Cleaning method of vanadium precipitation from stripped vanadium solution using oxalic acid

Abstract

Adding ammonium salt to the stripped vanadium solution followed by calcination is the most commonly used vanadium precipitation method in the vanadium industry. However, the problem of ammonia waste water and waste gas emission in this process urgently needs to be solved. To avoid the ammonia emissions and utilize the sodium ion, a hydrothermal method was used to precipitate NaV2O5 by stripped vanadium solution. Under optimal conditions of a pH of 4.0, a time of 10 h, a temperature of 220 °C, and a molar ratio of oxalic acid to vanadium of 0.50, a NaV2O5 product with 99.83% of purity and 98.79% of vanadium precipitation rate was obtained. In view of crystal form, microscopy and granularity changes of products, a rational reaction and growth mechanism is put forward and that is condensation (oxolation and olation)-intercalation-reduction and self-assembly. The sodium in the stripped vanadium solution also can be utilized in this study. In short, one-step vanadium precipitation of NaV2O5 via hydrothermal process is an innovative, cleaning and efficient method, and it will also play a great role in NaV2O5 synthesis.