Adsorption of (Poly)vanadate onto Ferrihydrite and Hematite: An In Situ ATR–FTIR Study
Date
2020-03-25
Authors
Vessey, Colton
Schmidt, Michael P.
Abdolahnezhad, Mojtaba
Peak, Derek
Lindsay, Matthew B. J.
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American Chemical Society (ACS) Publications
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Abstract
Vanadium (V) has been a useful trace metal in describing Earth’s biogeochemical cycling and development of industrial processes; however, V has recently been recognized as a potential contaminant of concern. Although Fe (oxyhydr)oxides are important sinks for aqueous V in soils and sediments, our understanding of adsorption mechanisms is currently limited to mononuclear species (i.e., HxVO4(3–x)–). Here we use in situ attenuated total reflectance – Fourier transform infrared spectroscopy to examine sorption mechanisms and capacity for (poly)vanadate attenuation by ferrihydrite and hematite from pH 3 to 6. Adsorption isotherms illustrate the low affinity of polyvanadate species for ferrihydrite surfaces compared to hematite. Mononuclear V species (i.e., [HxVO4](3−x)− and VO2+) were present at all experimental conditions. At low surface loadings and pH 5 and 6, H2VO4− adsorption onto ferrihydrite and hematite surfaces results from formation of inner sphere complexes. At [V]T above 250 µM, adsorbed polynuclear V species in this study include H2V2O72− and V4O124−. Whereas, HV10O286−, H3V10O285−, and NaHV10O284− are the predominant adsorbed species at pH 3 and 4 and elevated [V]T. Surface polymers were identified on hematite at all experimental pH values, whereas polymeric adsorption onto ferrihydrite was limited to pH 3 and 4. These results suggest that hematite offers a more suitable substrate for polymer complexation compared to ferrihydrite. Our results demonstrate the pH and concentration dependant removal of (poly)vanadate species by Fe(III) (oxyhydr)oxides, which has implications for understanding V mobility, behaviour, and fate in the environment.
Description
Copyright © 2020 American Chemical Society
Keywords
vanadium, polymerization, ferrihydrite, hematite, adsorption, ATR−FTIR, surface complexation
Citation
Vessey, C.J., Schmidt, M. P., Abdolahnezhad, M., Peak, D. & Lindsay, M. B. J. (2020). Adsorption of (Poly)vanadate onto Ferrihydrite and Hematite: An In Situ ATR–FTIR Study. ACS Earth and Space Chemistry, 4(4): 641–649. https://doi.org/10.1021/acsearthspacechem.0c00027
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Citation
Vessey, C.J., Schmidt, M. P., Abdolahnezhad, M., Peak, D. & Lindsay, M. B. J. (2020). Adsorption of (Poly)vanadate onto Ferrihydrite and Hematite: An In Situ ATR–FTIR Study. ACS Earth and Space Chemistry, 4(4): 641–649. https://doi.org/10.1021/acsearthspacechem.0c00027
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DOI
10.1021/acsearthspacechem.0c00027