Efficient and sustainable process for separating and recovering vanadium from Bayer vanadium sludge using PbSO4 as selective precipitant

Abstract

Traditional approaches of vanadium recovery from Bayer vanadium sludge (BVS) discharged during the Bayer alumina production process affords large quantities of unusable solid waste and wastewater. In this study, a novel and sustainable process based on PbSO4 precipitant was proposed to separate and recover vanadium from BVS. The results show that 99.09 % of vanadium was selectively extracted in the form of Pb5(VO4)3OH with a Pb/V molar ratio of 1.7, NaOH concentration of 60 g/L at 70 °C for 30 min, whereas along with only 0.52 % of arsenate, 0.53 % phosphate, and 0.16 % of fluoride. To facilitate further recovery, the remaining phosphate, arsenate, and fluoride were simultaneously separated from NaOH solutions by evaporation crystallization and enriched into residue in the forms of 2Na3AsO4·NaF·19H2O, 2Na3PO4·NaF·19H2O, and NaSO4·NaF. Subsequently, H2SO4 leaching followed by (NH4)2SO3 leaching realized the maximum vanadium leaching efficiency of 99.15 % from Pb5(VO4)3OH precipitate. Finally, the vanadium was deposited as (NH4)2V6O16 from leachate by adding stoichiometric (NH4)2S2O8 and then prepared the V2O5 product with a purity of 99.81 %. Herein, the whole process realized the internal circulation of PbSO4, NaOH, water and solved the difficult treatment of solid waste and wastewater, which provides a new strategy for cleaner comprehensive utilization of BVS.