Stanford Advisors

All Publications

  • Vanadate Retention by Iron and Manganese Oxides. ACS earth & space chemistry Abernathy, M. J., Schaefer, M. V., Ramirez, R., Garniwan, A., Lee, I., Zaera, F., Polizzotto, M. L., Ying, S. C. 2022; 6 (8): 2041-2052


    Anthropogenic emissions of vanadium (V) into terrestrial and aquatic surface systems now match those of geogenic processes, and yet, the geochemistry of vanadium is poorly described in comparison to other comparable contaminants like arsenic. In oxic systems, V is present as an oxyanion with a +5 formal charge on the V center, typically described as H x VO4 (3-x)-, but also here as V(V). Iron (Fe) and manganese (Mn) (oxy)hydroxides represent key mineral phases in the cycling of V(V) at the solid-solution interface, and yet, fundamental descriptions of these surface-processes are not available. Here, we utilize extended X-ray absorption fine structure (EXAFS) and thermodynamic calculations to compare the surface complexation of V(V) by the common Fe and Mn mineral phases ferrihydrite, hematite, goethite, birnessite, and pyrolusite at pH 7. Inner-sphere V(V) complexes were detected on all phases, with mononuclear V(V) species dominating the adsorbed species distribution. Our results demonstrate that V(V) adsorption is exergonic for a variety of surfaces with differing amounts of terminal -OH groups and metal-O bond saturations, implicating the conjunctive role of varied mineral surfaces in controlling the mobility and fate of V(V) in terrestrial and aquatic systems.

    View details for DOI 10.1021/acsearthspacechem.2c00116

    View details for PubMedID 36016759

  • Reactivity of manganese oxide at redox interfaces in diffusion controlled environments Ying, S., Abernathy, M., Mock, R., Lezama, J., Garniwan, A., Lake, L., Lee, I., Schaefer, M. AMER CHEMICAL SOC. 2018