A Sustainable Technique to Prepare High-Purity Vanadium Pentoxide via Purification with Low Ammonium Consumption

The general preparation method for V₂O₅ is ammonium salt vanadium precipitation, which inevitably produces large amounts of ammonia nitrogen wastewater. In this paper, we propose an environmentally friendly method for preparing high-purity V₂O₅ with low ammonium consumption. The purity of the V₂O₅ product reaches more than 99% while reducing the level of ammonium consumption. The vanadium precipitation efficiency reaches 99.23% and the V₂O₅ purity of the product reaches 99.05% under the following conditions: precipitation time of 1.5 h, precipitation temperature of 98 °C, initial precipitation pH of 2, ammonium addition coefficient of 2, purification time of 5 min with purification performed twice, purification temperature of 65 °C. In this study, compared with the use of ammonia spirit for vanadium precipitation and ammonium salt vanadium precipitation, the ammonia consumption levels are reduced by 79.80% and 80.00%, and the purity levels are increased by 0.70% and 1.01%, respectively. The compositions of the precipitated (NaV₃O₈∙xH₂O) and purified ((NH₄)₂V₆O₁₆·1.5H₂O) hydrolysis products are characterized via XRD. The TGA results show that NaV₃O₈∙xH₂O contains 1.5 times the amount of crystal water. The FTIR results explain that the two V₃O₈^- layers are combined end-to-end to form a V₆O₁₆^2- layer. The change of the product image indicates that the purification process includes three stages. Firstly, heating and NH₄⁺ attack expand the V₃O₈^- layer. NH4⁺ diffuses more easily into the V₃O₈^- layer. Secondly, NH₄⁺ destroys the electrostatic interaction between Na⁺ with the V₃O₈^- layer and replacing Na⁺. Finally, V₃O₈^- is polymerized into V₆O₁₆^2- to keep the crystal structure stable.