Assessing Iron Complexation by Dissolved Organic Matter Using Mediated Electrochemical Oxidation
Year: 2024
Type: article
Abstract: Fe II is an abundant reductant in the environment that participates in numerous biogeochemical cycles and pollutant attenuation. Fe II in aquatic environments can exist as a complex with dissolved organic matter (DOM), where organic ligands in DOM can modulate iron’s redox potential ( E H ) and henceforth reactivity as a reductant. Previous studies have assessed the reactivity of Fe II -complexes using probe compounds, although these compounds are limited in their ability to profile Fe II oxidation across multiple thermodynamic conditions (i.e., both pH and E H ) and fail to validate the E H of Fe(II)-complexes via their direct measurement. This study elucidated the redox potentials of Fe II -DOM complexes via mediated electrochemical oxidation (MEO) and assessed the extent of Fe II oxidation at two different applied E H and pH regimes. Furthermore, we used a Nernstian-based model calibrated with a training set between known iron-ligand thermodynamic stability constants and their respective measured potentials to indirectly determine the stability constants of both Fe II and Fe III -DOM complexes as a function of E H and pH. This work highlights the versatility of MEO as an electrochemical technique and is the first to assess stability constants of Fe-complexes with aquatic DOM isolates. We also discuss linkages between speciation modeling and redox reactivity of Fe II .
Source: ACS Earth and Space Chemistry
Institutions: Oregon Health & Science University, University of Delaware
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
Award: G2832923013
OpenAlex ID: W4401618186