Extraction of Vanadium From Vanadium Slag Through a New Technique Route Including Na₂O₂-Briquetting Roasting Process

Abstract

The material accumulation during roasting in the practical production causes the hypoxia of the internal materials, leading to the relatively lower vanadium recovery than that in theoretical studies. This work aims to solve the problem of material hypoxia through the Na₂O₂-briquetting roasting route. The vanadium slag and Na₂O₂ powders were mixed, briquetted, and roasted at various parameters. The generated phases and their distributions were analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, and electron probe microanalysis. The analyzing results showed that Fe₂O₃, Fe₃O₄, Mg_0.165Mn_0.835O, CaTiO₃, and Na₃VO₄ were generated during roasting. The solid–solid reaction between V₂O₅ and Na₂O was described using the vacancy-mediated diffusion mechanism. Na⁺ (or V⁵⁺), in the Na₂O (or V₂O₅) layer, jumped and diffused through the Na⁺ (or V⁵⁺) vacancies (in the Na₃VO₄ layer) to the Na₃VO₄/V₂O₅ (or Na₃VO₄/Na₂O) interface. Na⁺ (or V⁵⁺) reacted with V₂O₅ (or Na₂O) and O₂ decomposed from Na₂O₂ or transported from the air to generate Na₃VO₄. The roasted mixture was leached in an aqueous solution to study the effects of the roasting variables on the vanadium leaching recovery. The vanadium leaching recovery was very sensitive to the roasting variables, it showed very complicated relationships with the Na/V molar ratio, temperature, time, and briquetting pressure. The maximum vanadium leaching recovery of 95.57 pct was achieved when the Na/V molar ratio, temperature, time, and pressure were optimized as 3/1, 850 °C, 2.5 hours, and 5 MPa, respectively. The leaching solution containing vanadium was processed via precipitation and calcination to gather vanadium. The obtained compound was identified as V₂O₅ with a purity of 96.84 pct, based on the high consistency of diffraction peaks between the present work and that of the joint committee on powder diffraction standards.