Leaching of vanadium from waste V2O5-WO3/TiO2 catalyst catalyzed by functional microorganisms

Highlights: • Bioleaching of waste V₂O₅-WO₃/TiO₂ catalyst was performed using five methods. • The S-mediated way was demonstrated as a promising method to extract vanadium. • Direct and indirect mechanisms worked to leach vanadium effectively. • The direct vanadium bioleaching mechanism of the S-mediated way was first reported. Solid wastes are currently produced in large amounts. Although bioleaching of metals from solid wastes is an economical and sustainable technology, it has seldom been used to recycle metals from abandoned catalyst. In this study, the bioleaching of vanadium from V₂O₅-WO₃/TiO₂ catalyst were comprehensively investigated through five methods: Oligotrophic way, Eutrophic way, S-mediated way, Fe-mediated way and Mixed way of S-mediated and Fe-mediated. The observed vanadium bioleaching effectiveness of the assayed methods was follows: S-mediated > Mixed > Oligotrophic > Eutrophic > Fe-mediated, which yielded the maximum bioleaching efficiencies of approximately 90%, 35%, 33%, 20% and 7%, respectively. The microbial community analysis suggested that the predominant genera Acidithiobacillus and Sulfobacillus from the S-mediated bioleaching way effectively catalyzed the vanadium leaching, which could have occurred through the indirect mechanism from the microbial oxidation of S⁰. In addition, the direct mechanism, involving direct electron transfer between the catalyst and the microorganisms that attached to the catalyst surface, should also help the vanadium to be leached more effectively. Therefore, this work provides guidance for future research and practical application on the treatment of waste V₂O₅-WO₃/TiO₂ catalyst.