Photochemical and Photophysical Dynamics of the Aqueous Ferrate(VI) Ion

Authors

Cali Antolini, University of Rhode Island
Charles D. Spellman, University of Rhode Island
Christopher J. Otolski, Argonne National Laboratory
Gilles Doumy, Argonne National Laboratory
Anne Marie March, Argonne National Laboratory
Donald A. Walko, Argonne National Laboratory
Cunming Liu, Argonne National Laboratory
Xiaoyi Zhang, Argonne National Laboratory
Benjamin T. Young, Rhode Island College
Joseph E. Goodwill, University of Rhode IslandFollow
Dugan Hayes, University of Rhode IslandFollow

Document Type

Article

Date of Original Version

12-14-2022

Department

Chemistry

Abstract

Ferrate(VI) has the potential to play a key role in future water supplies. Its salts have been suggested as "green" alternatives to current advanced oxidation and disinfection methods in water treatment, especially when combined with ultraviolet light to stimulate generation of highly oxidizing Fe(V) and Fe(IV) species. However, the nature of these intermediates, the mechanisms by which they form, and their roles in downstream oxidation reactions remain unclear. Here, we use a combination of optical and X-ray transient absorption spectroscopies to study the formation, interconversion, and relaxation of several excited-state and metastable high-valent iron species following excitation of aqueous potassium ferrate(VI) by ultraviolet and visible light. Branching from the initially populated ligand-to-metal charge transfer state into independent photophysical and photochemical pathways occurs within tens of picoseconds, with the quantum yield for the generation of reactive Fe(V) species determined by relative rates of the competing intersystem crossing and reverse electron transfer processes. Relaxation of the metal-centered states then occurs within 4 ns, while the formation of metastable Fe(V) species occurs in several steps with time constants of 250 ps and 300 ns. Results here improve the mechanistic understanding of the formation and fate of Fe(V) and Fe(IV), which will accelerate the development of novel advanced oxidation processes for water treatment applications.

Publication Title, e.g., Journal

Journal of the American Chemical Society

Volume

144

Issue

49

Citation/Publisher Attribution

Antolini, Cali, Charles D. Spellman, Christopher J. Otolski, Gilles Doumy, Anne Marie March, Donald A. Walko, Cunming Liu, Xiaoyi Zhang, Benjamin T. Young, Joseph E. Goodwill, and Dugan Hayes. "Photochemical and Photophysical Dynamics of the Aqueous Ferrate(VI) Ion." Journal of the American Chemical Society 144, 49 (2022). doi: 10.1021/jacs.2c08048.