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