Effect of iron transformation on Acidithiobacillus ferrooxidans bio-leaching of clay vanadium residue

The acid bio-leaching process of vanadium extraction from clay vanadium water-leached residue was studied and the effect of the performance of iron transformation was investigated. Acidithiobacillus ferrooxidans affects the dissolution of vanadium through the catalytic effect on Fe3+/Fe2+ couple and material exchange. The passivation of iron settling correlates with ferrous ion content in bio-leaching solution. In medium containing A. ferrooxidans and Fe(III), the increment in Fe(II) concentration leads to the formation of jarosite, generating a decline in vanadium extraction efficiency. Analysis of cyclic voltammetry shows that Fe(II) ion is apt to be oxidized and translated into precipitate by A. ferrooxidans, which strongly adsorbed to the surface of the residue. Fe(III) ion promotes the vanadium extraction due to its oxidizing activity. Admixing A. ferrooxidans to Fe(III) medium elevates the reduction of low valence state vanadium and facilitates the exchange of substance between minerals and solution. This motivates 3.8% and 21.8% increments in recovery ratio and leaching rate of vanadium compared to the Fe(III) exclusive use, respectively. Moreover, Fe(II) ion impacts vanadium extraction slightly in sterile medium but negatively influences vanadium leaching in the presence of bacteria