Cleaner and cost-efficient hydrometallurgical process for extraction of vanadium from Bayer vanadium sludge based on BaSO4, NaOH, ammonium, and water circulation

Abstract

Bayer vanadium sludge(BVS) is a hazardous waste due to its high contents of V, P, As, and F. Full or partial utilization of this sludge could not only minimize the potential environmental risk but also promote resource recycling. In this work, a cleaner and cost-efficient process was proposed to selectively extract vanadium from BVS by employing BaSO4 as precipitant. Under the optimal conditions, a maximum vanadium precipitation efficiency of 97.86% is achieved, whereas only 1.15% arsenate and 0.12% fluoride are co-precipitated. Afterwards, the generation of 2Na3AsO4·NaF·19 H2O and NaSO4·NaF has enhanced the simultaneous removal of As and F during evaporation crystallization, and achieving the recycling of NaOH. A new strategy was adopted to in-situ convert Ba3(VO4)2 into Ba(VO3)2·H2O which can be directly leached in (NH4)2SO4 solution. Furthermore, 99.78% vanadium is precipitated as (NH4)2V6O16 from the leachate and the V2O5 product with a purity of 99.85% is prepared after calcination. The leaching residues and the spent liquor containing large amounts of NH4+ after (NH4)2V6O16 precipitation can be circulated to the next batch of vanadium precipitation and leaching, respectively. Herein, the process realizes the internal circulation of BaSO4, NaOH, ammonium, and water, saving production costs and avoiding environmental pollution.