Vanadate Bio-Detoxification Driven by Pyrrhotite with Secondary Mineral Formation

Vanadium(V) is a redox-sensitive heavy-metal con-taminant whose environmental mobility is strongly influenced by pyrrhotite, a widely distributed iron sulfide mineral. However, relatively little is known about microbially mediated vanadate [V(V)] reduction characteristics driven by pyrrhotite and concomitant mineral dynamics in this process. This study demonstrated efficient V(V) bioreduction during 210 d of operation, with a lifespan about 10 times longer than abiotic control, especially in a stable period when the V(V) removal efficiency reached 44.1 +/- 13.8%. Pyrrhotite oxidation coupled to V(V) reduction could be achieved by an enriched single autotroph (e.g., Thiobacillus and Thermomonas) independently. Autotrophs (e.g., Sulfurifustis) gained energy from pyrrhotite oxidation to synthesize organic intermediates, which were utilized by the heterotrophic V(V) reducing bacteria such as Anaerolinea, Bacillus, and Pseudomonas to sustain V(V) reduction. V(V) was reduced to insoluble tetravalent V, while pyrrhotite oxidation mainly produced Fe(III) and SO42-. Secondary minerals including mackinawite (FeS) and greigite (Fe3S4) were produced synchronously, resulting from further transformations of Fe(III) and SO42- by sulfate reducing bacteria (e.g., Desulfatiglans) and magnetotactic bacteria (e.g., Nitrospira). This study provides new insights into the biogeochemical behavior of V under pyrrhotite effects and reveals the previously overlooked mineralogical dynamics in V(V) reduction bioprocesses driven by Fe(II)-bearing minerals.

Automated summary

This study found that the presence of pyrrhotite can significantly enhance the bioreduction of vanadium(V), showing efficient reduction capability during the 210-day operation. Through the oxidation and reduction reactions of minerals, vanadium(V) was reduced to insoluble tetravalent vanadium, accompanied by a series of mineral transformations. This study provides new insights into the influence of pyrrhotite on vanadium(V) reduction and the dynamics of minerals in the process.