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Role of Ferryl Ion Intermediates in Fast Fenton Chemistry on Aqueous Microdroplets

Gu, Alan Y. and Musgrave, Charles and Goddard, William A., III and Hoffmann, Michael R. and Colussi, Agustín J. (2021) Role of Ferryl Ion Intermediates in Fast Fenton Chemistry on Aqueous Microdroplets. Environmental Science & Technology . ISSN 1520-5851. (In Press)

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In the aqueous environment, Fe^(II) ions enhance the oxidative potential of ozone and hydrogen peroxide by generating the reactive oxoiron species (ferryl ion, Fe^(IV)O^(2+)) and hydroxyl radical (·OH) via Fenton chemistry. Herein, we investigate factors that control the pathways of these reactive intermediates in the oxidation of dimethyl sulfoxide (Me_(2)SO) in Fe^(II) solutions reacting with O_3 in both bulk-phase water and on the surfaces of aqueous microdroplets. Electrospray ionization mass spectrometry is used to quantify the formation of dimethyl sulfone (Me_(2)SO_(2), from Fe^(IV)O^(2+) + Me_(2)SO) and methanesulfonate (MeSO_3^–), from ·OH + Me_(2)SO) over a wide range of Fe^(II) and O_3 concentrations and pH. In addition, the role of environmentally relevant organic ligands on the reaction kinetics was also explored. The experimental results show that Fenton chemistry proceeds at a rate ∼104 times faster on microdroplets than that in bulk-phase water. Since the production of MeSO_3^– is initiated by ·OH radicals at diffusion-controlled rates, experimental ratios of Me_(2)SO_(2)/MeSO_3^– > 102 suggest that Fe^(IV)O_2^+ is the dominant intermediate under all conditions. Me_(2)SO_(2) yields in the presence of ligands, L, vary as volcano-plot functions of E^0(LFe^(IV)O^(2+)+O_2/LFe^(2+) + O_3) reduction potentials calculated by DFT with a maximum achieved in the case of L≡oxalate. Our findings underscore the key role of ferryl Fe^(IV)O^(2+) intermediates in Fenton chemistry taking place on aqueous microdroplets.

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URLURL TypeDescription Information
Musgrave, Charles0000-0002-3432-0817
Goddard, William A., III0000-0003-0097-5716
Hoffmann, Michael R.0000-0001-6495-1946
Colussi, Agustín J.0000-0002-3400-4101
Additional Information:© 2021 American Chemical Society. Received: March 25, 2021. Revised: May 25, 2021. Accepted: June 22, 2021. This project was supported by the U.S. National Science Foundation, Grant AGS-1744353. Special thanks are extended to Drs. Nathan Dalleska and Sara Lijie Li for their assistance.
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Record Number:CaltechAUTHORS:20210709-151714645
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Official Citation:Role of Ferryl Ion Intermediates in Fast Fenton Chemistry on Aqueous Microdroplets Alan Y. Gu, Charles Musgrave, William A. Goddard, Michael R. Hoffmann, and Agustín J. Colussi Environmental Science & Technology Article ASAP DOI: 10.1021/acs.est.1c01962
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109756
Deposited By: Donna Wrublewski
Deposited On:09 Jul 2021 17:31
Last Modified:09 Jul 2021 17:31

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