A novel ammonium-free vanadium precipitation process for the integrated actions of ascorbic acid reduction and enhanced hydrolysis under hydrothermal influence

Abstract

Vanadium-titanium magnetite is an important source of vanadium, and V2O5 is the main vanadium product. At present, the production of V2O5 is mainly obtained by sodium salt roasting and ammonium salt precipitation, while ammonia nitrogen wastewater and NH3 discharge will cause serious environmental pollution. Calcium and iron salts are mainly intermediate products, and vanadium oxides cannot be obtained directly. Therefore, a clean and sustainable method is proposed to produce V2O5 by ascorbic acid hydrothermal reduction in one step. When the vanadium concentration is 25.48 g/L, under the optimal vanadium precipitation conditions: the ascorbic acid addition ratio is n(ASA): n(V) = 0.1:1, the reaction temperature is 210 °C, the solution pH is 1.25, and the reaction time is 10 h, the precipitation efficiency and V2O5 purity can be 99.60% and 99.12%, respectively. The kinetics and apparent activation energy of the reaction were investigated, and the apparent activation energy was calculated to be 68.80 kJ/mol. The product obtained was characterized by XRD, SEM-EDS, XPS and FTIR, proving that the final product is V2O5. The reaction mechanism of ascorbic acid and vanadium in solution is single electron transfer and recombination, and the formation process of V2O5 is: VO3- → VO2+ → VO2 or V2O3 → V2O5, and ascorbic acid is oxidized to dehydroascorbic acid. In conclusion, the production of V2O5 by hydrothermal reduction of ascorbic acid is environmentally friendly, clean, simple, and efficient.