 is found to decrease continuously with increasing H 2 SO 4 concentration and decreasing temperature. At 20°C, the solubility of VOSO 4 in distilled water is 3.280 mol/l whereas in 9 M H 2 SO 4 it is 0.260 mol/l. The drop in solubility with increasing H 2 SO 4 concentration is significant and is more pronounced at lower concentrations. A multivariable solubility prediction model has been developed as a function of temperature and total sulfate/bisulfate (SO 4 2− and HSO 4 − ) concentration using the extended Debye–Huckel functional form. The average absolute deviation of the predicted solubility values from experimental data is 4.5% with a maximum deviation of about 12% over the abovementioned temperature and sulfuric acid concentration range. When solubility data in the more useful H 2 SO 4 concentration range of 3–7 M is considered, the solubility correlation improved with an average absolute deviation of only 3.0% and a maximum deviation of about 7%.