| As a first step to obtain a high purity vanadium, the purification procedure of commercial grade vanadium pentaoxide has been studied. The V₂O_5 has been converted to V(OH)₂F₃ by fusing with NH₄F· HF at 160℃ To eliminate insoluble impurites, the product has been leached out with hot water. The precipitation of NH₄VO₃ from filtered leaching solution is carried out by adjusting pH with NH₄OH. Redissolving the precipitate and stabilizing Si as a complex by adding NH₄F·HF are found to be effective to reduce the Si content. However, the rate of second precipitation is extremely slow. To improve the rate, the effect of seed and alcohol has been investigated. The addition of C₂H_5OH as a catalyst not only accelerates the rate of ppt but improves recovery up to 98%. All the products have been examined by microscope, X-ray diffraction and ICP to clarify the structure and contents of impurities. |
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