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

The general preparation method for V(2)O(5) 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 V(2)O(5) with low ammonium consumption. The purity of the V(2)O(5) product reaches more than 99% while reducing the level of ammonium consumption. The vanadium precipitation efficiency reaches 99.23% and the V(2)O(5) 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 (NaV(3)O(8)∙xH(2)O) and purified ((NH(4))(2)V(6)O(16)·1.5H(2)O) hydrolysis products are characterized via XRD. The TGA results show that NaV(3)O(8)∙xH(2)O contains 1.5 times the amount of crystal water. The FTIR results explain that the two V(3)O(8)(−) layers are combined end-to-end to form a V(6)O(16)(2−) layer. The change of the product image indicates that the purification process includes three stages. Firstly, heating and NH(4)(+) attack expand the V(3)O(8)(−) layer. NH4(+) diffuses more easily into the V(3)O(8)(−) layer. Secondly, NH(4)(+) destroys the electrostatic interaction between Na(+) with the V(3)O(8)(−) layer and replacing Na(+). Finally, V(3)O(8)(−) is polymerized into V(6)O(16)(2−) to keep the crystal structure stable.