Preparation of V2O5 using Pb5(VO4)3OH recovered from Bayer vanadium sludge through H2SO4 pre-treatment, H2O2 leaching, V5O12∙6H2O and V10O24∙12H2O precipitation and oxidative roasting at 400 °C

Abstract

Bayer vanadium sludge (BVS), discharged during the Bayer alumina production, is a promising secondary resource for the supply of vanadium. Previous vanadium extraction process involving Pb5(VO4)3OH precipitation by PbSO4, H2SO4 and (NH4)2SO3 leaching, (NH4)2S2O8 oxidation followed by ammonium vanadate precipitation, suffered from large amounts of reagent consumption and discharge of ammonia-containing waste. In this study, a cleaner and cost-efficient process based on H2SO4 pre-treatment, H2O2 leaching, hydrolytic precipitation, and preparation of V2O5 through oxidative roasting was proposed to reduce reagent consumption and waste. Results show that the maximum vanadium leaching efficiency reached 99.7 % under the most suitable conditions of H2SO4 pre-treatment with H2SO4/Pb5(VO4)3OH molar ratio of 6.5, pulp density of 250 g/L at 90 °C for 4 h followed by H2O2 leaching with H2O2/V molar ratio of 3.0 at 15 °C for 10 min. Furthermore, 96.5 % of vanadium was precipitated in the forms of V5O12∙6H2O and V10O24∙12H2O by heating the leach liquors to 100 °C for 60 min, followed by the oxidative roasting at 400 °C for 2 h to prepare V2O5 product with a purity of 99.2 %, with only H2O as a by-product. This research provides new insights into vanadium extraction in a cleaner, cost-efficient, and sustainable industrial process which saves 147.4 $/t Pb5(VO4)3OH.