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. 2022 Jul 21;6(7):1666-1673.
doi: 10.1021/acsearthspacechem.1c00373. Epub 2022 Jul 6.

Mechanism of Arsenic Partitioning During Sulfidation of As-Sorbed Ferrihydrite Nanoparticles

Naresh Kumar  1   2   3 , Vincent Noël  4 , Johannes Besold  5 , Britta Planer-Friedrich  5 , Kristin Boye  4 , Scott Fendorf  6 , Gordon E Brown Jr  1   2   4
Affiliations

Mechanism of Arsenic Partitioning During Sulfidation of As-Sorbed Ferrihydrite Nanoparticles

Naresh Kumar et al. ACS Earth Space Chem. .

Abstract

Knowledge of how arsenic (As) partitions among various phases in Fe-rich sulfidic environments is critical for understanding the fate and mobility of As in such environments. We studied the reaction of arsenite and arsenate sorbed on ferrihydrite nanoparticle surfaces with dissolved sulfide at varying S/Fe ratios (0.1-2.0) to understand the fate and transformation mechanism of As during sulfidation of ferrihydrite. By using aqueous As speciation analysis by IC-ICP-MS and solid-phase As speciation analysis by synchrotron-based X-ray absorption spectroscopy (XAS), we were able to discern the mechanism and pathways of As partitioning and thio-arsenic species formation. Our results provide a mechanistic understanding of the fate and transformation of arsenic during the codiagenesis of As, Fe, and S in reducing environments. Our aqueous-phase As speciation data, combined with solid-phase speciation data, indicate that sulfidation of As-sorbed ferrihydrite nanoparticles results in their transformation to trithioarsenate and arsenite, independent of the initial arsenic species used. The nature and extent of transformation and the thioarsenate species formed were controlled by S/Fe ratios in our experiments. However, arsenate was reduced to arsenite before transformation to trithioarsenate.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Fe(II) concentrations in aqueous phase (<0.22 μm) measured after 70 days of sulfidation of ferrihydrite at different S/Fe ratios in vials where either arsenite or arsenate was the initial arsenic species added, along with a control where no As was added.
Figure 2
Figure 2
Total arsenic concentrations in aqueous phase (<0.22 μm) measured after 70 days of sulfidation of ferrihydrite at different S/Fe ratios in vials where either arsenite or arsenate was the initial arsenic species added.
Figure 3
Figure 3
Aqueous arsenic speciation measured after 70 days of reaction at different S/Fe ratios with either arsenite or arsenate as the initial arsenic species in the experiment.
Figure 4
Figure 4
As K-edge XANES spectra from the solid phase after 70 days of reaction at different S/Fe ratios batch microcosms using either arsenite or arsenate as the initial arsenic species.
Figure 5
Figure 5
Fe (II), total arsenic, sulfate, and thiosulfate measured in solution at various S/Fe ratios after 70 days of the sulfidation reaction.
See this image and copyright information in PMC

References

    1. Brown G. E. Jr.; Foster A. L.; Ostergren J. D. Mineral surfaces and bioavailability of heavy metals: A molecular scale perspective. Proc. Nat. Acad. Sci. U.S.A. 1999, 96, 3388–3395. 10.1073/pnas.96.7.3388. - DOI - PMC - PubMed
    1. Nordstrom D. K. Public health—worldwide occurrences of arsenic in ground water. Science 2002, 296 (5576), 2143–2145. 10.1126/science.1072375. - DOI - PubMed
    1. O’Day P. A.; Vlassopoulos D.; Root R.; Rivera N. The influence of sulfur and iron on dissolved arsenic concentrations in the shallow subsurface under changing redox conditions. Proc. Nat. Acad. Sci. U.S.A. 2004, 101, 13703–13708. 10.1073/pnas.0402775101. - DOI - PMC - PubMed
    1. Saalfield S. L.; Bostick B. C. Changes in iron, sulfur, and arsenic speciation associated with bacterial sulfate reduction in ferrihydrite-rich systems. Environ. Sci. Technol. 2009, 43, 8787–8793. 10.1021/es901651k. - DOI - PubMed
    1. Kocar B. D.; Borch T.; Fendorf S. Arsenic repartitioning during biogenic sulfidization and transformation of ferrihydrite. Geochim. Cosmochim. Acta 2010, 74, 980–994. 10.1016/j.gca.2009.10.023. - DOI

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