Recovery of Vanadium from Ba3(VO4)2 Precipitate Obtained from Processing of Bayer Vanadium Sludge: NaHCO3 Leaching Behaviors and V2O5 Preparation
摘要
Bayer vanadium sludge (BVS), discharged during the Bayer alumina production, is a promising secondary resource for the supply of vanadium. The previous studies found that vanadium can be selectively extracted from BVS in the form of Ba3(VO4)2 using BaCO3 and then be leached in NH4HCO3 solution. However, a large liquid-to-solid ratio is necessary due to the solubility limits of NH4VO3. In this study, the preparation of V2O5 from Ba3(VO4)2 by NaHCO3 leaching, NH4HCO3 precipitation, and calcination was investigated. The vanadium leaching efficiency reaches 97.95% after leaching at 60°C for 120 min in 175 g/L NaHCO3 solution with a liquid-to-solid ratio of 4:1 mL/g. Furthermore, over 81.4% vanadium is recovered in the form of NH4VO3 from leachate by adding NH4HCO3 with an NH4+/V ratio of 2, keeping pH at 8.5 with CO2 gas at 25°C for 4 h, and the V2O5 product with a purity of 99.85% is prepared after calcination. Interestingly, under low NaHCO3 concentrations, vanadium leaching efficiency presents a downward trend after reaching a peak as the time extended, which is due to the re-precipitation of Ba2V2O7 phase caused by the consumption of HCO3− increasing solution pH. The morphological evolution during the conversion of Ba3(VO4)2 to BaCO3 revealed that the BaCO3 product did not cover the unreacted Ba3(VO4)2 particles, instead of existing as dispersed particles.