Vanadate Bio-Detoxification Driven by Pyrrhotite with Secondary Mineral Formation

Abstract

Vanadium(V) is a redox-sensitive heavy-metal contaminant 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 SO4 2–. Secondary minerals including mackinawite (FeS) and greigite (Fe3S4) were produced synchronously, resulting from further transformations of Fe(III) and SO4 2– 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.

Vanadium in the Environment: Biogeochemistry and Bioremediation

“…92 Pyrrhotite can also be efficiently used by microbes for V(V) bioreduction, with a V(V) removal efficiency of 44.1% in a stable period. 149 Secondary minerals, for instance mackinawite and greigite, were produced synchronously in this bioprocess. Although natural organic matter abiotically reduces V(V) to V(IV) under lower pH, 150 there is no reduction above pH 6, without further reduction to V(III).…”

“…This passivation is significantly alleviated by microbial activity, which improves the longevity of mackinawite by 4.7 times in supporting V­(V) reduction . Pyrrhotite can also be efficiently used by microbes for V­(V) bioreduction, with a V­(V) removal efficiency of 44.1% in a stable period . Secondary minerals, for instance mackinawite and greigite, were produced synchronously in this bioprocess.…”

“…175,176 Microbial remediation provides a low-cost and sustainable solution for managing V-polluted sites. 19,149 Electron donors are critical for driving V(V) reduction. Soluble organic compounds, such as glucose, acetate, and citrate, have been utilized as electron donors; they can be directly utilized by heterotrophic V(V) reducers, 18 among which acetate as a nonfermentative substrate supports the maximum V(V) removal efficiency of 75.6% in a 12-h operation at initial 75 mg/L V(V).…”

“…The V(V) removal efficiencies of elemental sulfur and zerovalent iron are comparable to those of organic electrons, with V(V) removal efficiencies of 97.5% and 86.6% during the 5-d cycle. 28 When natural pyrrhotite is used for microbial V(V) reduction, the produced V(IV) is incorporated into the lattice of the produced greigite, preventing reoxidation and release again, 149 which is beneficial for bioremediation. In addition, autotrophs can assimilate CO 2 during this bioprocess, thereby reducing carbon emissions and contributing to carbon neutrality.…”

“…Diverse microbes coexist in environmental media, forming microbial communities that can reduce V­(V) to the less toxic and mobile V­(IV). , Microbial remediation provides a low-cost and sustainable solution for managing V-polluted sites. , …”