Fundamental Research Of Extracting Vanadium Based On Vanadium Leaching Agent And Producing High Purity V₂O₅ With Compact Process

China is one of the countries rich in vanadium（V） resources, and the vanadium slag is abundantly produced and discarded at an alarming speed every year. The utilization of these resources to recover vanadium and chromium is not only a way to prepare high-value vanadium production, but also an efficient method to resolve the environmental pollution issue. In this paper, by establishing the thermodynamic models of vanadium in aqueous and organic phases（extraction systems）, the speciation chemistry of vanadium in aqueous, the reaction equation and the mechanism of primary amine N1923 extracting vanadium were discussed. On the basis of these studies, the recover process of V and Cr was optimized, with which higy-purity V₂O₅ was prepared and the characterization was performed with several methods. New process and innovative results were achieved as follows:1) In the process of extracting vanadium, the extraction complexes were determined by equimolar series method, saturation capacity method and the slope method. The binding ratio of RNH₂-H₃VO₄, RNH₂-H₃V₃O₉, RNH_2-H₆V₁₀O₂₈ and RNH_2-H₂CrO₄ were 5/3, 1, 11/3 and 1, respectively, based on which, the extraction reaction equation were speculated and thermodynamic models of the extraction process were established. The extraction equilibrium data were regressed to obtain the Pitzer parameters and extraction equilibrium constants. Comparing the extraction equilibrium constants, the priority of N1923 extracting vanadium and chromium species is H₆V₁₀O₂₈ > H₃V₃O₉ > H₃VO₄ > H₂CrO₄, which is very important for the separation and recovery of vanadium and chromium.2) A chemical model, based on Bromley–Zemaitis model and Pitzer equation, is developed with a speciation approach to describe the solubility and chemistry of NH₄VO₃ in ammonium solution. The solubility data produced by author were regressed to obtain new model parameters with good agreement. The predictive ability of the new model was improved significantly in comparison with the previous model. The behabior of speciation chemistry and mean ionic activity coefficient for NH₄VO₃ in aqueous at various temperature, pH value and electrolyte media were explained with this model. All of these supported the precipitation of vanadium in industry.3) On the basis of extraction recovery of V and Cr, the low silicon and high-purity V₂O₅（ V₂O₅> 99.9%） is successfully prepared by technology improvement of intensifying desilicon, selective extracting vanadium, stripping and precipitation. The removal of silicon with LK–SI is more efficient than that with NaAlO₂ and calcium salt, which could reduce the silicon concentration from 900 ppm to below to 20 ppm. And the removal of element Al was determined by adjusting pH to 8.4. With selective extraction, only vanadium is extracted into organic phase and all the other impurities, such as Cr and Si, were left in raffinate, which minimizes the introduction of impurities. By analyzing the elements trend in the technical process and multiplicating experiments, the technology is certified to stable and reliable.4) The concentrations of impurities, such as Cr, Si, Al, Na, Fe, Ca, P and As, were analyzed with ICP-OES by redissolving prepared V₂O₅, and the result represents the impurity content of prepared V₂O₅ satisfy the high-purity V₂O₅ standard of Australia. At the same time, the characteration of prepared V₂O₅ was made by the methods of XRD, SEM, XPS, BET, particle size analysis and capacitive analysis.