Hydrothermal precipitation of V3+ ions in V-bearing oxalic acid leachate to prepare V2O3

Abstract

In our previous study, a novel method of direct leaching of V3+ ions in iron vanadate spinel minerals by oxalic acid synergized with Fe powder under hydrothermal conditions was developed. In the present study, we attempted to prepare V2O3 from this V-bearing oxalic acid leachate. First,the dissolution and precipitation behavior of V3+ ions in the V2O3-H2C2O4-H2O system were investigated at various mass ratios of V2O3 to H2C2O4 and temperatures. Then, according to the hydrothermal features of this system, two routes of preparing V2O3 were designed. In Route A, a certain amount of pure V2O3 reagent was added into the pregnant leachate as a nucleating agent and to adjust the ratio of V3+ to C2O42− ions in solution, and V2O3 was prepared from the V-bearing oxalic acid leachate by a one-step hydrothermal process. In Route B, a precursor composed of hybrid vanadium oxides was initially obtained from the V-bearing oxalic acid leachate by hydrothermal precipitation, and then the precursor was reduced in a 95% Ar + 5% H2 atmosphere at 700 °C to prepare the V2O3 product. Whether by route A or B, a V2O3 product with high crystallinity was obtained from the V-bearing oxalic acid leachate, and a higher extent of vanadium precipitation was achieved.