Performance and mechanism of bioleaching remediation of vanadium contaminated soil

Abstract:

[Objective] Soil contamination by heavy metal is a growing concern, of which vanadium is gradually becoming a research hotspot. Although leaching is an important tool for soil remediation, it can cause severe pollution and incur high cost. Bioleaching can be applied as an efficient soil remediation process because of its cost-effective and environmental- friendliness. However, current understanding of remediation of vanadium-contaminated soil is still limited. [Methods] In this study, we applied Acidithiobacillus ferrooxidans in the bioleaching of vanadium-contaminated soil. The optimal leaching conditions were investigated by changing the influencing factors. The scanning electron microscopy and energy dispersive X-ray spectroscopy were applied to analyze the changes of vanadium during the bioleaching process. The microbial metabolites were characterized. [Results] The microbial secondary metabolites could promote the leaching of vanadium from the soil. The leaching efficiency of vanadium from soil by Acidithiobacillus ferrooxidans was high, and the leaching rate of vanadium from soil reached 27.4% after 20 days. Further experiments on the influencing factors showed that the best leaching of vanadium from soil was achieved at a solid concentration of 3%, an inoculum volume of 10%, an initial pH of 1.8 and an initial Fe²⁺ concentration of 3.0 g/L. SEM-EDS analysis confirmed the reduction of vanadium content in the soil after leaching, and analysis of the vanadium morphology in the soil indicated that the vanadium present in the non-residue form in the soil was more easily leached. Metabolomic analyses showed that Acidithiobacillus ferrooxidans produced a large number of metabolites during the leaching process to cope with the high concentration of heavy metals in the environment. [Conclusion] The bioleaching technology can effectively remediate vanadium-contaminated soil. This study provides an environmentally friendly remediation approach for the restoration of vanadium-contaminated soil.